United States
Environmental Protection
Agency
EPA 402-F-13053 I December 2013 I www.epa.gov/iaq/moisture
Moisture Control
Guidance for Building
Design, Construction
and Maintenance
Indoor Air Quality (IAQ)
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Moisture Control Guidance for Building Design, Construction and Maintenance
U.S. Environmental Protection Agency
December 2013
www.epa.gov/iaq/moisture
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Foreword: How to Use this Guidance v
Acknowledgements vi
Chapter 1
Moisture Control In Buildings 1
Introduction 1
Health Implications of Dampness in Buildings 1
Moisture Damage in Buildings 2
Moisture Problems are Expensive 7
How Water Causes Problems in Buildings 7
Moisture Control Principles for Design 8
Moisture Control Principle #1: Control Liquid Water 8
Moisture Control Principle #2: Manage Condensation 14
Moisture Control Principle #3: Use Moisture-Tolerant Materials 19
The Basics Of Water Behavior 24
Chapter 2
Designing for Moisture Control 26
Introduction 26
Designing Effective Moisture Controls 26
Building Commissioning 26
Who Should Read this Chapter 27
Site Drainage 28
Foundations 32
Walls 38
Roof And Ceiling Assemblies 45
Plumbing Systems 54
HVAC Systems 57
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Chapter 3
Constructing to Prevent Moisture Problems 67
Introduction 67
Pre-Construction Planning 71
Site Drainage Construction 74
Foundation Construction 76
Wall Construction 78
Roof and Ceiling Assembly Construction 80
Plumbing System Installation 82
HVAC System Installation 84
Chapter 4
Operating and Maintaining Moisture-Controlled Environments 87
Introduction 87
Site Drainage Maintenance 90
Foundation Maintenance 92
Wall Maintenance 93
Roof and Ceiling Assembly Maintenance 95
Plumbing System Operation and Maintenance 98
HVAC System Operation and Maintenance 99
Appendix A - The "Pen Test" A-I
Appendix B - Roof Inspection Checklist B-I
Appendix C - Testing Moisture During Construction c-i
Appendix D - Air Pressure Mapping D-I
Appendix E - HVAC Inspection Checklist E-I
Appendix F - Site Drainage Maintenance F-I
Appendix G - Dampness & Mold Evaluation G-I
Glossary H-I
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Foreword: How to Use this Guidance
This document was developed by the U.S.
Environmental Protection Agency, Indoor
Environments Division. It provides practical guidance
on how to control moisture in buildings.1 It is not a
textbook, code or standard.
Chapter 1 focuses on principles of moisture control:
how water moves into and within a building and
why the movement of water should be controlled or
managed. Chapters 2, 3 and 4 provide profession-
specific guidance for the design, construction and
maintenance phases of a building's life. To illustrate
how core concepts and principles relate to each stage
of a building's life, each guidance chapter contains
hyperlinks to relevant principles described in Chapter
1 and other related material throughout the text. Each
guidance chapter also includes methods for verifying
the appropriate implementation of the moisture
control recommendations and a reference section
that identifies additional related resources for readers
interested in more detailed information.
Who Should Read this Guide
This guide can be used by anyone who designs,
builds, operates or maintains buildings and heating,
ventilating and air conditioning (HVAC) equipment. It
was developed specifically for:
• Professionals who design buildings and produce
drawings, specifications and contracts for
construction or renovation.
• Professionals who erect buildings from the
construction documents.
• Professionals who operate and maintain buildings,
conducting preventive maintenance, inspecting the
landscape, building interior and exterior equipment
and finishes and performing maintenance and
repairs.
'NOTE: This document does not address flood water control. For information about managing flood water, see http://www.epa.gov/naturalevents/flooding.html or http://www.epa.
gov/naturalevents/hurricanes/. Accessed on November 6, 2013.
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Acknowledgements
The United States Environmental Protection Agency, Office of Radiation and Indoor Air, Indoor Environments
Division would like thank the many professionals who contributed to this document, including Terry Brennan
and Michael Clarkin of Camroden Associates and Lew Harriman of Mason-Grant Consulting.
The Agency would also like to thank Christopher Patkowski for permission to use the photograph of water
droplets on the front and back covers.
The figures in this document came from several sources:
• Terry Brennan provided the photographs used in Figures 1-1 to 1-14.
• Christopher Patkowski created Figures 1-15, 1-16 and 2-14 based on illustrations in the Whole Building
Design Guide (www.wbdg.org), a program of the National Institute of Building Sciences.
• Terry Brennan drew Figure 1-17 and provided the spreadsheets used to create Figures 1-18 and 1-19. He
also provided the photograph for Figure 1-20.
• Christopher Patkowski created Figure 2-1. He also created Figures 2-2 to 2-4, Figures 2-6 and 2-7, and
Figures 2-9 to 2-12 based on illustrations provided by Joe Lstiburek of Building Science Corporation.
• The U.S. Department of Energy provided the map in Figure 2-5.
• Christopher Patkowski drew Figure 2-8 based on an illustration in a publication of the Canadian Mortgage
and Housing Corporation. He also drew Figure 2-13.
• Terry Brennan drew Figures 2-15 and 2-16.
• Lew Harriman provided Figure 2-17.
• Terry Brennan provided Figure 4-1 and drew Figures A-l to A-3.
• Christopher Patkowski drew Figures D-l to D-3 based on drawings by Terry Brennan.
• Figure G-l was provided by the National Institute of Occupational Safety and Health (NIOSH).
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Chapter 1: Moisture Control in Buildings
Introduction
Moisture control is fundamental to the proper
functioning of any building. Controlling moisture is
important to protect occupants from adverse health
effects and to protect the building, its mechanical
systems and its contents from physical or chemical
damage. Yet, moisture problems are so common in
buildings, many people consider them inevitable.
Excessive moisture accumulation plagues buildings
throughout the United States, from tropical Hawaii
to arctic Alaska and from the hot, humid Gulf Coast
to the hot, dry Sonoran Desert. Between 1994 and
1998, the U.S. Environmental Protection Agency
(EPA) Building Assessment Survey and Evaluation
(BASE) study collected information about the indoor
air quality of 100 randomly selected public and
private office buildings in the 10 U.S. climatic
regions. The BASE study found that 85 percent of the
buildings had been damaged by water at some time
and 45 percent had leaks at the time the data were
collected.2
Moisture causes problems for building owners,
maintenance personnel and occupants. Many
common moisture problems can be traced to poor
decisions in design, construction or maintenance. The
American Society of Heating, Refrigerating and Air
Conditioning Engineers (ASHRAE) notes that, more
often than not, the more serious problems are caused
by decisions made by members of any of a number of
different professions.3 However, such problems can
be avoided with techniques that are based on a solid
understanding of how water behaves in buildings.
Moisture control consists of:
• Preventing water intrusion and condensation in
areas of a building that must remain dry.
• Limiting the areas of a building that are routinely
wet because of their use (e.g., bathrooms, spas,
kitchens and janitorial closets) and drying them out
when they do get wet.
To be successful, moisture control does not require
everything be kept completely dry. Moisture control is
adequate as long as vulnerable materials are kept dry
enough to avoid problems. That means the building
must be designed, constructed and operated so that
vulnerable materials do not get wet. It also means
that when materials do get wet, the building needs to
be managed in such a way that the damp materials
dry out quickly.
Health Implications of Dampness in Buildings
At the request of the U.S. Centers for Disease Control
and Prevention (CDC), the Institute of Medicine (IOM)
of the National Academy of Sciences convened a
committee of experts to conduct a comprehensive
review of the scientific literature concerning
the relationship between damp or moldy indoor
environments and the appearance of adverse health
effects in exposed populations. Based on their review,
the members of the Committee on Damp Indoor
Spaces and Health concluded that the epidemiologic
evidence shows an association between exposure to
damp indoor environments and adverse health effects,
including:
• Upper respiratory (nasal and throat) symptoms.
• Cough.
• Wheeze.
• Asthma symptoms in sensitized persons with
asthma.
The committee also determined that there is limited
or suggestive evidence of an association between
exposure to damp indoor environments and:
• Dyspnea (shortness of breath).
• Lower respiratory illness in otherwise healthy
children.
• Asthma development.
2 http://www.epa.gov/iaq/base/. Accessed November 6, 2013.
3 Limiting Indoor Mold and Dampness in Buildings. 2013 (PDF) at https://www.as rirae.org/about-asrirae/position-documents. Accessed November 6, 2013.
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Details of the results of this review were published in
a 2004 report, Damp Indoor Spaces and Health.4 It
is also important to note that immuno-compromised
individuals, such as some categories of hospital
patients, are at increased risk for fungal colonization
and opportunistic infections.5
After the publication of the IOM report, a study by
Lawrence Berkeley National Laboratory concluded
that building dampness and mold raise the risk of
a variety of respiratory and asthma-related health
effects by 30 to 50 percent.6 A companion study by
EPA and Berkeley Lab estimated that 4.6 million
cases of asthma, 21 percent of the 21.8 million cases
of asthma in the U.S. at that time, could be attributed
to exposure to dampness and mold in homes.7
Moisture Damage in Buildings
In addition to causing health problems, moisture
can damage building materials and components. For
example:
• Prolonged damp conditions can lead to the
colonization of building materials and HVAC
systems by molds, bacteria, wood-decaying molds
and insect pests (e.g., termites and carpenter ants).
• Chemical reactions with building materials and
components can cause, for example, structural
fasteners, wiring, metal roofing and conditioning
coils to corrode and flooring or roofing adhesives to
fail.
• Water-soluble building materials (e.g., gypsum
board) can return to solution.
• Wooden materials can warp, swell or rot.
• Brick or concrete can be damaged during freeze-
thaw cycles and by sub-surface salt deposition.
• Paints and varnishes can be damaged.
• The insulating value (R-value) of thermal insulation
can be reduced.
The following photos show some of the damage that
can result from moisture problems in buildings.
Figure 1-1 Mold growing on the surface of painted gypsum board and trim.
Long-term high humidity is the source of the moisture that allowed the mold
growth. All of the walls experienced similar near-condensation conditions.
Consequently, the mold growth is widespread rather than concentrated in a
single damp area.
4 Institute of Medicine (2004) Damp Indoor Spaces and Health. http://www.iom.edu/Reports/2004/Damp-lndoor-Spaces-and-Health.aspx. Accessed November 6, 2013.
5 Institute of Medicine (2004) Damp Indoor Spaces and Health. http://www.iom.edu/Reports/2004/Damp-lndoor-Spaces-and-Health.aspx. Accessed November 6, 2013.
6 W. J. Fisk, Q. Lei-Gomez, M. J. Mendell (2007) Meta-analyses of the associations of respiratory health effects with dampness and mold in homes. Indoor Air 17(4), 284-295.
dohlO.llll /j. 1600-0668.2007.00475.x
7 D. Mudarri, W. J. Fisk (2007) Public health and economic impact of dampness and mold. Indoor Air 17 (3), 226-235. dohlO.llll /j.1600-0668.2007.00474.x
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Figure 1-2 Mold growth on painted concrete masonry. The cool masonry wall
separates a classroom from an ice rink. Humid air in the classroom provides
moisture that condenses on the painted surface of the masonry. That moisture
allows mold to grow on the paint film.
Figure 1-3 Mold growth on vinyl floor tile. Long-term high humidity provided
moisture that was absorbed into the cool vinyl tile and supported mold
growth. Also note that the high humidity caused the adhesive attaching the
tile to the floor to fail, allowing the tile to become loose.
Figure 1-4 Corrosion of galvanized fluted steel floor deck. The floor is at grade
level. The source of the water is rainwater seepage.
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Figure 1-5 Corrosion of structural steel in a ceiling cavity in a cold climate.
The steel extends into the exterior wall assembly. During cold weather, the
steel near the wall is chilled by cold outdoor air. The building is humidified,
and condensation from high indoor humidity provides the moisture that rusts
the cold steel.
Figure 1-6 Blistering paint on split face concrete block. Wind-driven rain
is the source of moisture contributing to the damage. Water wicks into
the concrete masonry unit (CMU) through pin holes in the paint. The sun
drives water vapor through the CMU. The assembly cannot dry to the interior
because low-vapor-permeability foam board, taped at the joints, insulates the
interior surface of the wall. The wall remains saturated throughout the spring,
summer and fall. The same paint on areas of the wall sheltered from sun and
rain shows no damage.
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Figure 1-7 Condensation behind vinyl wallpaper in a warm, humid climate.
Condensation and mold growth occurs behind the vinyl wallpaper on both
exterior and interior walls. Air leaks in the return plenum of the air handler
depressurizes the interior and exterior wall cavities. Warm, humid exterior air
is drawn from outside through air leaks in a heavy masonry wall.
Figure 1-8 Rainwater leaks in a rooftop parapet wall result in damaged plaster
and peeling paint. Rainwater is drawn into this brick assembly by capillary
action, and the moisture is aided in its downward migration by gravity. The
peeling paint contains lead and results in an environmental hazard as well as
physical damage to the plaster.
Figure 1-9 Interior plaster damaged by rain seeping around a window in a
brick building. The inside of the exterior wall is insulated with closed-cell
spray foam. Consequently, the wall cannot dry to the interior, so it retains
excessive amounts of moisture. At the point where the plaster on the window
return meets the brick wall, rainwater wicks into the plaster causing the
damage seen in this photo.
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Figure 1-10 Further rain damage to interior plaster. At another location on an
office window in the building shown in Figure 1-8, rain seepage turns gypsum
board joint compound to a fluid, causing the gypsum to bubble and lift.
Figure 1-11 Gypsum board on the lower edge of a basement wall dissolved by
seasonal flood waters. The water table is just below the basement floor during
dry weather and rises several inches above the floor during heavy spring rains.
Figure 1-12 Hardwood gymnasium floor warped by moisture in the cavity
below it. Water rises through the concrete sub-floor. The source of the
moisture is rainwater that has not been drained away from the foundation of
the building.
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Figure 1-13 Tile adhesive that failed to cure because of water in the concrete
and high pH. The tile can be removed by hand. The floor is a concrete slab-
on-grade. The water visible in the photo evaporates into the room after several
minutes. Its source may be liquid water wicking up from the sub-slab fill or
water vapor migrating through the slab.
Figure 1-14 Damage to bricks caused by the migration of soluble salt through
them. Salts in the brick or mortar dissolve in rainwater that wicks through the
brick. The water evaporates in the building's interior, and the salt left behind
crystalizes and splits the surface layer off the brick, exposing its interior. This
process is called sub-fluorescence.
Moisture Problems are Expensive
Health problems and building damage due to
moisture can be extremely expensive. Berkeley Lab
estimates that the annual asthma-related medical
costs attributable to exposures to dampness and mold
total approximately $3.5 billion in the U.S.8 But many
more adverse health outcomes due to damp buildings
have been reported, each with associated costs of
its own. And damage to the building itself is also
costly. Building owners and tenants bear a significant
proportion of these costs, including:
• Absenteeism due to illnesses such as asthma.
• Reduced productivity due to moisture-related health
and comfort problems.
• Increased insurance risk, repair and replacement
costs associated with corroded structural fasteners,
wiring and damaged moisture-sensitive materials.
• Repair and replacement costs associated with
damaged furniture, products and supplies.
• Loss of use of building spaces after damage and
during repairs.
• Increased insurance and litigation costs related to
moisture damage claims.
How Water Causes Problems in Buildings
Mention water damage and the first image that comes
to mind for most people is liquid water in the form
of rain, plumbing leaks or floods. Many water leaks
are easy to detect. When it rains, water may drip
around skylights, or a crawl space may fill with water.
If a toilet supply line breaks, the floor will likely be
flooded.
On the other hand, many water-related problems
are less obvious and can be difficult to detect or
diagnose. For example, the adhesive that secures
flooring to a concrete slab may not cure properly if the
slab is damp, resulting in loose flooring and microbial
growth in the adhesive. Or, humid indoor air may
condense on the cool backside of vinyl wallpaper that
covers an exterior wall, providing ideal conditions for
mold to grow. These problems are less obvious than
a leak because water is not running across the floor,
and the real damage is being done out of sight under
flooring or behind wallpaper.
Moisture problems are preventable. They do not
happen until water moves from a source into some
part of a building that should be dry. The actual
8D. Mudarri, W. J. Fisk (2007) Public health and economic impact of dampness and mold. Indoor Air 17 (3), 226-235. dohlO.llll /j. 1600-0668.2007.00474.x
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damage begins after enough moisture accumulates to
exceed the safe moisture content limit of moisture-
sensitive materials.
To diagnose or prevent a moisture problem, keep
in mind four key elements of moisture behavior in
buildings:
1. Typical symptoms of moisture problems. They
include corrosion of metals, the growth of surface
mold or wood-decaying molds, insect infestations,
spalling exterior brick or concrete, peeling paint,
failing floor adhesives, stained finishes and health
symptoms.
2. Sources of moisture. Among them are rainwater,
surface water, ground water, plumbing water,
indoor and outdoor sources of humidity and sewer
water.
3. Transport mechanisms. They include liquid water
leaking through holes, wicking through porous
materials, or running along the top or bottom of
building assemblies and water vapor carried by
warm, humid air leaking through assemblies and
by diffusion through vapor-permeable materials.
4. Common failures of moisture control elements and
systems. Moisture controls include site drainage,
gutter systems, above- and below-grade drainage
planes, effective flashing, condensate drainage
and humidity controls. Failures can occur during
any phase of a building's life and may include
poor site selection or design, poor material or
equipment selection, improper installation or
sequence of building materials and equipment,
insufficient coordination between trades during
construction and insufficient or improper
maintenance of materials or equipment.
Moisture Control Principles for Design
To control moisture for long building life and good
indoor air quality, follow these three principles:
1. Control liquid water.
2. Prevent excessive indoor humidity and water vapor
migration by air flow and diffusion in order to limit
condensation and moisture absorption into cool
materials and surfaces.
3. Select moisture-resistant materials for unavoidably
wet locations.
Armed with an elementary understanding of these
principles, readers will be prepared to control
moisture and prevent the vast majority of moisture
problems that are common in buildings.
Moisture Control Principle #1:
Control Liquid Water
The first principle of moisture control is to keep liquid
water out of the building. Sheltering occupants from
water is a primary purpose of building assemblies
including roofs, walls and foundations. Among the
sources of water from outside a building are:
• Rain and melting snow, ice or frost.
• Groundwater and surface runoff.
• Water brought into the building by plumbing.
• Wet materials enclosed in building assemblies
during construction.
Problem: Building Assemblies and Materials Get Wet
Moisture problems are common. By their very nature,
buildings and the construction process are almost
certain to encounter moisture problems that could
lead to poor indoor air quality and other negative
impacts. The most common liquid water problems
include:
• Rain and snow get inside. Rainwater, surface water
and ground water, including snowmelt, may enter
a building through leaks in roofs, walls, windows,
doors or foundations. In most climates, rain is the
largest source of water in buildings. Rainwater
intrusion can cause great damage to the building
itself and to its contents.
• Plumbing leaks. We intentionally bring water into
buildings for cleaning, bathing and cooking, and
we intentionally drain wastewater out of buildings.
Any water brought in and drained out is contained
in pipes, vessels and fixtures that can tolerate
being wet all or most of the time. However, leaks in
plumbing supply lines, drain lines, sinks, showers
and tubs may cause problems. Although model
plumbing codes require both the supply side and
drain/vent side of plumbing systems to be tested for
leaks, these tests are sometimes performed poorly
or not at all. Large plumbing leaks are immediately
obvious, but small leaks inside walls and ceiling
cavities may continue unnoticed for some time.
• Water during construction causes problems.
Some materials are installed wet because they
were exposed to rain or plumbing leaks during
construction. Wet concrete masonry units (CMUs),
poured or pre-cast concrete, lumber and the
exposed earth of a crawl space floor have all been
sources of problems in new buildings.
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• Some materials are installed wet because water is
part of the process. Poured concrete, floor levelers,
wet-spray insulation and water-based finishes all
contain water. Porous materials that appear dry may
contain enough water to cause problems if they
come in contact with moisture-sensitive materials
or if they humidify a cavity after they are enclosed.
Flooring, wall coverings and coatings will fail if they
are applied before surfaces are dry enough. Water
from these materials may indirectly cause problems
by raising the humidity indoors during a building's
first year of use, leading to condensation problems.
Solution: Control Liquid Water Movement
Effectively controlling liquid water intrusion requires
all of the following:
• Drain rain, irrigation water and snowmelt away
from the building. The first step in water control
is to locate the building in dry or well-drained soil
and use or change the landscape to divert water
away from the structure. In other words, drain the
site. This includes sloping the grade away from
the building to divert surface water and keep
subsurface water away from the foundation below
grade. After the site is prepared to effectively drain
water away from the building, the building needs
a storm water runoff system to divert rain from the
roof into the site drainage system.
• Keep rain and irrigation water from leaking into the
walls and roof. Leaking rainwater can cause great
damage to a building and to the materials inside.
In successful systems, rainwater that falls on the
building is controlled by:
• Exterior cladding, roofing and storm-water
management systems to intercept most of the
rain and drain it away from the building.
• Capillary breaks, which keep rainwater from
wicking through porous building materials or
through cracks between materials. A capillary
break is either an air gap between adjacent
layers or a material such as rubber sheeting that
does not absorb or pass liquid water. A few rain
control systems consist of a single moisture-
impermeable material, sealed at the seams, that
both intercepts rainwater and provides a capillary
break. Membrane roofing and some glass panel
claddings for walls work in this way.
• Keep water from wicking into the building by using
capillary breaks in the building enclosure. Moisture
migration by capillary action can be interrupted
using an air space or water-impermeable material.
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• Prevent plumbing leaks by locating plumbing lines
and components where they are easy to inspect and
repair, are unlikely to freeze, and are not in contact
with porous cavity insulation.
• Avoid enclosing wet materials in new construction
by protecting moisture-sensitive and porous
materials during transport and on-site storage and
by drying wet materials before they are enclosed
inside building assemblies or covered by finish
materials.
Drained Roofing and Wall Cladding
Roofing and cladding systems are frequently backed
by an air gap and a moisture-resistant material that
forms the drainage plane. Most of the water that
seeps, wicks or is blown past the cladding will drain
out of the assembly. The drainage plane prevents any
water that might bridge the air gap from wetting the
inner portions of the assembly. Some examples are:
• Roofs. Asphalt or wooden shingles, metal panels
and elastomeric membranes are common outer
layers for roofs.
• Walls. Wooden and vinyl siding, stucco, concrete
panels, brick, concrete masonry units and stone
veneers are common outer layers for walls.
• Drainage planes. Building felt, tar paper and water-
resistant barriers are commonly used as drainage
planes beneath roofing and wall cladding systems.
Single- and multi-ply roofing combine the drainage
plane with the outer layers of the roof—there is no
inner drainage plane material.
Figure 1-15 illustrates the concept of a drained
wall assembly. Although the cladding intercepts
most of the rainwater, some liquid will seep inward.
The air gap acts as a capillary break, and seepage
cannot jump that gap. Instead, seepage runs down
the back of the cladding until it is drained out by
the flashing. Some of the seepage may run to the
drainage plane along materials that bridge the gap,
for example, mortar droppings or cladding fasteners.
The impermeable surface of the drainage plane keeps
water out of the backup sheathing, CMU or concrete,
protecting the inner wall. Water flows down the
drainage plane and over the flashing, which diverts it
back outside.
Some roofing or siding materials absorb water (e.g.,
wooden shingles or siding, fiber cement siding,
traditional stucco and masonry veneers), while
others do not (e.g., roofing membranes, vinyl siding
and metal or glass panels). Historically, the porous
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Figure 1-15 Drained Wall Assembly
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materials were backed by an air gap. Examples
include wooden shingles on skip sheathing, masonry
veneers and heavy masonry walls with 1- to 2-inch
cavities separating brick walls and beveled siding
installed shingle style. The air gap between the
siding and the interior of the wall enables wet porous
materials to dry out to either the outdoor air or into
the air gap.
In either case, the drainage plane must be watertight
at all joints and penetrations. Table 1-1 lists
penetrations commonly found in roofs and walls and
presents ways to maintain the watertight integrity of
the drainage plane. This list is not comprehensive.
Any and all penetrations through roofing and exterior
cladding must be detailed to prevent rainwater
intrusion.
Windows, curtain walls and storefronts are all used
in wall assemblies and are among the more complex
penetrations to detail. Typically, standard details for
window head, jamb and sill flashing are provided
by the manufacturers of these components. Figure
1-16 illustrates a method of providing pan sill and
jamb flashings for walls constructed with an exterior
insulation and finish system (EIFS). Note that the
sill flashing protects the wall assembly from seepage
at the corners of windows and at the joints between
windows. Dams on the sides and back of the sill
pan flashing stop any seepage from running into the
building or into the wall beneath the window.
Foundations
The building foundation must be detailed to protect
the building from rainwater. The above-grade portions
of a foundation are often masonry or concrete. Much
of the rainwater that wets the above-grade wall simply
drains off the surface to the soil below. Masonry
walls are often protected below grade using Portland
cement-based capillary breaks (e.g., traditional
parging or proprietary coatings). Concrete walls may
be treated with additives that provide an integral
capillary break or may be so massive that absorbed
water is more likely to be safely stored in the wall—
drying out between storms—than to wick through to
the interior.
Landscape surfaces immediately surrounding the
foundation perform the same function for the walls
below grade as the roofing and cladding in the walls
above grade: they intercept rain and drain it away
from the building.
The damp-proof or waterproof coatings on below-grade
walls serve the same purpose as the drainage plane
in the above-grade walls. These coatings provide
a capillary break that excludes the rainwater that
saturates the surrounding fill. An additional capillary
break is formed by free-draining gravel or geotechnical
drainage mats placed against the below-grade walls.
These materials provide an air gap that allows water
to drain freely down the foundation wall.
At the bottom of the below-grade wall, a footing
drain system carries rainwater and ground water away
from the footing and the floor slab. Paint formulated
for use on concrete can be applied to the topside
of the footing to provide a capillary break between
the damp footing and the foundation wall. A layer
of clean coarse gravel, with no fines, can provide an
air-gap-style capillary break between the earth and the
concrete floor slab. Plastic film beneath the floor slab
provides a vapor barrier as well as a capillary break
beneath the slab. These drainage layers and the vapor
barriers beneath foundation slabs are often required
by building codes.
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Table 1-1 Maintaining Drainage Plane Water-Tightness in Roofs and Walls
Penetrations Commonly Found in Roofs How to Maintain Drainage Plane Water-Tightness
Joints between pieces of roofing
Roof edges
Roof intersections with adjoining, taller
walls
Skylights and roof hatches
Chimneys
Air handlers and exhaust fans
Plumbing vents
Shingling or sealing provides continuity
Overhangs, copings and drip edges provide capillary breaks
Through-flashing provides continuity where a lower story roof
intersects the wall of the higher level and where any roof meets a
dormer wall. Flashing and counter-flashing of veneers and low-slope
roof membranes keep water out of joints between materials
Flashing, curbs and counter-flashing provide continuity
Flashing, crickets and counter-flashing provide continuity
Flashing, curbs and counter-flashing provide continuity
Flashing and counter-flashing provide continuity
Penetrations Commonly Found in Walls How to Maintain Drainage Plane Water-Tightness
Windows
Doors
Outdoor air intakes
Exhaust outlets and fans
Fasteners
Utility entrances
The "Pen Test"
Head flashing, jamb flashing and panned sill flashing provide
continuity
Head flashing, jamb flashing and panned sill flashing provide
continuity
Head flashing, jamb flashing and panned sill flashing provide
continuity
Head flashing, jamb flashing and panned sill flashing provide
continuity
Sealants provide continuity
Sealants provide continuity
The waterproof layers of the walls, roof and foundation
must form a continuous, six-sided box with no gaps,
no cracks and no holes. It is difficult to achieve this
degree of integrity, especially at the long edges where
the walls meet the roof and the foundation. The
pen test is used before the architectural design is
complete to help make sure these continuous water
barriers, when installed according to the design, will
not leak.
When rainwater control has been well designed, it
should be possible to trace the waterproof layers that
form a capillary break around a sectional view of the
building without lifting pen from paper. This simple
test can be performed not only for the rainwater
control, but also for the thermal insulation layer and
the air barrier. The methods for all three are outlined
in Appendix A and are part of the requirements
for documenting compliance with the guidance in
Chapters 2, 3 and 4.
Figure 1-17 illustrates tracing the capillary break in a
sample section. Starting at the center of the roof:
• The roofing membrane is the first line of defense,
protecting the water-sensitive inner materials from
rain and snowmelt.
• Tracing the roofing membrane from the center
of the roof to the edge of the roof, the roofing
membrane flashes beneath a metal coping, which
in turn flashes to a metal fascia.
• The fascia forms a drip edge, channeling water
away from the cladding.
• An air gap between the drip edge and the brick
veneer forms a capillary break, protecting the
materials beneath the coping from rainwater
wicking into them.
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Figure 1-16 Pan Sill and Jamb Flashings for EIFS Walls
Insulated metal frame wall
Closure strip flashes to drain
plane/ air barrier
Base coat
Top coal
Flashing tape
Sub-sill flashing with up-turned
interior flashing leg and fully
sealed end-dams
Self-adhered membrane
window flashing
Exterior gypsum sheathing
Wall drain plane - continuous
drain plane/air barrier
Drained EIFS
Behind the brick veneer, air gap and foam board, a
water-resistant barrier (WRB) applied to the gypsum
sheathing forms a capillary break between the
damp brick and the inner wall assembly.
The WRB laps over the vertical leg of a head
flashing, protecting the window from rainwater with
a drip edge and an air gap.
The window frame, sash and glazing form a
capillary break system that sits in a pan sill flashing
at the bottom of the window.
The pan sill flashing forms a capillary break
protecting the wall beneath from seepage through
the window system.
The pan sill flashing shingles over the WRB in the
wall beneath, which shingles over a flashing that
protects the bottom of the wall system.
• A polyethylene foam sill seal makes a capillary
break between the foundation and the bottom
of the framed wall, connecting with an inch of
extruded polystyrene insulation that makes a
capillary break between the top of the foundation
wall and the edge of the floor slab. Polyethylene
film immediately beneath the slab provides the
code-required water vapor retarder and forms a
capillary break between the bottom of the slab and
the fill below. NOTE: If the bed of fill beneath the
slab consists of crushed stone greater than 1A inch
in diameter (and if it contains no fines), the bed
also forms a capillary break between the soil and
the slab.
Note the critical role of flashing in excluding water
and in diverting water out of the building if it leaks
in. Applying the pen test to the building design shows
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Figure 1-17 Tracing the Capillary Break in a Sample Section
The blue line traces the elements of the capillary break in the rainwater control system for a section through a
building.
Facia
Drip edge and
air gap
Spray foam insulate
I-beam
Coping
Steel "Z" angle
Tapered foam insulation
Roof membrane
Self-adhered membrane
covers gypsum wall and
seals to flashing
Gypsum sheathing
1" foam board
Air gap
Head flashing (flashes
beneath self-adhered
membrane)
Pan sill flashing
Self-adhered membrane
Gypsum sheathing
1" foam board
Air gap
Brick wall
Flashing
Foam insulation at
down perimeter wall
Concrete foundation wal
Gypsum foam
boardings deck
6" light steel stud
w/ Rid fiberglass
insulation
Roof drain --^J
Window
6" light steel stud
w/R19 fiberglass
insulation
Polyethylene film
Concrete slab
Drainage layer
(coarse aggregate with no fines)
the importance of flashing that is both well designed
and well installed. There are no certification programs
for the proper installation of flashing; however,
the following trade associations offer educational
materials and training programs for flashing design
and installation:
• Sheet Metal and Air Conditioning Contractors'
National Association (SMACNA), http://www.
smacna.org.
• National Roofing Contractors Association, http://
www.nrca.net/.
• National Concrete Masonry Association, http://www.
ncma.org.
• Brick Industry Association, http://www.bia.org.
• Spray Polyurethane Foam Alliance, http://www.
sprayfoam.org.
Prevent Plumbing Leaks
To avoid plumbing leaks, new plumbing systems must
be pressure tested at a stage of construction when the
plumbing lines are easily inspected and leaks can be
readily repaired. This is a code requirement in many
jurisdictions.
Supply lines must be pressurized to design values,
and drain lines must hold standing water. Plumbing
must be designed not only to prevent initial problems,
but also to permit easy maintenance to avoid future
problems.
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Further, plumbing should be located where:
• Leaks will be noticed quickly.
• Leaking water will not wet easily damaged
materials.
• Water inside the plumbing will not freeze in cold
weather.
Plumbing access panels allow critical maintenance
over the life of the building. They should be located
anywhere concealed valves or traps will need to
be inspected for leaks or accessed for adjustment,
maintenance or replacement.
No matter the climate, avoid placing plumbing lines,
valves and drain lines in exterior walls and ceilings
that have porous insulation. If the plumbing leaks,
insulation in those walls or ceilings will get wet. Once
wet, porous insulation takes a long time to dry (or may
never dry). This situation can lead to mold growth,
corrosion of structural fasteners and needless energy
consumption. Also, in climates with cold winters, any
plumbing located in exterior walls or above ceiling
insulation is more prone to freezing and bursting.
Avoid Enclosing Wet Materials in Building
Assemblies
Moisture-sensitive materials and equipment should
be kept dry during construction. In particular, gypsum
board, finished woodwork, cabinets and virtually all
mechanical equipment should be stored in a weather-
protected shelter or installed in their final, weather-
protected locations immediately upon delivery to the
site.
If moisture-sensitive or porous materials get wet, dry
them quickly before mold grows or physical damage
occurs. Masonry walls and concrete floor slabs, for
example, are very porous and can hold a great deal of
water. Masonry block and concrete must be thoroughly
dry before being coated or covered by water-sensitive
materials such as floor tile, carpeting, paint or paper-
faced gypsum board.
Water is added to some materials during installation
(e.g., concrete, water-based coatings, wet-spray fire-
proofing and wet-spray insulation). These materials
must be allowed to dry naturally, or force-dried using
specialized equipment before being enclosed in
building assemblies. These intentionally wet materials
may not suffer from long exposure to moisture, but
as they dry, they will transfer their moisture to nearby
materials that can support mold
dimension.
;rowth or change
Moisture Control Principle #2:
Manage Condensation
9 Dew point can be measured by cooling a mirrored surface until condensation just
mirror devices.
Limit indoor condensation and make sure
condensation dries out when and where it occurs.
Problem: Condensation Happens—
Keep Track of the Dew Point
Both indoor air and outdoor air contains water vapor.
Wherever air goes, water vapor goes. When humid
air contacts a surface that is cold enough, the water
vapor in the air will condense onto that cold surface.
The concept of the air dew-point temperature is very
useful in understanding when, why and how much
condensation will occur—and how to avoid it.
The dew point is the temperature of the air at which
condensation occurs. The higher the dew point, the
greater the risk of condensation on cold surfaces.
The dew point depends on how much water vapor the
air contains. If the air is very dry and has few water
molecules, the dew point is low and surfaces must be
much cooler than the air for condensation to occur.
If the air is very humid and contains many water
molecules, the dew point is high and condensation
can occur on surfaces that are only a few degrees
cooler than the air.9
Consider hot weather condensation inside a building.
Condensation can be prevented as long as the indoor
air dew point is below the temperature of surfaces
that are likely to be cold. If the dew point rises,
moisture will begin to condense on cold surfaces. For
example, humid outdoor air leaking into a building in
Miami will have a dew point above 70°F throughout
most of a typical year. During normal operation of
an air-conditioned building, there are many surf aces
that have a temperature below 70°F. For example, a
supply air duct carrying air at 55°F will have a surface
temperature near 55°F. If the infiltrating outdoor air
has a dew point of 70°F, its moisture will condense
on the outside of that cold duct, and possibly on the
supply air diffuser.
Dew Point vs. Relative Humidity
When most people think of humidity, they think of
relative humidity (RH) rather than dew point. But
gins to appear. Monitors that measure dew point directly in this way are called chilled
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relative humidity is just that, a relative measurement
and not one that expresses the absolute amount of
water vapor in the air. In simple terms, RH is the
amount of water vapor in the air compared to the
maximum amount the air can hold at its current
temperature.10 Change the air temperature and the
relative humidity also changes, even if the absolute
amount of water vapor in the air stays the same. So
knowing only the RH of the air is not much help in
predicting condensation.
Unlike RH, the dew point does not change with
air temperature. In that sense it is an "absolute"
measurement of the amount of water vapor in
the air. When you know the dew point of the air
and the temperature of a surface, you can predict
condensation. If the dew point is aboi/ethe
temperature of the surface, water vapor will condense
onto that cold surface. If the dew point is belowthe
surface temperature, moisture will not condense. So
it is simple to predict condensation, as long as you
know the dew point of the air surrounding the surface.
To be sure, knowing the dew point is not always easy
because many humidity instruments measure and
read only air temperature and relative humidity. So
if the instrument you are using does not display the
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air dew point, you will need a psychrometric chart to
find the dew point based on the temperature and RH
of the air. A psychrometric chart graphs the physical
and thermal properties of moist air.11 A simplified
psychrometric chart relating the air's temperature and
RH to its dew point at sea level is shown in Figure
1-18. With this chart and the readings from a low-
cost monitor to measure air temperature and RH, one
can determine the more useful value of air dew point
in a few seconds.
For example, assume an instrument shows the
outdoor air is 85°F and its RH is 60 percent. Plot
that point on the chart. Then, beginning at that point
move horizontally to the left until your line intersects
the saturation curve (i.e., the 100 percent RH curve
that forms the left edge of the chart). From that
intersection, read straight down to the bottom of the
chart to determine the dew point. As shown in Figure
1-18, the dew point of air at 85°F and 60 percent
RH is 70°F. In other words, air at those conditions
will begin to condense moisture when it contacts any
surface that has a temperature of 70°F or below.
The psychrometric chart reveals an important dynamic
between surface temperature, dew point and RH.
Notice that if the RH is 90 percent, a surface only
Figure 1-18 A Simplified Psychrometric Chart Relates Air Temperature, RH and Dew Point.
•H
X)
I
,0
"5
o
E
0.02
0.018
0.016
0.014
0012
0.01
0.008
0.006
0,004
0.002
100% 90% 80% 70% 60%
45 50 55 60 65 70 75 80 85 90 95
Temperature°(F)
10The technically more accurate definition of relative humidity is the ratio of vapor pressure in the air sample compared to the vapor pressure of that air if it were completely
saturated at the same temperature, expressed as a percentage. But the definition provided above is sufficiently accurate, easier to understand and useful for managing moisture
in buildings.
11 The psychrometric chart is a powerful tool for understanding the water vapor characteristics of air and the effects of heating and cooling moist air. Its history and use are fully
explained in theASHRAE publication Understanding Psychrometrics by Donald Gatley.
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Figure 1-19 The Difference Between Room Air Temperature and the Dew Point as a Function of RH
45
40
35
30
25
20
15
10
5
0
Room Air Temperature
80 Deg F
70 Deg F
60 Deg F
20 40 50 60 70 80 90 100
% Relative Humidity
has to be 3°F cooler than the air for condensation to
occur. It is very likely that during normal operation in
many seasons there will be surfaces in buildings that
are 3°F colder than room temperature.
At high temperatures, high RH may also mean there is
a strong risk of condensation. Figure 1-19 shows the
relationship between RH and the number of degrees
cooler a surface must be for condensation to appear
when the RH is between 25 percent and 100 percent.
This graph provides a way to think about dew point
in terms of RH. At 50 percent RH, a surface must be
around 20°F cooler than the room air for condensation
to occur. Under ordinary circumstances, few surfaces
in a building are 20°F cooler than room air.
Causes of Condensation in Buildings
Condensation may be the result of excessively high
dew point, unusually cold surfaces, or a combination
of the two.
The indoor dew point is a balance between the
addition and subtraction of water vapor from the air. A
building has both indoor and outdoor sources that add
water vapor, and its mechanical systems must have
adequate dehumidification capacity to remove it, in
order to keep the dew point within reasonable limits.
Inside residential buildings, people and their
activities, especially cooking and washing of floors
and clothes, are usually the leading sources of
humidity.
In humidified commercial and institutional buildings
such as hospitals, museums and swimming pool
enclosures, indoor humidity is very high by design or
necessity.
In low-rise buildings of all types, damp basements or
crawlspaces may add as much water vapor to the air
in a day as all the other internal sources combined.
During the cooling season, humidity loads from
outdoor air are far larger than loads generated inside
commercial and institutional buildings. The largest
sources of humidity are the ventilation air, the
makeup air that compensates for exhaust air, and the
air that infiltrates into the building through air leaks
in the enclosure. If the ventilation and makeup air is
kept dry and the building is tight so that it does not
allow much leakage, the contributions from outdoor
air will be low.
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Water vapor may be removed from indoor air
by dehumidification (e.g., air conditioners or
dehumidifiers) or by ventilation air when the outdoor
air is dry. Ventilating air only dehumidifies the indoors
when the outdoor air dew point is lower than the
indoor air dew point.
Exhaust air is a special case. When an exhaust fan
rids a building of highly humid air, from showers or
cooking, for example, the indoor humidity loads are
reduced. On the other hand, if the outdoor air that
replaces that exhaust air has a dew point above the
indoor dew point, the incoming outdoor air represents
a humidity load that must be removed by the
mechanical system.
Condensation Problems During Cold Weather
In cold weather, condensation is most likely to occur
on the inside of exterior walls or roof assemblies.
The temperature of sheathing and cladding on the
outside of the insulation and air barrier will be near
the temperature of the outdoor air. Indoor window
surfaces are often cooler than surrounding walls and
are typically the first sites of condensation during
cold weather. If the surface temperature of an indoor
wall is below the indoor dew point at a void in the
insulation or at an uninsulated framing member,
enough water may accumulate to support mold
growth. If there is a hole in the air barrier and the
building is under negative pressure at that location,
cold infiltrating air may bypass the insulation layer
and chill indoor surfaces to temperatures below the
dew point.
Condensation may occur within an assembly. For
example, a steel beam that passes through an exterior
wall will be much colder than the adjoining inner
surfaces of the wall because the beam conducts
heat from inside to outside hundreds of times faster
than an insulated portion of the wall. If the building
is under positive pressure, the warmer, more humid
indoor air will be forced into the enclosure through
holes in the air barrier and condensation within the
assembly may result.
Condensation problems within wall or roof assemblies
are hidden and may be mistaken for rainwater
or plumbing leaks. For example, warm air from a
humidified space, such as a swimming pool area,
may leak past the air barrier and insulation layers
into an attic during freezing weather. The water vapor
in the indoor air may form frost on the bottom of
the roof deck, accumulating there until a warm day
when it melts and leaks back through the ceiling. If
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Figure 1-20 Condensation on Uninsulated Metal Framing
in a Cold Climate
Condensation occurs on a C-channel at the top of a parapet
wall located in a cold climate. The building is humidified and
pressurized with filtered outdoor air to maintain specified interior
conditions.
it happens to be raining the day the condensation
problem is found, it might be mistaken for a rainwater
problem.
Air pressure can be higher inside a building than
outside for two reasons. First, the upper floors of a
building are usually under positive pressure during
cold weather due to the stack effect. Buoyant warm
air rises from the lower to the upper floors and then
flows out near the top of the building. As a result,
cold outdoor air is pulled into the building at its
base. During cold weather, condensation usually
occurs on the upper floors. Any gaps, cracks or holes
through the upper floors of the enclosure receive a
constant flow of warm, humid air exiting the building.
Condensation occurs where the warm humid air leaves
the cold enclosure.
The second reason air pressure can be higher inside
is that, to avoid uncomfortable drafts and freezing
pipes, the mechanical ventilation system generally
brings in more air from outdoors than is exhausted
to the outside. Condensation may occur when warm,
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humid air is forced out of the building through cold
walls. In addition, portions of a building may be
pressurized by mechanical system fans if the supply
air side of the air distribution system has more air
than the return air side. For example, a room that has
two supply diffusers but no dedicated return will be
under positive pressure when the windows and doors
are closed. If the interior surfaces of the exterior walls
near that room have gaps, cracks or holes, humid
indoor air under positive pressure will be forced into
the cold exterior wall.
Condensation Problems During Hot Weather
Condensation can sometimes be a problem in hot
weather. Hot weather condensation is more common
in buildings equipped with air conditioning (AC)
systems that are very large and difficult to control and
in buildings located in climates that have thousands
of hours of humid weather. Six factors contribute
to problems in buildings that have air conditioning
systems:
1. Air conditioning chills all the indoor surfaces—
some surfaces more than others.
2. When air conditioners do not run long enough
to dehumidify, they cool the air in the building
without removing moisture from the air, raising the
indoor dew point and increasing the chances of
condensation on cool surfaces.
3. Supply air ducts, diffusers and refrigerant or
chilled water lines are much colder than the room
air.
4. When a building's exhaust air exceeds the amount
of its makeup air, the building will draw in
unconditioned, moisture-laden outdoor air through
gaps, cracks and holes in the building enclosure.
That outdoor air will come into contact with
surfaces chilled by the AC systems.
5. Sun shining on wet masonry, stucco or wood will
raise the temperature of that material, evaporating
some of the stored water and "driving" a portion
of the evaporated water further into the assembly,
and sometimes into contact with colder indoor
surfaces.
6. Intentional or accidental vapor barriers on the
inside surfaces of exterior walls may cause
condensation during cooling conditions. For
example, water vapor driven in from outdoors may
condense when it encounters a vinyl wall covering
on the cool, inside surface of an exterior wall.
A similar dynamic occurs in below-grade walls.
Water vapor migrating into a basement from the
ground beneath may condense when it encounters
a vapor barrier on the inside of a finished
basement wall.
Solution: Control Condensation
Effective condensation control requires keeping the
dew point below the temperature of surfaces indoors
and within building cavities. The dew point can be
lowered by designing, installing and maintaining
HVAC systems to control indoor humidity in both
heating and cooling mode. Building enclosures can
be designed and constructed so surface temperatures
within the assemblies are above the dew point
regardless of season. Neither of these design elements
can succeed by itself. They must work together as a
system.
Use airtight HVAC systems to keep indoor dew points
low. To prevent condensation on indoor surfaces
during cooling mode, keep the indoor dew point
below 55°F (e.g., maximum 50 percent RH when the
indoor air temperature is 75°F). This can be done by
designing air conditioning systems that dehumidify
even when there is no need for cooling, or by using
dedicated dehumidifiers to dry the ventilation air
whenever the outdoor dew point is above 55°F. See
references below and in Chapter 2 for more details on
designing HVAC systems to manage indoor humidity.
The most important job of the air conditioning system
is to remove the large and nearly continuous humidity
load from the incoming ventilation and makeup air.
After that load is removed, the much smaller water
vapor loads from indoor sources may be removed by:
• Exhaust systems designed to remove water vapor
from known sources of humidity such as showers,
cooking areas and indoor pools.
• Ventilation with outdoor air in non-air-conditioned
buildings.
• Air conditioning systems equipped with dedicated
dehumidification components and controls that
activate them when the dew point rises above 55°F.
Design building enclosures to prevent condensation.
At minimum the exterior enclosure must:
• Be made airtight by using continuous air barrier
systems around the entire enclosure. These
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systems must greatly reduce leakage of inside air
into the exterior enclosure assemblies during cold
weather and leakage of outdoor air into the exterior
enclosure or interior wall, ceiling and floor cavities
during warm weather.12 Air sealing an enclosure
makes it easier to manage indoor-outdoor air
pressure relationships with practical airflow rates.
• Meet minimum R-values in accordance with the
2012 International Energy Code.
• Manage the flow of heat and water vapor through
all enclosure assemblies to avoid condensation on
materials inboard of the drainage plane.
Insulating materials must be used to manage heat
flow in order to keep the surface temperature of low-
permeability materials inside the enclosure above the
expected dew point. A continuous thermal barrier is
also necessary to prevent condensation on the interior
surfaces of exterior walls and ceilings during heating
conditions. The insulation layer must be continuous
to prevent condensation in low R-value components
of the enclosure (e.g., metal framing, concrete slab
edges and angle iron ledgers). The pen test can be
conducted to trace the thermal barrier's continuity.
To manage water vapor migration by diffusion, select
materials with appropriate water vapor permeability.
The materials in the wall or roof assembly must
be layered to keep low-perm materials above the
dew point during the heating and cooling seasons
and to allow the assembly to dry out if it gets wet.
This protection must be provided in all above- and
below-grade walls, floors, ceilings, plaza and roof
assemblies, including opaque walls and roofs, glazed
fenestration and skylights, curtain wall systems and
exterior doors.
Condensation control must be provided for typical
sections and at thermal bridges. Many standard
designs in published work detail assemblies that
provide condensation control for various assemblies
in many climates. For example, the International
Building Code covers condensation control for a
variety of wall types and all North American climates.
Straube (2011) includes systematic guidance for four
fundamental wall and roof assemblies in all North
American climates, plus a discussion of underlying
moisture dynamics. (See references below and in
Chapter 2. For designs and climates not covered
in published guidance, and for buildings with high
humidity levels indoors [e.g., swimming pools,
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hospitals, knitting mills and museums], analyses
should be performed by a knowledgeable person
using one of several computer simulations such as
WUFI or hyglRC. For more information on managing
condensation in the enclosure and hygrothermal
modeling, see references in Chapter 2).
It is important to note that a layer of porous material
which can safely store moisture may be used as a
buffer to improve the condensation resistance of
an assembly. For example, a fibrous cover board
beneath a fully adhered low-slope roofing membrane
reduces the risk of condensation that can damage
the adhesive layer. A concrete masonry backup wall
behind a fluid-applied drainage plane can safely store
moisture in the event of minor seepage.
Design HVAC systems to manage air flow and control
condensation. HVAC system pressurization may be
used to manage the direction in which air flows
through an enclosure. Controlling pressure in air-
conditioned buildings in hot, humid climates is
crucial to controlling condensation in the enclosure.
Buildings in those climates must be positively
pressurized to prevent warm, humid outdoor air from
entering building cavities and the building itself.
In climates with a significant cold season, humidified
buildings—such as swimming pools, hospitals and
museums—must not be positively pressurized,
otherwise humid air will be forced into cold building
cavities. In cold climates, slight depressurization is a
better strategy for humidified buildings.
Moisture Control Principle #3: Use Moisture-
Tolerent Materials
The final moisture control principle is to use building
materials that can withstand repeated wetting in areas
that are expected to get wet. Adequate control can
be achieved by using moisture-tolerant materials and
by designing assemblies that dry quickly. Moisture-
tolerant materials should be used in areas that:
get wet by design.
• Are likely to get wet by accident.
Areas that Get Wet by Design
Some locations and materials in buildings are
designed specifically to be wet from time to time.
12The U.S. Army Corps of Engineers (USAGE), for example, has chosen a maximum allowable air leakage rate of 0.25 cubic feet per minute per square foot of total enclosure
area at a pressure difference of 75 Pascals when tested in accordance with the USAGE test protocol. U.S. Army Corps of Engineers Air Leakage Test Protocol for Building
Envelopes Version 3 May 11, 2012.
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They include custodial closets, laundry rooms,
kitchens, baths, indoor pools, spas, locker rooms,
entryway floors and floors that are regularly mopped or
hosed down.
Areas Likely to Get Wet by Accident
Some areas are likely to experience water leaks over
the course of time. For example, spaces that contain
plumbing equipment, such as laundry, lavatory, bath
and utility rooms, are prone to water leaks and spills.
Below-grade wall and floor assemblies are at the
bottom of the building. Water from leaks below grade,
on the surface, or above grade is likely to end up on
the lowest floor. In these areas, use moisture tolerant
materials and assemblies that dry quickly.
Many materials can safely get wet as long as they dry
quickly enough. Stainless steel, copper, some stones,
china and porcelain tile contain no nutrients to
support the growth of molds or bacteria, do not absorb
water and are stable when wet. These characteristics
are why these materials have long been used in
bathrooms, kitchens and entryways.
In areas that may get wet from time to time, it is
best to avoid building materials that have proven
to be vulnerable to moisture damage. Among these
moisture-sensitive materials are untreated paper-faced
gypsum board, medium density fiberboard (MDF)
and oriented strand board (OSB). Moisture-sensitive
materials are vulnerable because they may:
• Contain nutrients that are digestible by molds,
bacteria or wood-decaying molds.
• Quickly and easily absorb liquid water and, once
wet, take longer to dry than materials that are
impermeable to liquid water.
• Have no anti-microbial characteristics.
• Delaminate, crumble, dissolve or deform when wet
or while drying.
Substitutes for vulnerable materials are now
commonly available at only a modest increase in cost.
For example, mold- and moisture-resistant gypsum
board, fiber cement board tile backers and sub-floors
are available in home improvement stores in addition
to builders' supply yards.
If in doubt, the moisture-resistant properties of
a building material can be determined by testing
according to ASTM D3273-00 (2005) Standard
Test Method for Resistance to Growth of Mold on
the Surface of Interior Coatings in an Environmental
Chamber. Designers can ask the manufacturer for the
results of these tests.
REFERENCES
The following references are included for further
reading and guidance.
Advanced Energy. Crawl Spaces. Advanced Energy. http://www.
crawlspaces.org/. Accessed Novembers, 2013.
(This condensed document provides details and technical
information for designing and constructing closed, insulated
residential crawl spaces. The full research reports underlying
the crawl space recommendations can also be downloaded
from the site www.crawlspaces.org. Although the research
was conducted in North Carolina, many of the results can be
applied to other climates.)
Air Conditioning Contractors of America. Manual D, Residential
duct systems. Arlington, VA:. (This guidance for duct design
and installation is the basis for building codes in several
states and is an ANSI-approved national standard.)
Air Tightness Testing and Measurement Association.
2006. Technical standard 1 measuring air permeability of
building envelopes. Air Tightness Testing and Measurement
Association
American Society for Testing and Materials. E06.41. ASTM
El 554-03 standard test methods for determining external air
leakage of air distribution systems by fan pressurization.
American Society for Testing and Materials. ASTM D 3273
standard test method for resistance to growth of mold on the
surface of interior coatings in an environmental chamber.
American Society for Testing and Materials. E06.41. ASTM £779-
03 standard test method for determining air leakage rate by
fan pressurization.
American Society for Testing and Materials. E06.41. ASTM
El 554-03 standard test methods for determining external air
leakage of air distribution systems by fan pressurization.
American Society for Testing and Materials. ASTM WK8681 new
standard test method for resistance to mold growth on interior
coated building products in an environmental chamber.
American Society of Heating, Refrigerating And Air-Conditioning
Engineers (ASHRAE). 2004. Position Document on Limiting
Indoor Mold and Dampness in Buildings, http://tinyurl.com/
ASHRAE-Mold-PD
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American Society of Heating, Refrigerating And Air-Conditioning
Engineers (ASHRAE). 2004. Ventilation for acceptable indoor
air quality, standard 62.1-2004. Atlanta, GA: ANSI/ASHRAE.
(The ASHRAE ventilation standard provides information
needed to determine ventilation rates for differing
occupancies plus a number of design operating and
maintenance requirements to ensure proper performance
of ventilation equipment. Section 6.2.8 specifically deals
with exhaust ventilation. Standard 62.1 applies to many
situations.)
American Society of Heating, Refrigerating And Air-Conditioning
Engineers (ASHRAE). 2004. Ventilation and acceptable indoor
air quality in low rise residential buildings, standard 62.2-
2004. Atlanta, GA: ANSI/ASHRAE.
(This standard applies to low-rise residential buildings. Exhaust
systems are covered in portions of sections 5, 6 and 7.)
American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE). 2004. Energy standard for buildings
except low-rise residential buildings standard 90.1-2004.
Atlanta, GA: ANSI/ASHRAE.
(This standard provides minimum requirements for the
energy-efficient design of all buildings, with the exception of
low-rise residential buildings.)
American Society of Heating, Refrigerating and Air Conditioning
Engineers (ASHRAE). 2008. Design criteria for moisture
control in buildings, standard 160 P. Atlanta, GA: ANSI/
ASHRAE.
ANSI/AMCA. 2007. AMCA standard 500-L-07 Laboratory
methods of testing louvers for rating. AMCA.
Atlanta Regional Commission. 2001. Georgia Stormwater
Management Manual, Volume 2: Technical Handbook.
(Volume 2 of the Technical Handbook provides guidance on
the techniques and measures that can be implemented to
meet a set of storm water management minimum standards
for new development and redevelopment. Volume 2 is
designed to provide the site designer or engineer with
information required to effectively address and control both
water quality and quantity on a development site. This
includes guidance on better site design practices, criteria
for selection and design of structural storm water controls,
drainage system design and construction and maintenance
information.)
Baker, M.C. 1972. Drainage From Roofs. Canadian Builders
Digest. 151. Ottawa.
(This digest is a general discussion of roofs and roof drainage
and highlights many roof drainage design considerations.)
Brennan, T., J.B. Cummings, and J. Lstiburek. 2002. Unplanned
Airflows and Moisture Problems. ASHRAE Journal. Nov.
2002: 44-49.
(This article reviews the moisture dynamics caused by
unplanned airflows during heating and cooling modes, and
discusses interventions that can be made to prevent or solve
the problems.)
Building Sciences Corporation. 2005. Read This Before You
Design, Build or Renovate.
Revised May 2005. http://www.buildingscience.com/
documents/guides-and-manuals/gm-read-this-before-vou-
design-buiId-renovate. Accessed November 6, 2013.
(This pamphlet offers guidance about remodeling practices
that foster healthy homes by reducing occupants' risk of
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exposure to known hazards. These practices also frequently
yield other benefits such as improved durability and reduced
operating costs.)
Canada Mortgage and Housing Corporation (CMHC). 2004. Best
Practice Guide Building Technology: Glass and Metal Curtain
Walls. C.M.H.C.
Canada Mortgage and Housing Corporation (CMHC). 2003. Best
Practice Guide Building Technology: Fire and Sound Control
in Wood-Frame Multi-Family Buildings. C.M.H.C.
Canada Mortgage and Housing Corporation (CMHC). 2002. Best
Practice Guide Building Technology: Architectural Precast
Concrete: Walls and Structure. C.M.H.C.
Canada Mortgage and Housing Corporation (CMHC). 2006. Best
Practice Guide Building Technology: Brick Veneer Steel Stud.
C.M.H.C.
Canada Mortgage and Housing Corporation (CMHC). 1997. Best
Practice Guide Building Technology: Brick Veneer Concrete
Masonry Unit Backing. C.M.H.C.
Canada Mortgage and Housing Corporation (CMHC). 2006. Best
Practice Guide Building Technology: Flashings. C.M.H.C.
Canada Mortgage and Housing Corporation (CMHC). 2006. Best
Practice Guide Building Technology: Wood Frame Envelopes.
C.M.H.C.
Canada Mortgage and Housing Corporation (CMHC). 2006. Best
Practice Guide Building Technology: Wood-Frame Envelopes
in the Coastal Climate of British Columbia. C.M.H.C.
Connecticut Department of Environmental Protection. 2004
Connecticut Stormwater Quality Manual, ed. Jane
A. Rothchild. Hartford: Connecticut Department of
Environmental Protection.
(This manual provides guidance on the measures necessary to
protect waters from the adverse impacts of post-construction
storm water. The guidance is applicable to new development,
redevelopment, and upgrades to existing development.
The manual focuses on site planning, source control, and
pollution prevention, and storm water treatment practices.)
Department of the Army. 1994. Site Planning and Design, TM
5-803-6.
http://www.wbdg.org/ccb/ARMYCOE/COETM/ARCHIVES/
tm 5 803 14.pdf. Accessed November 6, 2013.
(This technical manual describes the site planning and
design process used to develop a project to fulfill facility
requirements and create the optimal relationship with the
natural site. The manual focuses on the site planning and
design process as it leads from program and site analysis to
the preparation of a concept site plan.)
Ferguson, B.K. 2005. Porous Pavements. Boca Raton: CRC Press
(This book provides comprehensive guidance and case
histories for design, construction and maintenance, based on
25 years of practical experience with porous pavements, their
hydrology and their relationship to storm water drainage and
surface water management for buildings, roads, parking lots
and landscape vegetation.)
Gatley, D.P. 2000. Dehumidification Enhancements for
100-Percent-Outside-Air AHU's: Simplifying the decision-
making process, Part 1. HPAC Heating/Piping/AirConditioning
Engineering Sept.: 27-32.
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(This three-part series of articles describes the underlying
psychrometrics in ventilating buildings and provides
design guidance for several methods of enhancing the
dehumidification performance of air conditioning and
ventilation systems.)
Gatley, D.P. 2000. Dehumidification Enhancements for
100-Percent-Outside-Air AHU's: Recuperative heat exchange
is an energy-efficient way to accomplish reheat while also
reducing cooling capacity, Part 2. HPAC Heating/Piping/
AirConditioning Engineering Oct.: 51-59.
(This three-part series of articles describes the underlying
psychrometrics in ventilating buildings and provides
design guidance for several methods of enhancing the
dehumidification performance of air conditioning and
ventilation systems.)
Gatley, D.P. 2000. Dehumidification Enhancements for
100-Percent-Outside-Air AHU's: Enthalpy heat exchange,
the use of desiccants, and vapor compression dehumidifiers
are cost effective ways to maintain healthy and comfortable
buildings, Part 2. HPAC Heating/Piping/AirConditioning
Engineering N ov.: 51-59.
(This three-part series of articles describes the underlying
psychrometrics in ventilating buildings and provides
design guidance for several methods of enhancing the
dehumidification performance of air conditioning and
ventilation systems.)
Harriman, L, Brundrett, G. and Kittler, R. 2001. Humidity
Control Design Guide for Commercial and Institutional
Buildings. Atlanta, GA: ASHRAE. (This manual by ASHRAE
is an effort to expand the design of cooling equipment to
include dehumidification performance. Design analysis
includes peak outdoor air dew point performance as well as
peak outdoor temperature analysis.)
Henderson, H.I., D.B. Shirey, and R.A. Raustad. 2003.
Understanding the Dehumidification Performance of
Air Conditioning Equipment at Part-Load Conditions.
Presentation, ClBSE/ASHRAE Conference, Edinburgh,
Scotland. September 24-26, 2003.
(This technical paper presents analysis and data on
the degradation of dehumidification performance of air
conditioning equipment during part-load conditions. Controls
and systems that contribute to this problem are discussed.)
HyglRC (A hygrothermal modeler from the Institute for Research
in Construction in Canada http://archive.nrc-cnrc.gc.ca/
eng/projects/irc/hygirc.html. Accessed November 6, 2013.
HyglRC is a sophisticated modeler that is actively supported
by the IRC. Workshops are available. Like WUFI and MOIST,
HyglRC assumes no airflow through the assembly.)
International Code Council (ICC). 2012. International Building
Code 2012. ICC.
(Chapter 18 provides code requirements for soils and
foundations including requirements for excavation, grading
and fill around foundations. Section 1203.3.1 contains
requirements for ventilated crawl spaces.)
International Code Council (ICC). 2012. International Plumbing
Code 2012. ICC.
(Chapter 11 provides code requirements for storm drainage,
including roof drainage requirements. Section 312.2 to
Section 312.5 specify a gravity test of the drain and vent
side of plumbing systems.)
International Code Council (ICC). 2012. 2012 International
Energy Conservation Code. ICC.
(The IECC addresses energy efficiency in homes and
buildings. IECC is the successor to the council for American
Building Code Officials [CABO] Model Energy Code [MEC].
The IECC is revised on a 3-year cycle with a supplement
issued half-way through the cycle. Revisions to the code
occur through an open, public hearing process, and each
code or supplement is denoted with the year it was adopted
[e.g., 2006 IECC].)
Kanare, H. 2005. Concrete Floors and Moisture. Skokie, Illinois:
Portland Cement Association.
Lstiburek, Joseph 2006. Understanding Attic Ventilation.
ASHRAE Journal 48: 36.
Lstiburek, Joseph 2006. Understanding Basements. ASHRAE
Journal 48: 24
Lstiburek, Joseph 2006. Understanding Drain planes. ASHRAE
Journal 48: 30
(This ASHRAE Journal article covers the underlying
principles of rainwater control in buildings, focusing on
the use of weather-resistant materials that provide shingled
drainage beneath siding materials.)
Lstiburek, Joseph 2004. Understanding Vapor Barriers. ASHRAE
Journal 46: 40
(This ASHRAE article describes water vapor dynamics in
wall sections and provides a flow-chart method of selecting
materials for the inside and outside of cavity walls that have
appropriate water vapor permeability for specific climates.
Assemblies can be designed without resorting to computer
simulation.)
National Asphalt Pavement Association. Online. Internet.
Available at http://www.asphaltpavement.org/.
(The National Asphalt Pavement Association is a trade
association that provides technical, educational, and
marketing materials and information to its members, and
supplies technical information concerning paving materials.)
National Council of Architectural Registration Boards (NCARB).
Odom, J.D. and DuBose, G.H. 2005. Mold and Moisture
Prevention.Washington, D.C. (This manual is the 17th
monograph in NCARB's Professional Development Program. It
describes moisture and mold problems in buildings, specific
design and construction considerations for enclosures, and
HVAC systems as they relate to moisture and mold problems.)
National Institute of Building Sciences (NIBS). Building Envelope
Design Guide, http://www.wbdg.org/design/envelope.php.
Accessed November 6, 2013.
(The NIBS, under guidance from the Federal Envelope
Advisory Committee, has developed this comprehensive guide
for exterior envelope design and construction for institutional
and office buildings. Sample specifications and sections are
included.)
Rose, W. B. 2005. Water in Buildings: An Architect's Guide to
Moisture and Mold. New York: John Wiley & Sons.
(This is not a design guide, but rather a deeper look at water
and its peculiar behavior in regard to building materials,
assemblies, and whole buildings. Illustrated with specific
examples, it explains the how and why of moisture control.)
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Sheet Metal and Air Conditioning Contractors' National
Association. 1985. SMACNA Air Duct Leakage Test Manual.
Virginia. Sheet Metal and Air Conditioning Contractors'
National Association.
(A companion to HVAC Duct Construction Standards - Metal
and Flexible, this manual contains duct construction leakage
classification, expected leakage rates for sealed and unsealed
ductwork, duct leakage test procedures, recommendations on
use of leakage testing, types of test apparatus and test set-up
and sample leakage analysis.)
Sheet Metal and Air Conditioning Contractors' National
Association. 1993. Architectural Sheet Metal Manual -
Fifth Edition. Virginia. Sheet Metal and Air Conditioning
Contractors' National Association.
(The SMACNA Architectural Sheet Metal Manual provides
design criteria and details for roof drainage systems, gravel-
stop fascia, copings, flashing, building expansion, metal
roof and wall systems, louvers and screens and other metal
structures. Chapter 1 contains data, calculations, and charts
for designing roof drainage systems.)
Spray Polyurethane Foam Alliance. 2003. Spray Polyurethane
Foam for Exterior Subgrade Thermal and Moisture Protection.
Virginia: Spray Polyurethane Foam Alliance.
(A technical guide to specifying closed-cell spray foam
polyurethane on the outside of basement walls as thermal
insulation and moisture protection.)
Straube, John. 2011. High Performance Building Enclosures.
Somerville, MA: Building Science Press (This book includes
the fundamentals underpinning the physics of heat, air and
moisture control in high-performance building enclosures and
practical design guidance to achieve them for a wide array of
enclosure assemblies in all North American climate zones.)
Texas Water Development Board. 2005. The Texas Manual on
Rainwater Harvesting. Texas: Texas Water Development
Board, http://www.twdb.state.tx.us/innovativewater/rainwater/
docs.asp. Accessed Novembers, 2013.
(This manual presents a discussion on the history of rainwater
collection, harvesting system components, water quality and
treatment, system sizing and best management practices.)
United States Environmental Protection Agency. 2006. Alternative
Pavers (Post-Construction Storm Water Management in New
Development and Redevelopment). Washington, D.C.: United
States Environmental Protection Agency, http://cfpubl.epa.
gov/npdes/stormwater/menuofbmps/index.cfm?action=min
measure&min measure id=5. Accessed November 6, 2013.
(This resource is intended to provide guidance on the types of
practices that could be used to develop and implement storm
water management programs.)
www.epa.gov/iaq/moisture
United States Environmental Protection Agency. 2006
Construction Site Storm Water Runoff Control. Washington,
D.C.: United States Environmental Protection Agency.
(This resource provides detailed information on construction-
phase storm water management, including best management
practices.)
United States Environmental Protection Agency. 2006. National
Menu of Storm Water Best Management Practices.
Washington, D.C.: United States Environmental Protection
Agency. (This resource provides detailed information
including applicability, design criteria, limitations and
maintenance requirements on these and many other site
drainage methods.)
United States Environmental Protection Agency. 2006.Porous
Pavement. Post-Construction Storm Water Management in
New Development and Redevelopment.
http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.
cfm?action=min measure&min measure id=5. Accessed
November 6, 2013.
United States Environmental Protection Agency. 2001. Managing
Storm Water to Prevent Contamination of Drinking Water.
Source Water Practices Bulletin. EPA 816-F-01-020.
Environmental Protection Agency.
http://www.epa.gov/safewater/sourcewater/pubs/fs swpp
stormwater.pdf. Accessed November 6, 2013.
Water Management Committee of the Irrigation Association. 2010
Turf and Landscape Irrigation: Best Management Practices.
Irrigation Association.
WUFI: Hygrothermal modeling software to assess the water vapor
dynamics of wall and roof systems in numerous climates.
WUFI is available from the Fraunhofer Institute of Building
Physics http://www.hoki.ibp.fraunhofer.de/ in Germany and
Oak Ridge National Laboratory http://www.ornl.gov/sci/
btc/apps/moisture/. Accessed November 6, 2013. ORNL
conducts training for using WUFI.
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The Basics of Water Behavior
Water occurs at temperatures often found in buildings
as a liquid, a gas (water vapor) and in an in-between
state (adsorbed on solid surfaces).
Liquid water moves from one place to another in
several ways:
• Water runs through pipes and vessels. Water moves
from higher pressure to lower pressure in pipes and
fixtures. A leak in a pressurized pipe or tank can
release much more water than a similar leak on the
drain side of the plumbing system.
• Water runs downhill. Rainwater, surface water,
spilled water, water on the drain side of plumbing
fixtures and water in condensate pans are all
affected by gravity.
• Water wicks upwards. Water wicks up through tiny
cracks and holes. To see wicking in action, stand
two plates of glass on edge in 1A inch of water.
Push them together and as they get closer the
water wicks up between them. The closer together
the plates, the higher water wicks. This happens
because water molecules are attracted to the glass
and to other water molecules. What works for
cracks works for pores in materials. Stand a porous
material like paper, wood, concrete, a sponge or
gypsum board on edge in 1A inch of water and the
water wicks up into the material. How high it goes
depends on pore size and how quickly the water
can dry out the sides to the air. Water wicks through
materials in a process called "capillary action."
When water is in tiny pores, gravity is not the most
important force acting on it.
• Water runs along the bottom or sides of materials.
For the same reasons that water wicks up through
porous materials, water can cling to the sides
and bottoms of materials. Water is attracted to
many materials and to itself. Water from rain or
a plumbing leak may travel many feet along the
bottom of a floor joist or roof truss before collecting
in a drop big enough to fall. When water first
condenses on a mirror or a cooling coil, it clings to
the vertical surfaces. Water does not run down until
the droplets become large enough for gravity to
overcome the intermolecular forces.
Water vapor migrates from one place to another in
several ways:
• Water vapor in the air goes where the air goes.
This is, by far, the fastest and largest mechanism
of water vapor transport. All air, whether inside or
outside of buildings, is constantly moving from
areas of higher pressure to areas of lower pressure.
If dry air is pulled into the building from outdoors,
it will dehumidify the indoor air. If humid air is
pulled in, it will add to the humidity load that must
be removed by the mechanical system.
• Water vapor migrates through materials by
diffusion. Liquid water may not be present and
nothing may appear to be wet, but water vapor can
still slowly migrate through what appears to be solid
materials. Vapor molecules will slowly bump their
way through the spaces between molecules of the
material. The molecules are moving from an area
of higher water vapor concentration to lower water
vapor concentration. The more porous a material is,
the easier it is for water vapor to diffuse through it.
The rate water vapor diffuses through a material is
measured in "perms." Higher perms mean higher
water vapor flow rates.
Water changes from liquid to gas (evaporation) and
from gas to liquid (condensation).
• Water evaporates from liquid water on surfaces,
becoming water vapor. Most of the water vapor
that originates inside buildings is the result of
evaporation from open containers, sprays or damp
porous materials. Showers, fountains, pools, sinks,
pots on stoves, dishwashers and wash water on
floors are all sources of indoor humidity, as are
the building occupants themselves. People, plants
and animals release water vapor. In typical office
spaces, the occupants are probably the main source
of water vapor. Wet materials such as wet concrete
or exposed earth in crawl spaces or basements are
also sources of indoor humidity. The evaporation
rate depends on many factors including the
temperature of the water and the relative humidity
of the air. The warmer the water, the drier the air
next to the wet surface. The faster air blows across
a wet surface, and the larger the exposed surface
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area, the greater the evaporation rate. It takes more
energy to evaporate water from porous materials
than from impermeable materials because the water
molecules are more tightly bound by capillary forces
and it is difficult to blow dry, ventilating air through
many porous building materials.
• Water vapor condenses on a surface, becoming
liquid. If surface temperatures are below the dew
point of the air next to them, water molecules in the
surrounding air will condense on the cool surfaces.
Cold water pipes, air conditioning ducts and cold
roof decks experience condensation, just like a cold
drink sweats in the humid summer air.
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Water vapor is adsorbed onto surfaces. Water as a
gas moves around very freely. Water adsorbed onto
a solid surface is far less free to move around than
water vapor. In this state, it takes more energy to
break the water free than if it is a liquid or a gas.
Water molecules clinging to a solid surface are less
available for chemical or biological activity than is
liquid water.
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Chapter 2: Designing for Moisture Control
Introduction
The most common participants in the process of
designing a building are architects, engineers,
landscape architects and the clients. The design team
can also include:
• The owner of the building, if the building is being
designed and built for a specific person or entity.
The owner can help identify how and by whom the
building will be used.
• The future occupants of the building, if they are
known at the time the building is designed. They
can help set goals for durability, maintainability and
moisture protection.
• Building and grounds personnel representing the
owner, who can provide years of building operation
and maintenance (O&M) experience.
• The contractor that will construct the building,
if the contractor has been selected when the
design work begins.13 Experienced contractors and
subcontractors can bring the realities of managing
moisture during construction to the design of the
building.
Where there is a shortage of real estate for sale
or rent, buildings are often designed and built
on speculation. In such cases, the occupants,
programs and processes that eventually will reside
in the building are known only in general terms. For
example, when planning an office building, the design
team can assume the occupants will be ordinary office
workers and the building will have no special sources
of liquid water or humidity. However, the resulting
design will not have the benefit of input from the
owner, the actual occupants or the building and
grounds staff that will have to make the building work
over the years.
Designing Effective Moisture Controls
Providing good moisture control in the design of a
building is largely the responsibility of the design
team. Third parties that provide construction
management or commissioning services may play
critical roles in the design and implementation of
moisture controls. A construction management service
may participate in the management of the project at
varying levels from inception, design and construction
to turnover and occupancy. The goal of construction
management ordinarily is to manage the schedule,
cost and quality to the owner's satisfaction, but if a
construction manager is part of the design team, it
is crucial that the manager take on responsibility for
implementing the team's moisture control objectives.
Building Commissioning
HVAC systems have been commissioned for many
years by testing, adjusting and balancing (TAB).
However, commissioning entire buildings is a
relatively recent innovation in construction. In
1996, ASHRAE published The HVAC Commissioning
Process Guideline 1-1996, which extended the
scope of traditional TAB to include point-to-point
testing of digital controls and functional performance
testing to assess the performance of electrical and
mechanical systems that work together. Since then
this process has been extended to the electrical
systems; potable, sanitary, drainage and irrigation
systems; power production and cogeneration systems;
the building enclosure; sustainable aspects of the
project; and the entire building design process itself.
In 2005, the U.S. General Services Administration
(GSA) published The Building Commissioning Guide.
The guide provides a process for including building
commissioning in the planning, design, construction
and post-construction phases of a project. A table
in the guide summarizes commissioning activities
and recommends the commissioning agent review
the design for, among other things, the enclosure's
thermal and moisture integrity and its moisture vapor
13 Whether or not the contractor is on board during the design process, the contractor will have the important role of clarifying the design team's intentions regarding moisture
control, planning measures to control water during construction, and preparing response plans for accidental water events that occur during construction. This role is explored in
detail in Chapter 3.
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control. If a commissioning agent is involved in the
design and construction of a building, many of the
quality assurance procedures related to moisture
control and associated measures could easily fall
within the agent's scope. A general process for
building commissioning is presented in ASHRAE
Guideline 0-2005: The Commissioning Process—
the industry-accepted commissioning guideline.
The National Institute of Building Science (NIBS)
published Guideline 3-2006: Exterior Enclosure
Technical Requirements for the Commissioning
Process, which presents a process for building
enclosure commissioning and contains many annexes
to illustrate the steps in the process. In 2012,
ASTM published E2813-12 Standard Practice for
Building Enclosure Commissioning. This standard
practice follows Guideline 3 procedures and includes
functional testing required for fundamental and
enhanced enclosure commissioning.
Who Should Read this Chapter
This chapter is for the design team members who
produce the design, bid and construction documents.
It includes a list of design elements that will
protect a building from moisture-related problems.
The design team must understand the problems
that water causes in buildings and the dynamics
of moisture sources, moisture migration and
moisture control. This knowledge must be reflected
in the design documents, building drawings and
specifications.
Good design is a prerequisite for a building
that resists moisture problems; however, good
design alone is not enough. The design must be
implemented correctly during construction and
maintained during the building's operation by the
owner or manager. To that end, the design team in
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cooperation with the owner, contractor and third
parties:
• Documents overall moisture control goals.
• Plans water controls and water event responses to
be implemented during construction.
• Identifies inspection, testing, commissioning and
quality-assurance activities to ensure the intended
moisture-control measures are implemented as
designed.
• Establishes requirements of and responsibility for
providing, reviewing and accepting submittals, shop
drawings, proposed substitutions and scheduled
inspections.
• Documents the O&M procedures required to keep
the intended moisture control measures working
throughout the building's life.
This chapter has six subsections:
1. Site Drainage.
2. Foundations.
3. Walls.
4. Roof and Ceiling Assemblies
5. Plumbing Systems.
6. HVAC Systems.
Each subsection discusses techniques to provide
protection from moisture problems and specifies:
• The issue that is being addressed.
• The moisture-control goals for the issue.
• Guidance on implementing techniques to achieve
each moisture-control goal.
• Ways to verify that the moisture-control techniques
have been included in the building design and have
been properly installed or constructed.
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Site Drainage
Issue
Water from rain, snowmelt and irrigation systems
can infiltrate a building, damaging the structure and
its contents. Properly designed site drainage avoids
building damage and the need for potentially costly
remediation.14
Design the site so that water from rain, snowmelt and
landscape irrigation is prevented from entering the
building.
Guidance
Guidance 1: The site drainage design creates a
controlled condition to help move water away from the
building. To the extent possible, the design maintains
the rate of water-soil infiltration (i.e., the downward
entry of water into the surface of the soil) at the site
before the site was disturbed. Runoff (i.e., water that
does not infiltrate into the soil) must be managed by
other drainage methods.
Guidance 2: Avoid unnecessary impervious surfaces.
Avoiding unnecessary or large impermeable surfaces—
or using alternative, relatively permeable paving
materials—will allow more water to infiltrate, thus
reducing the size and cost of systems managing
runoff. Placing facilities on a site changes the site's
drainage characteristics by increasing the impervious
area, which, in turn, increases the volume of runoff
that must be managed. Where large expanses of
impervious surface are unavoidable, such as parking
lots, breaking the expanse into smaller areas or using
alternative permeable pavement techniques can help
reduce runoff.
Alternative paving materials such as pervious
pavement, modular porous paver systems or other
surfaces can be used to reduce runoff.
• Porous pavement is a permeable surface often built
with an underlying stone reservoir that temporarily
stores surface runoff before it infiltrates into the
subsoil. Porous pavements may be made using
asphalt or concrete. Medium-traffic areas are the
ideal application for porous pavement. Porous
pavement may be inappropriate in areas such as
truck loading docks and areas where there is a great
deal of commercial traffic.
• Modular porous pavers are permeable surfaces
that can replace asphalt and concrete; they can
be used for driveways, parking lots and walkways.
Alternative pavers can replace impervious surfaces,
resulting in less storm water runoff.
• The two broad categories of alternative pavers are
paving blocks and other surfaces, including gravel,
cobbles, wood, mulch, brick and natural stone.
Guidance 3: Use grading to slow down runoff and
achieve a more balanced infiltration rate. Topography
helps determine the amount, direction and rate
of runoff. To the extent possible, retain existing
contours so that the existing drainage patterns can
be maintained. Grading also can be used to correct
drainage problems. Where steep slopes contribute to
rapid runoff, re-grading to more moderate slopes can
reduce runoff velocity.
Guidance 4: Ensure positive site drainage principles
are met, including:
• Making certain water is moved away from the
building.
• Ensuring water is not allowed to accidentally pond
in low areas.
• Making sure the finished floor is elevated enough so
that water will not back up into the building if the
drainage systems are blocked.
Figure 2-1 illustrates positive drainage principles.
14 This document does not address flood waters from rivers or lakes, the sea or from other extreme weather events.
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Figure 2-1 Positive Drainage Principles
www.epa.gov/iaq/moisture
5% minimum grade
for first 101
2% minimum grade on
lawn areas
0.5% minimum grade on
pavement
Typical 8" drop at
foundation
Ensure positive drainage by
maintaining height of berms or
obstructions below floor elevations
Guidance 5: When runoff must be controlled and
redirected away from the building, identify and design
water runoff management approaches appropriate for
the site's characteristics. Potential approaches to use
include:
• Infiltration control methods such as swales or
infiltration trenches.
• A swale (i.e., a grassed channel, dry swale,
wet swale, biofilter or bioswale) is a vegetated,
open-channel management practice designed
specifically to treat and attenuate runoff for
specified water quality and volume. As water
flows along these channels, vegetation slows it to
allow sedimentation; the water filters through a
subsoil matrix or infiltrates the underlying soils or
both.
• An infiltration trench (i.e., infiltration galley)
is a rock-filled trench with no outlet that
receives runoff. The runoff passes through some
combination of pretreatment measures, such as
a swale and detention basin, and into the trench.
Runoff is stored in the spaces between the stones
in the trench and from there infiltrates through
the trench bottom and into the soil. The primary
pollutant removal mechanism of this practice is
filtering through the soil.
• Retention or detention control methods such as wet
or dry ponds.
• Wet ponds—storm water ponds, wet retention
ponds and wet extended-detention ponds—are
constructed basins that contain a permanent
pool of water throughout the year or at least
throughout the wet season. Ponds treat incoming
runoff by allowing particles to settle and algae
to take up nutrients. The primary removal
mechanism is settling, which occurs as runoff
resides in the pond. Pollutant uptake, particularly
of nutrients, occurs through biological activity.
Wet ponds traditionally have been widely used as
a storm water best management practice.
• Dry detention ponds—dry ponds, extended
detention basins, detention ponds and extended
detention ponds—hold runoff for some minimum
time to allow particles and associated pollutants
to settle. Unlike wet ponds, these facilities do not
have a large permanent pool of water; however,
they are often designed with small pools at the
basin's inlet and outlet. Dry detention ponds
also can contribute to flood control by providing
additional flood water storage.
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For detailed information including applicability,
design criteria, limitations and maintenance
requirements on these and many other site drainage
methods, visit EPA's storm water management
website.15
Guidance 6: Landscape irrigation systems must be
designed so that they do not spray the building or
soak the soil next to the foundation. Consider hiring
a qualified irrigation designer or irrigation consultant
to design the system, keeping in mind these
considerations:
• Spray heads and rotor heads spray water into the
air. When designing spray systems consider wind
conditions. Wind can carry airborne water beyond
the area intended to be covered, and the sprinklers
may spray the building or the soil around the
foundation.
• Drip irrigation is a slow, even application of water
through plastic tubing that delivers water directly
to plants. Drip irrigation systems use less water
than spray systems; however, they still can soak the
ground around the foundation and cause moisture
problems in a building.
• All irrigation systems, regardless of type, should be
properly controlled and monitored. Timers should be
installed to ensure the system shuts off. Water flow
meters should be installed to measure the volume
of water moving through the system. Regularly
monitored meters can be a source of information
about excessive water use due to timer problems
or system leaks. Consider installing devices such
as tensiometers or soil blocks to measure soil
moisture.
Guidance 7: Ensure water draining from one building
or site does not violate the good drainage of an
adjacent building or site. This can happen when a
building is constructed close to an existing building
and dumps drainage water (e.g., roof, surface, etc.)
onto or at the existing building, overwhelming its
drainage features.
Guidance 8: Consider green building practices that
minimize the need for irrigation or that capture
rainwater for use in irrigation.
• Select trees, shrubs, ground cover and other
landscaping elements based on their ability to grow
well with little or no additional water. Such plants
will minimize the use of water for irrigation.
• Explore the potential for capturing, diverting and
storing rainwater for landscape irrigation, drinking
and other uses. This approach can be used in all
climates. For more information, see the Texas Water
Development Board reference The Texas Manual on
Rainwater Harvesting.
Guidance 9: Develop a construction-phase storm-
water-management plan. The plan should address at a
minimum:
• Methods for minimizing the potential for storm
water runoff during construction.
• Methods to drain storm water from the site and
away from the structure during construction.
• Methods for preventing building materials from
getting wet.
• Methods for keeping the building or portions of the
building dry during construction.16
• Policies and methods for drying materials and the
building if they become wet.
• Construction-phase storm water management
supervisory roles and responsibilities.
For detailed information on construction-phase storm
water management, visit EPA's storm water best
management practices website.17
Guidance 10: Develop guides covering the O&M of
the storm water management system. The guides
should include:
• The theory of operation of storm-water-management
systems.
• Inspection procedures.
• Maintenance procedures and requirements.
For detailed information on post-construction storm
water management, visit EPA's storm water best
management practices website.18
15 http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm. Accessed Novembers, 2013.
16 For some large projects, interior work may begin before the upper floors have been completed. Special rainwater-control measures are needed to protect the lower floors. See
Chapter 3 on the construction phase for more details.
17 http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm. Accessed Novembers, 2013.
18http://cfpub.epa.gov/npdes/stormwater/menuofbmps/index.cfm. Accessed Novembers, 2013.
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Verification of Site Drainage • Provide the construction manager and the building
owner with a list of post-construction inspection
• If storm water from the site is to be conveyed to and maintenance requirements for the site drainage
a municipal separate storm sewer system (MS4), systems.
get a list of MS4 operator's requirements for the
municipality. Give the list to the construction
manager before construction begins.
• Provide the construction manager with a list
of construction-phase critical details and an
inspection schedule of the site drainage system,
identifying the sequence of inspections, parties
responsible for the inspections, and required
documentation of the inspection results.
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Foundations
Issue
Building foundations are vulnerable to moisture
problems for a number of reasons, including:
• Water from rain and from plumbing leaks is drawn
by gravity to foundations, which are exposed to
surface water, rain-soaked soil and, possibly, high
water tables.
• Water may condense on foundation materials during
warm weather because the materials are cooler than
the outdoor air.
• Crawl spaces and basements are holes in the
ground and have more extensive contact with soil
than slab-on-grade foundations.
• Many moisture problems can be avoided by properly
designing the foundation. Moisture problems
associated with improperly designed foundations
can be difficult and expensive to identify and
fix, can create the potential for health problems
resulting from mold growth, and can be a liability
for building owners.
Foundation Design Goal 1: Design the foundation to
prevent rainwater and groundwater incursions.
Foundation Design Goal 2: Avoid condensation on
slab-on-grade foundations, in crawl spaces and in
basement foundations.
Guidance
Foundation Design Goal 1: Design the foundation to
prevent rainwater and groundwater incursions.
Guidance 1: Plan the surrounding slope to divert
water away from the building. This guidance applies
to slab-on-grade foundations, crawl spaces and
basements.
• Specify a 5 percent—6 inches per 10 feet—slope
to the finish grade away from the foundation to
control the surface flow of water, or meet a more
stringent local building code requirement. Applying
this slope to a distance of 6 to 10 feet from the
foundation generally is acceptable.
• Reduce water infiltration into the soil surrounding
the building using a barrier at or slightly beneath
the surface (e.g., a cap of silty-clay soil or
subsurface drainage landscape membrane). Care
must be taken to prevent the roots of plants in this
zone from penetrating the barrier.
• Design the foundation and surrounding grade
so there is a minimum of 8 inches of exposed
foundation after the final grading.
Guidance 2: Design below-grade drainage systems
to divert water away from the foundation and specify
capillary breaks to keep water from wicking through
the foundation to moisture-sensitive materials (e.g.,
wooden framing and paper-covered gypsum board).
Slab-On-Grade Liquid Water Control (See Figure 2-2)
Below-grade perimeter drainage is not required
for concrete slab-on-grade foundations when the
surrounding finish grade is sloped as specified in
Guidance 1, the slab is elevated at least 8 inches
above finished grade, and the design includes
appropriate capillary breaks. Incorporate a capillary
break between:
• The foundation and the above-grade wall (e.g., a
layer of polyethylene foam sill seal, metal or rubber
flashing, or a damp-proof masonry course between
the concrete foundation and the wood or steel
framed walls or the concrete or masonry walls).
• The earth and the floor slab (e.g., a layer of
coarse aggregate with no fines, a plastic or rubber
membrane, or a layer of plastic foam insulation
placed beneath the slab). NOTE: While coarse
stone will provide a capillary break, a vapor barrier
directly beneath the slab is required to manage
water vapor migration.
• The earth and below-grade portion of the perimeter
stem wall or thickened edge slab (e.g., damp-proof
coating or a water-proof membrane placed on the
thickened edge slab or stem wall).
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Figure 2-2 Illustration of Ground Water Control for Slab Foundations
Down spouts carry rainwater
from the roof away from the
foundation
8" minimum
Ground slopes away from
the foundation
Capillary break under plate
Polyethylene vapor barrier
in direct contact with
concrete slab
Granular drainage pad
(coarse gravel, no fines)
Keep rain water away from the foundation perimeter
Do not place sand layer over polyethylene vapor barrier under concrete slab
Where vinyl flooring Is installed over slabs, a low water-to-cement (w/c) ratio (= 0.45 or
less is recommended] to reduce water content in the concrete; alternatively, the slab
should be allowed to dry (less than 0.3 g rams/24 hrs/ff) prior to flooring installation
If there is a joint between the slab's perimeter edge
and a stem wall, a capillary break may be needed
between the edge of the slab and the perimeter wall
to prevent water wicking from the perimeter wall into
the slab.
If the roof slopes to eaves without gutters, protect the
bottom of the above-grade portion of the wall against
rain splash (e.g., raise the foundation wall and slab
out of the ground 18 inches or more, or construct the
wall with robust drainage and drain plane protection).
Crawl Space and Basement Liquid Water Control
(See Figures 2-3 and 2-4)
• Design the basement or crawlspace so that the
interior floor grade is above the 100-year flood level
and the local water table.
• Specify a curtain of free-draining material (e.g.,
sand and gravel, coarse aggregate with no fines, or
a synthetic drainage mat) around the outside of the
foundation between the unexcavated earth and the
basement wall.
• Specify a drainage collection and disposal system
to be located below the top of the footing or the
bottom of the slab floor (e.g., perforated exterior
footing drain pipe surrounded by coarse aggregate
with no fines and filter fabric, drained to a preferred
disposal option such as daylight or a sump pump).
Locate the top of the pipe at or below the bottom
of the finished slab regardless of the location of the
pipe with respect to the footing.
Specify filter fabric to prevent fine soils from
clogging the curtain drain and the footing drain
system.
Incorporate a capillary break between:
• The top of the foundation wall and the first-floor
framing system (e.g., a layer of polystyrene sill
seal, metal or rubber flashing, or a masonry
damp-proof course between the concrete
foundation and the wood, steel, or concrete floor
structure).
• The earth and the basement floor slab (e.g., a
layer of coarse aggregate with no fines, a plastic
or rubber membrane, or a layer of styrene foam
insulation placed beneath the slab).
• The free-draining perimeter fill and the below-
grade portion of the basement wall (e.g., a damp-
proof coating or a water-proof membrane placed
on the outside of the basement wall).
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NOTE: A plastic or elastomeric membrane can
be used in place of a concrete slab to form a
capillary break and prevent evaporation from
the soil into the crawl space. A concrete slab
has the advantages of being more durable and
of blocking the entry of burrowing rodents.
Membranes are less expensive and easier to
install.
• Design a capillary break between the top of the
footings and foundation walls (e.g., painted-on
coating).
• Specify a drain in the foundation floor that leads to
an approved disposal site.
• Include in the plan:
• Assumptions about maximum rainfall or
snowmelt.
• Drainage surface areas including shapes, slopes,
superstructures or other obstructions.
• Estimated water flows.
• The location and capacities of all sub-grade
drainage features (e.g., drain lines, discharge
locations, man-holes, access pits).
Foundation Design Goal 2: Avoid condensation on
slab-on-grade foundations, in crawl spaces or in
basement foundations.
Slab-on-Grade Condensation
• Insulate slab-on-grade foundations (e.g., install
extruded styrene foam board beneath the slab) to
keep the floor from sweating during warm, humid
weather.
• Provide perimeter and sub-slab insulation to meet
the International Energy Conservation Code.
• Provide a vapor retarder sheet directly under the
concrete floor slab to prevent water vapor from
infiltrating the floor system. Vapor retarders should
meet the requirements of ASTM specification E
1745 Class A, B or C.
Basement Condensation Control (See Figure 2-3)
• Specify insulation for the above- and below-grade
basement walls to meet the ASHRAE Standard
90.1 requirements. NOTE: Do not insulate
basement ceilings.
• Provide a vapor retarder sheet directly under the
concrete floor slab to prevent water vapor infiltration
through the floor system. Vapor retarders should
meet requirements of ASTM specification E 1745
Class A, B or C.
• Mechanical equipment can be located in basements
that have insulated walls. Specify air-sealing details
to provide a continuous air barrier from the above-
grade wall down the foundation wall and ending in
the center of the basement floor. Use the pen test
(See Appendix A) to trace the continuity of the air
barrier. NOTE: The air barrier for the foundation is a
part of the whole building air barrier system.
• Specify a whole building air leakage rate when
tested at 75 Pascal pressure difference in
accordance with ASTM E779-10 Standard Test
Method for Determining Air Leakage Rate by
Fan Pressurization or ASTM £1827-96(2007)
Standard Test Methods for Determining Airtightness
of Buildings Using an Orifice Blower Door. For
example, the U.S. Army Corps of Engineers now
requires a maximum air leakage rate of 0.25 cubic
feet per minute at 75 Pascal pressure difference.
• When insulating on the outside of foundation walls:
• Specify insulating materials that can tolerate
exposure to the earth. Extruded styrene and
high-density expanded styrene foam boards,
closed-cell spray polyurethane foam insulation,
and fiberglass or mineral wool insulating drainage
panels have been successfully used to insulate
outside surfaces of foundation walls.
• Extend the insulation from the top of the footing
to the top of the sub-floor.
• Specify protective covering for the above-grade
portions of exterior insulation (e.g., stucco on
stainless steel lath).
• When insulating on the inside of foundation walls:
• Specify a layer of foam board or closed-cell spray
polyurethane foam insulation against the interior
side of the basement wall to keep warm humid
air away from the cool foundation.
• Specify an insulating value for the foam layer
high enough to meet the ASHRAE Standard 90.1
requirements, or specify a combination of foam
insulation and, on the foundation wall, moisture-
tolerant insulation in the wall cavity (e.g.,
fiberglass or mineral wool). The combination of
foam and fiberglass insulation meets the required
R-value, prevents condensation and allows the
assembly to dry to the interior (See Figure 2-3).
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Figure 2-3 Illustration of Basement Foundation Showing Drainage and Damp Proofing Only
Sloped lopsoil cap
Concrete foundation
wall
Damp proofing
(capillary break)
Geotechnig filter
fabric
-r
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• For vented crawl spaces:
• Specify one or more layers of insulation in the
floor system between the crawl space and the
first floor to achieve the insulation levels required
by ASHRAE Standard 90.1. NOTE: Mechanical
equipment cannot be located in vented
crawlspaces. Specify air-sealing details to provide
a continuous air barrier from the above-grade wall
across the floor between the crawl space and the
first floor. Use the pen test (See Appendix A) to
trace the continuity of the air barrier. NOTE: The
air barrier for the foundation is part of the whole
building air barrier system.
• Specify a whole building air leakage rate when
tested at 75 Pascal pressure difference in
accordance with ASTM E779-10 Standard Test
Methods for Determining Air Leakage Rate by
Fan Pressurization or ASTM £1827-96(2007)
Standard Test Methods for Determining
Airtightness of Buildings Using an Orifice Blower
Door. For example, the U.S. Army Corps of
Engineers requires a maximum air leakage rate of
0.25 cubic feet per minute at 75 Pascal pressure
difference.
• A plastic or elastomeric membrane can be used
instead of a concrete slab to form a capillary
break and prevent evaporation from the soil
into the crawl space. Concrete slabs are more
durable, provide a solid floor for the contractor
to work from, and block the entry of burrowing
rodents; however, membranes are less expensive
and easier to install.
• Provide screened vents to meet the International
Building Code requirements for ventilated crawl
spaces (Section 1203.3.1).
Figure 2-4 Components of an Unvented Crawl Space Foundation
Sealant
Flashing
Rigid insulation
3/8' fibercemenl board.
all surfaces coated
Ground slopes away
from wall at 5%
(6 inch per 10 foot)
Damp proofing
Filter fabric
Coarse gravel \
(no fines) '
Perforated drain
Cavity insulation
Sill gasket
Protective membrane strip
Concrete foundation wall
Sealant
Treated wood nailer
Continuous polyethylene
vapor barrier or air barrier
(all joints taped)
Damp proofing
Capillary break over footing
(damp proofing or membrane)
Concrete fooling
below frost depth
Source: Conditioned Crawlspace Performance, Construction and Codes, Building Science Corporation (http://www.buildingscience.com/
documents/bareports/ba-0401-conditioned-crawlspace-construction-performance-and-codes). Accessed November 6, 2013.
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Verification of Foundation Design
• Write a description detailing how the foundation
system manages rain and surface and sub-surface
water. This typically would be located in the basis-
of-design document.
• Provide details of sub-surface drainage systems in
construction documents.
• Use the pen test (See Appendix A) to verify
elements of the drainage system and the continuity
of the capillary break from the intersection of
the foundation with the first floor walls, around
the foundation wall footing, to the center of the
foundation.
• Provide two-dimensional sectional drawings where
two materials that form the rainwater control come
together and three-dimensional drawings where
three or more elements of the rain protection
system come together.
• Provide a list of critical details and an inspection
schedule for the drainage and capillary break
elements of the foundation that identifies the
sequence of inspections, the parties responsible for
the inspections, and the required documentation of
the inspection results.
• Provide a list of inspection and maintenance
requirements for the foundation drainage system.
• Write a description detailing how the foundation
system manages water vapor during cooling and
heating modes, as applicable. Prepare drawings
and specifications that detail water vapor migration
control and the permeability and insulating values
for all materials.
• Provide two-dimensional sections where two
materials that form the air barrier, insulation layer
and water vapor control intersect. Provide three-
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dimensional drawings where three or more elements
of the air barrier, insulation layer and water vapor
control intersect.
• Specify a fan pressurization test in design
specification documents to assess the entire
building enclosure using ASTM E779-10 Standard
Test Method for Determining Air Leakage Rate by
Fan Pressurization. Or ASTM £1827-96(2007)
Standard Test Methods for Determining Airtightness
of Buildings Using an Orifice Blower Door.
• Specify when the test should be conducted in
relation to the completeness of the air barrier
system.
• Identify the appropriate testing party.
• Specify how the results should be documented,
judged and accepted or rejected.
• Specify the remedies if the building fails the test.
• Specify quality assurance programs for the
installation of the hygrothermal control elements of
the enclosure. Provide a list of critical details and
an inspection schedule for the air barrier, insulation
layer and water-vapor-control elements of the
foundation. Specify the sequence of inspections,
the parties responsible for the inspections and the
required documentation of the inspection results.
• Provide a list of inspection and maintenance
requirements for the interior finishes if they are
critical to water vapor control. For example, if water
vapor control depends on a vapor-permeable interior
finish, low-perm vinyl wall coverings and paints
should be avoided during renovations. Pictures,
blackboards and mirrors should be spaced off the
wall.
• Specify, in the control guide for the building
operators, the maximum dew point levels allowed in
the interior of basements and crawlspaces.
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Issue
Moisture control is an important aspect of designing
an integrated building enclosure. Failing to properly
design walls to manage moisture and failing to
integrate moisture management system features
with those of other building enclosure components,
such as the roof and foundation, can lead to serious
moisture-related damage. Correcting problems
resulting from poorly designed walls can necessitate
the replacement of multiple building components
leading to high repair costs.
Goals
Wall Design Goal 1: Design exterior walls to manage
rainwater.
Wall Design Goal 2: Design exterior walls to prevent
condensation of water vapor on cool surfaces within
the dry portion of the exterior wall assembly, on the
inner surface of the exterior walls or within the interior
wall, floor or ceiling cavities.
Guidance
Wall Design Goal 1: Design exterior walls to manage
rainwater.
Guidance 1: Design walls to protect their inner
portions from direct rain and seepage through the
cladding.
• Design walls that have rainwater protection behind
the cladding in the form of air gaps and barrier
materials (i.e., the drain plane) to keep water from
wicking further into the wall.
• Specify in the design drawings and specifications
the flashing of penetrations—including windows,
doors and roof-wall intersections—to a designated
drain plane.
• Provide sections and specifications detailing
flashing for all wall penetrations. Flashing for larger
penetrations (e.g., windows, doors and exhaust
and intake grilles) must be carefully designed and
detailed. At the top, flashing must extend from
beneath the drain plane material, across the top
of the trim, and out past the siding and trim (See
Figures 2-6 and 2-7). The bottom must have a
pan flashing with end dams and a back dam. Side
flashing must cover the rough opening and extend
beneath the drain plane on the wall and flash down
over the end dams on the sill flashing.
• Among the most common problem areas for
flashings in walls are:
• Windows.
• Doors and trim.
• Outdoor air intakes, exhaust outlets and fans.
• Ducts, pipes and electric conduit entries and
exits.
• Through-wall flashings where a horizontal
element (e.g., roof) intersects the wall of a taller
portion of the building. Similar locations include
exterior stairway-wall intersections as well as
relieving angles, awning decks, and balcony
and plaza intersections with the wall of a taller
section of building (See Figure 2-8.)
Wall Design Goal 2: Design exterior walls to prevent
condensation of water vapor on cool surfaces within
the dry portion of the exterior wall assembly, on the
inner surface of the exterior walls or within the interior
wall, floor or ceiling cavities.
Guidance 1: Design walls to be sufficiently airtight to
limit water vapor migration by air flow.
Specify air-sealing details to provide a continuous air
barrier from the roof-wall intersection to the above-
grade wall-foundation intersection. Use the pen test
(See Appendix A) to trace the continuity of the air
barrier. NOTE: The air barrier for the walls is part
of the whole building air barrier system. Specify a
whole building air leakage rate when tested at 75
Pascal pressure difference in accordance with ASTM
E779-10 Standard Test Methods for Determining Air
Leakage Rate by Fan Pressurization or ASTM E1827-
96(2007) Standard Test Methods for Determining
Airtightness of Buildings Using an Orifice Blower
Door. For example, the U.S. Army Corps of Engineers
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requires a maximum air leakage rate of 0.25 cubic
feet per minute per square foot of air barrier surface
when measured at a pressure difference of 75 Pascals
between indoors and outdoors. The air barrier surface
area includes all six surfaces of the barrier: top,
bottom and all four sides.
• Select a layer of material in the wall assembly to
form the basis of the air barrier systems. Interior
gypsum board, foam board or spray foam insulation,
concrete, and oriented strand board (OSB) or
plywood deck are good choices for the basis of
air barrier systems in wall assemblies. Include
specifications for all accessory materials required to
provide durable continuity of the air barrier.
• Provide sections and specifications detailing
methods for providing air barrier continuity,
especially at penetrations, corners and edges:
• At penetrations through the air barrier layer (e.g.,
rough openings for windows, doors, pipes, shafts
and conduits).
• At transitions between one air barrier material
and another (e.g., wall-ceiling intersections and
wall-floor intersections).
• Where the air barrier must pass around structural
elements (e.g., heavy steel construction must
be carefully detailed where the exterior walls
encounter vertical steel posts or horizontal
beams).
• Provide sections highlighting the air barrier and
connecting materials and methods from the center
of the roof to the center of the foundation for each
section.
Guidance 2: Meet or exceed the R-value for walls
as described in the 2012 International Energy
Conservation Code.
• Provide two-dimensional sections detailing methods
for providing insulation layer continuity:
• At windows, doors, columns, conduits and other
penetrations through the air barrier layer.
• At transitions between one insulating material
and another (e.g., where roof insulation meets
wall insulation).
• At thermal bridges in the insulation layer (e.g.,
where steel members penetrate the insulation
layers).
Guidance 3: Design walls to manage heat flow and
vapor diffusion to avoid condensation in the wall
assembly and to dry toward the interior, exterior
or both. Designers may provide details about the
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continuity of the air barrier and the insulating layers
at penetrations and intersections.
Option 1: Follow published regulation or guidance on
combining insulation, air barriers and the permeability
of materials for walls to control condensation (See
references Chapter 2). Examples include:
• The 2012 International Building Code and
International Residential Code.
• High Performance Building Enclosures by
Straube (2011) provides systematic guidance for
condensation control in four types of roof and wall
assemblies for all North American climates.
• Understanding Vapor Barriers by Lstiburek
(ASHRAE August 2004) applies to all climate zones
(See Figures 2-9 through 2-12).
• The Building Envelope Design Guide on the Whole
Building Design Guide website includes brick and
stone veneer and curtain wall systems.
• The Canadian Mortgage and Housing Corporation
Best Practice Guides apply to climate zones 6 and 7.
Option 2: Model the performance of proposed wall
assemblies using a hygrothermal software program
(e.g., WUFI or hyglRC). Use design conditions from
ASHRAE Standard 160P for modeling. Note, however,
that the results of computer simulations should
be interpreted cautiously and in light of real-world
construction practices. For example, most computer
models assume that walls are airtight and that no
water vapor is transported through them by airflow.
Therefore, for the model to be valid, the assembly
must be designed, installed and tested to meet air
tightness standards. Also, the performance of any
assembly depends on its orientation in regard to solar
load and wind direction during heavy rains. Some of
the programs can model the dynamic of rainwater
absorbed by porous claddings and vaporized into the
assembly by the sun, but others cannot.
Guidance 4: Design brick and masonry-clad walls to
prevent the rain-sun-driven water vapor dynamic.
• If the cladding is brick or concrete masonry units
and the wall is insulated with high-permeability
(perm >10) porous insulation and located in
climate zones 1, 2, 3, 4 or 5 (See Figure 2-5):
• Back-vent the cladding.
• Use low-permeability (perm <1) insulating
sheathing and interior finishes with perm >2.
• In climate zones 1, 2 and 3, design the building
to operate at positive pressure.
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Figure 2-5 The International Energy Code Climate Zone Map Developed by the U.S. Department of Energy
Marine (C)
PurUjnd
All of Alaska in Zone 7 except for the following Boroughs in Zone 8: Bethel. Dellirkgham, Fairbanks. N. Star, Nome North Slope, Northwest Arctic. Southeast Fairbanks, Wade Hampton, and
Yukon-Koyukuk
Zone 1 includes: Hawaii, Guam, Puerto Rico, and the Virgin Islands
Verification of Wall Design
Write a description detailing how the wall system
manages rain. Include this description in the basis-
of-design document.
Use the pen test (See Appendix A) to verify the
continuity of the drain plane from the intersection
with the roof, through flashings, and around
penetrations to the foundation.
Provide two-dimensional sections where two
materials that form the rainwater control come
together and three-dimensional drawings where
three or more elements of the rain protection
come together. Sections must show continuity of
capillary breaks and flashing around penetrations
and interface with air barrier and insulation systems
(See Figure 2-8).
Specify a quality assurance (QA) program for
installation of the rainwater protection systems.
At a minimum, provide a list of critical details, an
inspection schedule and quality assurance tests of
the drainage and capillary break elements of the
wall systems. Specify the sequence of inspections
and tests, the parties responsible for them and
the required documentation of the results. Parties
involved in QA may include subcontractors, general
contractors, commissioning agents and independent
third-party inspection or testing providers. Provide a
list of inspection and maintenance requirements for
the exterior cladding, flashings and drain plane.
Use wall assemblies detailed in guidance or
journals that have been designed to manage
water vapor and condensation for the climate of
interest. Perform hygrothermal modeling when
no documentation through previous testing or
modeling of a wall assembly in a particular climate
is available.
Write a description detailing how the wall system
manages water vapor during cooling and heating
modes, as applicable. Prepare drawings and
specifications that detail water vapor migration
control and the permeability and insulating values
of all materials.
Use the pen test (See Appendix A) to verify
the continuity of the insulation layers and air
barriers from the intersection with the roof,
40
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through flashings, and around penetrations to the
foundation.
• Provide two-dimensional sections where two
materials that form the insulation layers and air
barrier come together and three-dimensional
drawings where three or more elements of the
insulation and air barrier come together.
• Specify in the design specification documents a
fan pressurization test to assess the entire building
enclosure in accordance with ASTM E779-10
Standard Test Method for Determining Air Leakage
Rate by Fan Pressurization, ASTM E1827-
96(2007)Standard Test Methods for Determining
Airtightness of Buildings Using an Orifice Blower
Door of the U.S. Army Corps of Engineers Air
Leakage Test Protocol for Building Envelopes.
• Specify the target airtightness level.
• Specify when the test should be conducted in
relation to the completeness of the air barrier
system.
• Identify the appropriate testing party.
www.epa.gov/iaq/moisture
• Specify how the results should be documented,
judged and accepted or rejected.
• Specify the remedies if the building fails the test.
• Provide a list of critical details, an inspection
schedule and QA tests for the air barrier, insulation
and vapor control elements of the walls. Specify
the sequence of inspections and tests, the parties
responsible for them, and required documentation
of the results.
• Specify QA programs for the installation of the
hygrothermal control elements of the enclosure.
Provide a list of inspection and maintenance
requirements for the interior finishes if they are
critical to water vapor control (e.g., if water vapor
control depends on a vapor-permeable interior
finish, then low-perm vinyl wall-cover ings and
paints should be avoided during renovations;
pictures, blackboards and mirrors should be spaced
off the wall).
• Specify maximum dew points to be maintained in
conditioned spaces during the heating and cooling
seasons.
Figure 2-6 Section Illustrating Window Flashing and Jamb Flashing for Stone Veneer Wall
Insulating element (foam board or
spray polyurethane foam)
Drain plane - WR8. self-adhered
membrane
Back-up wall
Exterior-grade (glass-mat shown)
sheathing. All joints sealed with
self-adhesive membrane
Mortar drainage mesh
Clay brick masonry with vented
weep (minimum one every 2-feet)
at window head flashing
Corrosion-resistant metal head
flashing with integral end-dams
Self-adhered membrane window
flashing
Thermally broken glazing system
with Insulating glass unit
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Figure 2-7 Section Illustrating Pan Sill Flashing and Jamb Flashing For Brick Veneer Wall
Insulslod nwlal (ram* wall
Closure amp flaUwi to
idf-adhefftd membrane
Flashing typ*
interior flaflhinj teg end tidy
sealed end-dams
Wall drannga plftn* - conteOM
dram pteneJa* banw
Figure 2-8 Detail Illustrating Through Flashing Where a Lower Roof Intersects a Wall
Brfckwtf
A* I vepa Otalf m»n*rwi».
tsmn-ijd Ultulfloil
adherwJ ID *f?vapw bamer
•nd onr M
P^mmjto Nl»f lutmc
RQUrauWUn
Roofing ni^iTtbiviv
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Figure 2-9 Concrete Block with Interior Rigid Insulation and Stucco
II
f^nnrmtfL Klsvlr 1
Rigid insulation (vapor semi-permeable)
- unfaced extruded polystyrene, unfaced
expanded polystyrene, fiber-faced
isocyanurate
Metal channel or wood furring
.
.
Latex paint or vapor semi-permeable
textured wall finish
^l^l^^l
' > -
. *
^
.
v *>
-
•*• i
f t
:
•W 3
*
^ " i,
» ••
' *
' t
• »
» - *
~
:
^
1
ta
„-
I
Vapor Profile
Figure 2-10 Concrete Block with Interior Rigid Insulation Frame Wall with Cavity Insulation and Stucco
Stucco rendering •-
Concrete block
- unfaced extruded polystyrene, unfaced
expanded polystyrene, fiber-faced
isocyanurate
Insulated steel or wood stud cavity
*
IP"
batts. spray-applied cellulose or
spray-applied low density foam)
i
Latex paint or vapof S8rni-permeable
u
^^^•^^^
.
«• i
»
-
V -•
• 1
- - t
• »
-, A
m
»
•
-
-»
•
I
I
Vapor Profile
43
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Figure 2-11 Frame Wall with Exterior Rigid Insulation with Cavity Insulation and Brick or Stone Veneer
Brick veneer/stone veneer — •
Exterior rigid insulation - extruded
polystyrene, expanded polystyrene,
isocyanurate, spray polyuretharte foam.
rock wool, fiberglass
Membrane or trowel-on or spray-applied
vapor banter (Class 1 vapor retarder), air
barrier and drainage plane (impermeable)
sheathing, plywood or OSB
Cavity insulation (unfaoed fiberglass
batts, sprayed-applied cellulose or
spray-applied tow density foam)
Latex paint or vapor semi-permeable
»
=
i
• «-
^
textured wall finish
Vapor Profile
Figure 2-12 Precast Concrete with Interior Spray-Applied Foam Insulation
LdlBA pail I!
Spray-applied low density or high
density foam insulation
Latex paint or vapor semi-permeable
textured wall finish
, *fc . A
•
,
.
«
- i»
' > . ' 9 .
* I*
s *• , A
'-•>'.'<
. f-
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;'t\'l'
i
*
Vapor Profile
44
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Roof and Ceiling Assemblies
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Issue
Improper detailing of the roof and ceiling assemblies
may result in unwanted water intrusions or
condensation problems that can lead to damage to
the building and its contents. Failure to properly
design the roof can result in more frequent and costly
roof maintenance or repairs and a shorter building
lifespan. In roof-and-ceiling assemblies, the rain
water control portion of the roofing system may be
separated from insulation and air barrier layers by
a vented attic space. In this case, rainwater control
continuity is traced through the roofing system,
while air barrier and insulation continuity may be
traced at ceiling level. In this section, the term roof
assembly refers to the entire assembly that provides
rain protection, thermal insulation, air barriers and
condensation control.
Goals
Roof and Ceiling Assembly Design Goal 1: The roof
collects and disposes of rainwater.
Roof and Ceiling Assembly Design Goal 2: Roof
assemblies are designed to prevent condensation of
water vapor on cool surfaces within the dry portion
of the roof assembly, on the interior surface of the
exterior roof assembly or within the interior wall, floor
or ceiling cavities.
Roof and Ceiling Assembly Design Goal 3: The roof
design considers maintenance for moisture control.
Guidance
Roof and Ceiling Assembly Design Goal 1: The roof
collects and disposes of rainwater.
Guidance 1: Slope the roof to drain rainwater toward
collection and disposal sites.
Determine roof slope, or pitch, based on ordinary
use and design requirements. For example, for safety
purposes a roof that serves as a plaza, garden area,
or other social space must have a slope low enough
Slopes and Typical Roof Coverings
• Low-slope roof coverings:
• Built-up roofs.
• Modified bitumen.
• Single-ply.
• Sprayed polyurethane foam.
• Metal panels.
• Steep-slope roof coverings:
• Metal panels and shingles.
• Asphalt shingles.
• Slate.
• Tile.
to be safe. Slightly higher slopes can be tolerated for
limited-access roofs where mechanical equipment
that requires routine inspection and servicing is
located, but the slope of these roofs still must be
low enough to allow safe walking. Higher roof pitch
may be selected for visual appeal, consistency with
surrounding buildings or for the ability to shed snow
or rain. Roofing materials selected for appearance or
performance may have minimum slope requirements.
For example, slate roofs should not be less than or
equal to a 3-in-12 pitch (3:12), while some low-slope
roof membranes have been used on essentially flat
roofs. For these materials, this guidance requires at
least a lA-'m-12 pitch (1A:12) to promote positive
drainage in the face of deflection and construction
tolerances. Even "flat" roofs should be sloped.
• Use roofing materials that are appropriate for the
pitch. Select roofing material in accordance with
the requirements of the Whole Building Design
Guide for low-sloped and steep-sloped roofs.
NOTE: Low-sloped roofs are defined as roofs with
a slope less than or equal to 3:12 (25 percent).
However, with the exception of metal roofs, most
low-slope roofs must have a minimum slope of
1A-.12 (2 percent). Steep-slope roofs are defined
as roofs whose slope is greater than 25 percent.
Some materials can be used on both low and steep
slopes, while others are limited to either low or
steep slopes.
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• Design site water collection and disposal systems to
provide positive roof drainage where:
• All loading deflections of the roof deck are
considered.
• Local rainfall rates are considered.
• The roofing manufacturer's drain placement
requirements are followed.
• Roof drainage within a maximum of 48 hours
after precipitation is ensured.
Guidance 2: Design the roof drainage system with
sufficient runoff-handling capacity.
The amount of water to be handled depends on
the area and slope of the roof and the intensity of
rainfall at the building site. Chapter 11 of the 2003
International Plumbing Code (IPC), Storm Drainage,
requires that the size of vertical conductors and
leaders, building storm drains, building storm sewers,
and any horizontal branches of such drains or sewers
be based on the 100-year hourly rainfall rate. Use
figures presented in that chapter or rainfall rates
derived from approved local weather data.
The building's design, appearance and location
influence the type of roof drainage system. Designers
may opt to use external drainage systems, internal
drainage systems or both.
External Gutter and Downspout Drainage Systems
Design external gutter and downspout roof drainage
systems in accordance with Chapter 1 (Roof Drainage
Systems) of the Sheet Metal and Air Conditioning
Contractors' National Association, Inc. (SMACNA)
Architectural Sheet Metal Manual. The SMACNA
manual provides guidance for sizing drainage
systems for 10-year and 100-year storms. Compare
net drainage capacity of design with local code
requirements.
• Size gutters and downspouts to effectively drain
maximum runoff by determining the amount of
water the drainage system must handle given the
area of the roof to be drained, its pitch, and the
rainfall intensity. For specific information, seethe
SMACNA Architectural Sheet Metal Manual or the
IPC requirements referenced in this section.
• Connect all downspouts to sloped leaders, with a
5 percent—6 inches per 10 feet—minimum slope
that extends at least 10 feet from the foundation or
that meets more stringent local code requirements.
Leaders may be placed either above or below
ground.
• For below-ground or above-ground leaders, use
materials conforming to the standards listed in
the IPC. Ensure that seams and joints in leaders
are watertight to prevent water from escaping next
to the foundation. In order to prevent root growth
within below-ground leaders, ensure that the
leaders are not perforated.
• If above-grade leaders are used, provide protection
from accidental damage or encroachment.
• Direct all leaders to code-approved disposal,
typically daylight, drywells, swales or ponds. But in
buildings making efforts to reduce rainwater runoff,
rainwater may be collected for use in building
operations. Proper disposal prevents potentially
contaminated storm water from adversely affecting
water quality.
• In climates with significant snowfall, design the
roof assembly to avoid ice dams on roofs that drain
to external gutter systems. See Roof and Ceiling
Assembly Design Goal 4 guidance.
Internal Roof Drainage Systems
Internal roof drainage systems consist of drains on the
roof surface connected to down pipes running through
the building's interior and leading to storm sewers or
other discharge points. Internal roof drainage systems
are the most practical solution for large, low-slope
roofs. They are resistant to ice dam problems on low-
slope roofs in areas of significant snowfall because
the drains are warmed by the down pipes passing
through the building. Internal drainage systems are
seldom used on high-slope roofs (greater than 3:12).
Figure 2-13 illustrates interior drain placement for a
low-slope roofing system.
• Size and locate drains to remove maximum
rainwater and snowmelt flows effectively. Refer to
IPC Chapter 11, Storm Drainage.
• Ensure that features such as superstructures and
roof-mounted HVAC units do not obstruct the flow
of water from the roof to the drain.
• Equip roof drains with strainers or other devices to
prevent leaves and other debris from clogging the
drain or the down pipe.
• Locate drains at the center of bays between
columns so that any structural deflection will
produce slopes to the drain. Provide allowance in
the leader connection for any vertical movement
resulting from the structural deflection.
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Figure 2-13 Plan Drawing Illustrating Interior Drain Location and Roofing Slope for a Low-Slope System
Perimeter wind-uplift
zone
Comer wind-uplift
zone
Upper roof
Corner wind-uplift
zone
Corner wind-uplift
zone
Area divider curb
Comer wind-uplift
zone
LEGEND:
* Roof drain
O Overflow drain
• Design all roofs with at least a 1A-.12 pitch
to overcome low spots caused by expected
roof member deflection or construction within
tolerances.
• Locate down pipes in interior chases. Down pipes in
chases along exterior walls are more vulnerable to
condensation.
• Allow easy access to down pipes for periodic
inspection and repair by providing access panels or
utility closets.
• For parapets or other architectural protrusions
above the roof line, provide a secondary method
for draining rainwater if the primary roof drainage
system does not function. Two methods are often
used:
• The installation of scuppers through the parapet.
• The installation of an additional system of roof
drains and down pipes.
Guidance 3: Design penetrations parapets and
roof and wall intersections to prevent the entry of
rainwater. Figures 2-14, 2-15 and 2-16 illustrate
rainwater control details for a gooseneck vent
penetrating a low-slope roof and for a low-slope roof
intersecting a parapet wall.
Drainage layers must maintain integrity at joints
and penetrations, where the enclosure is the most
susceptible to moisture problems. See Table 2-1 for
a list of penetrations commonly found in roofs and
for guidance on how to maintain integrity at those
penetrations.
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Figure 2-14 Three-Dimensional Drawing Detailing Rainwater Control Continuity at Intersection of Goose Neck Vent,
Flashing and Roofing Membrane
Prefabricated stainless steel
goose neck vent (cutaway)
Granular surfaced modified
bitumen flashing
Granular surfaced modified
bitumen cap sheet
Tapered insulation
Concrete topping
(If applicable}
Sheet metal sleeve
Roof cement cove at base
of penetration
Modified bitumen base sheet
Structural concrete deck
Set bottom flange ol goose
neck vent in bed or maslic
Table 2-1 Maintaining the Integrity of Drainage Layers at Joints and Penetrations
NOTE: Continuity of the air barrier and insulation layer must also be maintained at these locations.
Common Roof Penetrations
Joints between roofing materials
Roof edges
Joints between the intersection
of walls and roofs
Skylights and roof hatches
Chimneys
Air handlers and exhaust fans
Outdoor air intakes and passive
relief vents
Plumbing vents
Ways to Maintain Integrity of Rainwater Protection
Provide continuity by shingling or sealing
Provide capillary breaks by using overhangs, copings and drip edges
Provide continuity by using flashing where a lower story roof intersects a
wall of a higher level and where the roof meets the wall of a dormer
Provide continuity by using flashing, curbs and counter-flashing
Provide continuity by using flashing, crickets and counter-flashing
Provide continuity by using flashing, curbs and counter-flashing
Provide continuity by using flashing and counter-flashing
Provide continuity by using flashing and counter-flashing
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Roof and Ceiling Assembly Design Goal 2: Design
roof assemblies to prevent condensation of water
vapor on cool surfaces within the dry portion of the
roof assembly, on the interior surface of the exterior
roof assembly or within interior wall, floor or ceiling
cavities.
Guidance 1: Design the roof and ceiling assembly to
be sufficiently airtight to limit water vapor migration
and heat transfer by air flow.
• Specify air-sealing details to provide a continuous
air barrier from the center of the roof-and-ceiling
assembly to the roof-wall intersection. Use the pen
test (See Appendix A) to trace the continuity of the
air barrier. NOTE: The air barrier for the roof is part
of the whole building air barrier system.
• Specify a whole building air leakage rate when
tested at 75 Pascal pressure difference in
accordance with ASTM E779-10 Standard Test
Method for Determining Air Leakage Rate by Fan
Pressurization or ASTM £1827-96(2007) Standard
Test Methods for Determining Airtightness of
Buildings Using an Orifice Blower Door or the U.S.
Army Corps of Engineers Air Leakage Test Protocol
for Building Envelopes. For example, the U.S. Army
Corps of Engineers requires a maximum air leakage
rate of 0.25 cubic feet per minute per square
foot of air barrier surface (6 sides) at a pressure
difference of 75 Pascals.
• Use a layer of material in the roof or ceiling
assembly as the basis of the air barrier systems:
• Interior gypsum board, foam board or spray
foam insulation, concrete, and OSB or plywood
deck are good selections to form the basis of
air barrier systems in roof assemblies. Include
specifications for all accessory materials required
to provide durable continuity of the air barrier.
• Fully adhered roofing membranes can be used to
make the air barrier in non-vented low-slope roof
systems.
• Fluted steel deck is difficult to use as the basis
of an air barrier. (The flutes are difficult to air-
seal at the perimeter and joints.)
• A suspended T-bar ceiling—clipped or not—
cannot be used as an air barrier system.
• Provide two-dimensional sections detailing methods
for providing air barrier continuity at pipes, shafts,
skylight vaults, light fixtures, conduits and other
penetrations through the air barrier layer (See Table
2-1).
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• Provide two-dimensional sections highlighting the
air barrier and connecting materials and methods
for each section.
Guidance 2: Select the overall insulation R-value to
meet or exceed ASHRAE 90.1 or International Energy
Conservation Code requirements.
• Provide two-dimensional sections detailing methods
for providing insulation layer continuity:
• At pipes, shafts, skylight vaults, light fixtures,
conduits and other penetrations through the air
barrier layer (See Table 2-1).
• At transitions between one insulating material
and another (e.g., where roof insulation meets
wall insulation).
• At thermal bridges in the insulation layer (e.g.,
where steel members penetrate the insulation
layers).
Guidance 3: Collect the air barrier, the insulation
layer and the materials with the lowest water
vapor permeability (<2 perms) into an assembly of
consecutive, touching layers. NOTE: This does not
include the roofing or roof sheathing. Roofing and
sheathing may be in contact with these layers—non-
vented roof assembly—or separated by a space that
vents to the outdoors—vented roof assembly. Figures
2-17 and 2-18 illustrate condensation control in two
non-vented low-slope roof systems.
Step 1: Determine whether to use a vented or non-
vented roofing system based on climatic and space-
use considerations.
• Do not place mechanical equipment in vented attic
space.
• Condensation on roof bottom sheathings that results
from night sky radiation is most easily avoided by
using unvented roof assemblies.
• Non-vented roofing is more resistant to fire caused
by wildfire embers.
Step 2: Collect all the materials with low water vapor
permeability (< 2 perms) together on one side of any
vapor open cavity insulation layer. NOTE: Vented roof
and ceiling assemblies separate low-permeability
materials in the roofing-sheathing layer from low-
permeability materials in the ceiling, air barrier and
insulation layers by a vented space between them.
Both the roof and ceiling assemblies can dry to this
space. Apply either Step 3A or Step 3B.
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Step 3A: Follow published guidance on combining
insulation, an air barrier, and materials of appropriate
permeablility for vented and non-vented roofing
systems in the relevant climate zone.19 Depending on
the insulation systems selected, apply the following
specific guidance.
If using insulation composed entirely of low-
permeability foam insulation (e.g., closed-cell spray
polyurethane foam or foam board insulation), note
that:
• Spray foam provides an inherent air barrier,
insulation layer, and vapor control for all climates.
It still requires specific detailing at transitions
between the spray foam and adjoining assemblies.
• Foam board provides insulation and vapor
permeability control but requires air-sealing
details at the joints, penetrations and roof-wall
intersection. This can be achieved using a separate
air barrier system (e.g., wood panel or gypsum
board roof deck sealed to provide the air barrier) or
using the foam board as the basis of the air barrier.
Caution: In special high-moisture areas (e.g., indoor
swimming pools) using closed-cell spray polyurethane
or foam board insulation, non-vented low-slope roofs
may need a vapor retarder with a lower perm rating
than that of the roofing membrane. Special analysis is
needed for high internal moisture load uses (See Step
3B). If using all open-cell spray foam (Yz Ib./cu. ft.
spray):
• Foam provides an inherent air barrier.
• Separate interior vapor control is required in
climate zones 5, 6 and 7.
• Put materials (except roofing materials) with
perm <2 and the air barrier on the interior side of
the insulation layer.
• Use interior class II or III vapor barrier.
• Applies to vented and non-vented roofs.
If using all high-perm porous insulation (e.g.,
fiberglass, cellulose) for non-vented roofs:
• Use only in hot, dry climates.
• A separate air barrier system is required.
If using all high-perm porous insulation (e.g.,
fiberglass, cellulose) for vented roofs:
• A separate air barrier system is required.
• Separate water vapor control is required in climate
zones 5, 6 and 7.
• Put materials with perm <2 (except roofing
materials) and the air barrier on the interior side
of the insulation layer.
• Use interior class I or II vapor barrier in climate
zones 6 and 7.
• Use interior class III vapor barrier in climate zone
5.
• In all milder climate zones, put the air barrier on
the inside or outside of the insulation layer. Use
no materials less than 2 perms in the assembly
—excluding roofing.
If using a layer of high-perm insulation and a layer of
low-perm insulation together for non-vented roofs:
• All the low-perm materials (<2 perms) including the
foam insulation should be collected on the exterior
side of the high-perm insulation layer.
• Closed-cell spray polyurethane foam insulation
provides an inherent air barrier.
• Foam board insulation must have a separate air
barrier (e.g., roof sheathing or roofing membrane
or air-sealing details at the joints, penetrations and
roof-wall intersection).
• The temperature of the condensing surface should
be controlled using a ratio of low-perm R-value to
high-perm R-value. For ordinary indoor humidity
conditions, at least one-third of the overall R-value
should be provided by the foam insulation.
If using a layer of high-perm insulation and a layer of
low-perm insulation together for vented roofs:
• All the low-perm materials (<2 perms) including the
foam insulation should be collected on the interior
side of the high-perm insulation layer.
• Closed-cell spray polyurethane foam insulation
provides an inherent air barrier.
• Foam board insulation must have air-sealing details
at the joints, penetrations and roof-wall intersection
or a separate air barrier (e.g., roof sheathing or
roofing membrane).
Step 3B: Model the performance of proposed roof
assemblies using a hygrothermal software program
(e.g., WUFI or hyglRC). Use design conditions from
ASHRAE Standard 160-2009 for modeling. Note,
however, that the results of computer simulations
should be interpreted cautiously and in light of
'See Straube (2011) for all climate zones, Lstiburek (ASHRAE April 2006) for all climate zones and CMHC Best Practice Guides for climate zones 6 and 7.
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Figure 2-15 Moisture Control in an Unvented Low-Slope Roof Assembly with Structural CMU Walls
Air barrier transition membrane wraps (op—|
of framing connecting roof ail barrier to
WB« »r terror (NOTE; At bsmef and rood
ing m*frtbf»n* products from Me roofing
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real-world construction practices. For example, most
computer models assume that walls are airtight and
that no water vapor is transported through them by
airflow. Therefore, for the model to be valid, the
assembly must be designed, installed and tested to
meet air tightness standards. Also, the performance
of any assembly depends on its orientation in regard
to solar load and wind direction during heavy rains.
Some, but not all, of the programs can model the
dynamic of rainwater absorbed by porous claddings
and vaporized into the assembly by the sun.
Guidance 4: Control ice dams in climate zones 5, 6
and 7.
• Provide a carefully detailed, tested air barrier in the
roof system (See Guidance 2). Locate the air barrier
in the same plane as or adjacent to the insulation
layer for all assemblies.
• Drain non-vented, low-slope roofs to interior drains
or use spray or board foam to insulate non-vented
roofs that slope to eave drainage. The required total
R-value can be met using foam insulation alone
or by a combination of foam insulation and high-
perm porous insulation materials (e.g., fiberglass,
cellulose or mineral wool). The foam insulation
must be located in contact with, but outside of, the
porous insulation.
• Or use vented roofs that slope to eave drainage
and avoid sources of heat in vented attics and
vented roof sheathing systems.
Roof and Ceiling Assembly Design Goal 3: Roof
design considers maintenance for moisture control.
Guidance 1: Ensure that systems are easily
maintained and that maintenance plans are reviewed
with the owner.
• Materials in the roof and ceiling assembly that will
be difficult or expensive to remove and replace
must have an expected service life at least as long
as the materials enclosing them.
• Design assemblies to shed rainwater by use of
flashings and lapping materials to drain. Do not
depend on sealants alone to control rainwater entry
in areas that will be difficult or hazardous to inspect
and repair.
• Develop or require the contractor to develop
maintenance documents for the roofing systems
including warranty requirements, scheduled
inspections and maintenance, and appropriate
repair processes.
• Develop a plan for both surface and subsurface
drainage that specifies:
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Figure 2-16 Moisture Control in an Inverted Membrane Roof with Heavy Steel Frame and Light Steel In-Fill
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• Maximum rainfall or snowmelt assumptions.
• Drainage surface areas including shapes, slopes,
superstructures or other obstructions.
• Estimated water flows.
• The location and capacities of all conduits.
• Provide drainage system maintenance plan
requirements.
Verification of Roof and Ceiling Assemblies
• Write a description detailing how the roof system
manages rain. Include this description in the basis-
of-design document.
• Use the pen test (See Appendix A) to verify the
continuity of drainage surfaces, capillary breaks and
flashing around penetrations from the center of the
roof to the intersection with the exterior walls.
• Provide two-dimensional sections where two
materials that form the rainwater control come
together and three-dimensional drawings where
three or more elements of the rain protection come
together. Sections must show continuity of capillary
breaks and flashing around penetrations and
interface with air barrier and insulation systems.
• Provide a list of critical details, an inspection
schedule and quality assurance tests of the roofing,
inner capillary break (e.g., roofing felt, self-adhering
bituthene membrane), flashing and drainage
elements of the roof systems; identify the sequence
of inspections and tests, the parties responsible
for them and the required documentation of the
results.
• Provide a list of inspection and maintenance
requirements for the roofing, coping and flashing.
• Reference published roof assemblies designed
to manage water vapor and condensation within
the appropriate climate. Perform hygrothermal
modeling when documentation through previous
testing or modeling of a roof assembly in a
particular climate or for unusual space humidity
levels is not available.
• Write a description detailing how the roof system
manages water vapor during cooling and heating
modes, as applicable. Drawings and specifications
must identify vapor migration control details
and the permeability and insulating values of all
materials.
• Use the pen test (See Appendix A) to verify the
continuity of the insulation layers and air barriers
from the center of the roof to the intersection with
the walls.
-------
Provide two-dimensional sections where two
materials that form the insulation layers and air
barrier come together and three-dimensional
drawings where three or more elements of the
insulation and air barrier come together.
Specify a fan pressurization test in design
specification documents to assess the entire
building enclosure in accordance with ASTM
E779-10 Standard Test Method for Determining Air
Leakage Rate by Fan Pressurization, ASTM E1827-
96(2007) Standard Test Methods for Determining
Airtightness of Buildings Using an Orifice Blower
Door of the U.S. Army Corps of Engineers Air
Leakage Test Protocol for Building Envelopes.
• Specify the target airtightness level.
• Specify when the test should be conducted in
relation to the completeness of the air barrier
system.
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• Identify the appropriate testing party.
• Specify how the results should be documented,
judged and accepted or rejected.
• Specify the remedies if the building fails the test.
Specify quality assurance programs for the
installation of the hygrothermal control elements of
the enclosure. Provide a list of critical details and
a schedule for inspecting the air barrier, insulation
and vapor control elements of the roof assembly.
Specify the sequence of inspections, the parties
responsible for the inspections, and the required
documentation of the inspection results.
Provide a list of inspection and maintenance
requirements for the interior finishes if they are
critical to water vapor control.
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Plumbing Systems
Issue
Moisture problems associated with plumbing
equipment include:
• Leaks in pressurized pipes and vessels, in
appliances that use water and in pipes that drain
wastewater.
• Condensation on cold-water lines, chilled water
lines and toilets. The colder these surfaces are, the
more likely condensation will form.
• Mold growth on partitions, ceilings and floors
enclosing spaces that are subject to repeated
wetting.
Once installed, plumbing is difficult and expensive to
replace and relocate, so good design is very important.
Moisture problems associated with poorly designed
plumbing can cause damage that can affect almost
any location in the building, including places that are
not often seen or inspected or are difficult to access.
Unnoticed mold growth can result from leaks, posing
a health risk to building occupants. Gaining access to
poorly designed plumbing for repair or replacement
can necessitate demolishing obstructions, which leads
to higher repair costs.
Goals
Plumbing System Design Goal 1: Design supply lines,
drain lines, and fixtures to prevent water leaks and
facilitate leak detection and repair.
Plumbing System Design Goal 2: Design plumbing
systems to prevent condensation on cold water lines
and fixtures.
Plumbing System Design Goal 3: Select materials to
minimize mold growth in areas that are unavoidably
wet.
Guidance
Plumbing System Design Goal 1: Design supply lines,
drain lines and fixtures to prevent water leaks and to
facilitate leak detection and repair.
Guidance 1: Reduce initial leaks by specifying testing
of supply lines, drain lines and fixtures.
Determine specifications for pressure tests of supply
and drain lines and fixtures to identify leaks in
plumbing.
• Design specifications should require, at a minimum,
the testing of supply lines in accordance with
section 312.5 of the International Plumbing Code,
or relevant sections of other applicable local codes,
but they may require testing at higher pressures
depending on the requirements of the equipment
and plumbing system and the intent of the design.
• Design specifications should require, at a minimum,
testing the drain and vent side of the plumbing
system as required by the relevant building code.
For example, designs should specify a gravity test
of the drain and vent side of the system according
to sections 312.2, 312.3, and 312.4 of the
International Plumbing Code, or relevant sections
of applicable local codes. If all or a portion of the
drain side of the system will be pressurized during
operation, appropriate pressure testing must be
specified.
• Identify the test method and the design test
pressure.
• Specify when the tests should be conducted in
relation to the completeness of the plumbing
system and the closing of the cavities (e.g.,
while lines are exposed for inspection, but before
enclosing).
• Identify the appropriate testing party. Depending
on the scale of the project and the parties
involved, the appropriate testing party may be
a commissioning agent; a testing, adjusting,
balancing (TAB) contractor; a subcontractor to the
general contractor; or a plumbing contractor.
• Specify how the results should be documented,
judged and accepted or rejected.
• Specify the remedies if any portion of the plumbing
system fails the test.
Guidance 2: Design the plumbing system for easy
inspection and repair of components (e.g., pipes,
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valves, traps, grease traps, tanks, controls, heaters,
filters and connections to appliances).
Place pipes and valves where they can be easily
inspected and repaired, where leaks will be seen
quickly, and where even a small leak will not wet a
cavity made from moisture-sensitive materials. Avoid
locating water lines and other plumbing components
in exterior wall or ceiling cavities insulated with
porous insulation. NOTE: If pipes must be located
in an exterior wall or ceiling, they must be protected
so that outdoor temperatures do not affect them and
outdoor air cannot leak in to them. In addition to
any required pipe insulation, place a layer of closed-
cell board or spray-foam insulation between the pipe
and the exterior sheathing or curtain wall. If board
foam is used, it must be air sealed at the joints and
edges and connected in an airtight way to the air
barrier system at all perimeter edges. The object is
to surround the pipe with warm interior air when it is
cold outdoors and with cool, dry, conditioned air in air
conditioning mode.
Plumbing System Design Goal 2: Design plumbing
systems to prevent condensation on cold water lines
and fixtures.
Guidance 1: Design the plumbing system's insulation
and water vapor controls so the pipes, tanks and
other equipment that convey or contain water cooler
than the dew point of the outdoor air—or cooler than
the expected dew point of the air in the enclosure
where the equipment will be located—are free of
condensation.
• Specify the design temperature and humidity
conditions for the spaces that contain plumbing
components conveying cool or cold water (e.g.,
chilled water lines, cold water lines, toilets, cold
water storage tanks or water treatment tanks) and
the expected surface temperatures of these items
during the design condition.
• Specify the required R-value of the insulation and
the permeability and location of the water vapor
control element to prevent condensation on the
surface of the insulation or on the surface of the
pipe or plumbing component.
• Specify air-sealing methods and materials at joints
and seams in the insulation and water vapor control
elements.
• Provide details showing the continuity of the
insulation and water vapor control where pipes pass
through walls, ceilings or floors and where pipes
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join other plumbing components such as valves,
gauges, pumps and tanks.
• Require the inspection of condensation controls
for components that convey cool or cold water and
specify when in the construction sequence the
inspections must take place, the party responsible
for performing the inspections, the methods that
should be used to document the results of the
inspections and any remedies for failed inspections.
Plumbing System Design Goal 3: Select materials to
minimize mold growth in areas that are unavoidably
wet.
Guidance 1: In unavoidably wet areas, use materials
that tolerate repeated wetting and drying.
• Identify areas in the building that will get wet
because of their use (e.g., entryway floors,
bathroom floors, tub surrounds, showers, locker
rooms, pool and spa rooms, and kitchens). Specify
materials that are highly resistant to the growth
of mold. Among these materials are ceramic tile,
glass, plastic resins, metals and cement-based
products.
• For materials known to be vulnerable to mold
growth (e.g., untreated paper-faced gypsum
board and OSB), use products and paints that are
resistant to mold growth. Specify mold-resistance
testing criteria that are appropriate for these
materials (e.g., a score of 10 when tested using
ASTM D3273 Standard Test Method for Resistance
to Growth of Mold on the Surface of Interior
Coatings in an Environmental Chamber).
• Avoid specifying materials that provide nutrients
and sustain mold growth. Such materials include
untreated paper-based products and composite
wood materials.
Verification of Plumbing Design
Piping, Valves, and Controls
• Confirm that drawings and specifications document
the location of pipes, valves and other plumbing
system components and the location, size and type
of access panels for inspection and repair.
• Confirm that the pressure test requirements of
supply and drain lines, the specific responses
to success or failure, the testing schedule,
the responsible testing party and the required
documentation have all been specified.
• Provide a list of critical details and a schedule for
inspecting the plumbing system including supply
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lines, drain lines, air vents, plumbing fixtures,
appliances that use water, tanks and vessels.
Specify the inspection sequence, the parties
responsible for the inspections and the required
documentation of the inspection results.
Insulation and Vapor Retarders
• Confirm that drawings and specifications include
the design conditions, condensation control
elements, inspection procedures, responsible
parties and documentation as required.
• Provide a list of critical details and a schedule for
inspecting the plumbing system insulation and
vapor retarders, including supply lines and drain
lines. Specify the inspection sequence, the parties
responsible for the inspections and the required
documentation of the inspection results.
Wet Spaces
• Confirm that the drawings and specifications
identify appropriate moisture-resistant materials for
use in wet locations including bathrooms, showers,
locker rooms, pool and spa rooms, and kitchens.
• Provide a list of inspection and maintenance
requirements for the moisture-resistant materials
used in the unavoidably wet areas.
• Provide a list of critical details and a schedule for
inspecting the moisture-resistant materials and
associated liquid-water-control elements specified
for use in unavoidably wet areas. Specify the
inspection sequence, the parties responsible for the
inspections and the required documentation of the
inspection results.
• Provide a list of inspection and maintenance
requirements for the moisture-resistant materials
used in the unavoidably wet areas.
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HVAC Systems
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Issues
Some of the moisture problems in buildings can
be caused or accelerated—or reduced or avoided
altogether—through the design and installation of the
HVAC system. The HVAC components that dehumidify
the ventilation air deserve careful attention because
outdoor air constitutes most of the annual humidity
load for nearly all buildings.
Common HVAC-related contributors to moisture
problems include:
• Inadequate dehumidification by the HVAC system
during humid weather. The resulting high indoor
air dew point can lead to condensation, near-
condensation and mold growth. Comfort problems
also are common when the indoor dew point is
high because the relative humidity is also high.
Occupants often demand lower thermostat settings
in an attempt to be more comfortable. This is
counterproductive. Lowering the thermostat
overcools the building, which increases the risks
of condensation, excess moisture absorption and
subsequent mold growth. Cold temperatures also
further reduce comfort and increase energy costs.
• Leaking return and exhaust air duct connections,
leaking indoor air handler compartments operating
under suction, and leaking return air plenums.
These leaks create suction in building cavities,
pulling humid outdoor air into the building where
it can condense moisture onto cool surfaces and
support mold growth.
• Leaking supply air duct connections and leaking
indoor air handler compartments operating under
positive pressure. When the weather is hot or
humid, these cold air leaks chill surfaces behind
walls and above ceilings, creating condensation and
supporting mold growth. During cold weather these
same leaks can force warm, humid indoor air into
cold cavities where it can condense and support
mold growth and corrode structural fasteners.
• Oversized cooling systems. When cooling
systems, rather than dedicated dehumidification
components, are expected to control humidity, the
traditional inclination of designers is to increase
the cooling tonnage to remove the combined
sensible and latent loads. But overpowered cooling
systems have exactly the opposite effect. A large
cooling system removes the normal sensible load
very quickly. Then, to avoid over-chilling the space,
compressors are shut off or chilled water flow rate
is reduced before the coils can condense enough
moisture to control humidity. In nearly all cases,
oversized cooling systems do not solve humidity
control problems—instead, they cause them.
• Ineffective drainage of condensate collected inside
the HVAC system or condensation on the outside
of the system's cold and uninsulated surfaces.
Undrained and uncollected condensate leads to
water leaks, drips and subsequent moisture damage
and mold risk.
• Failure to exhaust indoor humidity sources such
as showers, bathrooms, spas, pools and kitchens,
especially in residential buildings and sports
facilities. Humid air can migrate from these sources
to cold surfaces, leading to condensation or near-
condensation and subsequent mold growth and
structural deterioration.
HVAC System Design Goal 1: Keep the indoor air dew
point low enough to reduce the risk of condensation
on cool surfaces and the risk of moisture absorption
by organic materials.
HVAC System Design Goal 2: Seal all duct
connections to prevent hot, humid outdoor air from
being pulled into the building by leaking return air
duct connections, leaking return air plenums and
unbalanced exhaust. Sealed connections also prevent
condensation caused by supply air escaping through
duct connections into unconditioned spaces.
HVAC System Design Goal 3: Prevent condensate
from cooling coils from overflowing into drain pans
and prevent condensation on the external surface
of cold pipes, valves, ducts, diffusers and indoor air
handler cabinets.
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HVAC System Design Goal 4: Limit indoor humidity
loads through effective exhaust ventilation—via duct
work with sealed connections—from showers, tubs,
kitchens, pools, spas and other significant sources of
moisture. Balance the exhaust air with dry makeup
air to prevent the exhaust from pulling unconditioned
outdoor air through the building enclosure.
Guidance
Building owners and HVAC designers will note that
this guidance is a necessarily brief summary of
several complex tasks. More detailed design methods
to achieve these goals are presented in the ASHRAE
Humidity Control Design Guide for Commercial and
Institutional Buildings.
HVAC System Design Goal 1: Keep the indoor air
dew point low enough to reduce the risks from
condensation on cool surfaces and from moisture
absorption by organic materials.
Guidance 1: For an air-conditioned building, design
the HVAC systems to include dehumidification
components and a control system that will keep the
indoor air below a 55°F dew point during humid
weather.
Indoor air held below a 55°F dew point cannot
condense moisture onto cool ducts carrying
supply air at 55°F. Nor will moisture condense on
surfaces chilled by that supply air as it leaves the
supply air diffusers. And only very small amounts
of condensation, if any, will form on incompletely
insulated chilled-water piping. A maximum 55°F
dew point control level provides an appropriate safety
margin to reduce the impact of minor shortcomings in
the building enclosure design and construction, and it
minimizes the risk of condensation from the inevitable
minor air leakage through duct connections.
Among the effective dehumidification techniques are:
• Drying all the ventilation air in a separate,
dedicated outdoor air system (DOAS) to a dew point
low enough to remove the internally generated
humidity loads. DOAS can also be designed to
have other significant risk-reduction benefits. They
can reduce ventilation air in response to reduced
occupancy, which greatly lowers annual humidity
loads, energy use and the risks associated with
moisture accumulation. During occupied hours,
dedicated outdoor air units can be used to provide
a slight excess of dry ventilation air, so most of the
air leaks in the building enclosure involve dry air
moving outward, rather than humid air moving into
the building. By providing a return air connection
with a damper, the system can keep the building
dry during unoccupied periods by recirculation,
without the need to either ventilate or to operate
the central cooling system.
• Arranging the main cooling system so it can
sufficiently dry ventilation and return air to remove
all of the humidity loads even when thermostats
are not calling for cooling. This drying can be
accomplished by using a separate dehumidification
coil, or by a variable air volume cooling system. In
both cases, the cooling coil must stay constantly
cold and not re-set to a higher temperature during
periods of low sensible heat load. In a variable
volume system, keeping the coil constantly cold
will require reheating the supply air to some
zones. To comply with energy codes and ASHRAE
Standard 90.1, reheat energy should come from
heat otherwise wasted, such as rejected heat from
refrigeration condensers or heat from exhaust air.
Also note that to avoid losing dehumidification
capacity, reheat coils should be located well
downstream from dehumidification coils. Otherwise,
the energy radiating from a closely coupled reheat
coil will re-evaporate some of the condensed water
as it drips from the dehumidification coil.
• Drying a portion of the blended return and
ventilation air with a secondary cooling coil or a
desiccant dehumidifier that operates in response
to a rise in the indoor dew point. In this alternate
arrangement, the air will follow a dual path: part of
it will be dried by the secondary coil or desiccant
dehumidifier and the rest will bypass the main
cooling coils unless there is a need for cooling.
Reheat or post-cooling usually is not required for
this arrangement. After the dry air blends back into
the supply, the blended mixture is generally warm
or cool enough for occupant comfort.
Guidance 2: Use the peak outdoor dew point design
conditions—not the peak sensible heat design
values—to estimate humidity loads when sizing
dehumidification components and systems.
• The largest sources of humidity load are nearly
always the ventilation air, the exhaust makeup air
and air infiltrating through the building enclosure.
These loads are at their peak when the outdoor
air is at a moderate temperature but a very high
humidity. At this peak outdoor dew point design
condition, the humidity loads are 30 percent to
100 percent greater than the humidity loads at the
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hottest outdoor dry bulb conditions. So for sizing
dehumidification loads and determining component
performance, it is very important to use the
ASHRAE peak dew point design conditions and not
the peak cooling design conditions.
Peak dew points along with their corresponding
humidity ratio values for major North American
and international locations are available in the
ASHRAE Humidity Control Design Guide. Those
data and values for many additional locations
also now appear in Chapter 14 of both the print
and electronic editions of the ASHRAE Handbook
2009—Fundamentals, as shown in Figure 2-17.
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Guidance 3: Limit the operation of any air-side
economizer to only when the outdoor air dew point is
below 55°F.
• Air-side economizers have been responsible
for significant problems related to moisture in
buildings, especially schools and libraries that
require only moderate cooling during lengthy
unoccupied periods—a task well suited to cooling
with outdoor air. However, unless that outdoor air is
dry as well as cool, the flood of air brought in during
the economizer cycle adds a tremendous amount
of moisture to the building and its contents.
Controlling the economizer with an enthalpy control
does not solve the problem because the outdoor
Figure 2-17 Peak Dew Point Data are Available in the Climatic Design Information Chapter of the ASHRAE Handbook—
Fundamentals
Dehumidification
Design Data
Peak Dew Point
***-"*
A3
Peak Dry Bulb
NOTE: The print edition of the ASHRAE Fundamentals volume for 2005 did not contain these values, but they are available on the
accompanying compact disk. The printed edition of the 2001 Fundamentals contains peak dew point values for a more limited set of
locations, as does the 1997 edition. Be aware, however, that the ASHRAE Fundamentals volumes from 1993 and earlier do not contain
values for peak dew point—only for the sensible cooling design extremes, which have much lower absolute humidity levels than the peak
dew point conditions.
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humidity can still be too high even when its
enthalpy is lower than indoors.
• An air-side economizer is still a useful energy-saving
feature in less-humid climates. But the decision
to bring in outdoor air for cooling should be made
based on the outdoor air dew point as well as the
outdoor dry bulb temperature. A maximum 55°F dew
point is a good rule of thumb. If the outdoor dew
point is above 55°F, do not bring in extra outdoor
air for cooling, even if its dry bulb temperature or its
enthalpy is below the indoor value.
Guidance 4: Design the system to keep the indoor
dew point near or below 35°F when the outdoor
temperature falls below freezing.
• To limit the risk of damage from moisture and mold,
the basic requirement for humidity control in the
winter is to avoid condensation inside the cold
exterior wall. The most appropriate maximum indoor
dew point in the winter depends on the annual
duration and severity of cold weather at the site,
and on the design and construction of the building
enclosure and its glazing.
• Higher indoor dew points provide more comfort
during the winter, but lower dew points are better
for avoiding condensation on cold surfaces on and
inside exterior walls. A 35°F dew point maximum
during winter weather is a prudent compromise
between these two competing goals for most
commercial and institutional buildings. That level is
at the lower boundary of the winter thermal comfort
zone as traditionally defined by ASHRAE Standard
55. And as noted in the ASHRAE Humidity Control
Design Guide, a 35°F dew point is still high enough
to help limit uncomfortable electrostatic discharges
and eye irritation for the general population.
• Museums, swimming pool enclosures and hospitals
are exceptions; they all have much higher winter
indoor dew points for important reasons. Their
building enclosures demand very careful attention
to interior-side air tightness and vapor retarders on
the inside surface of the exterior walls in order to
limit their high risk of moisture problems due to
wintertime condensation.
• For any type of building in an extremely cold
climate; the more hours below freezing, the
more important it will be to carefully analyze the
condensation potential of the exterior wall and
glazing designs and to install continuous air and
vapor barriers inboard of the buildings' insulation.
Better insulated and more air-tight building
enclosures can tolerate higher indoor dew points to
improve comfort for occupants.
• Most buildings are not mechanically humidified
during the winter, but in some cases such
humidification is useful and necessary. When
the building is humidified, the designer should
remember the advice of humidifier manufacturers,
which is repeated in the ASHRAE Humidity Control
Design Guide. Namely, consider splitting the
required humidification capacity between several
units in stages, rather than install one single,
large unit. Humidifier manufacturers warn that
building moisture problems are sometimes caused
by humidifiers that are so large they cannot be
controlled at the lower end of their capacity. These
units can overload the supply air with water vapor,
causing condensation, moisture accumulation and
water leaks from ducts.
HVAC System Design Goal 2: Prevent hot, humid
outdoor air from being pulled into the building by
leaking return air duct connections, leaking return
air plenums and unbalanced exhaust. Prevent
condensation caused by supply air escaping through
duct connections.
Guidance 1: Specify that all duct connections on the
supply and return air sides be sealed with mastic to
the standards established by SMACNA's HVAC Duct
Systems Inspection Guide for high-pressure duct work
(Seal Class A).
• Ducts and their connections need not be built
to resist high pressures if they are not operating
under high pressure. However, all duct connections,
especially where ducts meet air handlers, must be
sealed tight with mastic. NOTE: Recent energy code
changes in several states have made this guidance
a requirement. The requirement is based on the
considerable energy cost savings and equipment
size reductions made possible by preventing air
leaks into and out of duct work.
Guidance 2: Specify that all joints and penetrations
of all return air plenums be sealed with fire or smoke
sealant so that the plenum is open to air flow only
from the inside of the occupied space it serves—and
especially not open to inward leakage from exterior
walls, crawl spaces or basements.
• One classic problem area is an exterior wall where
the gypsum wallboard does not extend all the way
up to seal against the bottom of the floor or roof
above. Such openings to the inside of the exterior
wall must be plugged with backing material such
as glass fiber insulation and then sealed with
liquid-applied conformal film such as fire or smoke
sealant.
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• In commercial buildings, roof-mounted air
conditioning units are often mounted on curbs
above return air plenums. The joint between the
curb and the unit must be sealed tight because it is
effectively part of the duct system.
• Fire codes sometimes allow vertical plumbing
chases to be used as return air ducts, a situation
that can be found in low-cost construction. The
volume of air that leaks into such chases is likely
to be extreme, however, and likely to come from
undesirable locations such as basements and
crawl spaces, loading the return air with humidity,
particulates and microbiological contaminants. To
avoid problems, the designer should insist that all
spaces used as air ducts be sealed and tested for
air tightness.
• In low-rise school, office and retail strip mall
construction, the joint between the exterior walls
and roof often includes an open soffit under the
eaves. A return air plenum that can draw air
through that soffit becomes, by accident, an ail-
outside air system. Any building that has a soffit
requires special attention from the HVAC designer
to ensure that return air is pulled from the occupied
space and not from outdoors.
Guidance 3: Design the systems to manage indoor-
outdoor air pressure relationships. If a building
enclosure has been designed and constructed with
an effective air barrier, continuous insulation layers,
and rainwater control as required by this guide,
then for ordinary occupancies enclosure-related
problems are not very sensitive to indoor-outdoor
pressure relationships. In warm, humid climates (See
Climate Zone map, Figure 2-5) maintaining a slight
positive pressure during cooling conditions adds
extra protection against condensation in the building
enclosure.
To create a slight positive pressure, add up all the
exhaust air volumes from all zones served by a single
system. Design the air conditioning system for those
zones so that the total of the dry makeup/ventilation
air exceeds the total exhaust from those areas by 5 to
10 percent. Balance the exhaust and ventilation air
flows during humid weather so that the building stays,
on average, under slightly positive air pressure (5 Pa
or 0.02" WC). Use dry ventilation air to accomplish
this slight positive pressure.
Maintaining an average positive air pressure can also
be accomplished more explicitly and automatically
by sensing the pressure difference between indoors
www.epa.gov/iaq/moisture
and outdoors and using that signal to control a relief
damper on small buildings and one or more relief
air fans on larger buildings. Such a pressure control
system makes it easier for the building operations
staff to reverse the direction of the pressure difference
for winter operation.
• When outdoor air temperatures are below freezing
and indoor relative humidity must be maintained
above 35 percent, there are advantages to operating
under neutral or slightly negative air pressure so
humid indoor air is not forced into cold exterior wall
cavities, where it could condense moisture.
• Note that some buildings such as hospitals,
museums, and high-rise buildings, as well as areas
such as walk-in freezers and indoor swimming
pools, require special care with respect to air
balance. Their unique and sometimes critical needs
for specific pressure differences between spaces
necessitates consultation with industry-specific
references for more detailed and appropriate
guidance.
HVAC System Design Goal 3: Prevent normal
condensate from cooling coils from overflowing drain
pans and prevent condensation on the outside of cold
pipes, valves, ducts, diffusers and indoor air handler
cabinets, as recommended by ASHRAE Standard
62.1-2007.
Guidance 1: Specify that all cooling coils be
equipped with condensate drain pans that have these
characteristics:
• The pan is long enough in the direction of air flow
to catch any condensate blown off the coil during
heavy condensing conditions.
• The pan drains from its lowest point and slopes
towards that lowest point from two directions to
ensure there is never any standing water in the pan.
• Any drain pan that does not have a condensate
pump is equipped with a trap on the condensate
drain line deep enough to ensure no water remains
in the pan drain when the fan is operating.
• The trap is vented on the outlet side to ensure that
plug flow in the downstream condensate piping
does not siphon water out of the bottom of the trap.
• The condensate drain line and trap are accessible
and detachable to allow cleanout with a brush.
• Clearances around the duct work and duct access
doors allow for regular inspections and cleaning of
the condensate drain pan.
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Guidance 2: Specify that all interior faces of duct
work or plenums located immediately downstream
from cooling coils be lined with smooth, washable,
water-impermeable material to prevent accumulation
of moisture and dirt on those surfaces. It is a prudent
rule of thumb to have an impermeable and washable
surface for at least the first 10 feet downstream of
dehumidification coils. Also specify that:
• Any joints in the moisture-impermeable lining are
sealed watertight.
• The outlet duct work or plenum is equipped with
a gasketed door large enough to ensure access
adequate for inspecting and cleaning downstream
duct surfaces.
Guidance 3: Design the component layout so that
filters are located either upstream of cooling coils or
far enough downstream so they do not collect droplets
of moisture stripped from the coil during periods of
heavy condensation. For coils intended principally as
dehumidification components, specify:
• Coil fin height no greater than 4 feet above the
bottom of the drain pan, face velocity below 400
feet per minute, and spacing of eight fins per inch
or wider to minimize water accumulation on the fins
and subsequent droplet carryover into the supply air
under heavy condensing conditions.
• Maintenance access upstream of the coil through
one or more gasketed doors that are sufficiently
large to allow the full width and height of the coil
surface to be cleaned.
HVAC System Design Goal 4: Limit indoor humidity
loads through effective exhaust ventilation—through
duct work with sealed connections—from showers,
tubs, kitchens, pools, spas and any similar significant
sources of indoor humidity.
Guidance 1: Provide exhaust ventilation of strong
humidity sources (e.g., showers and bathtubs,
spas, cooking ranges, commercial dishwashers and
combustion devices), as recommended by ASHRAE
62.1-2007 and ASHRAE 62.2-2004. In addition:
• Specify sealing of all exhaust air duct work
connections to SMACNA seal class A using mastic.
Pay special attention to the joint where the ducts
connect to the exhaust grille collars and to the
inlets and outlets of fan compartments. This sealing
is important for all exhaust ducts in all buildings,
but it is especially important for ducts that have
continuously operating exhaust fans, such as those
in the bathrooms of hotels and eldercare buildings.
Many of these buildings have suffered frequent
mold problems as a direct result of leaking exhaust
duct connections. Such leaks create suction that
pulls humid air into the building, where its moisture
condenses or is absorbed into cool wall board and
onto ceiling tile and furnishings where the moisture
supports mold growth.
• For exhaust ducts from commercial kitchens,
spas, pools, athletic building showers and other
hot, high-humidity spaces, require duct insulation
in order to avoid internal condensation. Specify
similar insulation for exhaust ducts from residential
bathrooms and kitchens in cold climates, because
the dew point in the exhaust air is likely to be above
the cool indoor air temperatures in the unheated
cavities and attics that the ducts pass through on
their way to the outdoors.
• Design exhaust ducts to terminate outdoors and
not in unconditioned indoor areas such as attics or
crawl spaces.
• Do not terminate the exhaust duct by directing
exhaust air through the ventilated soffit under
eaves. The hot and humid air will quickly rise and
re-enter the attic space through nearby vents in the
same soffit, leading to mold growth in the attic and
on the roof's inside surface.
Verification of HVAC System Design
Cooling Season Dew Point Control
• Explain in the design specifications the operation
of the air conditioning and dehumidification
equipment at design dew point conditions and the
expected humidity removal under those conditions,
expressed in pounds of water vapor removed per
hour.
• Require that the supplier of the dehumidification
component or system provide written
documentation of the equipment's performance—
including pounds of water vapor removed per
hour, total air flow, and the temperature of air as
it leaves the device—when the system is operating
under peak outdoor dew point conditions. These
conditions will always be of reduced sensible heat
loads, so the suppliers' submittals for the peak dew
point conditions will provide very useful snapshots
of the behavior of the entire system's operation
under part-sensible-load conditions—temperature
conditions that occur for thousands, rather than
dozens, of hours every year.
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• Require that the dehumidification system be
tested, adjusted and balanced and that reports
from that process verify and document the system's
performance after the system is running. At a
minimum, measure and document the design
versus actual air flow through the device and the
temperature and humidity ratios of the air as it
enters and exits the device, then calculate the
equipment's performance in pounds of water vapor
removed per hour.
• Require that the economizer air-flow and damper
operation be tested, adjusted and balanced and
require reports from that process that will verify
and document the economizer air flow rate. The
Test, Adjust and Balance (TAB) report should also
confirm that the economizer damper has been seen
to open correctly and that the dampers and control
set points allow the economizer to operate only
when the outdoor air dew point is below 55°F.
Winter Condensation Control
• Design the installation surrounding any humidifier
in strict accordance with the manufacturer's
recommendations for exterior insulation and for
unobstructed lengths of straight duct downstream
for complete vapor absorption. Also ensure that
the controls allow smooth modulation of humidity
production down to 20 percent of the equipment's
peak design capacity.
• Require that any humidifier and its control system
be tested, adjusted and balanced and that the
ductwork downstream be checked for condensation
during operation of the humidifier. Require reports
that measure and verify total air flow and the
temperatures and humidity ratios of entering and
leaving air.
Air Distribution
• Minimal requirement: Require the general
contractor to inspect all sides of all joints between
ducts and air handlers and to provide a written
report that all sides of joints to and from air
handlers are sealed with mastic. Also require the
installer to certify that all other joints in the system
have been sealed with mastic.
• Robust requirement: Require that the completed
system, including air handlers, be tested for
air tightness in accordance with SMACNA
requirements for commercial buildings or with the
Air Conditioning Contractors Association (ACCA)
recommendations for residential buildings. Require
a written report of measured air leakage values in
accordance with the recommendations of those
organizations.
• Require the HVAC contractor to inspect all sides
of return air plenums and provide a written report,
including photographs, that documents all joints
and penetrations are effectively sealed.
• Require that the written TAB report provide
assurance that all exhaust duct joints, and
especially their connections to exhaust grilles and
exhaust fans, have been inspected to confirm they
have been sealed with mastic.
• Require that the air conditioning and exhaust
systems be tested, adjusted and balanced.
• Include in the TAB process a pressure map of the
building during air conditioning and heating modes
documenting indoor-outdoor pressure differences
over the course of daily sequences.
• Require reports from the TAB process that will
verify and document system air flows after the
system is running.
REFERENCES
Advanced Energy. Closed Crawl Spaces: A Quick Reference for the
Southeast. 2003. Online. Internet. Available at: http://www.
crawlspaces.org. Accessed Novembers, 2013.
(This condensed document provides details and technical
information for designing and constructing closed, insulated
residential crawl spaces. The full research reports underlying
the crawl space recommendations can also be downloaded
from the site [www.crawlspaces.org]. Although the research
was conducted in North Carolina, many of the results can be
applied to other climates.)
Air Conditioning Contractors of America (ACCA) Residential Duct
Systems - Manual D - ANSI/ACCA1-2002 ISBN 1-892765-
00-4 ACCA, 2800 Shirlington Rd, Suite 300, Arlington, VA
22206. ACCA.org
(This guidance for duct design and installation is the basis
for building codes in several states, and it is an ANSI-
approved national standard.)
Air Movement & Control Association, International, Inc. (AMCA).
AMCA 500-L-99 - Laboratory Methods of Testing Louvers for
Rating.
Air Tightness Testing and Measurement Association. Technical
Standard 1. Measuring Air Permeability of Building
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American Society for Testing and Materials (ASTM). ASTM 1554-
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American Society for Testing and Materials (ASTM). ASTM D
3273 - Standard test method for resistance to growth of
mold on the surface of interior coatings in an environmental
chamber.
American Society for Testing and Materials (ASTM). ASTM £779-
03 - Standard test method for determining air leakage rate by
fan pressurization.
American Society for Testing and Materials (ASTM). ASTM
WK4201 - New standard test method for resistance to mold
growth on building products in an environmental chamber.
American Society for Testing and Materials (ASTM). ASTM
WK8681 - New standard test method for resistance to
mold growth on interior coated building products in an
environmental chamber.
American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE). ASHRAE Handbook of Fundamentals.
ASHRAE Standard 62.1 - 2004 Ventilation for Acceptable
Indoor Air Quality, ASHRAE 2004.
(The ASHRAE ventilation standard provides information
needed to determine ventilation rates for differing
occupancies plus a number of design and O&M requirements
to ensure proper performance of ventilation equipment.
Section 6.2.8 applies specifically to exhaust ventilation.
Standard 62.1 applies to many situations.)
American Society of Heating, Refrigerating and Air- Conditioning
Engineers (ASHRAE). ASHRAE Handbook of Fundamentals.
ASHRAE 62.2 -2004 Ventilation and Acceptable Indoor Air
Quality in Low-Rise Residential Buildings.
(This standard applies to low-rise residential buildings.
Exhaust systems are covered in portions of sections 5, 6 and
7.)
American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE). ASHRAE Handbook of Fundamentals.
ASHRAE Standard 90.1-2004 and Addenda - Energy
Standard for Buildings Except Low-Rise Residential
Buildings.
(This standard provides minimum requirements for the
energy-efficient design of all buildings, with the exception of
low-rise residential buildings.)
American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE). ASHRAE Handbook of Fundamentals.
ASHRAE Standard 160 P - Design Criteria for Moisture
Control in Buildings.
Baker, M.C. Drainage From Roofs. Canadian Builders Digest no.
151. 1972.
(This digest is a general discussion of roofs and roof drainage
and highlights many roof drainage design considerations.)
Brennan, T, Cummings, J, Lstiburek, J. Unplanned Airflows and
Moisture Problems. ASHRAE Journal. November 2002.
(This article reviews the moisture dynamics caused by
unplanned airflows during heating and cooling modes and
discusses interventions that can be made to prevent or solve
the problems.)
Building Science Corporation. Read This Before You Design,
Build or Renovate. Revised May 2005. Available at
http://www.buildingscience.com/documents/guides-and-
manuals/gm-read-this-before-you-design-bui Id-renovate/
view?searchterm=read+this. Accessed November 6, 2013.
(This pamphlet offers guidance about remodeling practices
that foster healthy homes by reducing occupants' risk of
exposure to known hazards. These practices also frequently
yield other benefits such as improved durability and reduced
operating costs.)
Canada Mortgage and Housing Corporation (CMHC). Best Practice
Guides.
(Design guides with underlying building science discussions,
well-thought-through details for climate zones 6 and 7.
Guides are available for flashing, brick veneer and steel
studs, brick veneer and concrete masonry unit backing,
external insulation and finish systems, glass and metal
curtain walls, architectural precast concrete walls, and wood
frame envelopes.)
Connecticut Department of Environmental Protection. 2004
Connecticut Storm water Quality Manual.
(This manual provides guidance on the measures necessary to
protect waters from the adverse impacts of post-construction
storm water. It applies to new development, redevelopment
and upgrades to existing development. The manual focuses
on site planning, source control, pollution prevention and
storm water treatment practices.)
Department of the Army. Site Planning and Design. TM 5-803-6.
October 1994.
(This technical manual describes the site planning and
design process used to develop a project to fulfill facility
requirements and create the optimal relationship with the
natural site. The manual focuses on the site planning and
design process as it leads from program and site analysis to
the preparation of a concept site plan.)
Ferguson, Bruce K. 2005. Porous Pavements CRC Press/Taylor &
Francis, crcpress.com ISBN 0-8493-2670-2
(This 577-page book provides comprehensive guidance and
case histories for design, construction and maintenance
based on 25 years of practical experience with porous
pavements, their hydrology and their relationship to storm
water drainage and surface water management for buildings,
roads, parking lots and landscape vegetation.)
Gatley, Donald. Dehumidification Enhancements for 100-Percent-
Outside-Air AHUs, Parts 1-3. September, October and
November 2000.
(This three-part series of articles describes the underlying
psychrometrics in ventilating buildings and provides
design guidance for several methods of enhancing the
dehumidification performance of air conditioning and
ventilation systems.)
Georgia Stormwater Management Manual Volume 2: Technical
Manual First Edition. August 2001.
(This volume provides guidance on the techniques and
measures that can be implemented to meet a set of storm
water management minimum standards for new development
and redevelopment. It is designed to provide the site designer
or engineer with information required to effectively address
and control both water quality and quantity on a development
site.)
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Harriman, Brundrett, and Kittler. Humidity Control Design
Guide for Commercial and Institutional Buildings (ASHRAE
Humidity Control Design Guide). American Society of
Heating, Refrigerating, and Air-Conditioning Engineers. ISBN
1-883413-98-2.
(This manual by ASHRAE discusses the design of cooling
equipment to include dehumidification performance. Design
analysis includes peak outdoor air dew point performance as
well as peak outdoor temperature analysis.)
Henderson, H., Shirey, D., Raustad, R. Understanding the
Dehumidification Performance of Air Conditioning Equipment
at Part-Load Conditions. Presented at the CIBSE/ASHRAE
Conference, Edinburgh, Scotland 1-24-26 September 2003.
(This technical paper presents analysis and data on
the degradation of dehumidification performance of air
conditioning equipment during partial-load conditions.
Controls and systems that contribute to this problem are
discussed.)
HyglRC (A hygrothermal modeler from the Institute for Research
in Construction in Canada [http://archive.nrc-cnrc.gc.ca/
eng/projects/irc/hygirc.html]. Accessed Novembers, 2013.
HyglRC is a modeler that is actively supported by the IRC.
LikeWUFI and MOIST, HyglRC assumes no air flow through
the assembly.)
International Code Council (ICC). 2003 ICC International Building
Code.
(Chapter 18 provides code requirements for soils and
foundations including requirements for excavation, grading
and fill around foundations. Section 1203.3.1 contains
requirements for ventilated crawl spaces.)
International Code Council. 2003 ICC International Plumbing
Code.
(Chapter 11 provides code requirements for storm drainage,
including roof drainage requirements. Sections 312.2 to
312.5 specify a gravity test of the drain and vent side of
plumbing systems.)
International Code Council (ICC). International Energy
Conservation Code (IECC).
(The IECC addresses energy efficiency in homes and
buildings.)
Kanare, H. Concrete Floors and Moisture, Portland Cement
Association, Skokie, Illinois, cat. no. EB119, 156 pp., 2005.
Lstiburek, Joseph 2006. Understanding Attic Ventilation.
ASHRAE Journal 48: 36.
(This ASHRAE Journal article covers the underlying principles
of attic ventilation in buildings.)
Lstiburek, Joseph 2006. Understanding Basements. ASHRAE
Journal 48: 24
(This article identifies moisture control problems often
observed in basements and solutions to such problems.)
Lstiburek, Joseph 2006. Understanding Drain Planes. ASHRAE
Journal 48: 30
(This ASHRAE Journal article covers the underlying principles
of rainwater control in buildings, focusing on the use of
weather-resistant materials that provide shingled drainage
beneath siding materials.)
www.epa.gov/iaq/moisture
Lstiburek, Joseph. Understanding Retarders. ASHRAE Journal.
August 2004.
(This ASHRAE Journal article covers the underlying principles
of vapor retarders in buildings.)
Lstiburek, Joseph 2004. Understanding Vapor Barriers. ASHRAE
Journal 46:40
(This ASHRAE article describes water vapor dynamics in
wall sections and provides a flow-chart method of selecting
materials for the inside and outside of cavity walls with
appropriate water vapor permeability for specific climates.
Assemblies can be designed without using computer
simulation.)
MOIST (MOIST is a hygrothermal modeling program available
as a free download from the National Institute of Science
and Technology [http://www.nist.gov/el/highperformance
buildings/performance/moist.cfm]. Accessed November 6,
2013. The calculation kernel in MOIST is not as complex as
HyglRC or WUFI, but it is significantly better than simplified
steady state dew point-temperature profile calculations. It
provides a thermal network analysis, includes solar radiation
gains (but not rainwater or plumbing leaks), capillary
migration and partial-pressure-driven vapor migration. Like
WUFI and HyglRC, MOIST does not model airflow effects.)
National Asphalt Pavement Association. Online. Internet.
Available at http://www.asphaltpavement.org/.
(The National Asphalt Pavement Association is a trade
association that provides technical, educational, and
marketing materials and information to its members and that
supplies technical information concerning paving materials.)
National Institute of Building Sciences (NIBS). Building Envelope
Design Guide (Whole Building Design Guide). Online.
Internet. Available at http://www.wbdg.org/design/envelope.
php. Accessed November 6, 2013.
(Under guidance from the Federal Envelope Advisory
Committee, the NIBS developed this comprehensive guide
for exterior envelope design and construction for institutional/
office buildings. Sample specifications and sections are
included.)
Odom, J.D. and DuBose, G.H. Mold and Moisture Prevention.
National Council of Architectural Registration Boards.
Washington, DC, 2005.
(This manual is the 17th monograph in NCARB's Professional
Development Program. It contains substantial narrative
describing moisture and mold problems in buildings
and specific design and construction considerations for
enclosures and HVAC systems as they relate to moisture and
mold problems.)
Rose, William. Water in Buildings: An Architect's Guide to
Moisture and Mold. John Wiley & Sons, 2005. ISBN:
0471468509
(This is not a design guide, but rather a deeper look at water
and its behavior in regard to building materials, assemblies
and whole buildings. Illustrated with specific examples, it
explains the how and why of moisture control.)
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Sheet Metal and Air Conditioning Contractors' National
Association (SMACNA). SMACNA Air Duct Leakage Test
Manual. 1985.
(A companion to HVAC Duct Construction Standards - Metal
and Flexible, this manual contains duct construction leakage
classification, expected leakage rates for sealed and unsealed
ductwork, duct leakage test procedures, recommendations on
the use of leakage testing, types of test apparatus and test
set-up and sample leakage analysis.)
Sheet Metal and Air Conditioning Contractors' National
Association (SMACNA). Architectural Sheet Metal Manual -
Fifth Edition. 1993
(The SMACNA Architectural Sheet Metal Manual provides
design criteria and details for roof drainage systems, gravel-
stop fascia, copings, flashing, building expansion, metal
roof and wall systems, louvers and screens and other metal
structures. Chapter 1 contains data, calculations and charts
for designing roof drainage systems.)
Spray Polyurethane Foam Association. Spray Polyurethane Foam
for Exterior Subgrade Thermal and Moisture Protection.
(This publication is a technical guide to specifying closed-cell
spray foam polyurethane on the outside of basement walls as
thermal insulation and moisture protection.)
Straube, John. 2011. High Performance Building Enclosures.
Somerville, MA: Building Science Press (This book includes
the fundamentals underpinning the physics of heat, air and
moisture control in high-performance building enclosures and
practical design guidance to achieve them for a wide array of
enclosure assemblies in all North American climate zones.
There is a section on condensation control in wall and roof
assemblies.)
Texas Water Development Board. The Texas Manual on Rainwater
Harvesting.
(This manual presents an interesting discussion on the history
of rainwater collection, harvesting system components, water
quality and treatment, system sizing and best management
practices.)
United States Environmental Protection Agency. Alternative
Pavers (Post-Construction Stormwater Management in
New Development and Redevelopment). Online. Internet.
Updated May 2006. Available at http://cfpub.epa.gov/
npdes/stormwater/menuofbmps/index.cfm?action=min
measure&min measure id=5. Accessed November 6, 2013.
United States Environmental Protection Agency. Construction Site
Stormwater Runoff Control. Online. Internet. Updated May,
2006. Available at http://cfpub.epa.gov/npdes/stormwater/
menuofbmps/index.cfm?action=min measure&min measure
id=4. Accessed November 6, 2013.
(This resource provides detailed information on construction-
phase storm water management, including best management
practices.)
United States Environmental Protection Agency. National Menu
of Stormwater Best Management Practices. Online. Internet.
Updated May, 2006. Available at http://cfpub.epa.gov/npdes/
stormwater/menuofbmps/index.cfm. Accessed November 6,
2013.
(This resource provides detailed information including
applicability, design criteria, limitations and maintenance
requirements on these and many other site drainage
methods.)
United States Environmental Protection Agency. Porous
Pavement (Post-Construction Stormwater Management in
New Development and Redevelopment). Online. Internet.
Updated May, 2006. Available at http://cfpub.epa.gov/
npdes/stormwater/menuofbmps/index.cfm?action=min
measure&min measure id=5. Accessed November 6, 2013.
United States Environmental Protection Agency. Post-
Construction Stormwater Management in New Development
and Redevelopment. Online. Internet. Updated May,
2006. Available at http://cfpub.epa.gov/npdes/stormwater/
menuofbmps/index.cfm?action=min measure&min measure
id=5. Accessed November 6, 2013.
(This resource provides detailed information on post-
construction Stormwater management including O&M best
management practices.)
United States Environmental Protection Agency. Source Water
Practices Bulletin: Managing Storm Water Runoff to Prevent
Contamination of Drinking Water. EPA 816-F-01-020. July
2001. Available at http://www.epa.gov/safewater/sourcewater/
pubs/fs swpp stormwater.pdf. Accessed November 6, 2013.
(This fact sheet focuses on the management of runoff in
urban environments.)
Water Management Committee of the Irrigation Association. Turf
and Landscape Irrigation Best Management Practices.
(The Irrigation Association is involved with public policy
issues related to standards, conservation and water use on
the local, national and international levels.)
WUFI (Hygrothermal modeling software to assess the water vapor
dynamics of wall and roof systems in numerous climates.
WUFI is one of the more complete treatments of water
vapor dynamics in assemblies. WUFI is available from the
Fraunhofer Institute of Building Physics rhttp://www.hoki.
ibp.fraunhofer.de/1 in Germany. A limited version of WUFI
is available free from Oak Ridge National Laboratory Fhttp://
www.ornl.gov/sci/btc/apps/moisture/1.) Accessed November 6,
2013.
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Chapter 3: Constructing to Prevent Moisture Problems
Introduction
This chapter is for the people who turn design
documents into buildings. More attention is being
paid to moisture control during construction now than
ever before because of increased concern about mold
growth in buildings. In this chapter moisture control
issues are divided into two major topics:
1. Control of water during the construction of the
building.
2. Effective implementation of the moisture control
requirements specified by the designers in the
construction documents and associated contracts.
Erecting a building often involves several companies
providing services from multiple trades. The general
contractor has the primary responsibility and
contractual obligation for the building's construction.
The physical work often is carried out by specialized
subcontractors such as landscapers, roofers, glazers,
concrete and masonry contractors, steel fabricators,
electrical contractors, insulation and waterproofing
contractors and mechanical contractors. Providing
moisture control during construction is largely
the responsibility of the general contractor and
the subcontractors. However, firms specializing in
construction management or building commissioning
may have responsibilities for moisture control.
The concept of commissioning traditionally has been
applied to heating, ventilation, and air conditioning
(HVAC) systems. Commissioning has been very
effective in reducing problems and increasing energy
efficiency and comfort. Over the past decade, this
process has been extended to entire electrical
systems; potable water, sanitary, drainage and
irrigation systems; power production and cogeneration
systems; the building enclosure; sustainable aspects
of the project; and the entire building design process
(ASHRAE Guideline 0: The Building Commissioning
Process, GSA The Building Commissioning Guide,
and the National Institute of Building Science [NIBS]
Total Building Commissioning Program).
If a commissioning agent is involved in the design
and construction of a building, many of the quality
assurance procedures for moisture control and
associated measures could easily fall within the
commissioning agent's scope.
During the initial meetings, the contractor can
develop a plan to:
• Protect the building from, and respond to, moisture
problems during construction.
• Implement the moisture control elements,
verification activities and commissioning activities
detailed in the drawings and specifications.
Moisture control policies to protect the building
during construction and to ensure the design has been
effectively implemented should be in place before
construction begins. After agreement on moisture
control issues has been reached, the contractor must
implement and verify the moisture controls required
during construction and those required for the
successful operation of the building.
Control of Moisture During Building Construction
Construction companies have always had to deal with
moisture problems at the construction site. Materials
and equipment get wet from:
• Rain.
• Water used in materials that are installed wet.
• Leaks in temporarily or permanently installed
plumbing.
• Condensation in the building before it is enclosed.
• Poor humidity control after the building is enclosed,
but before the HVAC system is operational.
As the site work begins and before the building
is enclosed, contractors may use temporary site
drainage, pumps, and dunnage and tarps to keep
the site and materials relatively dry. Many of the
materials used in the early phases of a project will not
be damaged if they get wet, although some will have
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to be dried before they can be used. For example,
foundation materials need to be dry before some
coatings and flooring can be applied.
The sequence of activities plays an important role in
preventing moisture problems during construction
• Moisture-sensitive and moisture-absorbing material
and equipment should be scheduled for delivery
when dry, protected storage is available.
• Wet, porous materials should be dry before
moisture-sensitive materials are installed or
moisture-sensitive coatings are applied.
• Moisture-sensitive materials need to be protected
from the weather as they arrive on site. Measures to
keep rain away from the materials may also protect
them from damage by dust and wind.
• It is preferable to enclose the building so it
is weather-tight before the moisture-sensitive
materials arrive. While this situation can be
planned for smaller projects, it may not be possible
for larger ones. In these instances, contractors
may provide temporary shelter for materials and
equipment stored on site. They may protect partially
completed work with tarps, temporary enclosures,
or temporary bulkheads at floor penetrations. For
example, gypsum board, brick, concrete block
and wooden materials can be wrapped in plastic,
covered by tarps or plastic and stacked on pallets
in well-drained areas. Some materials that need to
be protected, such as brick and concrete masonry
units, can be delivered wrapped in plastic.
• The lower stories of high-rise buildings are often
being finished while the upper floors are still open
to the weather. This situation requires using upper
floors as temporary protection by making temporary
bulkheads at floor penetrations and draining floors
to the perimeter. Increasingly, contractors also use
dehumidification equipment to dry out buildings
that are enclosed, but not yet air conditioned.
• In spite of the best efforts to keep material and
equipment dry, accidents still happen and things
do get wet. Brick and concrete block may have
absorbed water before they were delivered or while
they were stored at the site. Heavy wooden timbers
may have been milled and installed while still
green. The earthen floor of a crawlspace foundation
is a large area of soil exposed to the weather right
up until the overhead floor deck is installed. Some
materials get wet accidentally because of rain or
for other reasons. It is important to dry out any
moisture-sensitive materials as quickly as possible.
Implementing the moisture control features of the
design consists of two essential actions
1. Understanding the moisture control design
features in detail and ensuring their
constructability.
2. Ensuring the moisture control features are
effectively installed.
Coordination between construction companies who
are obligated to control moisture in buildings as
specified in the construction documents and building
designers (architects and engineers) will enhance
moisture control in the building. The contractor
should review the moisture-control elements of
the enclosure and mechanical system designs and
discuss them with the designer(s) at the start of
the project. However, contractors, subcontractors,
construction management personnel, commissioning
agents, and owners frequently propose alternative
details, materials, or equipment. It is important to
note that these changes can lead to changes in the
moisture control requirements of the building and
must be included in moisture planning. This includes
proposals made during the bid process; during the
development and review of submittals; at initial
meetings between the contractor, designer, owner,
and construction management service; or during
meetings to review submittals, construction progress,
difficulties, and responses to problems that have
arisen. The contractor is urged to read Chapter 2 of
this document to become familiar with the moisture
control guidance for designers. The construction
documents can be compared with the design
recommendations of Chapter 2.
Scheduling is an ever-changing target that requires
juggling the schedules of numerous suppliers, sub-
contractors, supervisors and inspectors. This already
daunting task can be further complicated by larger
issues, such as changes in markets or disasters in
other parts of the world, that might affect the price
and availability of supplies. It is crucial that the
materials required to control moisture in the enclosure
and the equipment required to control humidity in
the building arrive so they can be installed in the
correct sequence. For example, the drain plane or air
barrier within a wall must be installed before the wall
is closed in; otherwise, proper installation becomes a
matter of demolition and reconstruction.
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Whether the general contractor is coordinating
the installation of moisture control systems or a
subcontractor is installing them, it is crucial to have
a quality assurance program in place to inspect, test
and document the correct installation and functioning
of the moisture control elements. This may mean
the difference between avoiding or having a moisture
problem. Some examples of moisture problems resulting
from poor or no quality assurance practices are:
• Missing flashing.
• Flashing installed with laps reversed.
• Flashing that stops short of becoming a through
flashing.
• Missing insulation.
• Missing sealant.
• Unsealed holes in the return plenum that cause
depressurization of wall cavities.
• Condensate pan drain lines, internal roof drains,
or basement sump crocks installed at the highest
point rather than the lowest.
• Impermeable flooring or moisture-sensitive flooring
installed on a concrete slab that is releasing too
much water vapor.
Inspecting moisture control elements as they
are installed is the most important aspect of
supervision—especially in the areas where inspections
may be most difficult. In addition to QA officers
who are employees of the general contractor or
subcontractor, inspections may be made by third
parties such as construction management or
commissioning firms.
The inspector must check that the specified materials
are on site and being installed so they will perform
their function. Sequence is often important in
effective installation. The following items must be
frequently and carefully inspected during installation:
• The air barrier.
• Air barrier materials should be installed so
they can be easily sealed at the joints and
penetrations.
• Sealants that complete the air barrier should
be installed before access to the air barrier is
blocked.
• Rainwater control.
• The shingling of the drain plane and the flashing
for roof, walls, windows, doors and other
penetrations should be correctly installed.
Insulation.
• Insulation should be installed so that it makes
as complete a layer as possible (i.e., no voids in
cavity insulation, no uninsulated cavities).
• Plumbing.
• The location of plumbing lines should be
checked.
• Cold water lines, chilled water lines and internal
roof drains should be insulated; pressure tests
should have been completed prior to installation
of insulation and enclosing finishes.
• Access to valves should be available.
• Wet rooms should be assembled using only
moisture- and mold-resistant materials.
• HVAC.
• Condensate pans should be sloped and plumbed
correctly.
• Access panels should be installed downstream
of the coils so the coils and ductwork can be
inspected and cleaned.
• Ductwork and return plenums should be air
sealed and tested.
• Duct insulation should be installed and the
ductwork sealed.
• Chilled water and refrigerant lines should be
insulated and sealed.
• Wet materials.
• Materials that need to be installed wet or that
became wet accidentally must be dry before
cavities are enclosed (e.g., concrete, concrete
masonry units or porous insulation must be
dry before they are enclosed by gypsum board
walls; crawlspaces must be drained and ground
covering installed before OSB floor decking
is installed) or flooring (e.g., vinyl flooring on
concrete slabs) is installed on them.
A number of tests may need to be performed to
demonstrate that a moisture control element is
working properly. Some of the tests are required by
code; some may be specified by the designers in the
construction documents; some may be required to
maintain a manufacturer's warranty and some may
be performed by the contractor for its own assurance.
The tests include:
• Air tightness of the enclosure test (ASTM E779-10,
ASTM E1827-96 [2002] or ACE [2012]).
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• Air leakage and rain penetration tests on mockups
or in situ portions of the enclosure (ASTM E783,
ASTM El 105).
• Water vapor emission test for concrete slabs before
installing flooring (ASTM F1869)orASTM F2170).
• TAB on exhaust airflows (ASHRAE).
• Pressure test of water supply system (International
Plumbing Code Section 312.5).
• Testing the drainage and vent air of plumbing
systems (International Plumbing Code Section
312.2, 312.3 and 312.4).
• Drainage tests for condensate drain pans in air
conditioners. (There are requirements for slope, etc.
in ASHRAE 62.1.)
• Air pressure difference tests.
• Duct leakage testing (SMACNA).
Documentation of the inspection and testing results
may include the date, location, purpose of inspection,
results, deficiencies and proposed corrective actions;
all items must all be recorded. Each inspection
and test must be documented with log entries,
photographs and checklists. The value of photographs
in documenting an inspection cannot be overstated.
Many industry associations offer quality assurance
guidance for building enclosure systems (ABAA,
NCRA, NFRC and RCI). Some offer certification for
those who provide enclosure consulting and quality
assurance services (ABAA, NFRC and RCI).
This chapter has seven subsections:
• Pre-Construction Planning.
• Site Drainage.
• Foundation Construction.
• Wall Construction.
• Roof and Ceiling Assembly Construction.
• Plumbing System Installation.
• HVAC System Installation.
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Pre-Construction Planning
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To protect a building from moisture problems during
construction and to ensure the design's moisture
control elements are properly implemented, the
contractor needs to incorporate moisture control
into the planning, scheduling and sequencing of
the project. The contractor also needs to coordinate
these activities with the owner and the owner's
representatives (e.g., the design team, construction
management service or commissioning agent).
Goals
Pre-Construction Planning Goal 1: Develop a moisture
control plan to be used while the building is under
construction.
Pre-Construction Planning Goal 2: Review the
moisture control details in the construction
documents with the design team, construction
management and subcontractors.
Guidance
Pre-Construction Planning Goal 1: Develop a moisture
control plan to follow while the building is under
construction.
Guidance 1: Establish with the owner and design
team the level of concern for moisture control during
construction and after turnover. In developing the
moisture control plan, the contractor can be guided
by the level of concern the owner and design team
express and by the level of concern implicit in the
construction drawings and specifications for the
design's moisture control elements, third-party
inspections, testing and commissioning.
Guidance 2: Plan the construction schedule and
the sequence of deliveries to meet the owner's and
design team's moisture control objectives. Keeping
the building site, building materials and equipment
dry during construction requires extra planning,
effort, equipment and materials. When the entire site
is exposed to the weather and when the building is
under construction but not yet closed in, moisture-
sensitive materials either must not be on site or must
be protected from the elements. Completely enclosing
the structure before moisture-sensitive materials
and equipment are delivered or are being installed
on lower floors may have a significant impact on the
schedule. The moisture control plan should address at
a minimum:
• Providing construction site drainage: temporary
drainage, dewatering.
• Providing protection from construction water and
from leaks from hoses and plumbing.
• Making the enclosure or portions of the enclosure
weather-tight before the delivery or installation of
moisture-sensitive materials.
• For smaller buildings, the entire enclosure may
be made weather-tight before sensitive materials
arrive at the site.
• For larger buildings, a portion of the enclosure
may be made weather-tight early enough to
store or to begin installing moisture-sensitive
materials.
• Before the top floor in high-rise construction is
reached and roofed, lower floor walls may be
made weather-tight and floor decks diked or
sealed at penetrations (e.g., stairwells, utility
chases and elevator shafts) and drained at the
perimeter.
• Providing rain protection for work and for stored
materials before the building is closed in.
• Preparing a list of materials that must be kept
dry, actions planned to protect them during
construction, and responses if they get wet.
• Most finish materials (e.g., paper-covered gypsum
board and wooden paneling) and some porous
insulating materials (e.g., fiberglass and cellulose
insulation) must be kept dry.
• Preparing a plan to store vulnerable materials so
they are protected from rain, snow and plumbing
leaks during construction (e.g., schedule delivery
after the building or a portion of the building is
weather tight; provide protection independent of the
building, such as pallets and tarps, shrink wrap or a
separate storage building).
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• Sequence the installation of these materials
when the building or a portion of the building is
weather-tight.
• Drying wet materials before finishing or enclosing.
• Prepare a list of materials that can tolerate
wetting, but must be dry before additional
materials in the foundation can be installed; the
critical points by which they must be dry; actions
planned to ensure they are dry at those times;
and responses in the event they are wet at a
critical time.
• Impermeable materials (e.g., anodized
aluminum, glass and extruded styrene foam
board) can tolerate a great deal of wetting, but
may need to be dry before sealants or adhesives
are applied.
• Some porous materials (e.g., exterior grade
gypsum board sheathing, plywood and oriented
strand board) can tolerate short-term wetting,
but they must be dry before coatings, tapes,
adhesives or interior finish materials are
applied. Obtain, read and follow manufacturers'
instructions.
• Some porous materials (e.g., concrete, concrete
masonry units and brick) can tolerate a great deal
of wetting for extended periods, but must be dry
before coatings, tapes, adhesives or interior finish
materials are applied. For example, a water-based
emulsion used as a spray-applied drain plane
may not cure correctly if applied to saturated
concrete masonry walls. Installing paper-covered
gypsum board next to a wet concrete wall can
result in mold growth on the gypsum board.
• Dehumidifying after closing in the building, but
before the HVAC system is operational.
• Commissioning and testing the enclosure, plumbing
and HVAC systems.
• Responding to moisture and mold problems that
happen in spite of these efforts.
• Surveillance.
• Emergency response.
• Drying, clean-up and repair.
• Clearance.
Guidance 3: Identify the parties responsible for
implementing each portion of the moisture control
plan.
Pre-Construction Planning Goal 2: Review the
moisture control details in the construction
documents with the design team, construction
management and subcontractors.
Guidance 1: Review moisture control details in the
construction documents and discuss them with the
design team:
• Review rainwater and subsurface water-control
details and specifications for the site with the
landscape and excavation contractors.
• Trace rainwater control, air barrier and insulation
layer details for continuity; review enclosure testing
and commissioning requirements (e.g., air pressure
testing the enclosure).
• Examine the water vapor dynamics of sections,
considering the design interior temperature and
relative humidity and the exterior climate for
condensation potential and for drying potential.
• Review ice dam potential in sections and roof
plans—air barrier, insulation level, roof venting,
drainage of snowmelt—where buildings are prone to
ice dams.
• Review the location of plumbing lines and chilled
water lines; check cold water and chilled water
lines for vapor barrier and insulation details; review
plumbing system commissioning and testing
requirements (e.g., pressure testing, start-up, owner
training).
• Review enclosure commissioning requirements.
• Review mechanical systems for:
• Indoor humidity control.
• Pipe and duct insulation and vapor control.
• Air pressure relationship requirements (e.g.,
accidental depressurization of air-conditioned
buildings, rooms or cavities in hot humid or
mixed humid climates; accidental pressurization
of buildings in cold climates).
• Location of air conditioning equipment within
thermal and air enclosures, drain pan slope
and positive drainage, insulation specifications,
adequate room around equipment for proper
installation of drains, and access panels.
• Mold-resistant materials in custodial closets,
bathrooms, toilets and other areas that will get
wet.
• Review mechanical system commissioning and
testing requirements (e.g., test and balance, duct
tightness testing, start-up and operator training).
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• Review moisture content test procedures before
installing or closing in porous materials (e.g.,
concrete).
• Present concerns, cautions and alternatives to the
owner and design team for discussion and final
disposition.
Guidance 2: Formalize the results of the discussions
and decisions made under Guidance 1 into changes
in the construction documents, shop drawings and
submittals.
Guidance 3: Schedule required inspection and testing
of moisture control elements (who, when, results
and remedies) so these activities can be completed
while moisture control details are exposed and can be
inspected.
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Verification of Pre-Construction Planning
Written meeting notes, modified construction
documents, plans for controlling moisture problems
during construction, planned emergency responses to
moisture problems during construction, and lists of
the parties responsible for installation, supervision,
inspection, and testing of moisture control design
elements provide verification of the process followed
and the decisions made.
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Site Drainage Construction
Issue
Improper site drainage can cause water from rain and
snowmelt to damage the building and its components
during and after construction. Mistakes made in
constructing drainage systems can be difficult and
expensive to fix if they are discovered after structures
are in place. Repeated flooding caused by poorly
constructed drainage systems can lead to moisture
damage, high insurance costs and increased liability
for building owners.
Site Drainage Goal 1: Water from rain and snowmelt
does not damage the building or its components
during construction.
Site Drainage Goal 2: Water from rain and snowmelt
does not damage the building or its contents after
construction.
Guidance
Site Drainage Goal 1: Water from rain and snowmelt
does not damage the building or its components
during construction.
Guidance 1: Comply with National Pollutant
Discharge Elimination System (NPDES) requirements
for construction, as implemented by the relevant
authority: U.S. EPA, state government or local
government.20 Determine whether there are
applicable state or local erosion, sediment control
and storm water management requirements.
Obtain local erosion, sediment control and storm
water management permits, as necessary, prior to
construction.
Guidance 2: Comply with design requirements for
maintaining water management during construction.
If design requirements are not provided, comply with
the following recommended minimum.
Minimize potential for runoff:
• Avoid clearing or grading stream buffers; forest
conservation areas; wetlands, springs and seeps;
soils highly susceptible to erosion; steep slopes;
environmental features; and runoff infiltration
areas.
• Group construction activities into phases to limit
soil exposure. Limit activities to the current phase
to decrease the time soil is exposed.
• Begin immediate efforts to stabilize exposed soils.
While the long-term goal is to establish permanently
stabilized soils, mulching, hydro-seeding or erosion
control matting may provide short-term protection.
• Avoid cuts and grading of steep slopes—greater
than 15 percent—wherever possible. If a steep
slope exists, diversions or a slope drain should be
used so all water flowing onto the slope is directed
away from the site to approved disposal areas.
• Train construction staff in storm water management
practices.
• Ensure positive drainage principles are met so water
drains from the site and away from the structure:
• Make certain water is moved away from the
building.
• Ensure water is not allowed to pond at low points
or in low areas, unless planned for.
• Make sure obstructions around the building and
site (e.g., dirt and gravel stockpiles, silt fencing)
do not cause water to back up into the building.
• Institute storm water management supervisory
roles and responsibilities by clearly describing
each contractor's responsibilities. Specify who will
inspect the features and how often.21
Site Drainage Goal 2: Water from rain and snowmelt
does not damage the building or its contents after
construction.
20 See http://cfpub.epa.gov/npdes/stormwater/authorizationstatus.cfm to determine whether EPA or your state is the relevant authority. See http://cfpub.epa.gov/npdes/stormwater/
const.cfm for the federal requirements. Accessed November 6, 2013.
21 For more information see http://cfpub.epa.gov/npdes/stormwater/menuofbmps/ index.cfm?action=min measure&min measure id=4. Accessed November 6, 2013.
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Guidance 1: Identify the water control elements
of the site design, such as finish grading and
sloping requirements, and the infiltration, retention
or detention controls. Work with the design team
to interpret and modify the drainage systems if
necessary.
Guidance 2: Ensure drainage systems are installed or
constructed as specified in the construction document
by supervising, inspecting and documenting
construction and installation of the site water control
elements. Examples include:
• Determining finished grade slope around the
building foundation by measuring the change in
height over distance.
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• Documenting grades and slopes for drainage
systems.
Guidance 3: Ensure all temporary water control
systems, such as silt fences, have been removed.
Verification of Site Drainage Construction
Create and use inspection checklists to document
construction and installation. The material in this
chapter can be helpful in identifying items to include
in such checklists.
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Foundation Construction
Issue
As the interface between a building and the
supporting soil, most foundation materials can
tolerate wet conditions for long periods of time
without deteriorating. However, the foundation must
be dry enough to permit the installation of damp-proof
coatings and materials used to form the insulation,
air barrier, vapor control and finish portions of the
foundation walls and floors. Failure to properly
construct a foundation can lead to problems that
are extremely difficult and expensive to fix once a
building is constructed.
Foundation Construction Goal 1: Keep foundation
assembly materials dry during construction.
Foundation Construction Goal 2: Construct
foundations to effectively implement the moisture
control systems in the design drawings and
specifications.
Foundation Construction Goal 3: Prepare operation
and maintenance materials regarding continued
effective moisture protection for foundations.
Guidance
Foundation Construction Goal 1: Keep foundation
assembly materials dry during construction.
Guidance 1: Implement the moisture control plan for
the construction phase, which should cover:
• Site drainage to control water in foundations during
construction.
• Response strategies for water problems that occur
during construction (e.g., have pumps available for
emergency response to heavy rains).
• Drying concrete and masonry walls and slabs before
installing interior wall insulation, interior gypsum
board wall covering and interior slab finishes.
• Preventing high-humidity conditions when crawl
spaces are enclosed by the overhead floor deck by:
• Sloping the earth in the crawl space to direct
water to a disposal location; installing a vapor
barrier over the earthen floor as soon as possible.
NOTE: If the crawl space has a concrete slab, the
vapor barrier will be part of the slab detailing.
• Monitoring the relative humidity to determine
whether dehumidification is needed; controlling
humidity in the crawl space to less than 65
percent RH using ventilation, if outdoor air dew
points are lower than 55°F, or with dehumidifiers.
• Designate someone to conduct concrete moisture
content or water vapor emission tests. Document
tests, results and remedies. Appendix C contains
an overview of testing the moisture content of
materials during construction.
Foundation Construction Goal 2: Construct
foundations to effectively implement the moisture
control systems in the design drawings and
specifications.
Guidance 1: Install foundation rainwater control,
insulation, air barrier and water vapor control in
accordance with construction documents. Implement
quality assurance program for:
• Exterior drainage and foundation wall damp-proof
coatings.
• Capillary breaks at footings and at the top of the
foundation wall.
• Insulation, air barrier and water vapor control.
• Air barrier and thermal insulation systems.
Foundation Construction Goal 3: Prepare operation
and maintenance materials regarding continued
effective moisture protection for foundations.
Guidance 1: Provide—or direct contractors,
subcontractors or manufacturers to provide—
operation and maintenance information required to
maintain moisture control elements of the foundations
including:
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• Signs of foundation drainage or damp-proofing
failure.
• Frequency of inspection.
• Method of repairing problems.
Verification of Foundation Construction
• Document quality assurance programs for the
installation of the hygrothermal control elements
of the enclosure. Document inspection quality
assurance testing and functional tests with field
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log books, test results and photographs. The
parties identified in the construction documents
or contracts should conduct testing as required
by the design or for internal quality assurance.
Archive the installation documentation, checklists,
photographs, log books and test results. Provide
required incidental labor, materials and equipment
to support third-party testing.
Develop written operations and maintenance
information, as required by contract.
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Wall Construction
Issue
Care must be taken during wall construction to
keep moisture-sensitive construction materials dry.
Moisture-sensitive wall materials that get wet during
construction may grow mold, corrode or deteriorate.
Walls must be constructed according to design
specifications to incorporate moisture and mold-
prevention measures.
Goals
Wall Construction Goal 1:
during construction.
Keep wall materials dry
Wall Construction Goal 2: Construct walls to
effectively implement moisture control systems in the
design drawings and specifications.
Wall Construction Goal 3: Prepare operation and
maintenance materials regarding continued effective
moisture protection for walls.
Guidance
Wall Construction Goal 1:
during construction.
Keep wall materials dry
Guidance 1: Take the steps developed in the
moisture control plan to ensure that materials meant
to remain dry, stay dry. Examine and reject materials
that arrive contaminated with mold. Store materials in
a clean, dry area protected from water (e.g., covered
and raised on pallets). Test the moisture content of
porous materials (e.g., those that can easily store
a great deal of liquid water) before closing them in
cavities or applying adhesives or finishes to them.
Guidance 2: Document moisture control efforts
undertaken during construction.
Wall Construction Goal 2: Construct walls to
effectively implement moisture control systems in the
design drawings and specifications.
• Guidance 1: Install moisture control elements
designed to meet the criteria specified in the
construction documents. Implement quality
assurance programs for the hygrothermal control
systems. Provide required incidental labor,
materials and equipment to support third-party
testing.
Inspect and verify moisture, air and heat flow control
details at these vulnerable locations:
• Cladding.
• Flashing above and below windows, doors and
intake and exhaust openings.
• Through-flashing details where a lower story roof,
balcony or deck intersects upper story walls.
• Building drain planes: weather-resistant-barriers,
felt-paper and spray-applied membranes.
• Insulation layer: Inspect the insulation layer for
continuity.
• Air barrier: Air seal and insulate wall and ceiling
areas that will be made inaccessible by interior
framing or fixtures. These areas include:
• Staircases, bathtubs, showers and cabinets
installed against exterior walls.
• Soffits beneath insulated ceilings, where interior
walls meet exterior walls.
• Areas around elevator and stair shafts.
• Air seal and insulate around windows and doors
before applying interior finishes.
• Plan air-sealing activities (e.g., caulking and
foaming) so they can be performed and inspected
easily and efficiently.
• Sequence delivery and installation of materials so
the critical elements of moisture protection can be
installed readily. For example, in a wall constructed
with a brick veneer/foam board insulation/spray-
applied membrane drain plane-air barrier/concrete
masonry wall, the membrane must be applied
before the foam board, and the foam board applied
before the brick veneer is installed. All these
materials must be on site and subcontractors must
be scheduled, or else a wall or portions of a wall
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may end up without the spray-applied membrane or
foam insulation behind the brick veneer.
Wall Construction Goal 3: Prepare operation and
maintenance materials regarding continued effective
moisture protection for walls.
Guidance 1: Provide or direct contractors,
subcontractors or manufacturers to provide operation
and maintenance information required to maintain
moisture control elements of the wall assemblies
including:
• Identifying signs of cladding failure.
• Inspection frequency.
• Method of repairing problems.
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Verification of Wall Construction
• Document quality assurance programs for the
installation of the hygrothermal control elements
of the enclosure. Document inspection quality
assurance testing and functional tests with field
log books, test results and photographs. The
parties identified in the construction documents
or contracts should conduct testing as required
by the design or for internal quality assurance.
Archive the installation documentation, checklists,
photographs, log books and test results.
• Develop written operations and maintenance
information, as required by contract.
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Roof and Ceiling Assembly Construction
Issue
Construct roof assemblies according to design
specifications that incorporate moisture- and mold-
prevention measures. Take care to keep moisture-
sensitive materials dry during construction. Moisture-
sensitive roof assembly materials that get wet during
construction may grow mold, corrode or deteriorate.
Goals
Roof Construction Goal 1: Keep roof assembly
materials dry during construction.
Roof Construction Goal 2: Construct roof assemblies
to effectively implement the moisture control systems
in the design drawings and specifications.
Roof Construction Goal 3: Prepare operation and
maintenance materials concerning continued effective
moisture protection for roof assemblies.
Guidance
Roof Construction Goal 1: Keep roof assembly
materials dry during construction.
Guidance 1: Follow the steps in the moisture control
plan to ensure that materials meant to remain dry,
stay dry. Examine and reject materials that arrive
contaminated with mold. Store materials in a clean,
dry area protected from water (e.g., covered and
raised on pallets). Test the moisture content of porous
materials (e.g., those that can easily store a great
deal of liquid water) before closing them in cavities or
applying adhesives or finishes to them.
Roof Construction Goal 2: Construct roof assemblies
to effectively implement the moisture control systems
in the design drawings and specifications.
• Guidance 1: Properly install the moisture control
elements designed to meet the criteria specified
in the construction documents. Implement
quality assurance programs for the hygrothermal
control systems. Provide required incidental labor,
materials and equipment to support third-party
testing.
• Inspect and verify details to control moisture, air
flow and heat flow at these vulnerable locations:
• Roofing — slope, installation.
• Flashing at roof edges, gutters, roof drains,
valleys, chimneys, dormers, skylights, equipment
curbs, pipe penetrations, structural support for
railing, signs, fences and screens.
• Through-flashing details where a lower story roof
intersects upper story walls.
• Roofing paper, peel-and-stick bituminous
membranes.
• Insulation layer — inspect for continuity.
• Soffit and roof peak ventilation openings, air
sealing and insulation details for vented roofs
that pitch to eaves.
• Air barrier:
• Air seal the joints between materials that form
the air barrier (e.g., foam board, gypsum board
thermal barrier and concrete plank or poured
concrete roof deck). NOTE: Fluted metal decks
are difficult to use as an air barrier and require
special detailing in order to be used as one.
Air seal between the roof air barrier material
and the wall air barrier material.
• Air seal and insulate the edge of fluted
metal decks, parapet wall, equipment curbs,
skylights, gaps around elevator shafts and other
areas that will be made inaccessible by interior
framing, equipment hung from ceilings, pipes,
ducts and ceilings.
Plan air-sealing activities (e.g., caulking
and foaming) so they can be performed and
inspected easily and efficiently.
• Sequence the delivery and installation of
materials so the critical elements of moisture
protection can be readily installed. For
example, if the air barrier in a low-slope roof
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system is to be made using two layers of
foam board sheets with the joints staggered
and taped, it is critical that the correct tape
is on hand when the foam board is being
placed.
• Plan air-sealing efforts (e.g., caulking,
foaming and membrane installation) so they
can be accomplished and inspected easily
and efficiently.
Roof Construction Goal 3: Prepare operation and
maintenance materials concerning continued effective
moisture protection for roof assemblies.
Guidance 1: Provide or direct contractors,
subcontractors or manufacturers to provide operation
and maintenance information required to maintain
moisture control elements of the roof assemblies. The
builder's responsibilities should be spelled out in the
contracts and may include:
• Signs of roofing and roof penetration failure.
• Frequency of inspection.
• Method of repairing problems.
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Verification of Roof and Ceiling Assembly
Construction
• Document quality assurance programs for the
installation of the hygrothermal control elements
of the enclosure. Document inspections, quality
assurance testing and functional tests with field
log books, test results and photographs. The
parties identified in the construction documents
or contracts should conduct testing as required
by the design or for internal quality assurance.
Archive the installation documentation, checklists,
photographs, log books and test results. Provide
required incidental labor, materials and equipment
to support third-party testing.
• Develop written operations and maintenance
information, as required by contract.
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Plumbing System Installation
Issue
Plumbing-related water problems can occur as
the result of leaks and other accidental releases
of plumbing water from charged systems during
construction. Delayed problems can occur because of
errors in installing water supply lines, drain lines and
appliances.
Goals
Plumbing System Installation Goal 1: Install water
supply lines, drain lines and appliances to prevent
pre- and post-occupancy leaks and to facilitate the
discovery and repair of problems during construction
and post-construction occupancy.
Plumbing System Installation Goal 2: Install pipe
insulation and water vapor controls on cold water lines
and appliances.
Plumbing System Installation Goal 3: Install materials
that will minimize mold growth in unavoidably wet
areas.
Plumbing System Installation Goal 4: Prepare
operation and maintenance materials concerning
continued effective moisture protection for plumbing
systems.
Guidance
Plumbing System Installation Goal 1: Install water
supply lines, drain lines and appliances to prevent
pre- and post-occupancy leaks and to facilitate the
discovery and repair of problems during construction
and post-construction occupancy.
Guidance 1: Review construction documents and
prepare shop drawings and submittals that ensure
pipes are not located in exterior walls and ceilings
that contain porous insulation. NOTE: If pipes
must be located in an exterior wall or ceiling,
install a continuous, air-sealed layer of closed-cell
foam insulation between the pipe and the exterior
sheathing, curtain wall or roof deck. Schedule
installation so testing can be done before piping and
components are closed in. This may require separately
testing sub-sections of the plumbing systems.
Guidance 2: Follow construction documents when
installing plumbing systems.
Guidance 3: Install plumbing so that it is easy to
access and repair. Orient valves, pipes and other key
components in locations where leaks will be easily
noticed and that are most accessible for inspection
and repair. Where appropriate, label key components
or affix instructions and diagrams to aid others
in accessing and repairing plumbing. These aids
may include diagrams of flow directions and valve
locations and functions.
Plumbing System Installation Goal 2: Install pipe
insulation and water vapor controls on cold water lines
and appliances.
Guidance 1: Install plumbing system insulation and
water vapor controls in accordance with construction
documents. Protect porous insulating and paper-
based water-vapor-control materials from rainwater.
Plumbing System Installation Goal 3: Install materials
that will minimize mold growth in unavoidably wet
areas.
Guidance 1: Install moisture-and mold-resistant
materials in unavoidably wet spaces in accordance
with design documents.
Plumbing System Installation Goal 4: Prepare
operation and maintenance materials concerning
continued effective moisture protection for plumbing
systems.
Guidance 1: Provide or direct contractors,
subcontractors or manufacturers to provide operation
and maintenance information required to maintain
plumbing systems, appliances, fixtures and moisture-
resistant materials used in wet rooms. Among the
topics that should be covered are potable water,
bathing and wash water, waste water, hydronic heating
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systems, chilled water cooling systems, spa and pool
systems, washrooms, custodial closets and locker
rooms. The builder's responsibilities for training
materials should be spelled out in the contracts and
may include:
• Signs of plumbing system failure and hydronic
heating and cooling system failure.
• Frequency of inspection.
• Method of repairing problems.
Verification of Plumbing System Installation
• Inspect installation of plumbing system insulation
and water vapor controls. Document inspections
with field log books and photographs. Quality
assurance is crucial to ensure complete coverage
with insulation and water vapor control on joints
and seams and where pipes interface with other
equipment (e.g., pumps, valves, tanks). Document
the inspections with signed checklists, log books
and photographs.
• Inspect plumbing for acceptability of installation
and materials, for compliance with design
documents, and for access to lines before
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performing tests. Use installation checklists and
provide signed documentation of all test results.
Pressure test water supply lines while they are
exposed for inspection (i.e., before they are
enclosed or insulated). At a minimum, pressure
test water supply lines according to section 312.5
of the International Plumbing Code or the relevant
sections of applicable local codes.
Test the drain and vent side of the plumbing system
when all lines are exposed for easy inspection and
repair in accordance with design specifications
and as required by relevant building codes. At a
minimum, gravity test the drain and vent side of
the system according to sections 312.2, 312.3
and 312.4 of the International Plumbing Code or
relevant sections of other applicable local codes.
Inspect plumbing and surrounding fixtures located
in unavoidably wet areas to ensure the use of
moisture- and mold-resistant materials. Document
the inspections with signed checklists, log books
and photographs.
Develop written operations and maintenance
information, as required by contract.
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HVAC System Installation
Issue
Improper installation of HVAC systems can create
condensation and moisture-control problems.
Examples include:
• Inadequate dehumidification and pressurization
performance of the HVAC system, which can lead to
occupant discomfort and mold growth.
• Condensation on HVAC equipment components,
which can damage components, increase
maintenance costs, decrease component and
system lifespan and lead to mold growth.
• Inadequate drainage of collected condensate or
other water, which can result in moisture damage to
the building and its contents and to mold growth.
• Inadequate ventilation of indoor humidity sources
(e.g., showers, bathrooms, spas and kitchens),
which can lead to mold growth and deterioration.
HVAC System Installation Goal 1: Keep HVAC
equipment and materials dry during construction and
provide temperature and humidity control as required
during the close-in phase of construction.
HVAC System Installation Goal 2: Install HVAC
systems to effectively implement moisture control as
specified in the design drawings and specifications.
HVAC System Installation Goal 3: Prepare operation
and maintenance materials for continued performance
of HVAC system moisture control.
Guidance
HVAC System Installation Goal 1: Keep HVAC
equipment and materials dry during construction and
provide temperature and humidity control as required
during the close-in phase of construction.
Guidance 1: Plan when and how the HVAC
equipment will be energized and used during
construction. Plan the required inspection and
testing—who, when, results and remedies—so these
activities can be completed before the plumbing,
ductwork and other components are closed in. In
addition, plan the installation sequence so testing can
be done before system components are closed in.
Guidance 2: Take steps to ensure that equipment
and materials meant to remain dry, stay dry. Prepare a
list of equipment and materials that must be kept dry,
actions planned to protect them during construction,
and responses if they get wet.
• Schedule the delivery of HVAC system components
so they can be protected immediately from
rainwater and plumbing leaks. Uninsulated,
galvanized ductwork can tolerate some wetting,
but air handlers, insulated components, electronic
components, chillers, compressors and controls all
need positive protection from weather and moisture.
• Schedule the installation of HVAC components for
when the building or a portion of the building has
been made weather-tight.
• Inspect insulated ductwork and components for
moisture damage and mold growth when they are
received and before they are installed.
Guidance 3: Control temperature and humidity during
the close-in phase of construction. Plan the transition
from unconditioned interior space to conditioned
interior space in conjunction with the designers and
owners:
• Identify situations and processes that will require
humidity control for installation and drying of
materials. For example, concrete slabs may need
to be dried before finish flooring goes down; below-
grade concrete walls may need to be dry before
interior insulation and finishes are installed;
and temperature and humidity may need to be
controlled before painting or varnishing takes place.
• Use the permanent HVAC systems to provide
required conditioning, if possible. Follow the
guidance in Duct Cleanliness for New Construction
Guidelines (SMACNA 2010).
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• If the permanent HVAC equipment cannot be
used, plan for temporary heating, cooling and
dehumidification. NOTE: Non-vented combustion
devices add a great deal of water vapor as well as
heat to a space and cannot be used to dehumidify.
HVAC System Installation Goal 2: Install HVAC
systems to effectively implement moisture control
systems in the design drawings and specifications.
Implement quality assurance programs for the
hygrothermal control systems. Provide required
incidental labor, materials and equipment to support
third-party testing.
Guidance 1: Plan required inspections—who, when,
results and remedies—so they can be completed
before HVAC components, particularly the distribution
systems, are closed in.
Guidance 2: Install HVAC systems, condensation
collection and drainage systems, system insulation,
air barriers and water vapor controls in accordance
with construction documents.
Inspect the installation of:
• Drain pans, drain pan outlets, traps and disposal.
• HVAC ductwork including seams and sealing prior
to the installation of duct insulation.
• Insulation and vapor retarders on exposed surfaces
that are expected to be below the dew point of
ambient air (e.g., chilled water lines, refrigerant
lines, air conditioning air handlers and chillers),
especially at transitions (e.g., penetrations through
walls, floors and ceilings; support clamps; valves;
dampers; pumps; blowers; and gauges).
• Access panels to allow inspection and maintenance
of HVAC components (e.g., air handlers, filters,
coils, drain pans and the supply duct near the air
handler).
• Exhaust ventilation systems for duct sealing,
insulation and vapor control.
HVAC System Installation Goal 3: Prepare operation
and maintenance materials for continued performance
of HVAC system moisture control.
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Guidance 1: Provide or direct contractors,
subcontractors or manufacturers to provide operation
and maintenance information required to maintain
moisture control elements of the HVAC system
components. The builder's responsibilities should be
spelled out in the contracts and may include:
• Requirements for filters, coils, condensate drainage
systems, ductwork, piping, insulation and vapor
barriers, pumps, valves, fans, belts, lubrication and
controls.
• Frequency of inspection.
• Methods of repairing problems.
Verification of HVAC System Installation
• Write a plan for moisture control in regard to
HVAC equipment and dedicated drying equipment
during construction. Use photographs, log books
and written reports to document moisture-control
activities, water problems and responses to water
problems.
• Parties identified in the construction documents or
contracts should perform tests as required by the
design or for internal quality assurance. These tests
include:
• Creating air pressure difference maps for each
mode of operation.
• Testing for air duct tightness target—before
installation of ductwork insulation.
• Testing drainage of condensate drain pans in air
conditioners.
• Testing, adjusting and balancing the HVAC
system as designed.
• Performing other tests and inspections required
by the commissioning plan.
• The tests and inspections should be documented
with field log books, moisture content and vapor
emission tests, and photographs.
• Develop written operations and maintenance
information, as required by contract.
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REFERENCES
American Society for Testing and Materials. 2003. Standard test
method for determining air leakage rate by fan pressurization.
E779-03. Pennsylvania. American Society for Testing and
Materials.
American Society for Testing and Materials. 1996. Standard
test methods for determining airtightness of buildings using
an orifice blower door. E1827-96. Pennsylvania. American
Society for Testing and Materials.
American Society of Heating, Refrigerating and Air-Conditioning
Engineers. 2004. ASHRAE Handbook of Fundamentals.
Ventilation for Acceptable Indoor Air Quality. Standard 62.1.
Atlanta, GA: American Society of Heating, Refrigerating and
Air-Conditioning Engineers.
(The ASHRAE ventilation standard provides information
needed to determine ventilation rates for differing
occupancies plus a number of design, operation and
maintenance requirements to ensure proper performance
of ventilation equipment. Section 6.2.8 specifically deals
with exhaust ventilation. Standard 62.1 applies to many
situations.)
International Code Council. 2003. ICC International Plumbing
Code. Sections 312.2 -312.5. Washington, DC: International
Code Council.
(Sections 312.2 to 312.5 of these codes specify a gravity
test of the drain and vent side of plumbing systems.)
Mold Litigation Task Force of the Associated General Contractors
of America, Inc. 2003. Managing the risk of mold in the
construction of buildings. CONSTRUCTOR, http://www.agc.
org/galleries/conrm/may03 mold.pdf. Accessed November 6,
2013.
United States Environmental Protection Agency. 2005.
Authorization Status for EPA's Stormwater Construction and
Industrial Programs: States, Indian Country and Territories
Where EPA's Construction General Permit (CGP) and Multi-
Sector General Permit (MSGP) Apply. Washington, DC:
United States Environmental Protection Agency. http://cfpub.
epa.gov/npdes/stormwater/authorizationstatus.cfm. Accessed
November 6, 2013.
(This website outlines the relevant authority—U.S.
EPA, state, or local government—for compliance with
National Pollutant Discharge Elimination System [NPDES]
requirements for construction in a given state.)
United States Environmental Protection Agency. 2006.
Construction Site Stormwater Runoff Control. Washington,
DC: United States Environmental Protection Agency, http://
cfpub.epa.gov/npdes/stormwater/menuofbmps/index.
cfm?action=min measure&min measure id=4. Accessed
November 6, 2013.
(This website outlines best management practices [BMPs] for
controlling storm water runoff at construction sites.)
United States Environmental Protection Agency. 2006.
Stormwater Discharges from Construction Activities:
Overview. Washington, DC: http://cfpub.epa.gov/npdes/
stormwater/const.cfm. Accessed November 6, 2013.
(This website outlines the federal requirements for complying
with National Pollutant Discharge Elimination System
[NPDES] requirements for construction.)
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Chapter 4: Operating and Maintaining Moisture-Controlled
Environments
INTRODUCTION
The people who keep buildings working—the HVAC
mechanics, carpenters, plumbers, electricians,
engineers, custodians and managers—inherit the
good points and the bad points of the design and
construction.
This chapter consists of the following sections:
• Site Drainage Maintenance.
• Foundation Maintenance.
• Wall Maintenance.
• Roof and Ceiling Assembly Maintenance.
• Plumbing System Operation and Maintenance.
• HVAC System Operation and Maintenance.
Each section is concerned with regular inspection; the
cleaning, lubrication, repair or replacement that may
result from the inspection; and the documenting of
inspections and responses. Several of these sections
require the development of specific operation and
maintenance plans. The section-specific plans can be
assembled into a master moisture-control plan.
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Table 4-1 Troubleshooting Common Indoor Water Problems
SYMPTOMS MOISTURE PROBLEM
Mold growth
Peeling paint
Wood decay
Corrosion
Plumbing leaks
and spills
Water travels to
materials that
cannot tolerate
wetting
Leaks in the building
enclosure due to problems
with rain and groundwater
controls
Insufficient
dehumidification by HVAC
system'31
Condensation on dirty
surfaces inside HVAC
systems
Wet materials enclosed in
building assemblies
Leaks in the building
enclosure due to problems
with rain and groundwater
controls
Improper design
Improper installation
during construction
Improper operations and
maintenance practice
Capillary action (water
wicks through porous
building materials such as
concrete or wood)
POTENTIAL CAUSES
DESIGN I CONSTRUCTION
Missing or poorly designed Missing flashing or
details building wrap
Incorrect sloping
Damaged sub-grade
drainage
Air conditioning equipment Failure to properly wire
oversized humidity sensors
Air conditioning equipment
not designed for sufficient
dehumidification at design
and part load
Poor condensate drain
design
Air handler inside surfaces
insulated or hard to clean
Moisture-sensitive
materials shown touching
porous materials that are
likely to get wet
No values for moisture
content or emission given
in the specifications
Missing or poorly designed
details
Locating water lines in
a space that reaches
freezing temperatures
Poorly designed shower
pan
Moisture barrier omitted
from building design
Drainage layer beneath
slab omitted from building
design
Flooring placed on slab
while it is too damp
Vapor emission tests on
slab may not have been
conducted
Missing flashing or
building wrap
Incorrect sloping
Damaged sub-grade
drainage
Defective pipe joining
Accidental penetration
of pipe by one or more
dry wall screws
Moisture barrier
not installed during
construction
Drainage barrier
not installed during
construction
Failure to identify and
repair settled grading near
foundation
Damaged flashing on
rooftop air handler curb
Missing shingles
Chilled-water temperature
set-point too warm
Economizer set-point that
allows introduction of
humid outdoor air
Continuously running
air handler regardless of
cooling demand
Failure to clean HVAC
system cooling coils
Clogged drain pan
Failure to seal penetrations
during maintenance, repair
or installation of new
equipment
Failure to identify and
repair settled grading near
foundation
Damaged flashing on
rooftop air handler curb
Missing shingles
Failure to inspect
plumbing and repair
problems
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Table 4-1 Continued
SYMPTOMS MOISTURE PROBLEM
Condensation
Delamination
Improper curing
Warm, moist outside air
enters enclosure through
cracks and holes during
warm, humid weather*1
Warm, moist indoor air
leaves enclosure through
cracks and holes during
cold weather*1
Vapor barriers installed
improperly in exterior walls
Non-vented or poorly
vented moisture sources
(e.g., swimming pools,
spas, aquariums,
dishwashers, combustion
devices, kitchens and
showers)
Wet materials enclosed in
building assemblies
DESIGN
Air barrier omitted from
building design
Building design did not
call for positive pressure
operation of the building
Air barrier omitted from
building design
Air barrier detailed for attic
assembly is impossible to
install
Building designed to
operate at positive
pressure in an extremely
cold climate
Vapor barrier specified
on both sides of a wall
assembly
Vapor barrier specified on
interior surfaces in hot,
humid climates
HVAC system design
omitted exhaust ventilation
for moisture sources
Insufficient exhaust
ventilation specified in
HVAC system design
Moisture-sensitive
materials shown touching
porous materials that are
likely to get wet
No values for moisture
content or emission given
in the specifications
POTENTIAL CAUSES
CONSTRUCTION
Controls poorly
implemented during
construction (e.g.,
concrete block left out of a
soffit area)
Air barrier installed poorly
Holes cut in well-installed
air barrier to permit
passage of wire, conduit
or ducts
Unintentional vapor
barriers such as vinyl
wall covering, mirrors or
blackboards installed on
inside of exterior walls in
hot, humid climate (can
create a vapor barrier on
the cold side of the wall)
Exhaust duct leaks
Poor balancing on
multiple-inlet exhaust
systems
Exhaust dampers closed
Flooring placed on slab
while it is too damp
Vapor emission tests on
slab may not have been
conducted
Failure to reseal access
holes cut through an
assembly
Changes in HVAC
system operations cause
building to run at positive
pressurization
Vinyl wall covering, mirrors
or blackboards added on
inside of exterior walls in
hot, humid climate (can
create a vapor barrier on
the cold side of the wall)
Broken belt in a fan
Clogged exhaust grilles or
ducts
(a)This problem may also occur during the bidding, contract negotiation or value engineering phases of a project when, for example, different air
conditioning equipment is substituted for the equipment called for in the design.
(b)The air leak may be due to holes in the enclosure made by occupants, contractors or maintenance personnel, or it may have been caused by changes
in the control sequence of outdoor air and exhaust systems.
(c)The problem of indoor condensation can be greatly aggravated if there are large sources of humidity inside the building.
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Site Drainage Maintenance
Issue
Failure to maintain drainage systems can lead to
unexpected flooding during events of heavy rain or
snowmelt, causing extensive property damage.
Site Drainage Goal 1: Facility maintenance systems
and preventive maintenance plans effectively address
site drainage.
Site Drainage Goal 2: All runoff from parking lots,
sidewalks and other impermeable or low-permeability
surfaces is diverted to a designed drainage system.
Site Drainage Goal 3: Future site development or
building modifications or additions do not interfere
with existing site drainage systems.
Guidance
Site Drainage Goal 1: Facility maintenance systems
and preventive maintenance plans effectively address
site drainage.
Guidance 1: Develop and implement a preventive
maintenance plan for landscaping and engineered
structures. The purpose of the plan is to ensure that
all drainage systems serve the purpose for which they
were designed. The plan should include:
• An introduction and general information.
• Name and contact information for persons
responsible for operation and maintenance.
• A narrative overview describing the site and the
theory of operation of the drainage systems.
• A definition of the inspection requirements for each
drainage feature.
• Inspection frequency should be specified (See
Appendix C).
• What to look for.
• Definitions of the maintenance activities necessary
to keep each drainage feature operating as
intended. Examples include:
• Cleaning debris from diversion systems to prevent
water flow from being obstructed.
• Removing sediment from the bottom of swales
(See Appendix F for sample checklists).
• Maintenance agreements and contacts. If
contractors are responsible for some or all of the
maintenance requirements, list the contractors'
names, contact information and responsibilities.
Guidance 2: Develop and implement a preventive
maintenance plan to maintain parking lots, sidewalks
and other impermeable surfaces.
• Read, understand and comply with the designer's
inspection and maintenance requirements or best
management practices for impervious surfaces.
• Develop an inspection checklist and logbook (See
Appendix F for sample checklists).
Site Drainage Goal 2: All runoff from parking lots,
sidewalks and other impermeable or low-permeability
surfaces is diverted to a designed drainage system.
Guidance 1: Ensure that actions such as plowing
snow from sidewalks and parking lots do not obstruct
drainage or pile snow against the building.
Guidance 2: Inform all lawn-care subcontractors and
landscapers about drainage systems on the site so
their work does not interfere with the drainage. Have
them watch for drainage problems as they work.
Site Drainage Goal 3: Future site development or
building modifications or additions do not interfere
with existing site drainage systems.
Guidance 1: Make sure changes such as additional
parking areas (even dirt parking areas) do not
overburden existing system capacity or redirect runoff
into buildings. Even small projects such as adding
planters or walkways can affect infiltration capacity
and redirect runoff.
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Guidance 2: Persons charged with maintaining Verification of Site Drainage Maintenance
drainage systems should participate in the design of
any development or building modification. KeeP and maintain records of all inspections,
including completed checklists. Include photographs
and test reports so that changes in conditions can be
verified.
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Foundation Maintenance
Issue
Rainwater and snowmelt can cause unwanted
moisture intrusion through the foundation of a
building. Foundations are vulnerable to chronic
moisture problems from rainwater, ground water,
plumbing leaks, and condensation. Regular
inspection, particularly of areas not ordinarily
occupied, is critical to reduce the risk of serious
damage to the foundation and the risk of adverse
health effects to the occupants.
Foundation Drainage Goal 1: Foundation drainage
systems divert water away from the structure.
Guidance
Foundation Drainage Goal 1: Foundation drainage
systems divert all water away from the structure.
Guidance 1: Inspect the exterior of the foundation
and the surrounding landscape.
• Check whether the surrounding landscape diverts
water away from the building envelope. Note any
soil settlement or pooled rainwater.
• Check the condition of roof drain leaders.
• Inspect the foundation for changes in existing
cracks and for new cracks that might indicate water
problems.
• Inspect the intersection and slope of sidewalks,
patios and pavements with the adjoining building
for potential seepage.
• Look for newly sprouted or planted trees near drain
lines. Remove or prune as needed.
• Check exterior plumbing fixtures, hoses and
irrigation lines for leaks.
• Conduct inspections semi-annually and after heavy
rains or rapid melting of snow.
Guidance 2: Inspect the interior of the foundation.
• Inspect the foundation for changes in existing
cracks and for new cracks that might indicate water
problems.
• Check the condition and operation of the sump
crock, drains and pump.
• Look for signs of seepage or wicking (e.g., water
stains, damp materials, efflorescence, peeling
paint or mold growth) on foundation materials and
interior finishes.
• Check for musty odors.
• Look for swollen, warped or moldy wooden
materials.
• Determine the temperature and relative humidity.
Record the date, time and operation of mechanical
systems, the temperature and the relative humidity.
• Look for stained carpet, sheet or vinyl composition
tile (VCT) floors with blisters and for bubbles
indicating adhesive failures as well as adhesives
oozing from joints between tile.
• Look for condensation on pipes, tanks, toilets,
pumps, ducts, walls and floors.
Verification of Foundation Maintenance
• Document inspections and responses using a
checklist and work order system.
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Wall Maintenance
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Issue
Failure to properly inspect and maintain interior
and exterior walls can result in moisture problems
going unnoticed or unrepaired. Unnoticed damage to
walls can lead to a need to repair multiple building
components at high cost and can create health risks
associated with mold growth in the interior of walls.
Goals
Wall Maintenance Goal 1: Create and operate
verification and inspection systems to detect potential
moisture problems before harm is done.
Wall Maintenance Goal 2: Effectively maintain walls
to prevent moisture problems, as intended by the
design.
Guidance
Wall Maintenance Goal 1: Create and operate
verification and inspection systems to detect potential
moisture problems before harm is done.
Guidance 1: Develop inspection checklists and
record-keeping systems.
• Develop a wall assembly manual and logbook.
Include the type of wall, contractor information,
maintenance procedures, a record of inspections
and related items.
• Develop a wall assembly inspection checklist.
Use it as a guide for evaluating masonry units,
flashings and counter flashings, caps and drainage
assemblies.
• Develop elevation drawings to map and locate
problems found during the inspections.
• Develop and keep inspection and repair records
for all exterior walls, including before and after
pictures to document results of maintenance and
repair activities.
Wall Maintenance Goal 2: Effectively maintain walls
to prevent moisture problems, as intended by the
design.
Figure 4-1 Interior Wall Showing Water Damage and
Mold
Guidance 1: Conduct inspections, record the results
and make necessary repairs.
• Inspect walls periodically and after heavy winds and
rains. Conducting inspections during each season is
recommended.
• Check interior walls and ceilings for signs of water
damage or staining (See Figure 4-1).
• Inspect exterior walls and roof overhangs:
• Look for signs of moisture, cracking or
movement.
• Look for cracked, loose or spalled units on brick
masonry walls.
• Inspect joints for deteriorated mortar.
• Look for mold or algae growth.
• Be aware that ivy growing on brick walls can
penetrate voids in mortar and may lead to
moisture penetration.
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• Open weep holes by probing with a wood dowel or • Identify and repair problems before they cause
stiff wire. NOTE: Care must be taken to prevent water damage to walls.
damaging flashing when cleaning weeps. . |ncorporate the resu|ts of each inspection into the
• Inspect caulking and sealants at junctions of the user's manual and logbook.
brickwork and other materials such as windows,
doors and expansion joints. Verification of Wall Maintenance
• Inspect flashings and counter flashings. Look for
loose flashing or missing fasteners, open ends or Incorporate completed inspection forms and
lap joints, unsealed corners, and rusted or corroded completed checklists into the user's manual and
metal. logbook.
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Roof and Ceiling Assembly Maintenance
ISSUE
Roof and ceiling assemblies can deteriorate due to
normal wear, severe weather, building movement,
and improper design, construction and maintenance.
Failure to correct roof and ceiling problems quickly
can cause additional damage to the building envelope
and the interior of the building. Uncorrected roof
and ceiling problems can also cause loss of occupant
productivity, damage to building contents and failure
of structural integrity.
Roof Maintenance Goal 1: Facility maintenance
systems and preventive maintenance plans effectively
address moisture control issues for roof and ceiling
assemblies.
Roof Maintenance Goal 2: Moisture does not
penetrate roof and ceiling assemblies or collect in
exterior elements, except as intended by the design.
Roof Maintenance Goal 1: Facility maintenance
systems and preventive maintenance plans effectively
address moisture control issues for roof and ceiling
assemblies.
Guidance 1: Read, understand and comply with the
manufacturers' or installation contractors' warranty
terms and conditions.
Guidance 2: Develop tools for routine inspection and
maintenance.
• Develop a roof and ceiling assembly inspection
checklist (See Appendix B for a sample). Use it as
a guide for observing and evaluating the roof and its
systems, equipment mounted on the roof, drainage
problems and traffic patterns.
• Develop a roof and ceiling assembly user's manual
and logbook. Include such information as:
• The type of roof, gutter, external downspout
system and internal drain and cover.
• Installation contractor information.
• Roof, ceiling assembly and drainage system
manufacturers.
• Warranty information.
• Record of inspections.
• Prepare a map showing all roof and ceiling
assembly features such as scuttles, HVAC
equipment, drains, gutters, downspouts, scuppers,
vents and roof angle changes. Use this map
to locate items of interest observed during the
inspection. (See Appendix B for a sample map of a
roof and ceiling assembly.)
Roof Maintenance Goal 2: Moisture does not
penetrate roof and ceiling assemblies or collect in
exterior elements, except as intended by the design.
Guidance 1: Inspect the roof and ceiling assemblies to
determine whether they are performing their intended
functions; to identify signs of weakness, deterioration
or hazards; and to identify needed repairs.
Frequency of Inspection
• Inspect semi-annually or in accordance with
manufacturer's requirements and as soon as
possible after heavy winds or rains.
• Conduct special inspections after events such as
construction on the roof or adjacent roofs, rooftop
equipment installation, fire or vandalism.
Prepare for Inspections
• Review, learn and follow roof safety procedures.
• Review past inspection reports, construction
documents and past maintenance and repair reports
before inspecting the roof.
Conduct Inspections
• Use ladders to inspect steep roofs. Ensure all
ladders comply with, and are maintained and
used in accordance with, the Occupational
Safety and Health Administration (OSHA) 29
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CFR Occupational Safety and Health Regulation
requirements.
• Do not rest ladders against gutters. When on the
roof, take care to step on the flat portions of the
panels over structural members and not on side-
laps or standing seams.
• Inspect interior walls and ceilings for signs of water
penetration (i.e., water damage or staining) or
structural distress. If possible, check the underside
of the roof deck. Look for water or insect damage,
deterioration of the deck, rusting, settling or other
physical damage. Inspect the interior surface
of exterior walls and roof overhangs for signs of
moisture, cracking or movement.
• Inspect exterior walls and roof overhangs for signs
of moisture, cracking or movement. Inspect exterior
grounds around buildings for signs of ponding,
which may indicate blockage.
• Inspect the roof covering and edge for continuity.
Look for deterioration, damaged or loose laps and
seams, loose or missing fasteners, rust or corrosion,
physical damage to the roof covering, and the
accumulation of debris and vegetation. Look for soft
roof insulation and cracked, spalled or discolored
walls.
• Inspect for moisture infiltration. Pay attention
to areas where walls or parapets intersect roofs,
around rooftop HVAC units, and around skylights or
other roof penetrations. Check for missing or broken
weather seals on equipment housings and cracked
or missing caulking.
• Inspect flashings at roof-wall intersections and at
curbs. Look for loose flashing or missing fasteners,
open ends or lap joints, unsealed corners and
rusted or corroded metal. If caulk or roofing tar
has been used as a temporary repair, inspect for
cracks. Also inspect flashings around curbs, access
hatches and rooftop equipment. Where deflection is
required, make sure that roof panels and flashings
move independently.
• Inspect hips, ridges and valleys. Look for loose or
missing fasteners, open ends or open lap joints,
damage from foot traffic and corroded metal. In
valleys, check to make sure the roof covering is
secured at the valley edges and that there are no
obstructions blocking water flow.
• Inspect the drainage system. Check gutters and
downspouts for loose or missing fasteners, loose
joints, corrosion and debris. Make sure sealants and
solder are in good condition. Check downspouts,
interior roof drains, scuppers and outlets to ensure
they are not blocked. If possible, shine a flashlight
down each downspout and leader to check for
blockage. If blockage is suspected in a downspout
running through the interior of the building, snake
out the downspout or use a mechanical auger.
Do not use water to try to flush out an interior
downspout suspected of being blocked. If a roof
drain is blocked by ice, do not try to open it by
chipping or breaking the ice. Ensure that all joints
are properly sealed. Inspect masonry weep holes for
signs of dripping.
• Look for ponding or standing water on the roof. Pay
particular attention to areas around scuttles, curbs,
skylights and other features that may impede roof
drainage. Another indication of a failed drainage
system is accumulated debris on the roof. Remove
all litter and debris from the roof surface. Standing
water can damage the gravel and the granule
or liquid coatings on roofs. Once these coatings
are damaged, sunlight can degrade the roofing
membrane. Look in the gutters for mineral granules
from shingles, which may indicate that the shingles
are worn. A small penetration can allow standing
water to seep under the membrane. Deflection
may indicate structural problems that must be
addressed.
• Include non-destructive tests such as infrared
thermography or other appropriate tests if moisture
intrusion is suspected.
• Record and report inspection findings.
• Report immediately any unsafe working conditions
or potential system failures.
Special Considerations for Membrane Roofs
• Pay particular attention to areas between roof
trusses and beams, which are likely spots for roof
deflection.
• Inspect the roof membrane for moisture intrusion.
Pay particular attention to the joints between two
sheets of membrane and to changes in the angle of
the roof:
• Built-up bituminous membrane roofs: Look for
blisters caused by the expansion of air or water
vapor trapped beneath. Also look for cracks in
the membrane, splits, ridges and lifting of the
membrane at the seams.
• Elastomeric membranes: Look for open seams,
shrinkage and backed-out fasteners. Inspect the
roof for damage after windstorms. Pay particular
attention to the membrane surface, roof edge
metal, flashings, gutters and downspouts.
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• Ballasted roof systems: Look for missing or
displaced ballast and insulation boards beneath
the roof membrane.
• Adhered roof systems: Look for loose areas of
the membrane, displaced insulation boards
and tented insulation fasteners and plates. On
mechanically attached roof systems, look for cuts
in the membrane, displaced insulation boards
and tented roof fasteners and plates. Inspect for
loose flashing. Also inspect rooftop HVAC units
for loose or missing sheet metal components.
Special Considerations for Asphalt Shingle Roofs
Pay particular attention to the tops of the vertical
slots between tabs. This area is usually the last to dry.
Moss and lichen growth on asphalt roofs keeps the
roofing materials damp, so use a water hose and
nozzle to remove moss and lichen. Spray from the
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roof facing down the slope to avoid spraying water up
under the shingles.
Guidance 2: Repair as needed to meet or exceed
warranty requirements.
Develop a maintenance work plan to correct deficient
conditions in a timely manner.
Verification of Roof and Ceiling Assembly
Maintenance
• Incorporate the completed checklist and map into
the user's manual and logbook upon completion of
each inspection.
• Keep and maintain records of all inspections,
including the checklist. Include photographs and
test reports so that changes in roof conditions can
be verified.
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Plumbing System Operation and Maintenance
Issue
Improperly maintained plumbing systems can cause
flooding or condensation build-up. Since plumbing
is often located in areas that are not often viewed by
occupants, poor maintenance can lead to unnoticed
mold growth that can damage the building and its
contents, as well as pose health risks to occupants.
Goals
Plumbing Maintenance Goal 1: Plumbing systems
are inspected and maintained to prevent flooding or
condensation.
Guidance
Plumbing Maintenance Goal 1: Plumbing systems
are inspected and maintained to prevent flooding or
condensation.
Guidance 1: Develop a plumbing system inspection
and maintenance plan. The plan should include:
• The name, address and telephone number of the
person or persons responsible for inspection and
maintenance of the plumbing systems.
• Specific preventive and corrective maintenance
requirements, which can be in the form of
checklists. Inspection checklists should be
developed for:
• Water supply and distribution piping, pumps and
valves.
• Water usage equipment such as sinks and
drinking fountains.
• Hot water heaters and storage tanks.
• Fire sprinkler systems, which should be
inspected in accordance with National Fire
Protection Association (NFPA) standards or local
code requirements.
• Building drainage systems such as floor drains,
sumps and pumps.
• Other facility plumbing systems and components
such as pipe insulation.
• A schedule of regular inspections and routine
maintenance tasks.
• Detailed logs of all preventive and corrective
maintenance tasks, including all maintenance-
related work orders.
• Necessary maintenance equipment, tools and
supplies.
• Emergency response actions.
• Procedures and equipment necessary to protect the
safety and health of inspectors and maintenance
workers.
• System component manufacturers' literature and
warranties.
• As-built construction plans.
• Training of maintenance personnel.
Guidance 2: Inspect plumbing systems and
components. Make sure:
• Inspections are performed according to the
timetable in the plumbing system inspection and
maintenance plan.
• Inspection results are logged into the plumbing
system inspection and maintenance plan.
• Work orders are prepared for maintenance
requirements found during the inspections.
Guidance 3: Maintain plumbing systems and
components by performing regularly scheduled
preventive maintenance and unscheduled
maintenance to correct problems discovered during
inspections. Regular maintenance will save money in
the long run.
Verification of Plumbing System Operation and
Maintenance
• Completed inspection checklists.
• Completed maintenance checklists.
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HVAC System Operation and Maintenance
Issue
Failure to adequately maintain HVAC systems can
lead to moisture problems including loss of humidity
control, condensation and overflowing drain pans.
Regularly scheduled inspections and maintenance
can prevent unexpected equipment failure and reduce
the equipment's life-cycle cost. Properly maintaining
HVAC systems helps to ensure occupant comfort and
healthy indoor air quality.
Goals
HVAC Operations and Maintenance Goal 1: Facility
maintenance management systems and preventive
maintenance plans effectively address moisture
control in HVAC systems.
HVAC Operations and Maintenance Goal 2: HVAC
systems are maintained as intended by manufacturer's
specifications and system design to effectively control
moisture.
Guidance
HVAC Operations and Maintenance Goal 1: Facility
maintenance management systems and preventive
maintenance plans effectively address moisture
control in HVAC systems.
Guidance 1: Develop and implement facility
maintenance management systems and HVAC system
preventive maintenance (PM) plans, or review and
revise existing systems and plans, to control moisture
effectively. Maintenance management systems and
PM plans for HVAC systems should:
• Incorporate moisture control into the functional
objectives that guide the maintenance program
(e.g., as a stand-alone objective, as part of an
indoor air quality objective or as part of a reliability
or long-term cost-minimization objective).
• Develop a performance objective for moisture
control (e.g., number of unanticipated leaks, dollars
spent on leak repair, number of hours when indoor
relative humidity falls within the specified design
range, etc.) and track performance to determine
whether that objective is being met.
• Maintain records of all HVAC system installations,
inspections and maintenance, along with warranty
information and requirements.
• Incorporate best practices for moisture control in
the inspection and maintenance of HVAC systems.
Particular attention should be paid to coils and
drain pans, humidifiers, cooling towers, the
introduction of humidity-laden air and the potential
for condensation. (See HVAC Operations and
Maintenance Goal 2 for more detailed guidance on
conducting HVAC maintenance inspections.)
• Ensure that planners and schedulers assign
inspectors who are knowledgeable about the HVAC
and plumbing systems being inspected.
• Schedule regular inspections at least semi-annually
or in accordance with manufacturer's requirements.
Additional inspections should be scheduled as soon
as possible after heavy winds or rains or after any
construction or installations that could affect the
integrity of these systems, especially their outdoor
components.
• When developing work orders for moisture-related
maintenance tasks, include best practices and
checklists for detailed inspections and maintenance
tasks (See HVAC Operations and Maintenance Goal
2) in the scope of work and instructions.
• Incorporate best practices and checklists (See
HVAC Operations and Maintenance Goal 2) into
training programs for inspectors and maintenance
personnel who deal with these drainage systems.
• Give priority to moisture-control issues in preventive
maintenance, major maintenance and repair, and
capital renewal planning and budgeting.
HVAC Operations and Maintenance Goal 2: HVAC
systems are maintained as intended by the
manufacturer's specifications and the system design
in order to effectively control moisture.
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Guidance 1: Maintain HVAC system components in
accordance with the manufacturer's requirements
and the moisture control recommendations in
this guidance. At a minimum, the following HVAC
components should be inspected as part of a PM
program:
Thermostats
• Thermostats should be checked in the fall and
spring, shortly after switching to or from daylight
saving time, or whenever complaints about thermal
comfort are received.
Checking Thermostat Operation and Calibration
• If the thermostat is programmable, make sure
the time is set correctly and the thermostat is
programmed for the hours when the building is
occupied.
• Place a calibrated thermometer next to the
thermostat. Place a paper towel or other material
between the thermometer and the wall to make
sure the wall temperature is not influencing the
thermometer reading.
• Allow the thermometer to stabilize. How long this
takes will depend on the thermometer used.
• Compare the thermostat and thermometer readings.
If the thermostat differs by more than 1°F, there is a
problem and you should do the following:
• Remove the faceplate and check whether the
thermostat is dirty. Carefully brush or blow away
any accumulated dust.
• If contact points are accessible, clean them
with a soft cloth. Do not use sandpaper or other
abrasive materials.
• If the thermostat has a mercury switch, check
that it is level. Be very careful not to break the
vial that contains the mercury.
• Check behind the thermostat to make sure the
hole for the wires is caulked to prevent air within
the wall from influencing the thermostat reading.
• Allow temperatures to stabilize and compare the
thermostat and thermometer readings again. If
they still differ by more than 1°F, replace the
thermostat.
Control Sequence
• Make sure the clocks on all systems read the
correct time and date (if applicable); adjust if
necessary.
• Check that equipment is turned off or energized
according to the control sequence. (Observe the
actual operation of fans, dampers and valves as well
as the operation of the control unit.)
Outdoor Air Intakes
• Inspect the area around intakes for potential
contaminant sources such as dumpsters, garbage
cans, decaying organic matter and automobile
idling or parking areas. If there are contaminant
sources near the intakes, move them if possible.
If contaminant sources are not mobile, other steps
may be required to prevent the intake of airborne
contaminants. These steps may include relocating
intakes or instituting policy changes such as
prohibiting vehicle idling.
• Inspect the outdoor air intake louver and the debris
screen behind it. Check for signs of rain leaks and
clogged screens. If rainwater intrudes into the
outdoor air intake, modify as needed to prevent
entry. Remove grass clippings, leaves, dust and
other materials that obstruct the air intake. Take
care when doing this during the warmer months
because bees, wasps or other stinging insects
may have nested in the intake. NOTE: Do not use
a pesticide if insects are found in the outdoor air
intake.
• If outdoor air intakes are close to ground level,
ensure that all landscape plantings are at least 5
feet from the intake. Require lawns to be mowed in
a manner that directs the cut grass away from the
building and the intakes.
Outdoor Air Dampers
• Determine the outdoor air damper control sequence,
then change the parameters to force the dampers to
open and close. Do not rely on observing linkages;
watch the outdoor air dampers for movement. Make
necessary repairs to ensure dampers open and close
in accordance with the control sequence.
• Measure outdoor air volumes on a regularly
scheduled basis and whenever indoor air quality
problems arise. Either purchase equipment such
as balometers, anemometers, manometers and
pitot tubes to take these measurements, or hire a
qualified contractor.
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Cooling Coils, Drain Pans, and Condensate Lines
• Inspect coils, pans and condensate lines regularly
for cleanliness and to ensure the drain is operating
correctly. Clean or repair faulty drains as necessary.
• Ensure that all traps have water in them. During
times of the year when the HVAC system is not
used, or when condensate formation is low, the trap
can dry out, allowing sewer gases or other gases in
the drainage system to be drawn into the HVAC unit
and distributed through the building. Fill empty
drain traps with water.
• Closely inspect the ducts downstream from
the cooling coil for mold growth or signs of
condensation being blown off the coil. If mold is
found growing on hard-surface ductwork (e.g., sheet
metal) or closed-cell insulation, have the ductwork
evaluated by a mold remediation specialist or a
qualified duct cleaner. If mold is found growing on
internal porous duct insulation, remove and replace
the insulation because it cannot be effectively
cleaned.
Evaporative Cooling Equipment (Common in Dry
Climates)
• Inspect the evaporative pad media regularly for
cleanliness, and even wetting, across the full face
of the pad. Replace clogged media to ensure that
supply air is not constricted and forced into high-
velocity flow, which could pull water off the media
and into the air stream and ductwork downstream.
Similarly, make sure the water flow is even across
the full face of the pad (for effective cooling) and
not excessively high in any one spot, which could
also result in water droplets being pulled off the
media and into the air stream.
• Ensure the overflow drain is operating correctly.
Clean out or repair the drain lines as necessary
to ensure that water does not collect in the sump
and overflow the edge of the pan. (Overflows can
otherwise leak into ductwork or into the building
itself.)
• Ensure that the media is not contacting standing
water in the sump when the unit is not operating.
The sump overflow adjustment must be low enough
to prevent water from wicking back up into the
media and supporting microbial growth.
• Check the controls to ensure that the evaporative
cooler does not operate when it is raining outdoors.
Otherwise, the unit could overload the incoming
air with humidity at a time when little evaporative
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cooling needs to be accomplished. Needlessly
loading the indoor air with extra humidity can
lead to excess moisture accumulation, even in dry
climates.
• Closely inspect the ducts downstream from the
evaporative cooler coil for mold growth or signs
of moisture being blown off the media. If mold is
found growing on hard-surface ductwork (e.g., sheet
metal) or closed-cell insulation, have the ductwork
evaluated by a mold remediation specialist or a
qualified duct cleaner. If mold is found growing on
internal porous duct insulation, remove and replace
the insulation because it cannot be effectively
cleaned. Before the equipment is placed back in
operation, locate and correct the problem that led
to the carryover of water droplets which supported
the mold growth.
Air Filters
• Do not rely solely on pressure drop warning
equipment to determine the need to replace
filters. Clogged filters can be sucked out of their
frames and air may bypass the filter, resulting
in no noticeable pressure drop. Visually inspect
and replace air filters on a regular schedule. Turn
unit fans off when changing filters to prevent
contamination of the air. Be aware that some filters
may need more frequent replacement than others
because different areas of a facility may have
different airborne particle burdens.
• Record the date of the filter change in the
maintenance manual and write the date of the
change on the filter, if possible.
Ducts and Supply Diffusers
• Inspect ducts regularly, typically once a year or
whenever modifications have been made to the
ducts or the areas they serve.
• Information about the potential benefits and
possible problems of air duct cleaning is limited.
The North American Air Duct Cleaners Association
(NADCA) recommends duct cleaning if there is
a significant build-up of particles, if the duct is
contaminated with mold spores and trace mold
growth, or if there is obvious mold growth. If mold
is growing in ducts lined with porous insulation,
the NADCA guidance recommends removing the
insulation. When cleaning ductwork, follow the
2006 NADCA guidance Assessment Cleaning and
Restoration of HVAC Systems.
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• Inspect ducts for physical damage. Look for
crushed or disconnected ducts. Reconnect, repair
or replace as necessary.
• Inspect all accessible duct seams and joints for
leaks and seal all leaks with appropriate materials.
Seal duct leaks with mastic, metal-backed tape
or aerosol sealant. Duct tape should not be used
because it dries out quickly and fails to hold and
because it cannot withstand high temperatures. All
sealing materials must comply with Underwriter's
Laboratory Standard UL 181A; check the labels.
• Inspect supply diffusers and the ceiling around
diffusers for dirt and dust that can indicate dirty
ducts or missing, inefficient or bypassed filters.
Note that dirt and dust patterns on supply diffusers
or ceilings do not necessarily mean the HVAC
system is the source of the dirt. The vortexes
created as air exits the diffuser can deposit dust
from the ambient air onto surfaces.
• Send dirt and dust samples to an environmental
laboratory for microscopic examination to determine
whether the particles look like soot, lint, mold, sand
or something else.
• Look for mold growth on diffusers supplying cooled
air to the space. Condensation caused by cooling
the diffuser below the dew point can support mold
growth. Clean as needed and determine what
actions are necessary to prevent condensation.
Return Air Plenums
• Return air plenums are spaces that do not have
ducts and typically are found above T-bar ceilings—
suspended ceilings—and below the roof or floor
deck above. Dust, mold and other contaminants
within the space can migrate back to the HVAC
unit and be distributed to the occupied areas of the
building.
• Periodically inspect buildings that have return
air plenums for water-stained ceiling tiles, which
may indicate mold growth. If mold growth is found
or suspected, consult a qualified professional
to determine the extent of the problem and
remediation requirements.
Guidance 2: Monitor temperature and humidity while
commissioning or recommissioning the HVAC system
to ensure humidity control is functioning effectively.
• Penetrations in the return plenum may draw outdoor
air into the system. If it is hot and humid outside
this can cause condensation on chilled surfaces,
in internal building cavities, or in walls or ceilings.
Monitoring temperature and relative humidity in
the building, supply air, return air, and outdoor air
during HVAC commissioning or recommissioning
allows tracking of humidity sources. The absolute
humidity or humidity ratio can be calculated from
these data and mass balance can be made to
determine whether there is a source of humidity on
the return side of the system.
• The dehumidification performance of the building
commissioning or recommissioning should be
tested when the building is occupied.
Verification of HVAC System Operation Maintenance
Set inspections and routine maintenance efforts in
accordance with equipment warranty requirements.
Appendix E contains a sample HVAC inspection
checklist. Inspection records should be kept to track
the results and any subsequent repairs needed.
REFERENCES
American Society for Testing and Materials. 2003. Standard test
method for determining air leakage rate by fan pressurization.
E779-03. Pennsylvania. American Society for Testing and
Materials.
American Society for Testing and Materials. 1996. Standard
test methods for determining airtightness of buildings using
an orifice blower door. E1827-96. Pennsylvania. American
Society for Testing and Materials.
American Society of Heating, Refrigerating and Air-Conditioning
Engineers. 2004. ASHRAE Handbook of Fundamentals.
Ventilation for Acceptable Indoor Air Quality. Standard 62.1.
Atlanta.,GA: American Society of Heating, Refrigerating and
Air-Conditioning Engineers.
(The ASHRAE ventilation standard provides information
needed to determine ventilation rates for differing
occupancies plus a number of design, operation and
maintenance requirements to ensure proper performance
of ventilation equipment. Section 6.2.8 specifically deals
with exhaust ventilation. Standard 62.1 applies to many
situations.)
International Code Council. 2003. ICC International Plumbing
Code. Sections 312.2 to 312.5. Washington, DC:
International Code Council.
(Sections 312.2 to 312.5 of these codes specify a gravity
test of the drain and vent side of plumbing systems.)
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Mold Litigation Task Force of the Associated General Contractors
of America, Inc. 2003. Managing the risk of mold in the
construction of buildings. CONSTRUCTOR, http://www.agc.
org/galleries/conrm/may03 mold.pdf. Accessed November 6,
2013.
North America Air Duct Cleaners Association (NADCA). 2006.
ACR 2006 Assessment, Cleaning and Restoration of HVAC
Systems, National Air Duct Cleaners Association, Washington,
DC. http://www.nadca.com/sites/default/files/userfiles/
ACR%202006.pdf. Accessed November 6, 2013.
United States Environmental Protection Agency. 2005.
Authorization Status for EPA's Stormwater Construction and
Industrial Programs: States, Indian Country and Territories
Where EPA's Construction General Permit (CGP) and Multi-
Sector General Permit (MSGP) Apply. Washington, DC:
United States Environmental Protection Agency. http://cfpub.
epa.gov/npdes/stormwater/authorizationstatus.cfm. Accessed
November 6, 2013.
(This website outlines the relevant authority—U.S.
EPA, state, or local government—for compliance with
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National Pollutant Discharge Elimination System [NPDES]
requirements for construction in a given state.)
United States Environmental Protection Agency. 2006.
Construction Site Stormwater Runoff Control. Washington,
DC: United States Environmental Protection Agency, http://
cfpub.epa.gov/npdes/stormwater/menuofbmps/index.
cfm?action=min measure&min measure id=4. Accessed
November 6, 2013.
(This website outlines best management practices [BMPs] for
controlling storm water runoff at construction sites.)
United States Environmental Protection Agency. 2006.
Stormwater Discharges from Construction Activities:
Overview. Washington, DC. http://cfpub.epa.gov/npdes/
stormwater/const.cfm. Accessed November 6, 2013.
(This website outlines the federal requirements for complying
with National Pollutant Discharge Elimination System
[NPDES] requirements for construction.)
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Appendix A - The "Pen Test"
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PURPOSE
By tracing the continuity of all the materials for
each control function, the "pen test" checks the
completeness of:
• Rainwater protection.
• The insulation layer.
• The air barrier.
To verify continuity, create sections in which each
of these moisture-control elements is traced in a
different color to show that the design specifically
accounts for them. Contractors can then easily check
the sections against their experience with materials,
trades and sequencing. The sections will also provide
maintenance workers in buildings and grounds with
information useful in ordinary maintenance work or in
the event of a problem during building use.
Rainwater Protection Continuity
To demonstrate complete rainwater protection using
the section drawing, place a pen on a material that
forms a capillary break between the rain-control
materials that get wet and the inner portion of the
enclosure that must stay dry. Without lifting the
pen off the paper, trace from the center of the roof
around the walls, windows, and doors and along the
foundation to the center of the foundation floor.
Figure A-l serves as documentation of rainwater
protection continuity. The following describes the
traceable capillary break in a sample section. Starting
at the center of the roof:
• The roofing membrane separates wet materials from
the inner dry materials.
• Tracing to the edge of the roof, the roofing
membrane flashes beneath a metal coping, this in
turn flashes to a metal fascia.
• The fascia forms a drip edge, channeling water
away from the cladding.
• An air gap between the drip edge and the brick
veneer forms a capillary break protecting the
materials beneath the metal coping from rainwater
wicking from below.
• An air gap and water-resistant barrier behind the
brick veneer form a capillary break between the
damp brick and the inner walls.
• The water-resistant barrier shingles over a head
flashing, protecting the window from rainwater with
a drip edge and air gap.
• The window frame, sash and glazing form a
capillary break system that sits in a pan sill flashing
at the bottom of the rough opening.
• The pan sill flashing forms a capillary break
protecting the wall beneath from seepage through
the window system.
• The pan sill flashing shingles over the water-
resistant barrier in the wall beneath.
• The water-resistant barrier shingles over a flashing
that protects the bottom of the wall system where:
• The foam sill seal makes a capillary break
between the foundation and the bottom of the
framed wall, connecting with:
One inch of extruded styrene foam insulation
making a capillary break between the top of the
foundation wall and the edge of the floor slab.
• Polyethylene film immediately beneath the slab
forms a capillary break between the bottom of
the slab and the fill below. NOTE: If the bed of
fill beneath the slab consists of pebbles greater
than 1A inch in diameter and contains no fines,
then it forms a capillary break between the soil
and the slab.
Apply the same procedure to the insulation layer
(Figure A-2) and the air barrier (Figure A-3).
A-l
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Figure A-1 The Blue Line Traces the Elements of the Capillary Break in the Rainwater Control System for a Section
Through a Building
Facia
Drip edge and
air gap
Spray foam insulate
I-beam
Self-adhered membrane
covers gypsum wall and
seals to flashing
Gypsum sheathing
1"foam board
Air gap
Head flashing (flashes
beneath self-adhered
membrane)
Pan sill flashing
Self-adhered membrane
Gypsum sheathing
1"foam board
Air gap
Brick wall
Flashing
Foam insulation at
down perimeter wall
Concrete foundation wall
Coping
Steel "Z" angle
Tapered foam insulation
Roof membrane
Fluted steel deck
Self-adhered
membrane
Gypsum foam
boardings deck
6" light steel stud
w/R19 fiberglass
insulation
Roof drain
Window
6" light steel stud
w/R19 fiberglass
insulation
Polyethylene film
Concrete slab
Drainage layer
(coarse aggregate with no fines)
A-:
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Figure A-2 The Red Line Traces Continuity of the Insulation Layer
www.epa.gov/iaq/moisture
Facia
Drip edge and
air gap
Spray foam insulate
I-beam
Self-adhered membrane
covers gypsum wall and
seals to flashing
Gypsum sheathing
1" foam board
Air gap
Head flashing (flashes
beneath self-adhered
membrane)
Pan sill flashing
Self-adhered membrane
Gypsum sheathing
1" foam board
Air gap
Brick wall
Flashing
Foam insulation at
down perimeter wall
Concrete foundation wall
Coping
Steel "Z" angle
Tapered foam insulation
Roof membrane
Fluted steel deck
Self-adhered
membrane
Gypsum foam
boardings deck
6" light steel stud
w/R19 fiberglass
insulation
Roof dram
Window
6" light steel stud
w/R19 fiberglass
insulation
Polyethylene film
Concrete slab
Drainage layer
(coarse aggregate with no fines)
A-3
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Figure A-3 The Purple Line Traces the Air Barrier Components
Self-adhered
membrane
Facia
Drip edge and
air gap
Spray foam insulate
I-beam
Self-adhered membrane
covers gypsum wall and
seals to flashing
Gypsum sheathing
1" foam board
Air gap
Head flashing (flashes
beneath self-adhered
membrane)
Pan sill flashing
Self-adhered membrane
Gypsum sheathing
1* foam board
Air gap
Brick wall
Flashing
Foam insulation at
down perimeter wall
Concrete foundation wall
Coping
Steel "Z" angle
Tapered foam insulation
Roof membrane
Gypsum foam
boardings deck
6" light steel stud
w/ R19 fiberglass
insulation
Roof drain --^
Window
6" light steel stud
w/R19 fiberglass
insulation
Polyethylene film
Concrete slab
Drainage layer
(coarse aggregate with no fines)
A-4
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Insulation Layer Continuity
To demonstrate a continuous layer of insulating
material around a section, place the pen tip on the
insulating layer in the center of the roof and trace
from one insulating material to the next around to
either the bottom of the foundation wall or the center
of the foundation floor.
Figure A-2 shows the continuity of thermal insulation
in a sample section.
• Beginning at the center of the roof, trace through
foam insulation to the edge of the roof.
• One- or two-part polyurethane foam insulation
applied in the field fills the top and bottom voids
created by the fluted steel deck, providing both
insulation and air barrier continuity.
• The field-applied foam connects to the top of the
exterior foam insulation sheathing and the top
channel of steel wall framing.
• The steel wall framing is filled with cavity
insulation, and the thermal bridge through the steel
is insulated by the exterior foam insulation.
• The rough opening between the exterior foam
sheathing and the window jamb is insulated
(and air sealed) with field-applied canned foam
insulation.
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• The window jamb, sash and glazing system provide
insulation continuity to the rough opening at the
bottom of the window, which is insulated with
canned foam.
• The exterior insulating foam sheathing and
cavity insulation carry the insulation layer to the
foundation.
• Foam sill seal provides thermal insulation between
the bottom of the wall and the concrete foundation,
which carries thermal protection below grade to the
bottom of the foundation wall.
• Vertical foam insulation applied to the interior of
the foundation wall.
Air Barrier Continuity
Continuity of the air barrier is demonstrated using
the same method used for rainwater control and the
insulation layer. Air barrier materials and the sealants
used to connect them are identified from the center of
the roof to the center of the foundation floor.
In this case foam insulation on the roof and walls,
windows and the concrete floor slab forms the basis
of the air barrier. The insulation components are
connected with sealants (e.g., field-applied canned
foam) and gasket-like materials (e.g., foam sill seal).
A-5
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www.epa.gov/iaq/moisture
Appendix B - Roof Inspection Checklist
Parts of this inspection checklist are adapted from and used with the permission of the Government of The Northwest Territories Public Works and
Services Asset Management Division.
Before performing a roof inspection:
• Review past inspection reports, construction documents and maintenance and repair reports.
• Review, learn and follow roof safety procedures.
• Use ladders to inspect steep roofs. Ensure all ladders comply with, and are maintained and used in
accordance with, the Occupational Safety and Health Administration (OSHA) requirements in Title 29 of the
Code of Federal Regulations (29 CFR).
Building:.
Address:
Roof Area or ID:
Inspected by:
Date:
Item
Interior
Exterior
ID - Number to be used to identify problem on roof sketch
G - Good, no action needed
F- Fair, monitor condition periodically, plan necessary repairs
P - Poor, immediate action needed
N/A - Not applicable
Interior Walls
Water stains
Water damage
Other wall problems
Ceilings
Water stains
Water damage
Other ceiling problems
Roof Deck
Water damage
Rusting
Settling/deflection
Deck deterioration
Other roof deck problems
Downspouts/Leaders
Missing pieces
Loose pieces
Evidence of blockage
Damaged joints
Split joints
Surface ponding
Other downspout/leader
problems
ID
1
2
3
ID
4
5
6
ID
7
8
9
10
11
ID
12
13
14
15
16
17
18
G
G
G
G
F
F
F
F
P
P
P
P
N/A
N/A
N/A
N/A
REMARKS
REMARKS
REMARKS
REMARKS
B-l
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Roof
Drainage
System
Roof Features
Exterior Walls
Water stains
Water damage
Other wall problems
General Conditions
General appearance
Traffic problems
Unauthorized access
Ponding
Debris
Physical damage
Deflection
Compressed insulation
Other roof problems
Gutters
Missing pieces
Loose pieces
Damaged pieces
Split joints
Corrosion
Loose fasteners
Debris in gutters
Slope to downspout
Other gutter problems
Internal Roof Drains
Missing drain screens
Blocked drain
Other drain problems
Scuppers
Blockage
Other scupper problems
Perimeter Edging/ Fascia/
Gravel Stop
Missing pieces
Loose pieces
Damaged pieces
Split joints
Corrosion
Loose fasteners
Other
Flashings
Missing pieces
Loose pieces
Damaged pieces
Split joints
Corrosion
Loose fasteners
Other flashing problems
ID
19
20
21
ID
22
23
24
25
26
27
28
29
30
ID
31
32
33
34
35
36
37
38
39
ID
40
41
42
ID
43
44
ID
45
46
47
48
49
50
51
ID
52
53
54
55
56
57
58
G
G
G
G
G
G
G
F
F
F
F
F
F
F
P
P
P
P
P
P
P
N/A
N/A
N/A
N/A
N/A
N/A
N/A
REMARKS
REMARKS
REMARKS
REMARKS
REMARKS
REMARKS
REMARKS
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Roof Covering
Roof-mounted Equipment
(HVAC, Signs, Skylights,
Etc.)
Flashings
Loose/missing access
panels
Condensate piped to drain
Contamination around
exhaust fans
Other equipment problems
Membrane Roofs
Bare spots in gravel or
displaced ballast
Cuts/punctures
Cracks/all igatoring
Blisters/fishmouths
Loose laps/seams
Ridging/wrinkling
Fastener back-out
Membrane shrinkage
Other
Shingled Roofs
Missing shingle(s)
Loose shingle(s)
Buckled shingle(s)
Curled shingle(s)
Missing tab(s)
Granular loss
Other shingle problems
Metal Roofs
Loose or damaged seams/
joint(s)
Loose panel(s)
Worn panel(s)
Damaged panel(s)
Loose fastener(s)
Finish condition
Other metal roof problems
ID
59
60
61
62
63
ID
64
65
66
67
68
69
70
71
72
ID
73
74
75
75
77
78
79
ID
80
81
82
83
84
85
86
G
G
G
G
F
F
F
F
P
P
P
P
N/A
N/A
N/A
N/A
REMARKS
REMARKS
REMARKS
REMARKS
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Use this graph paper to sketch the roof plan. Include north arrow and the location of problems found during the
inspection. Use the roof ID numbers on the checklist to identify specific problems.
B-4
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Appendix C - Testing Moisture During Construction
The moisture content of wood, wood products and
other porous materials is an important factor in
mold growth and other moisture-related problems. A
porous material susceptible to mold growth, such as
wood, oriented strand board (OSB), medium density
fiberboard (MDF) or untreated paper-faced gypsum
board, will experience mold growth if its moisture
content is too high. Damp porous materials that are
resistant to mold growth, such as concrete products
and treated lumber, may indirectly support mold
growth by wetting vulnerable materials that are in
contact with them. For example, untreated paper-
faced gypsum board attached to damp lumber or
concrete may be the site of mold growth until the
damp materials dry.
Wood and wood products that contain a great deal
of moisture should not be used in construction until
their moisture content is below a certain percentage.
Unfortunately, research on this dynamic is mostly
confined to laboratory research and anecdotal reports
from forensic cases. The California Builder's Guide
to Reducing Mold Risk suggests an upper threshold
of 19 percent moisture content for wooden materials.
To avoid problems with shrinking or expansion, wood
ideally should be installed at moisture content levels
as close as possible to the average moisture content
it will experience in service. The in-service moisture
content of exterior wood depends on the outdoor
relative humidity and exposure to rain and sun. The
in-service moisture content of interior wood depends
on the indoor relative humidity, which in turn is a
function of moisture sources, ventilation rates and
dehumidification. The in-service moisture content of
exterior and interior wood depends on the climate in
which the building is located and on the building's
design and intended use. The U.S. Department of
Agriculture's Wood Handbook recommends average
moisture content of 15 percent or less, with maximum
readings of 19 percent or less, to avoid dimensional
change problems.
The moisture content of materials is usually expressed
as the percentage of the weight of water in the
material relative to the weight of the dry material.
In laboratories, moisture content can be calculated
by weighing the test sample while damp, drying
the sample using heat or desiccant salts, and then
reweighing the sample. Electronic meters with direct
reading scales or displays have been developed for
wooden materials. Their use on lumber is extensively
documented. ASTM D 4444-92 (Reapproved 2003)
Standard Test Methods for Use and Calibration of
Hand-Held Moisture Meters describes several types of
moisture meters, their use on wooden materials, and
quality assurance/quality control (QA/QC) procedures.
Knowing the moisture content of porous building
materials other than wood or wood products, such as
gypsum board and concrete slabs or concrete masonry
units, is also important. Some electronic moisture
meters have calibrated scales for materials other than
wood, for example concrete, brick and plaster. It has
become common practice in the building diagnostic
field to test materials other than lumber using
electronic meters and to report the results using the
scale for lumber. In this way, investigators report the
moisture content of gypsum board, MDF and OSB as
the wood moisture equivalent (WME). The California
Builder's Guide to Reducing Mold Risk suggests an
upper limit of 16 percent WME for gypsum board
before finishing or installing cabinets. This limit
translates roughly to 0.9 percent moisture content by
weight for gypsum board.
The ability to measure material moisture content
after construction is valuable for diagnosing
post-construction problems such as water leaks,
condensation and mold growth. It is recommended
that builders and facility managers measure the
moisture content of materials during post construction
diagnosis and problem solving.
A second moisture dynamic, the emission rate of
water vapor from materials such as concrete floors,
can have a dramatic impact on flooring materials.
For example, floor covering manufacturers specify
the maximum water vapor emission rate of concrete
over which coverings such as tile and carpet can
be installed. Installing a covering on concrete that
exceeds the maximum emission rate may cause the
covering to fail, promote mold growth and void the
c-i
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manufacturer's warranty. It is recommended that the
vapor emission rate of a floor be measured before
coverings are installed (even when the installation
occurs long after the building was constructed);
whenever lifting tiles, blistered sheet vinyl, or other
signs of floor failure are found; or when unexplained
high indoor relative humidity in ground-contact
spaces is encountered.
ASTM E 1907-06a Standard Guide to Methods of
Evaluating Moisture Conditions of Concrete Floors
to Receive Resilient Floor Coverings identifies eight
methods of testing concrete slabs. The two most
commonly used methods are:
• F 1869 Test Method for Measuring Moisture
Vapor Emission Rate of Concrete Subfloor Using
Anhydrous Calcium Chloride. This test is conducted
using commercially available test kits. It is a
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quantitative test that provides a measure of the
vapor, in pounds of water in a 1,000 square foot
area, emitted over a 24-hour period. The test
involves weighing a canister of calcium chloride
desiccant, placing the canister on the slab to
be tested, and covering the canister with an air-
tight plastic dome supplied with the kit. The test
typically is conducted for 60 to 72 hours. After
that time, the canister is reweighed and the vapor
emission rate is calculated. This test method is
accepted by most floor covering manufacturers.
F 2170 Test Method for Determining Relative
Humidity in Concrete Floor Slabs Using in situ
Probes. This method measures the head space
relative humidity in a hole drilled partway through
the concrete slab. It is gaining popularity in the
field and has been used in Europe for many years.
C-2
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Appendix D - Air Pressure Mapping
Air pressure mapping is used to determine whether
air is moving through a building in a manner that
contributes to condensation problems. Unplanned
airflow will cause problems if either:
• Air is moving from the warm side of an exterior wall,
the ceiling, or the basement to the cool side.
• Cold air is blowing from an air conditioning diffuser
into a space where humidity is high.
To generate an air pressure map of a building, use:
• Floor plans showing the layout of each floor and
the location of air handlers, supply diffusers, return
grilles, and exhaust grilles.
• A micromanometer and flexible plastic tubing to
measure pressure differences between indoor air
and outdoor air, rooms and corridors, room air and
plenum air, and room air and building cavities.
• A smoke bottle to determine the direction of air
flow.
As depicted in Figure D-l, use a micromanometer
to measure the pressure difference across a closed
door. Note that the tubing is run from one port of the
micromanometer to the far side of the door, while
the other port (with no tubing) senses the pressure
in the room. The micromanometer reads the pressure
difference. The minus sign on the micromanometer
interface indicates that the room is under negative
pressure relative to the other side of the door.
Figure D-2 shows the pressure map of a building that
consists of a single room with an operating 100-cfm
exhaust fan. The room is depressurized 4 Pascals
by the exhaust fan. The exhaust fan is represented
by a box with an X in it and an arrow showing the
direction of airflow out of the building. The line with
an arrowhead on one end and a circle on the other
signifies that air is being drawn into the building from
outside.
This procedure can be applied to more complex
buildings and airflows to document air pressure
differences between rooms, indoors and outdoors,
attics, basements, crawlspaces, utility chases and
wall and ceiling cavities. Figure D-3 illustrates a
pressure map of a more complex building when the air
handler is running, the exhaust fans in the bathrooms
are running, there is no wind, and all the interior and
exterior doors are closed.
D-l
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Figure D-1 Measuring Pressure Difference Using a Micromanometer
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\L
Figure D-2 Pressure Map of a Building Consisting of a Single Room
100cfm
Exhaust Fan
4 pascals
D-2
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Figure D-3 Pressure Map of a More Complex Building
e-
1.6 Pa 0 CD1.3P
Exhaust Fan Air handler
1.3 Pa
-e
0.0 Pa
0.0 Pa 0
0.0 Pa
2.3 Pa 0
-e
0.0 Pa
R
-9 1.6 Pa
R
-8 1.6 Pa
-e
LEGEND:
R
Supply diffuser
Return grille
D-3
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Appendix E - HVAC Inspection Checklist
Building:.
Location:
Date:
Equipment:
Other ID:
Manufacturer:
File # :
Prepared by:
Parameter
Outdoor Air Intake
Bird screen
Air flow unobstructed
No close-by pollutant sources
Mixing Plenum
Clean
Coils and Condensate Pans:
Clean, no corrosion
No odors
No microbial growth
Pans draining, traps filled
Humidifiers
Clean
No standing water or overflow
No microbial growth or mineral
deposits
Controls
Set points
Functioning
Fans
Clean, no corrosion
No excess vibration
Belts
No excess noise or vibration
No leakage
Pressurization
Filters
General condition
Installed properly (no bypass)
No odors/visible pollution
Condition
OK
Not OK
Notes
Priority
L, M, H
E-l
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Appendix F - Site Drainage Maintenance
Regular maintenance of site drainage systems
is necessary to ensure they perform effectively.
Failing to regularly maintain drainage systems
can lead to reduced performance or system
failure. To help provide proper maintenance, a site
drainage maintenance plan that describes specific
maintenance requirements and schedules should be
developed and used by the persons responsible for
drainage maintenance.
The maintenance plan differs from the checklists
provided in this appendix. The plan encompasses the
entire site drainage maintenance requirements, while
the checklists provide requirements for a specific
drainage feature.
Maintenance Plan Requirements
The following site drainage maintenance plan
requirements have been adapted from the New Jersey
Storm Water BMP Manual (NJDEP04). Plans should
include:
• The name, address and telephone number of
the person or persons responsible for preventive
and corrective maintenance of the site drainage
systems.
• Specific preventive and corrective maintenance
requirements. These requirements may be in the
form of checklists.
• A schedule of regular inspections and tasks.
• Detailed logs of all preventive and corrective
maintenance tasks, including all maintenance-
related work orders.
• Necessary maintenance equipment, tools and
supplies.
• Emergency action responses.
• Procedures and equipment required to protect the
safety and health of inspectors and maintenance
workers.
• Approved disposal and recycling sites and
procedures for the sediment, debris and other
materials removed from the drainage systems
during maintenance.
• System component manufacturer's literature and
warranties.
• As-built construction plans.
In addition, the plan should address the training of
maintenance personnel in the operational theory of
site drainage and in maintenance and health and
safety procedures.
Site Drainage Inspection and Maintenance
Recommendations
The following inspection and maintenance
recommendations and checklists should be
augmented by state or local code requirements as well
as best management practices learned by persons
maintaining the site drainage system.
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Dry wells are to be inspected four times each year and after every storm that exceeds 0.5 inches of rainfall.
Whenever possible, dry wells are also to be inspected before a major storm. Inspection consists of measuring
infiltration rates and drain times by observing the water level in the test well. The actual drain time of the well
should be compared with the time it would take to drain the maximum design storm runoff volume. If significant
increases in drain time are noted, or if the dry well fails to dry within the design drainage time, maintenance is
required.
Dry well maintenance involves removing debris, trash or sediment that may have washed into the well. In
addition to the dry well, any roof gutters, sumps or traps connected to the dry well are to be inspected and
cleaned or repaired as necessary.
Building:.
Address:
Dry Well ID/Location:
Inspected by:.
Date:
ITEM
Roof
Gutters,
Leaders,
Sumps
and Traps
Test Well
Inspection
ID - Number to be used to identify problem on site sketch
G - Good, no action needed
F - Fair, monitor condition periodically, plan necessary repairs
P - Poor, immediate action needed
N/A - Not applicable
Missing pieces
Loose pieces
Evidence of
blockage
Damaged joints
Split joints
Surface ponding
Cleaning required
Other problems
Water level
Obvious debris
ID
1
2
3
4
5
6
7
8
9
10
G
F
P
N/A
REMARKS
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F-3
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Vegetated swales are to be inspected four times each year and after every storm that exceeds 0.5 inches of
rainfall. If swale vegetation consists of fast-growing grasses, the swales are to be inspected weekly. Whenever
possible, swales are to be inspected before a major storm. Inspection consists of looking for debris, evidence of
clogging and observable vegetation growth.
Vegetated swale maintenance consists of removing debris and sediment, maintaining the vegetation and
ensuring the swale drains within 48 hours.
Building:.
Address:
Swale ID/Location:
Inspected by:
Date:
ID - Number to be used to identify problem on site sketch
G - Good, no action needed
F - Fair, monitor condition periodically, plan necessary repairs
P - Poor, immediate action needed
N/A - Not applicable
Pea gravel diaphragm cleanliness
Grass or other vegetation
requires mowing
Trash/debris in inflow forebay
Erosion problems
Vegetation requires replacement
Swale does not drain within 48
hours - requires rototilling or
cultivating
Bottom sediment built up to 25
percent of original design volume
- requires sediment removal
Other problems
ID
1
2
3
4
5
6
7
8
G
F
P
N/A
REMARKS
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Dry extension ponds are to be inspected twice each year and after every storm that exceeds 0.5 inches of
rainfall. If side-slope vegetation consists of fast-growing grasses, the ponds are to be inspected weekly.
Whenever possible, ponds are to be inspected before a major storm. Inspection consists of looking for debris,
sediment build-up, erosion and observable vegetation growth.
Pond maintenance consists of removing debris and sediment, repairing erosion, managing pesticides and
nutrients and maintaining the vegetation.
Building:.
Address:
Pond ID/Location:
Inspected by:
Date:
ID - Number to be used to identify problem on site sketch
G - Good, no action needed
F - Fair, monitor condition periodically, plan necessary repairs
P - Poor, immediate action needed
N/A - Not applicable
Erosion on pond banks
or bottom
Damaged embankment
Sediment accumulation
in the facility or forebay
Side slopes need
mowing
Pesticide and nutrient
management required
Ground cover requires
attention
Bottom sediment built
up to 25 percent of
original design volume
- requires sediment
removal
ID
1
2
3
4
5
6
7
G
F
P
N/A
REMARKS
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Wet ponds are to be inspected monthly and after every storm that exceeds 0.5 inches of rainfall. Whenever
possible, ponds are to be inspected before a major storm. If side-slope vegetation consists of fast-growing
grasses, wet ponds are to be inspected weekly. Inspection consists of looking for invasive species, debris, signs
of damage or erosion, sediment accumulation and the need for managing or harvesting wetland plants.
Pond maintenance consists of removing invasive species, debris, and sediment; repairing erosion; and managing
the vegetation.
Building:.
Address:
Pond ID/Location:
Inspected by:
Date:
ID - Number to be used to identify problem on site sketch
G - Good, no action needed
F - Fair, monitor condition periodically, plan necessary repairs
P - Poor, immediate action needed
N/A - Not applicable
Invasive species
Erosion
Sediment build-up in pond
or forebay
Debris
Wetland plant management
required
ID
1
2
3
4
5
G
F
P
N/A
REMARKS
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F-S
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Pervious pavement areas are to be inspected weekly and after every storm that exceeds 0.5 inches of rainfall.
Whenever possible, pervious pavement areas are to be inspected before a major storm. Inspection consists
of looking for debris, sediment build-up, proper drainage after a storm, surface deterioration or spalling and
observable vegetation growth.
Pervious pavement maintenance consists of removing debris and sediment and maintaining the vegetation.
Building:.
Address:
Pavement ID/Location:
Inspected by:.
Date:
ID - Number to be used to identify problem on site sketch
G - Good, no action needed
F - Fair, monitor condition periodically, plan necessary repairs
P - Poor, immediate action needed
N/A - Not applicable
Area requires
cleaning
Improper draining
Sediment build-up
Upland area
requires mowing or
reseeding
Surface
deterioration or
spalling
ID
1
2
3
4
5
G
F
P
N/A
REMARKS
F-10
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F-ll
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Areas paved with porous modular pavers are to be inspected weekly and after every storm that exceeds 0.5
inches of rainfall. Whenever possible, areas are to be inspected before a major storm. Inspection consists
of looking for debris, sediment build-up, proper drainage after a storm, surface deterioration or spalling and
observable vegetation growth.
Pervious pavement maintenance consists of removing debris and sediment and maintaining the vegetation.
Building:.
Address:
Pavement ID/Location:
Inspected by:.
Date:
ID - Number to be used to identify problem on site sketch
G - Good, no action needed
F - Fair, monitor condition periodically, plan necessary repairs
P - Poor, immediate action needed
N/A - Not applicable
Area requires
cleaning
Improper draining
Sediment build-up
Adjacent area
requires mowing or
reseeding
Surface deterioration
or spalling
ID
1
2
3
4
5
G
F
P
N/A
REMARKS
F-12
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F-13
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REFERENCES
American Society for Testing and Materials (ASTM). ASTM
D4263- Standard test method for indicating moisture in
concrete by plastic sheet method.
American Society for Testing and Materials (ASTM). ASTM
F1869-04- Standard test method for measuring moisture
vapor emission rate of concrete subfloor anhydrous calcium
chloride.
Claytor, R.A., and T.R. Schueler. Design of Stormwater Filtering
Systems. The Center for Watershed Protection. (CWP)
Silver Spring, MD. Prepared for the Chesapeake Research
Consortium, Solomons, MD, and USEPA Region V, Chicago,
IL. 1996.
Code of Federal Regulations (29 CFR). Title 29- Labor.
(Title 29 of the CFR outlines requirements of Occupational
Safety and Health Administration [OSHA] for workers, which
include standards for ladder use and maintenance.)
Forest Products Laboratory. Wood handbook: Wood as an
engineering material. General Technical Report FPL-
GTR-113. United States Department of Agriculture, Forest
Service, Forest Products Laboratory. 1999.
James, William L. Electric Moisture Meters for Wood. General
Technical Report FPL-GTR-6. United States Department of
Agriculture Forest Service, Forest Products Laboratory. June
1988.
New Jersey Department of Environmental Protection, (NJDEP04).
New Jersey Stormwater Best Management Practices Manual.
Trenton, NJ. April 2004.
F-14
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Appendix G - Dampness & Mold Evaluation
The National Institute for Occupational Safety and
Health (NIOSH) has developed an observational
assessment tool for dampness and mold in buildings.
As of October 1, 2013, the tool was in review to
become an official NIOSH document. The goal of
the tool is to provide information for motivating
remediation, prioritizing intervention, and evaluating
remediation effectiveness.
The tool consists of:
1. A form used to evaluate signs of dampness, water
damage, mold growth, and musty odors in rooms
and areas throughout the building.
2. A Visual Basic® data entry application to enter
data collected from hard copy evaluation forms
for electronic record keeping and reports. Data
is stored in a Microsoft Access® database. The
software may also be implemented on PC-based
tablets. The software is under development. Once
completed, the software will be made available at
http://www.cdc.gov/niosh/topics/indoorenv/mold.
html.
For additional information or to receive a form and
instructions for use, contact moldsheet#l@cdc.gov
(mailto: moldsheet#l@cdc.gov).
Figure G-1 NIOSH Dampness and Mold Assessment Form for Schools
NIOSH PILOT-DRAFT NIOSH CcnU.:! Michel c. u,in-n 3CW-zeE-E73J or tc-d'= "ooi? 1 .£cdcgov
Damoness & Mold Assessment Checklist
Date:
Observer:
_Building:_
_Wing:_
Floor:
G Classroom
O Storage o library
o Stairwell Other
Room Number:
O Office o Hallway c Conference room
o Cafeteria oGym o Auditorium
_Room Type: Fiti the bubbte for the following room types.
O Bathroom o Custodial closet O Mechanical room
O Kitchen o Locker room o Entrance area
MOLD ODOR o NONE o MILD o MOO o HEAVY Source'.
Be sure tu *m*li mold odor when you flr»t walk Into th« roomrar**-
NA
i.' j, .
FHI the
bubbles
for each
column and
row.
DAMAGE
or STAINS
0=NONE
MOLD
AREA
0=MO«E
MOLD
DENSITY
0=NONE
WET or
DAMP
Q=NQNi
3«HEAW
0123
It 1 2 3
0123
0123
o Source Unknown
NOTES
Totals
Colling
(3)
(5) (J)
:H: :'0
(J) (T>
(0 <2>
HVAC »yitem*
0)
(2)
OB
Pipes
Furnishings
©
© ©
© ® © 3)
Supplies & Material*
Other
Totals
Average
QJ
® © © ©
® © © CB
@ ®
® ©
0)
G-1
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Glossary
www.epa.gov/iaq/moisture
Term
Definition
Air barrier
Air handler
Alligator ing
ASHRAE
Asphalt
ASTM
Ballast
Bitumen
Blister
Built-up roofing
(BUR)
Cant strip
Capillary break
Chase
Cladding
CMU
Commissioning
Coping
Crack
Any material, combination of materials or manufactured assemblies that are intended, by
design, to control the movement of air across an exterior wall system or assembly.
Equipment that includes a blower or fan, heating or cooling coils and related equipment
such as controls, condensate drain pans and air filters. Does not include ductwork,
registers or grilles, or boilers and chillers.
Shrinkage cracking of the bituminous surface of built-up or smooth surface roofing,
producing a pattern of deep cracks resembling alligator hide.
American Society of Heating, Refrigeration, and Air-Conditioning Engineers, Inc.
A highly viscous hydrocarbon produced from the residue left over after the distillation of
petroleum. Asphalt is used to water-proof built-up roofs.
American Society for Testing and Materials.
An anchoring material such as rock, gravel or pavers used to resist wind uplift forces on
roof membranes.
A generic term for asphalt or coal tar pitch roofing.
A spongy raised portion of a roofing membrane as a result of pressure of entrapped air or
water vapor.
A continuous semi-flexible roof covering consisting of laminations or piles of saturated or
coated felts alternated with layers of bitumen.
A continuous strip of triangular cross-section fitted into the angle formed by a structural
deck and a wall or other vertical surface. Used to provide a gradual transition for base
flashing and horizontal roof membrane.
A slot or groove intended to create an opening too large to be bridged by a drop of water
in order to eliminate the passage of water by capillary action.
A groove or indentation cut into masonry to accommodate electric or plumbing lines.
A panel applied to a structure to provide durability, weathering, corrosion and impact
resistance.
Concrete masonry unit.
Start-up of a building that includes testing and adjusting HVAC, electrical, plumbing
and other systems to ensure proper functioning and adherence to design criteria; also
includes the instruction of building representatives in the use of the building systems.
The material or units used to form a cap or finish on top of a wall, pier, pilaster or
chimney; a protective cap at the top of a masonry wall. It should be waterproof, weather
resistant and sloped to shed water.
A break in a roofing membrane as a result of flexing, often occurring along a ridge or
wrinkle.
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Term Definition
Cricket
Drainage or drain
plane
Dry well
Eave
Enthalpy
EPDM
Expansion joint
Fascia
Fishmouth
Flashing
Fore bay
Gravel stop
HVAC
Hygrothermal
Impervious
Micromanometer
Modified bitumen
OSB
Parapet
Plenum
Ponding
A chimney flashing on the uphill side, resembling a small roof ridge, to divert rainwater
around the chimney.
Any element exposed to weather or otherwise residing at the line between the "wet" and
"dry" zones of an exterior wall system or assembly.
A deep hole, covered and usually lined or filled with rocks, that holds drainage water
until it soaks into the ground.
The protective overhang at the lower edge of a sloped roof.
A measure of the total energy of a thermodynamic system. It includes the internal energy,
which is the energy required to create a system, and the amount of energy required to
make room for it by displacing its environment and establishing its volume and pressure.
Ethylene propylene diene monomer, a synthetic rubber sheet used in single-ply roof
membranes.
A deliberate separation of two roof areas to allow expansion and contraction movements
of the two parts.
The finish covering the edge of eaves of a flat or sloping roof or roof overhang.
An opening of the lapped edge of applied felt in built-up roofing due to adhesion failure.
Connecting devices that seal membrane joints, drains, gravel stops and other places
where membrane is interrupted. Base flashing forms the upturned edges of the watertight
membrane. Cap or counter flashing shields the exposed edges and joints of the base
flashing.
A small pool located near the inlet of a storm basin or other storm water management
facility. These devices are designed as initial storage areas to trap and settle out
sediment and heavy pollutants before they reach the main basin.
A flanged device, normally metallic, designed to prevent loose aggregate from washing
off the roof. It also provides the finished edge detail for built-up roofing assemblies.
Heating, ventilation and air conditioning.
Pertaining to heat and humidity.
Not letting water or moisture pass through or be absorbed.
An instrument designed to measure minute differences in pressure.
Asphalt with the addition of polymer modifiers to increase cold temperature flexibility
and warm temperature flow resistance and stability.
Oriented Strand Board. A type of particle panel product composed of strand-type flakes
that are purposefully aligned in directions that make a panel stronger, stiffer and with
improved dimensional properties in the alignment directions than a panel with random
flake orientation.
The part of the wall assembly above the roof.
Space between a suspended ceiling and the floor above that may have mechanical and
electrical equipment in it and that is used as part of the air distribution system. The
space is usually designed to be under negative pressure.
The collection of water in shallow pools on a roof surface.
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Term
Definition
PVC
R-value
Scuppers
Section
Shingle-wise
Slope
SMACNA
Soffit
Spall
Stem wall
Sump crock
Swale
TAB
Tensiometer
Vapor barrier
WBDG
Weep Holes
A generic term for single-ply plastic sheet membrane (polyvinyl chloride). Seams are
fused by solvent or hot-air welding techniques.
The number of minutes (seconds) required for 1 Btu (joule) to penetrate one square foot
(square meter) of a material for each degree of temperature difference between the two
sides of the material. The resistance of a material to the passage of heat. The reciprocal
of conduction (1/c).
An opening for draining water, as from a floor or the roof of a building.
A drawing showing the kind, arrangement and proportions of the various parts of a
structure. It shows how the structure would appear if cut through by a plane.
The overlapping of materials shingle style so that impinging water, such as rainwater, will
run harmlessly down and out.
The ratio between the measures of the rise and the horizontal span.
Sheet Metal and Air Conditioning Contractors' National Association.
The finish on the underside of the roof overhang.
A fragment, usually in the shape of a flake, detached from a larger mass by a blow, by
the action of weather, by pressure or by expansion within the larger mass.
The vertical part of a concrete or masonry retaining wall.
A hole designed to collect water and other spilled fluids.
A vegetated, open-channel management practice designed to treat and attenuate runoff
for specified water quality and volume.
Test, adjust and balance.
An instrument used to measure the surface tension of liquids.
Material used to retard the movement of water vapor into walls and prevent condensation
in them; applied separately over the warm side of exposed walls or as a part of batt or
blanket insulation.
Whole Building Design Guide.
Small openings left in the outer wall of masonry construction as an outlet for water inside
a building to move outside the wall and evaporate.
H-3
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Indoor Air Quality (IAQ)
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