EPA-600/8-90-063
August 1990
ENGINEERING DESIGN CRITERIA FOR SUB-SLAB DEPRESSURIZATION
SYSTEMS IN LOW-PERMEABILITY SOILS
Charles S. Fowler
Ashley D. Williamson
Bobby E. Pyle
Frank E. Belzer
Ray N. Coker
Southern Research Institute
2000 Ninth Avenue South
P.O. Box 55305
Birmingham, Alabama 35255-5305
Cooperative Agreement No. CR-814621-01-0
EPA Project Officer: David C. Sanchez
Air and Energy Engineering Research Laboratory
Research Triangle Park, North Carolina 27711
Prepared for:
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
ii
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ABSTRACT
Engineering design criteria for the successful design, installation, and
operation of sub-slab depressurization systems have been developed based on
radon (Rn) mitigation experience on fourteen slab-on-grade houses in south-
central Florida. The Florida houses are characterized as hard to mitigate
houses because of low sub-slab permeabilities. Pre-mitigation indoor
concentrations ranged from 10 to 100 pCi/L. Mitigation experience and results
have been combined into tables and graphs that can be used to determine
recommended numbers and placement criteria for suction holes. Fan and exhaust
pipe size selection is assisted by other tabulated and derived information.
Guidance for installation of the sub-slab system to enhance the systems
operation and effectiveness is also provided. This guidance is being reported
in the form of a design manual for use by mitigators when they are dealing with
houses similar to these.
This report was submitted in fulfillment of CR-814621-01-0 by Southern
Research Institute under the sponsorship of the U.S. Environmental Protection
Agency. This report covers a period December 1987 to June 1990, and work is
still in progress.
iii
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TABLE OF CONTENTS
Page
Abstract i]1
Figures Vli
Tables vii
Acknowledgments viii
Metric Conversion Factors IX
1. Introduction 1
Purpose 1
Scope 2
2. Background Information 4
Problem assessment 4
House summary information 4
Determining entry points 5
Determining house differential pressures 5
Sub-slab communications and permeability 6
Decision making 6
3. Sub-Slab Depressurization Decision Process 10
Determining the number of suction points 10
Determining the size and capacities of the fan to be used 10
Selecting the optimum pipe size(s) for the system 12
4. Suction Hole Determination 15
Determining the number of suction holes 15
Determining the suction hole placement 18
5. Fan Selection 22
Determining the sub-slab flow curves •. 22
Comparing with various fan curves 22
Fan choice considering other factors 24
6. Pipe Selection 27
Air flow versus applied suction 27
Applicability and availability 31
7. Suction Hole Installation 32
Selecting the specific center for drilling 32
Drilling the slab hole 33
Excavating the suction pits 33
Finishing the suction holes 35
Other types of installation 35
8. Piping Layout and Fan Placement 42
Interior applications 42
Exterior applications 44
9. Roof Penetrations 47
Cutting the exit hole 47
Installing roof flashing 48
Placing a vent cap 48
10. System Indicators and Labeling 51
Monitoring 51
Labeling 52
v
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TABLE OF CONTENTS (Continued)
References 54
Appendices
A. Summary Matrix of House Diagnostics Measurements 56
B. Equipment Supplies 58
C. House Summary Information 63
0. Alpha Scintillation Cell Sub-Slab Radon "Sniffs" 75
E. Differential Pressure Measurement 78
F. Subslab Communication Test 81
G. Radon Durability Diagnostics - 1 83
Radon Durability Diagnostics - II...... 84
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FIGURES
Number Page
1 Approximate pressure contours from a suction hole in a 7
representative house plan.
2 Problem diagnosis plan for houses on low-permeability soils 9
being considered for SSD systems.
3 Flow chart for deciding the number of suction points to be 11
planned.
4 Decision process for fan/blower selection. 13
5 Decision process for pipe size selection. 14
6 Minimum number of suction holes based on effective radius of 17
extension, r, and area of slab.
7 Illustration of "boxing in" the suction pipe in a corner 20
of a room where no closet corners are close enough to extend
the pressure field.
8 Sub-slab flow curves for two permeabilities plotted with fan 23
curves for four different kinds of fans.
9 Friction chart for average pipes.
10 Illustration of a typical interior suction point. 36
11 Illustration of a garage suction pipe horizontal installation. 38
12 Illustration of a garage suction pipe 45° installation. 39
13 Exterior suction hole detail. 41
14 Sample attic piping layout for the house plan of Figure 1. 45
15 Schematic of the fan placement and the roof penetration of
a typical installation. 50
TABLES
Number Page
1 Approximate Friction Loss Equivalencies for Various Fittings 30
vii
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ACKNOWLEDGMENTS
The authors would like to express their appreciation to several individuals
and organizations for their efforts on behalf of this project. We would like
to thank Terry Brennan and Wade Evans of Camroden Associates for their
assistance in developing and implementing the mitigation plans for the first
houses. We also wish to thank especially Mike Gilley, formerly of the Polk
County Health Department and currently with the Florida Department of Health
and Rehabilitative Services, Wesley Nail, Tom McNally, and Lee Forgey, all of
the Polk County Health Department for their invaluable contributions and
cooperation throughout this project. We also want to thank the EPA Project
Officer and the entire Radon Mitigation Branch for their capable and
constructive assistance, support, and encouragement in this project. Special
thanks are also in order for David Hintenlang of the University of Florida,
Ken Kirby of Southern Research, Terry Brennan of Camroden Associates, Arthur
Scott of Arthur Scott and Associates, and D. Bruce Henschel and Merrill D.
Jackson both of the Air and Energy Engineering Research Laboratory of the U.S.
EPA for their review and valuable comments on this manuscript. Finally, our
deepest gratitude goes to the homeowners who opened their houses for
diagnostics, installations, and monitoring of systems. Their patience,
hospitality, and endurance were most appreciated.
VI ii
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METRIC CONVERSION FACTORS
Readers more familiar with the metric system may use the following factors
to convert to that system.
Nonmetric Multiplied bv Yields Metric
°F 5/9 (°F-32) "C
ft 0.305 m
ft2 0.093 m2
ft3 0.028 m3
ft3/min 0.00047 m3/sec
gal. 3.785 L
in. 2.54 cm
in. wc 0.249 kPa
in.2 6.452 cm2
mil 25.4 jim
pCi/L 37.0 Bq/m3
ix
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SECTION 1
INTRODUCTION
1.1 PURPOSE
Sub-slab depressurization (SSD) is generally the most common and most
effective radon (Rn) mitigation strategy employed in basement and slab-on-grade
houses. In many areas of the country, the standard building practice is to
place a layer (often. 4 in. [100 mm] or so) of coarse gravel directly beneath a
vapor barrier before pouring the slab. When this has been done, an SSD system
is usually quite effective because of the good permeability and communications
afforded by the gravel layer. However, many older houses were built before
using gravel became a common practice, and in some areas of the country gravel
is not readily available. In these houses the slabs are poured over either the
native soil or a fill soil that has been compacted to some degree to prevent
settling away from the slab once the concrete has hardened. Most of the time
such a soil fill has much lower permeability to air flow. In such instances an
SSD system will not operate as effectively as it would over a coarse aggregate
bed. Since much of the literature (1-4) about SSD systems addresses slabs
poured over gravel, guidance in the installation of SSD systems over low perme-
ability soils has generally been lacking. Ericson et al. (5) in Sweden and
other researchers (6) have reported cases of low permeability beneath the slabs
and have made either some generic observations about the average slab area
affected by given suction holes or have offered unique remedies found to work
in specific houses. However, no uniform guidance document uniquely addressing
design and installation strategies for solving this problem seems to exist.
In 1987, the Radon Mitigation Branch (RMB) of the U.S. Environmental
Protection Agency's Air and Energy Engineering Research Laboratory (AEERL),
Research Triangle Park, North Carolina, initiated a regional demonstration of
radon mitigation in slab-on-grade houses in the phosphate mining area of Polk
County, Florida. The South Central Florida (Polk County) area is one area in
the U.S. where coarse gravel is not readily available. The customary building
practice is to prepare a base of compacted fill soil, overlay it with a vapor
barrier, and then pour the slab.
1
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From December 1987 to September 1989, fourteen single-story slab-on-grade
houses with living areas of about 1300-2600 ft2 (120-240 m2) and initial indoor
radon concentrations of 10-100 pCi/L (400-4,000 Bq/m3) have been mitigated with
(SSD) systems. The systems have ranged from central- and perimeter-located
single suction hole systems to up to four central and/or five perimeter suction
holes, with a variety of combinations. Suction pits ranged from no pits to up
to 12-20 gallons (0.05-0.09 m3) in size. Different sizes of fans and pipes
have been installed. Suction holes were drilled through the slab and through
stem walls under the slab. Fans have been located in attics and outside the
houses. Appendix A contains a summary of house diagnostics measured in the
fourteen houses.
This design guide is an outgrowth of the results that have been measured
in these houses over the last two years. This document has several purposes.
It is hoped that it will be used by mitigators to aid them in the design and
installation of SSD radon mitigation systems. Since radon mitigation is a
relatively new industry, in some areas where this document may be used it may
also provide a reference as to supplies, equipment, and sources useful in the
mitigation field. Because this document reports some lessons learned during
the demonstration and research conducted in these fourteen houses, another
purpose is to alert mitigators to potential pitfalls and problems in installa-
tions, often discovered too late by experience.
1.2 SCOPE
Every house is a unique structure. There are many variables, from geolog-
ical or physical characteristics, to construction features, to operational
house dynamics, to seasonal environmental factors, to home owner inputs that
may affect the potential for radon's entry into that structure. Fourteen
houses is not an adequate sampling to predict all possible problems or situa-
tions. It is hoped, however, that the guidance offered here helps the mitiga-
tor get started in the right direction and helps the user structure the
planning and installing process in a proper framework. Situations will occur
where the information provided in this document will not be applicable or
adequate. There are some houses in which SSD is not the preferred, or even a
2
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recommended, mitigation option. For instance, if there are any unsealed
openings in the slab or extensive cracking whereby the sub-slab space is in
direct conmunication with the indoor space, then sealing the known openings nay
be sufficient to reduce the indoor concentrations. Having unblocked cracks
allowing direct communications between the sub-slab and house space not only
allows soil gas entry, but also provides routes whereby the pressure field of
an SSD system may be truncated. Professional judgment is still the most
important element in the design and installation of radon mitigation systems.
There is also continuing research being conducted relevant to design
criteria for sub-slab mitigation systems in the same areas and other areas of
Florida and across the U.S. and in other parts of the world. The University of
Florida, in particular, is contributing much complimentary research to houses
in a different part of the state. Other local mitigators who have worked
through problems and situations unique to their areas and/or building practices
are also good potential sources of information on possible changes or permuta-
tions in these guidelines. Two years is too short of a time frame, considering
the life of a house, to be able to state definitely that these guidelines will
be the final word in SSD systems in low-permeability soils. Because radon
mitigation is a field growing in breadth and application, readers are encour-
aged to seek additional information. EPA Regional Offices and appropriate
state and local agencies should be good sources of the latest information or of
suggestions for how to obtain the information.
The scope of this report includes a description of background information
necessary or useful to know before installing a system, keys to the selection
of good suction hole locations, fans and pipe sizes, installation suggestions
for suction holes, piping, fans, and exhausts, and recommendations of system
indicators and labeling. A section on commercial equipment is included as
Appendix B to help identify potential sources of supply for products that may
be unfamiliar or unavailable to the reader.
3
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SECTION 2
BACKGROUND INFORMATION
2.1 PROBLEM ASSESSMENT
Before a mitigator or home owner starts to design a radon mitigation
system, it should of course be established that there is an indoor radon
problem. With all of the publicity that radon has received from often-times
less-than-informed sources, home owners may be acting or reacting without
knowing the seriousness or even the certainty of their problem. It is reason-
able and ethical for a mitigator to communicate to the home owner the recom-
mended EPA protocols for screening and follow-up measurements. The EPA
publication "Interim Protocols for Screening and Follow-up Radon and Radon
Decay Product Measurements" (7) presents guidance for making reproducible
measurements of radon concentrations in residences, including recommendations
for using the results to make well-informed decisions about the need for addi-
tional measurements or remedial action. Another complimentary publication that
gives more detail and updated information on the specific use of measurement
techniques is "Indoor Radon and Radon Decay Product Measurement Protocols." (8)
Both of these publications, or others containing essentially parallel guidance
(9), should be available through the EPA Regional Offices.
2.2 HOUSE SUMMARY INFORMATION
Once it is determined that the house in fact does have elevated radon
concentrations, before any other action is taken, certain basic house informa-
tion needs to be obtained. The U.S. EPA Office of Research and Development RMB
uses an extensive House Summary Information form which, because of the research
purposes for which it was compiled, contains more detail than would be neces-
sary for most mitigators. However, because it can be used as a reasonable
guide for someone to develop a personalized form, it is presented as Appendix
C. Some of the most crucial elements to note include the house identification,
the substructure type, any existing mitigation techniques, the aforementioned
indoor radon or progeny measurements, the depth of any floors below grade, the
4
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area of the slab(s), the sub-slab media or aggregate, the floor and ceiling
covering, wall construction and coverings, the existence of any interior load-
bearing walls, whether they penetrate the slab, and the existence of interior
footings. Any information that can be determined about the slab/wall interface
is important, as is the existence of any slab cracks and utility penetrations.
The type of heating and air conditioning and the location of the duct work and
returns are also very helpful to know, as is the approximate location of
plumbing lines, both supply and sewage. Other features of the house and
lifestyle of the owners are useful pieces of information, such as combustion
units, dryers, attic or whole-house fans, exhaust units in kitchens and bath
rooms, and house features such as thermal bypasses. Some of this information
can be obtained from the home owner, from either existing knowledge or plans,
documents, or pictures taken during construction or renovations. The rest may
be visually noted or measured during a visit to the house.
2.3 DETERMINING ENTRY POINTS
A visit and visual inspection provides an excellent opportunity to check
for potential radon entry points into the building shell. The cracks and
utility penetrations noted above are certainly likely candidates. Although
there are several devices on the market that nay be used to obtain a rapid
measurement of Rn near potential entry routes (see Appendix B.l) and perhaps
some newer technology by the time this is being read, one current technique for
detecting radon gas almost instantaneously is called the radon "sniff". Such
an investigation is strictly a diagnostic tool and has no set EPA protocol.
However, a recommended procedure used during this project is presented as
Appendix D. Such a device and procedure tests the candidate entry points for
higher radon concentrations.
2.4 DETERMINING HOUSE DIFFERENTIAL PRESSURES
During the same visit or on a subsequent one, it is informative to deter-
mine the extent of the "driving force" present to pull the radon into the house
with the soil gas. Procedures that attempt to quantify this phenomenon are
often called house differential pressure measurements. Since the pressures
that are being measured are often very small, the equipment with the necessary
5
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sensitivity is often somewhat expensive. Appendix B.2 lists some of the air
measurement equipment sources available to the nitigator market. One set of
recommended procedures for making house differential pressure measurements is
presented in Appendix E.
2.5 SUB-SLAB COMMUNICATIONS AND PERMEABILITY
All of the information received to this point in the investigation process
is useful regardless of the type of mitigation plan to be employed. It may
even help in choosing between simple ventilation, sealing, house pressuriza-
tion, heat exchange ventilation, or SSD. If SSD seems to be the system of
choice, one other diagnostic test needs to be run. The diagnostic sub-slab
communications and permeability measurement involves drilling at least one
1^-14 in. hole just penetrating through the slab in the corner of some closet
or other space designated by the home owner and drilling several 3/8-1/2 in.
pressure and velocity sample holes at various distances in several directions
from the suction hole. A variable speed/suction vacuum cleaner is used to
depressurize the volume beneath the slab at the suction hole. Instruments
capable of measuring pressures in the 2-20 in. WC (or 500-5000 Pa) range and
low flows (1-40 cfm) are needed to make the sub-slab permeability measurements,
and a micromanometer capable of making measurements down to 0.001 in. WC (or
0.2 Pa) is needed for the pressure field extension (communications) test.
Again, some of the equipment sources are listed in Appendix B.2. Appendix F
presents procedures for making the sub-slab communications and permeability
measurements. Figure 1 is a floor plan of a house in which one suction hole
was drilled in a back bedroom closet and nine test holes were drilled in
available corners of rooms and closets. The resulting approximate pressure
contours have been drawn.
2.6 DECISION MAKING
Once all of the diagnostic information is in hand, the mitigator must
decide what system is best to install. If the indoor radon concentrations are
less than 10 pCi/L and the most probable radon entry points have been identi-
fied and can be sealed, then this action should be attempted first before an
SSD system is installed. However, Scott and Findlay (10) and the EPA training
6
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Utility
Garage
Breakfast
Room
Porch
Ref
Kitchen
Dining
Room
Porch
Q.
Foyer
Qui
jving
(pom
ledroom
Lin
Cloi
(Hoset
Bedrooi
Bath
Bedroom
Bedroom
8 feet
Figure 1. Approximate pressure contours from a suction hole in a representative
house plan.
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course (11) indicate Chat staple sealing alone usually produces about a 0-60%
reduction in indoor levels. The lesser reductions usually correspond to
houses in which the radon entry locations are hard to detect or remedy. The
greater reductions seem to occur when the major entry points are able to be
identified and sealed easily. The decisions that now must be made are
summarized in Figure 2, which follows generally the decision-making algorithms
found in Turk, et al. (12), Mosley and Henschel (13), and the EPA training
course (11).
8
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No
Yes
No
Stop
Yes
Ukely entry
points
identified
and
accessible?
No
No
Yes
Yes
Seal
entry
points
Consider SSD >
system for
radon mitigation
- see next
.chapter J
'Annual \
average
above
thresholds
Indoor \
concentrations
above 10
pCi/i? /
Perform follow-up measurements if/as indicated
Measure short-term closed house radon concentrations
Characterize structure, soils, and potential entry points
Perform diagnostic sub-slab
communications and permeability
measurements
Figure 2. Problem diagnosis plan for houses on low-permeability soils being
considered for SSD systems.
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SECTION 3
SUB-SLAB DEPRESSURIZATION DECISION PROCESS
The initial and follow-up screening measurements are made to determine if
the house has a radon problem and to confirm the seriousness of the problem.
Figure 2 from the last section shows how the measurements and observations may
lead to the choice of installing an SSD system to mitigate a home. This
section continues the decision-making process once this choice has been made.
The subsequent three sections deal with the specifics of design of the system,
and the next four relate to the actual installation and testing.
3.1 DETERMINING THE NUMBER OF SUCTION POINTS
The inputs into making these decisions come from information about the
house structure that was collected from the home owner, from physical observa-
tion, and from certain diagnostic measurements. Specific information used
includes the number of slabs in the house, the size of each slab, the pressure
field extension under each slab, and the existence, location, and influence of
any interior footings, sunken or elevated slab areas, expansion joints, sub-
slab obstructions, or geometry features that may limit sub-slab communications.
Figure 3 illustrates some of the ways decisions may be made taking these
factors into account. The result of this decision-making process is a minimum
number of suction holes required to have a good potential for reducing the
indoor radon concentrations. Section 4 contains specific guidance and sugges-
tions on how the design process uses these inputs to determine the number and
locations of the suction holes.
3.2 DETERMINING THE SIZE AND CAPACITIES OF THE FAN TO BE USED
Because radon mitigation is a relatively new industry, it has had to make
use of existing materials and equipment for construction of mitigation systems.
In some cases a wide range of suitable choices for system components are not
available. The availability of exhaust fans or blowers is one such instance.
10
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Decision Criteria
At least one suction point
for each major slab.
With any SSD system, major openings and
cracks in the slab should be closed.
Determine the number of separate
slabs in living space.
Determine minimum number of
suction holes per slab area as
in Section 4.
Determine if pressure field
extension measurements indicate
unreached areas of any slab.
If holes can be placed so as to
bridge the discontinuity under
a slab or between slabs, do so;
otherwise plan at least one
suction point for each isolated
area.
For each slab, determine if there
are any interior footings, sunken
slab areas, obstructions, or
corners that my hamper or prevent
communications to any part of the
slab.
Figure 3. Flow chart for deciding the number of suction
points to be planned.
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The permeability measurements taken at the suction hole during the sub-slab
communication test give the best indication of the nature of the sub-slab
environment that the mitigation system will be evacuating. Section 5 will
demonstrate the development of a sub-slab flow curve. The various fan manufac-
turers usually make available the performance criteria of their fans. When
sub-slab flow curves and fan performance curves are simultaneously plotted, the
intersection of the plots provide an indication of about where an installed
system will operate. The home owner/mitigator then must determine which fan
gives the most benefit within the constraints of costs and other considerations
discussed in Section 5. Figure 4 reflects most of the elements involved and
considered in the process of fan selection.
3.3 SELECTING THE OPTIMUM PIPE SIZE(S) FOR THE SYSTEM
The same plots that aided the decision-making process for fan selection
can give essential information for the proper selection of pipe sizing once the
fan is chosen. The volume of air flow is the primary parameter to be consid-
ered in making this decision. The volumetric air flow is the product of the
air flow velocity and the pipe cross-sectional area. The air velocity deter-
mines the amount of friction loss in the pipe. Therefore, a larger pipe size
means a lower velocity, thus a reduced friction loss. However, in these
tightly packed soils the air flow is usually low, allowing for smaller pipes
without significant friction loss. Other factors that also contribute to the
ultimate performance of the system include the length of the runs of pipe, the
number and severity of bends, and the presence of any constrictions or other
flow inhibitors. Additionally, the availability of the pipe and its necessary
fittings in the size range to be used should be ascertained. Figure 5 illus-
trates the major considerations in selecting the proper pipe size. Section 6
gives the specific details and procedures for pipe selection.
The next four sections overview some of the major aspects of the installa-
tion process. Section 7 focuses on the suction hole installation, including
aligning the hole, drilling through the slab, and evacuating the pit beneath
the slab. The piping layout and the fan placement are discussed in Section 8,
while the roof penetration is covered in Section 9. Section 10 deals with
recommended mitigation system indicators and labeling.
12
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Determine
durability
likelihood.
Estimate
approximate
purchase and
operating costs.
Collect fan information from
available manufacturers.
Conduct sub-slab permeability
diagnostic test.
Consider
wiring
requirements
(costs) and
other
installation
factors.
Plot sub-slab flow curve and various fan curves
on the same axes.
Consider noise levels
(keeping in mind fan
placement and possible
higher installation
costs if sound-
proofing) .
Where the sub-slab curve and each fan curve
intersect indicates approximately the possible
operating pressure differential and resulting
air flow.
Decide the fan which best seems to suit the sub-slab
characteristics and falls within the costs and other
requirements of the owner.
Figure 4.
Decision process for fan/blower selection.
13
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Conduce sub-slab permeability diagnostic test.
Estimate the approximate flow from each suction hole.
Determine the appropriate minimum size piping
for acceptable friction loss.
Estimate length of piping runs and approximate
number of 90* or 45* bends.
Ensure that adequate fittings, elbows, reducers,
etc. are available in this pipe size.
Figure S. Decision process for pipe size selection.
14
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SECTION 4
SUCTION HOLE DETERMINATION
4.1 DETERMINING THE NUMBER OF SUCTION HOLES
As discussed in Section 3, once che decision has been made to install an
SSD system for radon mitigation purposes, the first and most critical question
to answer is that of how many suction holes will be needed to remedy the
problem and where to put them. If the house has more than one slab, then for
determining the number of suction holes, each slab is treated separately. The
following process should be conducted for each separate slab area. The single
most useful diagnostic tool to use as input in this determination is the sub-
slab pressure field extension measurement. Following the procedures outlined
in Appendix E, the mitigator should have a reasonable feel for what types of
communications are present under the slab. The procedure calls for a small
test hole to be placed about 12 in; from the vacuum cleaner suction hole. With
the vacuum cleaner set to produce a pressure differential at that test hole of
about the magnitude you expect a mitigation system to maintain (usually about
1.5-2 in. WC (375-500 Pa), the pressure field measurements should be taken at
2-3 locations within 3 ft of the suction hole, another 2-3 within 10 ft,
another 2-3 within 15 ft, and a few others at greater distances if it seems
appropriate. These test holes should sample as many radial directions from the
suction hole as is possible. At most of the close test holes some differential
pressure may be measured, but at some of the more distant ones, more than
likely no consistent reading will be possible.
It is important to remember that in low-permeability soils sufficient time
must be allowed for the pressure field to be established (3-5 minutes for close
holes and successively longer times for the more distant ones). The distance
from the suction hole at which a pressure differential of about 0.016 in. UC
(4 Pa) was recorded should be taken as the effective radius of extension, r, of
the pressure field from a suction hole in that location. (The pressure differ-
ential 0.016 in. WC [4 Pa] was found to be a reasonably high value for normal
indoor pressure differences; a mitigation system must be able to overcome that
value. In some houses its magnitude may be different.) In the house repre-
sented in Figure 1 in Section 2, the effective radius of extension, r, was
15
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determined to be about 17 ft. (There may be some farther test holes in other
directions that record a detectable pressure field. These are worth noting for
later considerations, but for the present purposes, the r thus determined will
be used.) This effective radius is developed to be s one what conservative.
Although the suction by design is about what the SSD system is expected to
produce, the flow and some other parameters are probably not the same.
However, in these installations, it is usually the pressure field that
determines system effectiveness more than the other parameters.
Once the effective radius of extension from the suction hole is deter-
mined, the next input required is the approximate area (in ft2) of the slab
being considered. Figure 6 is a graph in which the effective radius of
extension is plotted on the x-axis (from right to left) and the area of the
slab is plotted on the y-axis. The diagonal lines divide the regions of the
effective coverage area of the indicated number of suction holes. Find the
effective radius of extension, r, that was determined, go straight up parallel
with the y-axis until you find the area of the slab. The region between the
diagonals where the radius and area intersect indicates the approximate minimum
number of suction holes required by that slab. For the house represented in
Figure 1, the approximate area is 2314 ft2, and the minimum number of holes
would be three. This number may need to be increased if some of the features
mentioned briefly in Section 3--interior footings, sunken slab areas, sub-slab
obstructions, or geometrical shapes of the slab--seem to limit sub-slab
communications. Erratic or discontinuous results of the communication test
will indicate the possibility of such a condition. Figure 3 in Section 3 may
be helpful in the decision process.
In the sample house of Figure 1, since the house is too wide for a suction
hole to reach from front to back, the holes should be staggered so as to get
more complete coverage. The sunken living room slab can be reached by a hole
in the front bedroom closet. The kitchen end of the house may best be covered
by a suction hole through the stem wall in the garage. The specifics of this
procedure will be discussed in Section 7. Generally in low-permeability soils,
there is little likelihood in producing too great a flow for the depressurizing
fan, so when in doubt, an extra hole is a better option than not having enough.
16
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20
5
Effective Pressure Field Radius of Extension, r (ft)
Figure 6. Minimum number of suction holes based on effective radius of extension,
r, and area of slab.
17
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One other factor to consider before the final decision of how many suction
holes to install is whether the soil moisture varies much beneath the slab.
The soil permeability discussed in Section 2 and Appendix F is actually not a
constant but very definitely varies with soil moisture. If the diagnostic test
was made when the sub-slab soil was unusually dry, then the soil peraeability
and the pressure field extension determined will Host probably be greater than
those that would have been measured during a wetter season. In this case, the
mitigator may be wise to Increase the number of suction holes per given slab
area. The pressure field extensions represented in Figure 1 were measured
during a relatively dry season.
4.2 DETERMINING THE SUCTION HOLE PLACEMENT
If the mitigation system is being installed in an unfinished space such as
a basement then there may be few restrictions on the placement of the suction
holes. A flQor plan drawn to scale, perhaps one on which the sub-slab communi-
cations are plotted, is a very useful tool at this point. Sketching in the
effective areas of pressure field extension from various suction hole place-
ments will give an idea of the optimum configuration to try to ensure the best
coverage of the slab. Geometry suggests that holes located about one effective
radius, r, away from the closest exterior wall(s) will give the widest cover-
age. However, in practice, sometimes the soil near the edge of a slab has not
been compacted as well as that near the center, producing either a possible
"settling space" between the top of the soil and the bottom of the slab or else
just a more permeable trench near the perimeter of the slab. If the diagnostic
communication test was run with both a near-perimeter and an interior suction
hole, then the optimum placement may be indicated by those results. If a
greater pressure field extension resulted from the near-perimeter suction hole
without much greater air flow, then the placements of suction holes nearer to
the perimeter is recommended. If, however, the communication test showed much
greater flows from perimeter holes without much greater pressure field exten-
sion, then slab cracks or other leakage is probably limiting the pressure field
extension, and perimeter suction holes should be avoided.
18
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In situations in which the slab being mitigated is predominantly in
finished space, such as a finished basement or a slab-on-grade house, practical
locations are usually far more restricted. In such a circumstance a floor or
house plan is very helpful to have. The finished basement scenario is probably
the more difficult system to design. Usually the best locations from the home
owners' viewpoint are corners of closets because there the installations will
be less noticeable and obtrusive. However, quite often closets will not be
spaced to give full or adequate pressure field coverage. If that is the case,
one may consider placing the suction hole in the corner of a room and then
perhaps "boxing off" that corner if the home owner does not want the pipe to
show (see Figure 7). Boxing off can be used for more central locations as
well. The added difficulty with finished basement installations involves
finding a place or places for the pipes to penetrate the basement ceiling which
will line up with an acceptable first story floor penetration. Some possible
selections of piping layout for such systems will be discussed in Section 8.
Slab-on-grade houses usually also have most, if not all, of the area to be
mitigated as finished space. So many of the problems encountered are similar
to those found in finished basements. There may be a few more options avail-
able to the mitigator, but sometimes a few more or different problems as well.
Closets may be spaced more advantageously than are often found in finished
basements. Usually each bedroom has at least one, there is usually at least
one foyer or entry closet, and each bath may have a linen closet. Moreover,
there may be a pantry or other location where a suction hole may be concealed.
Often there is no upper floor through which an exhaust route must be found.
There may still be large areas that cannot be affected by near-closet
suction holes. These are most typically open living room/dining room/kitchen/
den areas. Quite likely there would be more resistance from the home owner to
placing any interior piping, even concealed, in such spaces. One possibility
to pursue in such a situation would be an exterior suction hole penetrating
horizontally through a stem wall beneath the slab rather than vertically
through the slab in an interior space. What is required for such an exterior
penetration to succeed is that the stem wall must be accessible from outside
the house, i.e., no porches, patios, or concrete or paving directly adjacent to
19
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1.5 - 4 in. (38-100 mm)
PVC pipe to the attic fan
Furring strips
Trim and paint to
match existing wall
finish
Figure 7. Illustration of "boxing in" the suction pipe in
a ccrner of a room where no closet corners are
close enough to extend the pressure field.
20
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the outside wall where the penetration is proposed and that it can be installed
without losing the pressure field to slab cracks and stem wall leakage as was
mentioned earlier with near-perimeter placements in basements. If the stem
wall seems to be too leaky, then inserting the suction pipe completely through
the block and sealing as well as possible the pipe to the inner surface of the
stem wall may help, as well as digging the pit inward while leaving as much
soil as possible in contact with the stem wall. There are other situations in
which to avoid these or other perimeter placements in slab-on-grade houses. If
the footing is on expansive soils or there seems to be foundation or structural
weaknesses near the stem wall in question, a suction hole should not be placed
in that location.
One other possible suction point location in some slab-on-grade houses is
through an attached garage area. Some garages actually have a portion of the
house slab exposed at one end of the space. Even if not, other garages are a
few steps down from the house floor level. In such an instance, the house stem
wall may form the lower course or two of the interior wall of the garage. Then
a horizontal penetration through the stem wall beneath the slab could be a good
suction point. Even if the garage is just a small step down from the house
slab, it may be possible to penetrate the garage slab and extend the system
depressurization under the house. A potential problem with using a garage
penetration is that often the garage slab has settled and/or cracked, leaving
possible by-passes where garage air may be drawn into the system, reducing the
effective suction head and limiting the effectiveness of the system. Piping
details for these systems will be discussed in Section 8.
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SECTION 5
PAN SELECTION
5.1 DETERMINING THE SUB-SLAB FLOW CURVES
While the pressure field extension measurements of the sub-slab communica-
tions diagnostic test give a conservative approximation of an effective
depressurization radius, the pressure and flow measurements are indicators of
the sub-slab permeability. Specifically, the procedures in Appendix F call for
the simultaneous measurement of the suction at the scaling baseline hole and
air flow from the 1.25 or 1.5 in. suction hole at suctions of at least 2, 8,
and 20 in. WC (0.5, 2.0, and 5.0 kPa) under the slab at the baseline hole.
When these measured values are plotted on an x-y axis such as in Figure 8 for
one of the highest permeabilities (10"5 cm2) and one of the more typical
(10"7 cm2) encountered in the Polk County, Florida, study houses, one obtains a
flow curve for the sub-slab fill material.
5.2 COMPARING WITH VARIOUS FAN CURVES
Also plotted in Figure 8 are fan performance curves taken from the EPA
Training Course Manual (11) and from other published fan company figures. The
RDS and R-150/K-6 are inline centrifugal fans that have been widely used in
radon mitigation. The radial and vortex blowers are higher suction instruments
that may be adapted for use in mitigation systems. On such a simultaneous
plotting, the intersections of the soil curves with the fan curves give an
indication of about where the system will operate. Figure 8 suggests that for
both soils, but especially the one with the lower permeability, the system will
tend tc operate near the high suction/low flow end of the fan curves for the
RDS, R-150/K6, or the radial blower. The fan curve for the vortex blower
intersects the higher permeability soil curve at a higher pressure and air flow
than was the case for the other fans and blower. Although its data did not
extend further than the 6 in. WC (1.5k Pa) suction shown in the plot, it
obviously would intersect with the lower permeability soil curves at a more
advantageous point as well.
22
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K vortex blower
i
Radial blower
RDS fan
150/K-6fan
100
200
300
Radial btower
Low-permeability soil
High-permsabslity soil
vorteMblower
R-150/K-6 fan
RDS fan
Air Flow (cfm)
Figure 8. Fan curves for four different kinds of fans/blowers (top) with sub-slab
flow curves for soils with two different permeabilities plotted on an
_ expanded air flow scale (bottom).
23
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5.3 FAN CHOICE CONSIDERING OTHER FACTORS
5.3.1 Fan Durability
Because the mitigation field experience in low-permeability soils is still
in an early phase, it is not clear what the durability of a fan will be when it
is operated at low flows and relatively high suctions. Most manufacturers have
recommended that the K-6 type fan be operated at a maximum pressure differen-
tial of about 1.6 in. VJC (400 Pa). Some indications suggest that fan failure
may occur sooner in a worse operating environment. As will be discussed in
Section 8, the fans are often placed in attics which will be quite hot during
the cooling season. High heat with low flows through the fans may lower the
durability of the fans. Research is currently underway to determine if the
system deteriorates with time or if it maintains a fairly constant flow until
some type of effectiveness failure occurs abruptly. Princeton University has
developed a diagnostic checklist which investigates the durability of operating
fans, as well as the mitigation system as a whole, after the system has been
operating for some time. A copy of the diagnostic form is included as Appendix
G.
5.3.2 Purchase and Operating Costs
The inline centrifugal fans, since they have been designed for radon
mitigation situations, have been kept fairly lightweight and affordable.
Appendix B-4 lists some of the potential suppliers from whom prices can be
obtained. The blowers that produce the higher suctions are generally built for
industrial applications and therefore are somewhat heavier and more costly to
purchase. But in addition to purchase costs, the power requirements to operate
these various fans will differ quite widely. The inline centrifugal fans are
designed to perform in the 75-150 watt power range. The higher suction blowers
are in the 150-250 watt range. Therefore, the operating costs may vary with
the choice of mitigating fan. Since research data has not been collected for a
long enough time in this area, it is not clear how to predict the long-term
costs of these various systems. If the inline fans have too short of a
lifetime, replacement costs may make this system more expensive. If their
durability is long enough, then their lower initial cost and operating costs
may make them the more cost-effective system. Other operating costs that are
very difficult to-predict and compare include the heating/cooling penalty
24
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caused by an undetermined amount of conditioned air being pulled from inside
the house and exhausted to the outside. Other aspects of installation (and re-
installation) costs are covered later, but another factor that must be consid-
ered is whether the home owner will perform any replacements or have to hire
someone else to do the job.
5.3.3 Noise
The inline centrifugal fans are designed to run very quietly (less than 6
sones), and according to most reports receive very little, if any, criticism
from home owners in this regard, as long as the fans are mounted properly to
avoid vibrations of joints and other such potential problems. However, the
larger, more powerful blowers, especially if designed for industrial applica-
tions, characteristically produce quite a bit more noise, often a steady, high-
pitched whine. This noise factor usually is dealt with by installing the fan
as far from the living space as possible and including varying degrees of
sound-proofing when the system is first installed. Both of these options may
increase the initial installation costs, and an extreme fan placement may
require longer piping runs which have a potential to reduce the system effec-
tiveness if the air velocity is large enough. Even with the additional precau-
tions to limit the noise output, some people sensitive to noise may still
object to the larger fans on these grounds.
5.3.4 Other Installation Factors
So far in this section, fan selection based on predicted performance
ranges, fan durability, purchase and operating costs, and noise has been
described in terms of feasibility and home owner acceptance. This final
section will suggest some of the other, sometimes less obvious, features that
may somehow influence health and/or safety and may further impact installation
costs beyond just purchase prices or other factors previously considered.
In the discussion of suction hole placement in Section 4, decisions on
interior versus exterior suction holes and piping may definitely have a bearing
on fan selection. If the exhaust pipe from suction holes in a basement is
routed out through a rim joist (see Section 8) to the outside, or if a suction
hole in a slab-on-grade house is through an exterior stem wall, then the fan
will probably be placed somewhere outside the house. Such a fan must be rated
-------
for exterior applications. In some model lines these fans are more expensive
than interior fans. If the suction hole(s) in a slab-on-grade house is (are)
through an exterior stem wall, then the expected air flow will probably be
greater; perhaps enough so that an inline centrifugal fan may be clearly the
more appropriate choice to a radial or vortex blower. Most fans, even some
designed for radon mitigation, may have to be partially disassembled and
potential leakage areas sealed prior to installation. Even though the fans
should be placed outside the living shell of houses (see Section 8), there are
many opportunities for reentrainment of high-concentration radon-laden soil gas
through attics, unfinished basements, or garages, or even from near-building
exterior placements of fans. The likelihood and projected cost of sealing
should be considered when selecting the fan/blower for the job.
Other features of the fan operations to consider in selecting the instru-
ment are the sizes and placement of the intakes and exhausts of the units.
Generally the inline centrifugal fans have 4, 5, 6 in., or larger openings,
whereas the other blowers are often quite a bit smaller or irregular in size.
(However, some models are available with 3-6 in. round fittings.) Moreover, as
the name suggests, the intakes and exhaust are along the fan axis in the inline
fans. In most radial or vortex blowers, the exhaust flow is perpendicular or
180° relative to the intake. It is possible to lay out the design and piping
to accommodate either of these configurations, but careful thought will have to
be given in routing the pipe and planning for condensate drainage. The ease of
handling and weight of the units within the confines of the spaces and with the
supports required are other aspects to include in the fan selection process.
26
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SECTION 6
PIPE SELECTION
Generally most mitigators use PVC pipe when installing SSD systems. It is
lightweight, easy to cut and handle, convenient for fittings and accessories,
strong in its glueing characteristics, noncorrosive, and smooth so as to offer
low resistance to air movement. For permeable sub-slab environments conducive
to high volumes of air flow, 4-in. or larger PVC pipes are generally used. For
the low flows resulting from the low permeability soils addressed in this
document, 4-in. or smaller PVC pipes are usually adequate. The smaller sizes
have the added advantages of being lighter and easier to handle, less obtrusive
to the home owner and easier to conceal if desired, and usually less expensive
for the pipe, fittings, and accessories. Therefore, an important determination
is what size of pipe is the best to use for the given mitigation project.
Figure 5 from Section 3 may be useful.
6.1 AIR FLOW VERSUS APPLIED SUCTION
The choice of pipe size is most directly governed by the volume rate of
flow (or velocity) expected to move through the pipe. Any volume of fluid
moving through a confined space will lose some of its force of movement or
pressure due to friction between the fluid and the wall of the confining
structure. Larger volumes of air moving through a pipe must move at a greater
velocity, resulting in greater friction loss. Therefore, pipe diameter must be
selected to keep air velocity in a range to minimize friction loss. The best
inputs for estimating the optimum pipe size for a mitigation system again come
from the sub-slab communications diagnostic pressure/flow measurements. The
point of intersection of the fan curve with the sub-slab flow curve will give a
good approximation of the air flow that can be expected in the system.
From the air flow estimate, one may use a chart such as Figure 9 to
estimate the friction loss in various sizes of pipes or ducts. This chart,
like most of the available documentation on air flow through pipes or duct work
(14), is calculated for "average" pipe, which is usually some type of iron pipe
27
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o
o
*—
CO
CO
o
-J
c
o
s
0.1
0.01
100
Air Flow (cfm)
Figure 9. Friction chart for average pipes
28
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with a given smoothness arid joints estimated to be present at some regular
frequency. PVC pipe is less resistive to air movement because of greater
smoothness (14) and usually fewer joints. Therefore, these approximations
usually overestimate the friction loss that would actually be found in PVC
pipes. If the fan selected is one in which the sub-slab flow curve intersec-
tion with the fan curve is in the 1.5-2 in. WC range, then one would probably
want to keep the friction loss to 0.2-0.4 in. WC per 100 ft of pipe. If the
fan curve intersects the sub-slab curve at something greater than 4 in. WC,
then a friction loss of 0.8-1.2 in. WC per 100 ft of pipe could be tolerated.
To use a chart such as Figure 9, find on the x (horizontal) axis the air
flow determined from the sub-slab fan curve intersection. Go up (vertically)
until you are in the friction loss range (y-axis) you determined as above. The
closest pipe size diagonal (those rising from left to right) would be approxi-
mately the best pipe size to achieve your goal. It is advantageous from the
perspective of friction loss to go with the larger pipe, but if other factors
such as expense, ease of handling, or home owner preference indicate otherwise,
the smaller pipe would probably still be a safe choice, especially in light of
the lower friction of PVC pipe discussed previously. To obtain the total
friction loss due to pipe length, multiply the loss figure from the y
(vertical) axis of Figure 9 by the approximate number of 100 foot lengths of
pipe to be installed. In the house of Figure 1, the flow at 2 in. WC was
estimated to be about 9 cfm. From Figure 9, to keep the friction loss between
0.2 and 0.4 in. WC per 100 ft of pipe, 2 or 3 in. PVC would be recommended.
Assume that the home owner insists on 2 in. PVC in the closets. One could
still use 3 in. PVC in the attic. For 2 in. PVC the friction loss would be
0.22 in. WC/100 ft from Figure 9, and for 3 in. PVC, the friction loss would be
0.038 in. WC/100 ft. If multiple suction holes are installed (as would be
recommended in this house), the flow, and thus the friction loss, in the 2 in.
closet risers would be slightly less because the suction at each of the four
holes would be less than it would be for a single hole.
The friction loss in straight pipes is only part of the loss of suction
head that is experienced in a system. Usually the next most significant
features contributing to friction loss are the bends or tees in the system. A
90° elbow or tee in a pipe usually contributes the greatest pressure drop
29
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potential of any of these features. A 45° elbow has slightly over half the
friction loss of a 90" elbow, and a 30° elbow has less than half that of a 90°
one. Table 1 lists the approximate length of pipe that produces the same
friction loss as each of several of the more commonly used connectors.
Table 1. Approximate Friction Loss Equivalencies
for Various Fittings
Equivalent Run of Pipe (ft)
Pipe Diameter (in.)
Type of Fitting 1.5 2 3 4
Tee 1.5 2 3 5
90° Elbow 1 1.5 2 3
45° Elbow 0.75 1 1.5 2
30° Elbow 0.5 0.75 1 1.5
To determine the friction loss in inches of water column (in. WC) for a
system, determine the total length of pipe and the number and kinds of fittings
for each pipe size. Multiply the number of fittings for a pipe size by the
equivalency from Table 1 for that fitting and pipe. Add the total equivalent
feet so determined to the actual length of pipe to be used to get the adjusted
total length of pipe. Then use the friction loss factor determined from Figure
9 to multiply by that adjusted total. Dividing by 100 yields the friction
loss for that size pipe. Repeat the calculation for each pipe size and add the
total together for the whole system.
In the sample house used earlier, we shall assume four suction holes are
to be installed, with each pulling about 9 cfm of soil gas from below the slab.
Suppose that 9 ft of 2 in. PVC is used as "risers" from each suction hole and
that there are two 30° elbows and a 90° elbow in the 2 in. pipe. There are
40 ft of 3 in. PVC and two tees and two 90° elbows to be used in the attic
"trunk line." The two 30° elbows contribute 2 x 0.75 — 1.5 ft equivalent run
of 2 in. PVC and the 90° elbow contributes 1.5 ft of run. These add to 3 ft of
equivalent run plus the 9 ft of actual pipe to yield 12 ft of 2 in. PVC. The
friction loss factor for 2 in. PVC from Figure 9 was 0.22 in. WC/100 ft, so the
30
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total friction loss for the 2 in. section is 0.22 x 12/100 - 0.026 in. WC.
Similarly, the two tees in the 3 in. PVG are equivalent to 2 x 3 - 6 ft of
3 in. PVC and the two elbows are equivalent to 2 x 2 — 4 ft of 3 in. PVC. This
added to the 40 ft of pipe yields 50 ft. Assume about half (25 ft) of this
3 in. PVC has the air flow from one suction hole (9 cfm), and about half
(25 ft) has the air flow from two (18 cfm). Multiplying the lengths by the
friction loss factors from Figure 9 (0.038 and 0.11 in. WC/100 ft, for the 9
and 18 cfm air flows, respectively) and dividing by 100 yields
25 x 0.038/100 + 25 x 0.11/100 - 0.010 + 0.028 - 0.038 in. WC friction loss in
the 3 in. PVC. Summing these two yields 0.026 + 0.038 = 0.064 in. WC system
friction loss. If this total were far above the range mentioned earlier
(0.2-0.4 in. WC), then larger pipe size should be considered and calculated.
Since this value is well below the target maximum range, this is an acceptable
friction load loss. This example has been simplified considerably from the
actual case for illustration purposes, but the numbers are approximately what
would reasonably be expected.
6.2 APPLICABILITY AND AVAILABILITY
If the above calculation indicates a larger pipe size than is feasible or
desired by the home owner, then perhaps a fan that can draw a larger suction at
lower flows is called for. If, however, a certain pipe and fitting size is
determined that is acceptable, then local supply stores should be investigated
to ensure that enough pipe, fittings, and accessories are easily available.
PVC pipe comes in a variety of thicknesses (sometimes called schedules). The
thicker walls are for high-pressure applications and subsequently that PVC is
heavier and more expensive. The applications described here require no extra
thickening, so the thinnest-walled PVC pipe is usually adequate and preferred
for its weight, ease of cutting, and cost. However, some of the fittings and
couplings for one schedule will not fit properly or tightly on the same size
pipe of a different schedule. So a crucial part of the pipe selection process
is that there be an adequate supply of fittings and accessories for the size
and schedule of the PVC selected. Other couplings, reducers, bushings, etc.,
should be investigated at this phase of the process to ensure complete compati-
bility and availability for the system. These are used chiefly at the various
interfaces--pipe to slab, pipe to fan, and fan to exhaust.
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SECTION 7
SUCTION HOLE INSTALLATION
The processes described up to this point in this document have focused on
the design and plans for an SSD radon mitigation system. This and the
following three sections will attempt to step through some of the common
processes involved with the actual installation procedure. Each house and each
system may have unique circumstances, problems, and applications, so these
sections present some of the generic situations that will probably be
encountered in most SSD installations.
7.1 SELECTING THE SPECIFIC CENTER FOR DRILLING
Any hole drilled through the slab as part of the evacuation of the sub-
slab soil gas in a mitigation system must be carefully aligned with other house
features and must simultaneously meet with the home owner's wishes. Whatever
is found below the slab (pipes, ducts, lines, etc.) must be dealt with. The
interface with what is overhead is equally important. Any plans or experiences
that may contribute information about the sub-slab environment should be
thoroughly investigated and studied. The environment immediately above the
suction hole can usually be studied directly. The pipes will need to run
between the joists that support the structure overhead. The size of pipes
being used will directly impact the amount of flexibility in choosing the
exhaust route.
When the general location of the suction hole is identified and the slab
in the area is exposed to the degree possible, a small hole is usually drilled
into the overhead directly above the optimum placement with as long a bit as is
available. Another team member in the space above locates the penetration and
determines the feasibility of having a pipe come through that location. From
there, a plumb bob is used to mark the exact center for the suction hole. If
the overhead and the slab requirements cannot be exactly aligned, then a
lateral displacement with two 45° elbows can be effected just above the slab.
32
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7.2 DRILLING THE SLAB HOLE
Generally the hole drilled or cored through the slab is a 5-in. diameter
hole or larger. This size is required even if small pipe is going to be used
because of the need to excavate some of the sub-slab fill material (soil) as
discussed later. Some mitigators may choose to break out a much larger hole,
excavate, and later pour concrete to restore the slab (see Mosley and Henschel
(13)). In an unfinished basement or a garage or other unfinished space, a
water-cooled core drill may be used to open a hole where pouring new concrete
will not be necessary. In a finished living space, a rotary hammer drill may
be used to drill several small holes and then chisel out the larger hole. A
dry core drill is a neat, relatively quick option, but a little more
expensive.
In all of these methods, there are unwanted by-products of the procedure
that must be minimized. The process of puncturing a concrete slab is going to
produce either dust (dry methods) or a slurry (wet method). A vacuum cleaner
should be kept running as near to the drilling location as is possible to pick
up and remove the dust or slurry as quickly as possible. If dust is the
contaminant, then the vacuum exhaust should be routed outdoors and as far from
the house as possible. Some type of air filtering mask should be used when
breathing in this dusty environment. Once the slab is penetrated, the use of a
respirator designed for radionuclides and radon decay products is recommended
because of the potential for contamination by high concentrations of radon and
radon decay products in the soil gas. The noise generated by most, if not all,
of these methods is sufficiently loud to warrant the wearing of sound
suppressors. Care should be taken to try to contain the drill to just through
the slab. Pipes, sometimes PVC as well as metal, may be found under the slab
in places you would least expect to find them.
7.3 EXCAVATING THE SUCTION PITS
The biggest problem with SSDs in low-permeability soils is that it is very
difficult to extend the pressure field. One reason for this problem is when
air is pulled through compacted porous media, the pressure drop is a function
of the velocity of the air movement through the pores. Therefore, the larger
33
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the surface of the air-soil interface, the larger is the total pore space
exposed, and the suction is distributed over a larger pore volume. The
velocity and pressure drop is less in any given pore. Therefore theoretically,
the larger one could dig a pit from which to take the suction, the greater
would be the potential for a better pressure field extension. Data collected
in the Polk County, Florida, research confirmed this hypothesis. However,
there is a practical limit to how much soil one can remove from under the
suction hole. Personal communication with a structural engineer suggested
that, with the typical quality of slab concrete, one probably would not want to
remove any more than a 4 ft x 4 ft surface of soil from under a slab and
perhaps less, depending on circumstances.
Even more practical, the physical process of excavating the soil from
under an existing slab through a limited access hole often makes the goal of
10-15 gallons (0.05-0.09 m3) of soil a much more reasonable target. Opening
another hole is a better option both by performance and cost standards than
expanding a single hole much larger than this. Indications from some limited
studies have suggested that a wide shallow hole is usually more effective than
a deep narrow hole of approximately the same volume (15). A possible exception
would be the case in which the upper layer of soil has been well compacted and
a deeper hole may penetrate a more permeable layer if the radon entering the
house is coming from that layer. A deep pit is also desirable if the system is
to span an interior footing or a sunken slab area. The pit for a suction hole
near a stem wall should be dug toward the interior of the house. Too much
exposure of the stem wall in the suction pit may result in suction head loss
through the porous blocks or penetrations. If a large section of slab was
removed later to be restored, then the width of the pit is physically limited
only by the area of slab removed, but the practical advantages of multiple pits
still remain. If the excavation is being accomplished through a 5-inch core
hole, then the process is limited by one's reach and ability to remove the
loosened soil from the pit. One technique often employed involves loosening
the soil by any of several means and evacuating the soil with a wet/dry vacuum
cleaner. Damp soil and the occurrence of rock or nodules can easily clog
vacuum hoses and make this a labor- and time-intensive process. The exhaust
from the vacuum cleaner should definitely be routed out of the house and as far
away as possible." Wearing an appropriate respirator as mentioned earlier is
required in this environment.
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7.4 FINISHING THE SUCTION HOLE
If a large portion of slab was removed and a pit excavated so that
concrete must be restored, then a lip of undisturbed soil of sufficient width
to help support the weight of restored concrete must be left around the
perimeter of the pit. Usually a piece of pressure-treated plywood or sheet
metal with a PVC flange at the suction point is placed on that lip of soil.
The PVC exhaust pipe is fastened to the flange, and the concrete is poured on
top of the supporting sheet and around the pipe and finished flush with the
existing slab. The choice of plywood or sheet metal should be determined
according to local code specifications, including, but not limited to, termite
requirements.
If a large section of slab is not removed, and a 5-inch (approximately)
hole Is drilled or cored through the slab, then some combination of PVC
sleeves, bushings, flanges, and/or reducers can be put together to fill the
slab hole and join with the pipe size chosen in accordance with Section 6. The
outermost piece of hardware should be securely caulked into the slab hole both
to provide stability and to seal any potential leaks. Usually a quality
urethane caulk is recommended. The remaining hardware components used to
reduce from the resulting slab hole to the pipe size should fit quite tightly
and be glued securely one to another to prevent leaks. The schematic in Figure
10 illustrates one such combination of PVC fittings. The University of Florida
has improvised a handy wye-gate arrangement just above the slab so that a
limited access may be maintained to the suction pit after the system is
functioning. This may be more convenient for a research effort than useful to
a mitigator.
7.5 OTHER TYPES OF INSTALLATIONS
The previous four divisions of this section have dealt mainly with the
most common SSD suction holes, namely the vertical penetration through the
house slab. Most of the features mentioned are directly applicable to other
suction hole orientations. This section will try to highlight a few of the
differences of applications that may be encountered.
35
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1.5 - 3 in. (38-75 mm)
PVC pipe to attic fan
All PVC joints and
junctions must be
glued tightly
PVC reducer
4 i r.. ! 10 0 mm)
PVC pipe or
sleeve
PVC collar
Urethane caulk for
an air-tight seal
r
Figure 10,
Illustration of a typical interior suction point
showina the 4 — 5 in. (100 — 125 ihti) hole drilled ^
throuah the slah, ths 12—20 gallon (0.05 — 0.09 ni )
pit excavated under the slab/ and a sampling of
PVC collars, sleeves, reducers, etc. leading to
the exhaust pipe going into the attic.
36
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7.5.1 Garage Installation
A suction hole through a portion of a house slab that extends into the
garage is just like one in an interior space. Usually however, it is near a
stem wall or the edge of the house slab, so all efforts should be to dig the
pit and direct the pressure field extension toward the interior of the house
proper. Any suction holes in or near a garage may draw in garage air through
garage floor-wall cracks or other cracks likely to be more prevalent in garages
than in the main body of a house. Therefore, all large cracks should be
caulked, and any others that are questionable should be checked with smoke
sticks to determine if air is being pulled in and if so, caulking is required.
If none of the garage slab is a part of the house slab, a suction hole may
still be placed there. If the house and garage slabs are separated by a stem
wall, then horizontal penetration through that stem wall may be possible from
the garage. If the vertical displacement between the floor levels is not great
enough, this process may require removing a portion of the garage slab and sub-
slab fill. When the garage slab is just a step-down form pour from the house
slab, then a suction hole may still be installed in one of two ways. A section
of the garage slab may be cut away large enough to sink the PVC pipe with a 90°
elbow and to dig an adequate pit from tinder the house slab. A piece of sheet
metal through which the elbow can be sealed should be placed vertically as a
barrier between the pit under the house slab and the soil that will be back-
filled into the garage hole before the garage slab is restored. Figure 11
illustrates this type of an installation. The second possibility is to drill
through a garage/house slab interface on a 45° angle. The resulting core hole
is usually longer and thus more difficult to penetrate to evacuate the soil
from the pit. However, the finishing steps are a bit simpler than having to
restore part of the garage slab. Figure 12 illustrates this type of a hole and
pit.
7.5.2 Exterior Installation
As mentioned in Section 4, sometimes portions of the house slab cannot be
effectively mitigated through closet, pantry, garage, or other interior holes.
Other times, interior suction holes are not practical or feasible. In such
37
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To attic vent piping system and fan
Leave pit open
under the house
s lab
House slab
fipis
Seal interface between new
concrete and pipe with
flovable urethane or other
lexible sealant
New concrete slab over 6 mil
or greater poly vapor barrier
(concrete thicXness to match
existing slab)
Clean cut thoroughly and apply
even coat of epoxy adhesive
efore installing new concrete
1
Sheet metal or
other acceptable
soil barrier
Existing fill
or native soil
Refill cavity under garage
slab with previous fill material
Figure 11- Illustration of a garage suction pioe horizontal
installation into a pit under the house slab in
a house where the garage slab is a step-down form
pour from the house slab. If the house and
garage slabs are separated by a stem wall, then
the pipe goes in through that wall rather than
the sheet metal as pictured here.
38
-------
To attic vent piping system and fan
Dig as large a pit as
possible (12-20 gallons)
from under the house
Caulk thoroughly the
pipe-slab interface
rJm* '
Figure 12. Illustration of a garage suction pipe 45°
installation to a pit under the house slab in
a house where the garage slab is a step-down
form pour from the house slab.
39
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cases, if access to the stem wall beneath the slab in the necessary locations
can be reached easily from outside the house, then a horizontal penetration
through that stem wall has been shown to be a good alternative at not too much
greater cost than interior penetrations. If the stem wall is of concrete block
construction, then the holes in those blocks may be filled or empty. If they
are filled, they must be drilled or cored through just as was described in the
house slab. If the holes are mostly hollow, then the penetration may be much
easier. Once the sub-slab space is entered, the horizontal pits are dug
similar to vertical ones. The greatest effort is to extend the pit as far
toward the slab area to be mitigated as possible. Leaving as much undisturbed
soil along the stem wall as possible will help reduce any leakage or short-
circuiting through that wall. The schematic in Figure 13 illustrates some of
the installation details. (Other guidance schematics which may be consulted
are those of Henschel (1), Tappan (16), and others (17).) The pipe or sleeves
or bushings or whatever the combination being used should be sealed as well as
possible along the interior wall of the concrete block, since it is usually the
sub-slab environment (1000's pCi/L) that is being treated rather than the more
porous wall cavity (10's-100's pCi/L).
40
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Exhaust pipe is routed up the side
of the house, around the eaves,
above the roof line and away from
windows or doors that may be left
open
Mitigation fan must
be rated and wired
for exterior
applications
Reduce
be nec
on the
sizes
r/couplers may
essary depending
fan and pipe
Liberal quantities of
foam or urethane caulk
should be used to prevent
air leakage around the
pipe
Figure 13. Exterior suction hole detail showing the
horizontal hole through the stem wall, the
12-20 gallon (0.05-0.09 m3) suction pit
and the exterior-mounted mitigation fan.
Multiple exterior suction holes may be
routed to the same fan.
41
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SECTION 8
PIPING LAYOUT AND FAN PLACEMENT
Section 4 reviewed steps to be taken in locating the suction holes, and
Section 7 discussed the details of installing them. This section will focus on
aspects of routing and placement of the pipes and fan.
8.1 INTERIOR APPLICATIONS
Most of the time it seems preferable to keep the piping and fan within the
shell of the house. They may be easier to conceal there, and worries of
exposure to weather and exterior wiring requirements may be avoided. Such
installations are usually able to be accomplished in single-story slab-on-grade
houses or multi-level houses with adequate spaces to act as pipe chases.
Usually in single-family residences, concerns such as firewall penetrations are
not encountered. However, in multi-family units and other large buildings,
strict compliance with local codes dealing with firewall and ceiling penetra-
tions must be observed. From the suction holes in such houses, the pipes
usually run vertically through the overhead and into the space above, ultimate-
ly to the attics. Exceptions are when things do not line up well. In such
cases, 30° or 45° bends are preferred to 90° ones if at all possible to reduce
friction losses in the lines as discussed in Section 6. However, with lower
air flow velocities, the friction loss is reduced sometimes to levels such that
the differences are inconsequential.
8.1.1 Attic Piping
Once the attic is reached, usually a 90° bend is necessary to run the pipe
just over the tops of the ceiling joists. It is a good idea to spend a little
extra time planning for the piping runs rather than wasting time, effort, and
materials in putting together a less attractive and less effective system.
Some of the key elements to incorporate in the system design include minimizing
the total length of run of the pipes, minimizing the number of bends, using 30°
or 45° bends rather than 90° ones where possible, locating the fan at the
42
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optimum placement for the home owners desires and effectiveness of the system,
and keeping the pipe sloping downward from the fan toward the suction holes to
permit any condensation to return to the suction holes so as to avoid in-line
air flow blockages. Generally a trunk-line type of arrangement will incorpo-
rate these features and conform to the overall layout of the attic as well. If
several suction lines feed into a central trunk line, then it may need to have
a larger diameter than that of pipe coming from the individual suction holes.
Adding the expected flows together and referring back to Figure 9 of Section 6
will give a very conservative indication of the best size to use.
When bringing the pipe into an attic or moving it around, it is a good
idea to keep the ends taped to minimize insulation or other foreign debris from
being picked up. It is hard to detect and get out and may adversely affect fan
operation if left undetected and not removed. In the restricted space of an
attic, it is a good idea to keep the piping runs as much out of the traffic
pattern as possible for unobstructed future attic access. Of course, there
will quite often be ventilation duct work or other already present obstructions
to avoid as well. To keep the slopes favorable and the pipe less conspicuous,
the run from the suction holes usually starts from the tops of the ceiling
joists. When a trunk line is reached, it may rest on one side on a truss.
This adds some measure of support, since it needs to be above the tops of the
joists and rising gradually. In all cases where the pipe touches wood or other
materials, the use of padding is recommended to reduce possible vibration and
noise. If trusses are not available, especially at a bend that is unsupported
in some dimension, straps may be suspended from a rafter to keep a section of
pipe from sagging.
By the time the fan is reached, especially if trunk lines are coming from
more than one direction, it is necessary for the juncture to be level without
creating a low spot in one of the lines. Often this union occurs just below
the fan. If that be the case, ic may be a good idea to place some blocks or
other means of support under the fixtures so that the weight of the fan and
stack will not produce a depression there. In fact, the fan should be
supported from above by strapping or other means as much as possible.
43
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8.1.2 Attic Fan Placement
If quiet in-line centrifugal fans are used, it is usually a good idea to
try to locate the fan near a central point in the piping system to reduce the
longest piping runs if appreciable air flow is expected. Power will have to be
run to a location relatively close to the fan, so that should also be consid-
ered. There are some advantages to having the fan fairly close and accessible
to the attic entrance in the event of fan failure or maintenance. At least a
switch for the fan should be located so that it can be operated from the attic
access, but the switch must be within eyesight of the fan to conform with elec-
trical codes. Figure 14 shows a sample attic piping diagram for the house plan
of Figure 1. If one of the noisier fans is installed, it will probably be best
to locate it over a garage or somewhere as far from bedrooms as possible. In
either case, in attics with fairly limited vertical room the fans will need to
be placed with adequate space above and below. This usually places them fairly
near the peak. Most home owners will probably want the stack on the back side
of the peak.
8.2 EXTERIOR APPLICATIONS
8.2.1. Pine and Fan Placement
In houses with basements, where the exhaust piping is routed out through a
rim joist, or In slab-on-grade houses, where an exterior suction hole is
installed, the piping and usually the fan will be placed exterior to the house
shell. In houses with basements, there is usually just one pipe coming through
the wall to the outside. The pipe may run horizontally for a distance along
the side of the house until a suitable location for the vertical run is
reached. The fan should be mounted shortly after the turn upward and may need
to be supported in some way. The fan itself must be rated for exterior appli-
cations as mentioned in Section 5, and the wiring must be adequately shielded
to meet all local codes.
While many of the considerations mentioned above hold true for slab-on-
grade houses as well, there may be further things to consider such as more than
one suction hole being piped to the same fan. It is conceivable that suction
44
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Attic Access
22
Fan Q
tl
Figure 14. Sample attic piping layout for the house plan of Figure 1.
45
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holes from four sides of a house could be routed to the same fan. If one fan
of adequate size and rating is being used for more than a single hole, the
factors to consider in pipe and fan placement include the length of the runs,
the number of bends, home owners desires, and the topography of the yard. The
requirement for slightly upward sloping pipe from the suction hole to the fan
is still valid, so the fan cannot be located on the lowest side of the house
without extensive digging at the suction holes on the higher sides. So the
length of run and number of bends may be more difficult to control than with
attic installations.
The pipe that goes from a suction hole around the perimeter of the house
can often be placed in shallow trenches and/or covered by shrubbery or mulch.
The situation of more than one suction hole tying into a common line may neces-
sitate an upgrade in pipe size as was mentioned in the attic case. Support for
pipe may not be as much of an issue because of the proximity to the ground, but
the need to support the fan at its junction may be more of a problem because
the soil may settle, allowing an unsupported fan to sink slightly. This action
could produce the unwanted water collection that could conceivably reduce or
destroy the suction field at remote locations.
8.2.2 Exhaust Routing
For either of these two exterior fan placements, the exhausts usually go
straight up the side of the house and then angle out to go under the eave
similar to the routing of a down spout. The exhaust stack should extend
several feet above the roof at the eave so that the possibility for reentrain-
ment in windows or other openings (including soffit vents) is minimized. A
rain cap is required at the end of the pipe. Some form of strapping should be
used for support, usually at the end of the eave.
46
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SECTION 9
ROOF PENETRATIONS
Those houses in which the piping and fan terminate in the attic will have
a roof penetration for the exhaust stack to exit. The size of this pipe varies
with the fan type. The inline centrifugal fans have 4, 5, or 6 inch exhaust
ports. It is usually convenient to use a reducing coupler, usually made from a
neoprene-like material, to get down to a 4 inch exhaust pipe. With the low
flows normally encountered, there is no problem in reducing the pipe size in
this manner. In many of the more powerful fans designed for high suctions and
low flows, the exhaust ports may be between 1 and 2 inches in diameter. A
straight coupling to an exhaust pipe of the same diameter works best in this
situation. In all cases local codes covering roof penetrations should be
consulted and followed. In regard to reentrainment and downwash, Sanchez (18)
concludes that dilution due to roof-top venting is more effective for lower
exhaust velocities which would result from larger diameter exhaust stacks.
Moreover, the best overall design for minimizing inlet concentrations is to
locate the vent near the center of the roof and have any inlet as far away as
possible. It is preferable not to locate any inlets on the roof. A roof stack
that is high enough or generates a vertical emissions plume rise greater than
150 percent of the height of the building would be necessary to escape all
building downwash effects.
9.1 CUTTING THE EXIT HOLE
Whatever the exhaust pipe selected, a hole saw of just large enough diame-
ter for the pipe to slide through easily should be selected. The exact exit
point must be carefully determined. But perhaps the most difficult and impor-
tant step in the process is to cut the hole as close to vertical as is possi-
ble . Drilling through a slanting roof up from a restricted attic space and
keeping the cut perfectly vertical is more of a practiced art than a science.
Once the pipe exits the attic, most of the rest of the installation centers on
the roof itself.
47
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9.2 INSTALLING ROOF FLASHING
Some sort of roof flashing is required to prevent leaks around the pene-
tration. In some areas of the country a lead flashing seems to be more common,
but a neoprene-like material has been found to work well. In any case, the
locally approved practice will probably be the safest to follow. Several of
the neoprene flashings have been tried, and some of them produced less than
desirable results. The pipe must fit very snugly in the flashing, and the top
of the flashing must be flexible enough to accommodate movement of the pipe and
any deviations from the angle alignments caused either by installation error or
non-standard pitch of the roof.
Extreme care must be taken in blending the flashing in the shingles on the
house to prevent any water leaks from occurring because of the installation.
Some shingles may have to be removed, and several will have to be loosened in
order to place the flashing properly. Depending on the age, condition, and
temperature of the shingles, they may be very brittle or easy to tear. This is
one area where haste can be quite costly. The flashing lip must be placed
under shingles on the up-slope side and over shingles on the down-slope side.
Liberal quantities of a high quality roofing tar or caulk should be applied to
all places and areas where the shingles have been disturbed and the flashing
has been placed.
9.3 PLACING A VENT CAP
A vent cap of some nature is sometimes necessary to prevent water damage
to the fans and water collection in the pipes. Just about any kind of stove
cap or other cover will suffice, as long as it permits the free and unobstruct-
ed exhaust of the air while preventing most of the possibility of water entry.
A PVC tee connector has been used successfully. With the lead flashing, some
sort of vent cap may have to be improvised because rain should be prevented
from entering the stack since the fan is usually immediately below the roof in
the attic. Homeowner approval and acceptance is, of course, required. If
there is a large air flow from the stack, a vent cap may offer a significant
back pressure. In such a case, it may be better to go without a cap because it
is better for the-large-volume plume to jet straight up (deflecting rain)
48
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rather than to be deflected along the roof where reentrainment is possible. A
schematic of some of the salient features of the roof penetrations discussed in
this section is presented in Figure 15.
There is at least one brand of a box-like vent exhaust that fits directly
against the roof so that it performs as both a roof flashing and a vent cap.
The exhaust PVC pipe fits into this box and is fitted into the fan in the
attic. The advantages of neatness and unobtrusiveness combine with eliminating
the need for two separate items to be purchased and installed. However, once
this exhaust is in place, modifications to the fan or other movements of the
pipe are somewhat more difficult because of the semipermanent nature of the cap
since its role as a roof flashing fixes it in the roofing shingles. This
feature is especially undesirable if the system is going to be monitored for
its flow characteristics on several occasions in the future, as is often done
in research situations. Moreover, the likelihood of reentrainment is greater
with the high concentration radon exhaust exiting just at roof level rather
than from a higher stack (18); so this type of vent cap may not be recommended
as the best practice. Moreover, with much air flow, these offer significant
back pressure.
49
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Vent cap
Roof flashing; blend
in shingles correctly
Caulk roof penetration
well
Mitigation fan; wire
to run continuously
Glue all PVC joints tightly
PVC vent pipes to various collector pipes'1
(slight slope away from fan)
Figure 15. Schematic of the fan placement and roof
penetration of a typical installation.
50
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SECTION 10
SYSTEM INDICATORS AND LABELING
Radon itself is an odorless, tasteless, invisible gas. People are not
aware of its presence unless an area's air has been monitored (sampled and
analyzed). Most of the design guidance in this document has been directed
toward installing quiet, unobtrusive, efficient systems that have high proba-
bilities of reducing the entry of invisible radon into the house living
environment. If these systems work as planned, the home owners will hardly
even be reminded of their existence. It may be very easy for them to forget
about the system altogether. If for some reason the system should stop without
some type of warning, such as a bad fan bearing that makes a lot of noise, then
the home owners could easily go for days, weeks, or months without any idea
that the radon concentrations may have increased. Indeed, given a long enough
time of quiet, uninterrupted service, the home owners may forget about some
system components altogether! In time when the house changes hands, it is very
conceivable that the owners may forget to mention parts or even the whole
system. Moreover, if the transaction occurs through some third party agent,
such as a realtor, then the possibility of incorrect, limited, or no informa-
tion getting passed on is even greater. This section briefly discusses two
approaches to limit or minimize the possibility of the system's being neglected
or completely forgotten about.
10.1 MONITORING
The primary physical adjustment that an SSD makes in performing its func-
tion of reducing indoor radon concentrations is reducing the air pressure in
the sub-slab environment both to exhaust sub-slab gas that is high in radon
concentration and to cause any air movement through cracks or openings to go
from the house to the sub-slab space rather than vice versa. Therefore, if the
system is functioning properly, the system pressure is below what the house
pressure is. By installing a pressure differential gauge that measures the
difference between sub-slab and house pressures in an accessible place, the
mitigator enables the home owners to monitor the relative effectiveness of the
51
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system any time they want or think of it. Typically the pressure tap is made
somewhere in the duct. However, this is a rather passive method of monitoring
and requires that the owners think of the system and check on it periodically.
Then, too, gauges can fail, be tampered with, get out of adjustment, or as
mentioned, just be ignored or forgotten about.
An alternative to a pressure differential gauge is some type of system
pressure alarm that turns on if the pressure difference falls below some preset
level. Such an alarm may be less expensive and more active in its performance
than a gauge. Of course, it does not have the sensitivity of a gauge that may
indicate a slow deterioration of the system's performance before the alarm
threshold is reached. The alarm may be a light or a sound that attracts the
attention of the home owner when the system fails. The EPA Radon Contractor
Proficiency Program (RCPP) radon mitigation guidelines recommends that
provisions should be made to provide the client with such methods to detect
system failures. Whatever the device, it usually will need its own power
source so that it will function in the event of blower malfunctioning or air
leaks somewhere in the system.
10.2 LABELING
If the system performs as planned, its alarms will never go off, and the
home owner may still forget about it. Therefore, it is important that the
various components of the system be properly labeled so that any worker who may
know nothing of radon or mitigation systems can be alerted that this pipe or
switch or line or duct is part of a system that should not be tampered with.
First, the breaker box should be labeled in accordance with standard electrical
safety procedures. The specific breaker or fuse that powers the mitigation
system should be so marked, especially if it is on a line with some other
electrical component.
Every SSD system should have an independent switch so that it does not get
turned off by accident and yet it can be isolated in case some type of repair
or adjustment needs to be made to the system. There is at least one commercial
company that markets a variety of plastic, pressure sensitive, multi-colored
52
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OSHA guideline labels that may be appropriate for such uses. Appendix B-7
includes this company as well as others in related functions. The home owner
or mitigator may also want to label the pipes or ducts as to the direction of
flow. The light or other system alarm or monitor could be labeled indicating
what to do if the light comes on, the alarm sounds, or the gauge is reading
below a certain level. Generally, this would include checking the power
(possibly listing the breaker/fuse number and location of the power switch),
checking the fan (give directions), inspecting the suction hole locations for
pipe or connection damage, investigating the pipe runs, and contacting a
mitigation professional (name, address, telephone). The RCPP recommends that
the systems be labeled to identify their function and proper operation. The
labels should be legible from a distance, placed in prominent locations, and
include a system description, a contact name, and a phone number.
53
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REFERENCES
1. Henschel, D. B. Radon Reduction Techniques for Detached Houses:
Technical Guidance (second edition). EPA-625/5-87-019 (NTIS PB88-
184908), U. S. Environmental Protection Agency, Research Triangle Park,
NC, 1987. 192 pp.
2. Osborne, M. C. , T. Brennan, and L. D. Michaels. Radon Mitigation in 10
Clinton, New Jersey, Houses: A Case History. EPA-600/D-87-164 (NTIS
PB87-191847), Presented at APCA meeting, Cherry Hill, NJ, April 1987.
12 pp.
3. Michaels, L. D., T. Brennan, A. S. Viner, A. Mattes, and W. Turner.
Development and Demonstration of Indoor Radon Reduction Measures for 10
Homes in Clinton, New Jersey. EPA-600/8-87-027 (NTIS PB87-215356),
U. S. Environmental Protection Agency, Research Triangle Park, NC, 1987.
166 pp.
4. Findlay, W. 0., A. Robertson, and A. G. Scott. Testing of Indoor Radon
Reduction Techniques in Central Ohio Houses: Phase 1 (Winter 1987-
1988). EPA-600/8-89-071 (NTIS PB89-219984), U. S. Environmental
Protection Agency, Research Triangle Park, NC, 1989. 301 pp.
5. Ericson, S. -0., H. Schmied, and B. Clavensjo. Modified Technology in
New Constructions and Cost Effective Remedial Action in Existing
Structures, to Prevent Infiltration of Soil Gas Carrying Radon.
Radiation Protection Dosimetry 7:224-225, 1984.
6. Scott, A. G. , A. Robertson, and W. 0. Findlay. Installation and Testing
of Indoor Radon Reduction Techniques in 40 Eastern Pennsylvania Houses.
EPA-600/8-88-002 (NTIS PB88-156617), U. S. Environmental Protection
Agency, Research Triangle Park, NC. 388 pp.
7. Ronca-Battista, M., P. Magno, and P. Nyberg. Interim Protocols for
Screening and Follow-up Radon and Radon Decay Product Measurements.
EPA-520/1-86-014, U. S. Environmental Protection Agency, Cincinnati,
Ohio, 1987. 22 pp.
8. U. S. Environmental Protection Agency. Indoor Radon and Radon Decay
Product Measurement Protocols. EPA-520-1/89-009 (NTIS PB89-224273),
Washington, DC, 1989. 102 pp.
9. U. S. Environmental Protection Agency. A Citizen's Guide to Radon.
OPA-86-004, Washington, D.C., 1986. 13 pp.
10. Scott, A. G., and W. 0. Findlay. Demonstration of Remedial Techniques
against Radon in Houses on Florida Phosphate Lands. EPA-520/5-83-009
(NTIS PB84-156157), U. S. Environmental Protection Agency, Montgomery,
AL, 1983. 180 pp.
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11. U. S. Environmental Protection Agency. Reducing Radon in Structures
(2nd Edition). Washington, D.C. 356 pp.
12. Turk, B. H. , J. Harrison, R. J. Prill, and R. G. Sextro. Diagnostic
Procedures for Radon Control. EPA-600/8-88-084 (NTIS PB88-225115) ,
U. S. Environmental Protection Agency, Research Triangle Park, NC, 1987.
58 pp.
13. Mosley, R. B. and D. B. Henschel. Application of Radon Reduction
Methods. EPA-625/5-88-024 (NTIS PB89-122162), U. S. Environmental
Protection Agency, Research Triangle Park, NC, 1988. 129 pp.
14. American Society of Heating, Refrigerating and Air-Conditioning
Engineers, Inc. 1989 ASHRAE Handbook Fundamentals. Atlanta, Georgia,
Chapter 32.
15. Pyle, B. E., A. D. Williamson, C. S. Fowler, F. E. Belzer, M. C.
Osborne, T. Brennan. Radon Mitigation Techniques in Crawl Space,
Basement, and Combination Houses in Nashville, Tennessee. In:
Proceedings: The 1988 Symposium on Radon and Radon Reduction
Technology, Volume 1. EPA-600/9-89-006a (NTIS PB89-167480) , U. S.
Environmental Protection Agency, Research Triangle Park, NC, 1989.
pp. 7-51 - 7-64.
16. Tappan, J. T. Radon Mitigation Seminar. State of New Jersey -
Department of Housing and Development - Bureau of Construction Code
Enforcement. Rutgers, New Jersey, 1986. 50 pp.
17. Pennsylvania Department of Environmental Resources Bureau of Radiation
Protection. Final Report of the Pennsylvania Radon Research and
Demonstration Project. Harrisburg, Pennsylvania, 1988. 160 pp.
18. Sanchez, D. C. Technical Issues Related to Emission Releases from
SubSlab Radon Mitigation Systems. Presented at ASCE National Conference
on Environmental Engineering, Austin, XX, 7/9-12/89.
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APPENDIX A
SUMMARY MATRIX OF HOUSE DIAGNOSTICS MEASUREMENTS
House ID
A1
B2
A3
B3
A4
A7
B8
Bll
Date of visit
11/10/87
11/10/87
11/10/87
11/10/87
11/11/87
11/12/87
11/12/87
11/13
** HOUSE CHARACTERISTICS **
Slab type
SSW
SSW
MS
SSW
SSW
SSW
SSW
SSW
Slab ti2e (ft2)
1696
2210
1376
1667
1500
2373
2570
1700
Foundation shape
Rect.
Rect.
Rect.
Rect.
"L"
"L"
Rect.
"L"
Wall construction
CB
CB
CB
CB
CB
CB
CB
CB
Attic space adequate
Yes
Yes
Yes
N/A
Yes
Marginal
Yes
Yes
Fireplace type
none
none
none
Done
none
none
none
none
Heating fuel
Elec. Res.
Elec. Res.
Elec. Res.
Elec. Res.
Kerosene
Elec. Res.
Elec. Res.
Elec. ;
Air handler
Attic
Attic
Attic
Attic
Attic
Attic
Attic
Attic
Return air
Ceiling
Wall
Ceiling
Ceiling
Ceiling
C/W
Wall
Wall
** SUB-SLAB COMMUNICATION ~*
Pressure ext. (ft)
18
16
15
19
15
20
17
17
Commu. category
Good
Good
Good
Good
Good
Good
Good
Good
- RADON (pO/L) '
INDOOR RADON
Screening
12.1
61.2
83.5
19.3
8.7
64.7
36.0
39.8
Alpha track
73
25.9
23.0
4.5
39.8
22.3
31.7
Post-visit canister
17.7
50.7
37.0
6.9
59.2
37.5
42.0
Grab
4.2
69
12.3
26.4
0.7
. 77
30.9
28.6
SUB-SLAB RADON
Average sniff
9062
15532
20817
10675
3850
17125
14571
5606
Average grab
3600
25835
23113
4460
25000
11493
IN-WALL RADON
Maximum
46
182
36
70
25
143
nm
nm
Minimum
17
8
11
7
42
nm
nm
•* HOUSE DYNAMICS
**
DELTA P (house closed)
Air handler off
nm
nm
-0.004
nm
-0.004
nm
nm
-0.001
on
0.008
nm
nm
nm
nm
nm
0.040
nm
LEAKAGE
E£f leak area (in2)
105
86
96
241
119
120
173
121
KEY:
Slab type SSW - slab on stem wall, MS - monolithic slab
Foundation shape Rect. - rectangular
Wall construction CB - concrete block
Attic space adequate N/A for B3 - exterior installation so attic not used
Heating fuel Elec. Res. • electrical resistance strips
56
-------
SUMMARY MATRIX OF HOUSE DIAGNOSTICS MEASUREMENTS (com.)
House ID
CI
C2
C3
C4
CS
C19
Date of visit
2/16/89
2/17/89
2/17/89
2/16/89
2/16/89
2/17/89
» HOUSE CHARACTERISTICS **
Slab type
SSW
SSW
M5
SSW
SSW
KB
Slab size (ft2)
2314
1747
1739
1733
1740
1775
Foundation shape
Rectangular
"L"
"L"
"L"
"L"
Rectangular
Wall construction
CB
WF/S
CB
WF/BV
SF/S
CB
Attic space adequate
Yes
Yes
Yes
Yes
Yes
Yes
Fireplace type
none
Pre-fab.
none
none
none
Pre-fab.
Heating fuel
Elec. Res.
Elec. Res.
Elec. HP
Elec. Res.
Elec. Res.
Elec. HP
Air handler
Attic
Attic
Attic'
Attic
Attic
Closet
Return air
Wall
Ceiling
Ceiling
Ceiling
Ceiling
Wall
»• SUB-SLAB COMMUNICATION »
Pressure ext. (ft)
15
16
20
14
12
1 1
Commu. category
Good
Good
Good
Good
Fair
Fair
•• RADON (pCi/L) —
INDOORRADON
Screening
69.6
21.4
44.6
103.3
23.8
26.0
Alpha track
41.7
13.8
13.6
41.2
15.7
5.7
Post visit canister
51.8
16.6
32.9
38.2
17.9
14.1
Grab
62
20
30
67
16
17
SUB-SLAB RADON
Average sniff
10392
15423
11951
5000
8281
15116
IN-WALL RADON
Maximum
51
20
23
45
23
76
Minimum
18
7
4
7
7
9
•~HOUSE DYNAMICS**
DELTA P (bouse closed)
Air handler off
0
-0.004
-0.018
0
-0.007
-0.005
on
0
-0.001
-0.009
0.005
-0.001
-0.010
LEAKAGE
Eff leak area (in2)
149
163
128
130
149
97
KEY:
Slab type
Wall construction
Fireplace type
Heating fuel
SSW - slab on stem wall, MS - monolithic slab
CB - concrete block, WF - wood frame, S - stucco, BV - brick veneer, SF
Pie-fib. - pre-fabricated
Elec. Res. - electrical resistance strips, Elec. HP - electric heat pump
steel frame
57
-------
APPENDIX B
EQUIPMENT SUPPLIERS
B-l Radiation Measurement Equipment
Alpha Nuclear Company, 1125 Derry Rd. East Mississaqua, Ontario, Canada,
L5T 1P3, (416) 676-1364, radon progeny measurement equipment.
Bicron Corporation, 12345 Kinsman Rd., Newbury, OH 44065, (216) 564-2251,
spectrometric and other radiation measurement equipment.
Dosimeter Corporation, 11286 Grooms Rd. Cincinnati, OH 43242, (513)
489-8180, radiation measurement devices.
EDA Instruments, Inc., 9200 E. Mineral Ave., Suite 370, Englewood, CO
80112, (303) 790-2541, radon and radon progeny measurement equipment.
EG7G Ortec, 100 Midland Road, Oak Ridge, TN 37831-0895, (800) 251-9750 and
(615) 482-4411, nuclear physics, materials analysis, and gamma spectra
spectrometry.
Femto-Tech, P.O. Box 8257, 150C Industry Dr., Carlisle, OH 45005, (513)
746-4427, passive radon monitor with data recording.
Honeywell, Residential Division, 1985 Douglas Dr. North, Golden Valley, MN
55422, At Ease Passive Radon Monitors.
Luolum Measurements, Inc., P.O. Box 810, 501 Oak St., Sweetwater, TX,
(915) 235-5494, radon and other radiation measurement equipment.
The Nucleus, P.O. Box 2561, Oak Ridge, TN 37831-2561, (615) 482-4041,
pulse weight analyzers, alpha spectrometers, and other radiation
measurement equipment.
Pylon Electronic Development Company, Ltd., 147 Colonnade Rd., Ottawa,
Ontario, Canada, K2E 7L9, (613) 226-7920, radon and other radon
measurement equipment, radon sources, etc.
Rad Electric Inc., 5330 J Spectrum Dr., 270 Technology Park, Frederick, MD
21701, (301) 694-0011, E-PERM electret radon monitors and readers.
Sun Nuclear Corp., 415-C Pineda Court, Melbourne, FL 32940, (305)
259-6862, At Ease radon monitors (passive).
Thermo-Electron Corp., Eberline Instruments Division, P.O. Box 2108, 2108
Airport Rd., Santa Fe, NM 87504-2108, (505) 471-3232, radon and other
radiation measurement equipment.
Thomson & Nielsen Electronics Ltd., 4019 Carling Ave., Kanata, Ontario,
Canada K2K 2A3, (613)592-3019, radon progeny measurement equipment.
58
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JLl2 Air Measurement Equipment
Dwyer Instruments, Inc., P.O. Box 676, Willow Grove, PA 19090, (215)
657-6240 or (219) 872-9141, manometers, gauges, controls, flowmeters,
etc.
Cole-Parmer, 7425 N. Oak Park Ave., Chicago, IL 60648, (800) 323-4340,
flowmeters, anemometers, pulse pumps, assorted scientific supplies, etc.
SKC Inc., 334 Valley View Road, Eighty Four, PA 15330-9614, (412)
941-9701, (800) 752-8472, pump calibrators, air flow and sampling
equipment.
Gilian Instrument Corporation, 8 Dawes Highway, Wayne, NJ 07470, (201)
831-0440, air pumps, calibrators, flow and sampling equipment.
Brailsford & Co., Inc. 870 Milton Road, NY 10580, (914) 967-1820,
diaphragm pumps for air sampling.
Shortridge Instruments, Inc., 14609 N. Scottsdale Road, Scottsdale, AZ
85254, (602) 991-6744, air balancing systems, flowhoods, microiaanometers,
air velocity, temperature, and flow instruments.
Retrotec, P.O. Box 939, Ogdensburg, NY 13669, (613) 723-2453, fan doors
and fan door accessories.
Minneapolis Blower Door, 920 West 53rd St., Minneapolis, MN 55419, (612)
827-1117, blower doors.
Infiltec, P.O. Box 1533, Falls Church, VA 22041, (703) 820-7696, blower
doors.
Neotronics, P.O. Box 370, 2144 Hilton Dr., S.W., Gainesville, GA 30503,
(404) 535-0600 or (800) 535-0606, microiaanometers and other air and gas
measurement equipment.
Alnor Instrument CO., 7555 N. Linder Ave., Skokie, IL 60077, (312)
677-3500, industrial measuring instruments.
Setra Systems, Inc., 45 Nagog Park, Acton, MA 01720, (617) 263-1400,
digital pressure measurement systems.
BGI Inc., 58 Guinan St., Waltham, MA 02154, (617) 891-9380, gas sampling
bags.
Aerovironment Inc., 825 Myrtle Ave. Monrovia, CA 91016-3424, 818 357-9983,
pulse pumps.
59
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B-3 CaulkitiF arid Joint Fillers
Bondex International, Inc., 3616-T Scarlet Oak Blvd., St. Louis, MO 63122,
(314) 225-5001, Bondex Quick Plug hydraulic cement.
General Electric Co., Silicone Products Division, Waterford, NY 12188,
'(301) 840-3626, Silicone II sealant.
Garon Products, Inc., Rasritan Center, 1924 Hwy 35 CN 20, Wall, NJ 07719,
(800) 631-5380, Garon Seal #70016 expanding/reducing polysulfide joint
sealer and Concord #25002 polyurethane sealer.
Dow Corning Corp., P.O. Box 0994, Midland, MI 48640, silicone sealant.
W. R. Meadows, P.O. Box 543, Elgin, .IL 60121, (312) 683-4500, Sealtight
588 non-shrink grout.
Mameco, 4475 E. 175th St., Cleveland, OH 44128, (800)-321-6412, Vulkem
polyurethane sealants.
Sika Corp., Box 297T, Lyndhurst, NJ 07071, (201) 993-8800, Sikaflex
polyurethant multicaulk.
Dap, Inc., P.O. Box 277, Dayton, OH-45401, (513) 667-4461, sealants and
caulks.
Bostik Construction Products, P.O. Box 8, Huntingdon Valley, PA 19006,
(215) 674-5600, Chemculk 950, etc.
Insta-Foam Products, Inc., 1500 Cedarwood Dr., Dept. T, Joliet, IL 60435,
(815) 741-6800, Great Stuff foam sealant, two component polyurethane,
foams, and foam kits.
Smooth-On, Inc., 1000 Valley Road, Gillette, NJ 07933, (201) 647-5800,
epoxy resins, polysulfides, polyurethanes, and other polymers.
Convenience Products, 4205 Forest Park Blvd., St. Louis, MO 63108-2892,
(314) 535-6229, Touch and Seal single component polyurethane foam;
packaged in 12 oz., 24 ox., 10 lb. and 16 lb. cans with applicators.
Fomo Products, Inc., P.O. Box 4261, 1900 Jacoby Road, Akron, OH 48321,
(216) 753-4585, Fomofill, hard foam 1-60.
Universal Foam Systems, Inc., Box 548, 6001 S. Pennsylvania, Cudahy, WI
53110, (414) 744-6066, two component urethane foam.
Progress Unlimited, Inc, 200-T Madison Ave., New York, NY 10016, (212)
689-7030, joint fillers, compresion seals, building gaskets, vapor
barriers, etc.
60
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PH Sales Co., P.O. Box 372, Edison, NJ 08818, (201) 287-5300, expansion
joint closures, packings, etc.
Gore-Tex, 100 Airport Road, P.O. Box 1010, Elkton, MD 12921, (301) 392-
3200, joint/gap fillers, backer rod.
Geocel Building Products Corp., 53282 Marina Dr., P.O. Box 398-T, Elkhart,
IN 46514, (219) 264-0645, Geocel Brushable Sealant, elastomeric co-
polymer, co-polymer and urethane caulks.
3M Washington DC Sales Center (Government Sales Only) 1101 15th St. NW,
Suite 1100, Washington, DC 20005-5085, (202) 331-6900, sealants and
caulks.
Pecora International Corp., 165 Wambola Rd., Harleysville, PA 19438,
(215) 723-6051, Urexpan NR-201 one part pourable polyurethane sealant.
Tremco, 10701 Snaker Blvd., Cleveland, OH 44104, 216) 292-5000, Tremco
THC-900 two part flowable urethane.
Calbar Inc., 2626 N. Marth St., Philadelphia, PA 19125-1493, (215) 739-
9141, sealants and caulks.
B-4 Fans and Related Equipment
R. B. Kanalflakt, Inc., 1121 Lewis Ave., Sarasota, FL 33577, (813)
366-7505, fans and accessories.
W. W. Grainger, Inc., 819 East Gate Dr., Mt. Laurel, NJ 08054, (609)
234-8550, wholesale fan, blower, electrical and other materials supplier.
Radon Detection Services, Inc., P.O. Box 419, Ringows, NJ 08551,
(201) 788-3080, RDS vent fan.
Current Indoor Air Systems, P.O. Box 18075, Boulder, CO 80308, (303)
440-8555, inline vent fans and fabricated ventilation system.
Fernco, 300 S. Dayton St., Davison, MI 48423, (313) 653-9626 or (800)
521-1283, pipe connectors.
Fantech Corp., 13826 Struikman Road, Cerritos, CA 90701, (213) 926-0752,
inline centrifugal fans.
61
-------
B-5 Do-It-Yourself Suppliers and Safetrv
Infiltec, P.O. Box 8007, Falls Church, VA 22041, (703) 820-7696, fans,
couplings, gauges, alarms, test kits, etc. for the do-it-yourselfer.
Safe-Air, 162, E. Chestnut St., Canton, IL 61520, (309) 647-0419 or (800)
331-2943, fans, couplings, gauges, instruments, etc.
Sensidyne, Inc., 12345 Starkey Rd., Suite E, Largo, FL 33543,
(800) 541-9444, CAT. NO. 501 smoke tubes.
Mine Safety Applicances Co. (MSA) MGA Bldg., P.O. Box 426, Pittsburgh, PA
15235, (800) 672-2222, smoke tubes, air samplers, protective equipment,
etc.
E. Vernon Hill, P.O. Box 7053, Corte Madre, CA 94925, (415) 924-6837,
smoke guns, smoke sticks, smoke candles.
Superior Signal Co., Inc., P.O. Box 96, Spotswood, NJ 08884, (201)
251-0880, smoke candles, smoke bombs, smoke blowers.
Robin Air, Robinair Division, Sealed Power Corp, Robinaire Way,
Kontpelier, OH 43543-0193, (419) 485-5561, halogen devices.
National Draeger, INc., P.O. Box 120-T, Pittsburgh, PA 15230, (412)
787-8383, respiratory protection, gas detection, etc.
Direct Safety Co., 7815 South 46th St., Phoenix, A2 85044, (800) 528-
7405.
62
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•/a,
APPENDIX C
HOUSE SUMMARY INFORMATION
HOUSE IDENTIFICATION CODE: 21 PC-ODE:
MAJOR HEATING AND AIR
CONDITIONING (HAC)
SYSTEM:
j A - FORCED AIR
| B - HOT WATER
| C " ELECTRIC RADIANT
j D - WOOD OR COAL STOVE/FIREPLACE
i E - OTHER
HOUSE SUBSTRUCTURE TYPE:
A - BLOCK WALL BASEMENT
E - POURED WALL BASEMENT
C - STONE WALL BASEMENT
D - WOOD WALL BASEMENT
E - SLAB-ON-GRADE
F - BASEMENT AND SLAB-ON-GRADE
G - CRAWL SPACE
H - SLAB-BEL0W-5RADE
I - BASEMENT AND CRAWL SPACE
J - SLAB-ON-GRADE AND CRAWL. SPACE
K - BASEMENT, SLAB-ON-GRADE, AND
CRAWL SPACE
L - UNDERGROUND HCUSE
| KIT ISA"ION TECHNIQUE INSTALLED (IF MORE THAN ONE TECHNIQUE IS
| INSTALLED CONCURRENTLY, INDICATE ALL TECHNIQUES IN THE SYSTEM'¦ :
A - S'JBSLAB VENTILATION :
E - SUBMEM3RANE VENTILATION j
C - BLOCK WALL VENTILATION 'i
D - DRAIN TILE VENTILATION j
E - SEALING ONLY j
F - FRESSURI ZAT ION j'
Ld — INCREASED VENT I LA ! ION (NATU^'riL 9 FAN ASS I STED, Hr.1-.') i
H - TREATMENT OF INDOOR AIR ]
I - REMOVAL OF RADON IN WATER ;
J - TREATMENT OF RADON-CONTAINING BUILDING MATERIALS [
I
FOR MORE THAN CNE TEST OF A SYSTEM, INDICATE
INSTALLATION NUMBER:
63
-------
:/3
RADON nEASURE ME NT=
< IF MC-RE THAN ONE MEASUREMENT WAS COLLECTED It
LOCATION, USE BEST JUDGEMENT)
FREMITI BAT ION:
RADON (pCi/L)
TEST START DATE
TEST COMPLETION DATE
MEASUREMENT DEVICE *
F'OSTMITIEAT ION:
RADON (pCi/L)
TEST START DATE
TEST COMPLETION DATE
MEASUREMENT DEVICE *
I PERCENT REDUCTION
BASEMEN'
/
/
/
/
1st FLOOR
/
/
2nd FLOOR
/
/
/
/
/
/
/
/
yrtj )
CRAWL SPACE;
! * RADON
MEASUREMENT
DEVICE:
A - CHARCOAL CANISTER
B - ALPHA TRACK DECTECTO
C - PYLON
D - E-PERM
E - FEMTO-TECH
F - OTHER
'PROGENY MEASUREMENTS (IF MORE THAN ONE MEASUREMENT WAS COLLECTED IN A GIVEN {
i LOCATION, USE BEST JUDGEMENT) 1
basemen:
1st FLOOR
iFREMITIGAT ION:
PROGENY
TEST START DATE
TEST COMPLETION DATE
MEASUREMENT DEVICE *
POSTMITIGATI ON:
PROGENY iWl.1
TEST START DATE
TEST COMPLETION DATE
MEASUREMENT DEVICE *
/ /
/ /
2nd FLOOR
/ /
/ /
/
/
I PERCENT REDUCTION
PROGENY A
MEASUREMENT E
DEVICE: C
UUNTINUOU3 WUKkIN3 LEVEL MONITOR
RPISU
RADON PROGENY GRAB SAMPLE
64
-------
basement characteristics form
HOUSE IDENTIFICATION CODE:
1 DEPTH OF FLOOR BELOW GRADE (FT): FRONT; . RT:
i AVERAGE DEPTH OF TOTAL BASEMENT BELOW GRADE (FT):
BACK: . LF:
AREA
-------
POTENTIAL RADON ENTRY ROUTES IN BASEMENT
I
(YES, NO, UN'K} WIDTH (IN) TOTAL LENGTH '.FT) i
FLOOR/WALL JOINT . . (
TQTAi_ LENGTH OF ALL OTHER CRACKS (FT) POSSIBLE UNKNOWN!
< 1/16 IN. WIDTH > 1/16 IN. WIDTH CRACKS I
BASEMENT FLOORS . . |
BASEMENT WALLS . . j
SEALED PENETRATIONS UNSEALED PENETRATIONS ;
UTILITY PENETRATIONS j
A - MANY B - SOME C - FEW D - NONE E - UNKNOWN j
EASEMENT DRAINAGE
SUMP (T,F): FLOOR DRAINS A - SUMP C - DRY WELL
NUMBER OF FLOOR DRAINS: EMPTY TO: B - SURFACE D - UNKNOWN
66
-------
5LAB-0N-SRADE CHARACTERISTICS FOF'N HOUSE IDENTIFICATION CODE:
DEPTH OF FLOOR BELOW GRADE (FT): FRONT: . RT:
AVERAGE DEPTH OF TOTAL SLAB BELOW GRADE (FT;:
BACK: . LF
AREA (SO FT)
SLAB:
A - FLOATING
B - ON STEM WALL
C - MONOLITHIC
D - UNKNOWN
IF SLAB IS ON STEM WALL,
SLAB LOCATION RELATIVE TO
FOUNDATION WALL:
A - TOP
B - IN L-BLOCK
C - UNKNOWN
INTERIOR SUBSLAB
FOOTINGS:
A - YES
B - NO
C - UNKNOWN
ISUBSLAB MED I A/AGGREGATE:
A
B
C
D
POOR
MODERATE
GOOD
UNKNOWN
AIR SUPPLY DUCTS LOCATED
UNDER SLAB (T,F):
AIR RETURN DUCTS LOCATED I
UNDER SLAB (T,F i: |
FLOOR COVER
RELATIVE 7.
NONE
DIRT
CARPET
TILE/LINOLEUM
WOOD
TERRAIZO
OTHER
WALL CONSTRUCTION:
WALL COVER-
RELATIVE
A - POURED CONCRETE
B - CINDER BLOCK
C - CONCRETE BLOCK
D - STONE
E - BRICK
F - WOOD
G - OTHER
PAINT
SHEET ROCK
PLASTER
WOOD PANELING
OTHER
NONE
c
67
-------
POTENTIAL RADON ENTRY KGUTES THROUGH 5LAE
(YES, NO, UNK) WIDTH (IN)
FLOOR/WALL JOINT
TOTAL LENGTH (FT >j
i
1
TOTAL LENGTH OF ALL OTHER CRACKS (FT)
< 1/16 IN. WIDTH > 1/16 IN. WIDTH
SLAB
F'OSSIBLE UNKNOWN j
CRACKS (T,F j 1
i
SEALED PENETRATIONS UNS
UTILITY PENETRATIONS
EALED PENETRATIONSj
j
A - MANY B - SOME C - FEW D - NONE
E - UNKNOWN |
DRAINASE
SL'MP T, F: FLOOR DF.'AINS
NUMBER OF FLOOR DRAINS: EMPTY TO:
i
A - sur-F j
B — SUr. FACr. j
C - DRV WELL j'
D - UNKNOWN j
68
-------
CRAWL SPACE CHARACTERISTICS FORM
HOUSE IDENTIFICATION CODE:
HEIGHT OF OVERHEAD ABOVE GRADE (FT):FRONT: . RT:
I AVERAGE DEPTH Oc TOTAL CRAWL SPACE ABOVE GRADE (FT):
back::
LF:
[CLEARANCE FROM SURFACE TO FLOOR (FT): FRONT:
i AVERAGE CLEARANCE FROM SURFACE TO FLOOR (FT)
BACK
IARFA (S3 FT:
CONNECTION
BASEMENT:
TO
1 r
A - FULL DOOR
B - ACCESS OPENING
C - ACCESS DOOR
D - OTHER
E - NONE
CRAWL SPACE
WALLS:
A - POURED CONCRETE
B " CINDER BLOCK
C - CONCRETE BLOCK
D - STONE F - WOOD
E - BRICK G - OTHER
1 CRAWL SPACE
_ . _ . 1
RELAiIVF j
FLOOR COVER
•• I
DIRT
1
|
CONCRETE
i
1 GRAVEL
j
| PLASTIC
j
| OTHER
i
NUMBER OF PIERS:
I NUMBER OF FOUNDATION VENTS
TOTAL AREA OF VtNTS ibu FT)
UNDER FLOOR
INSULATED:
WATER PIPES
INSULATED:
A - YES
B - NO
C - PART7 ALLY
D — UNKNOWN
UTILITY PENETRATIONS TO LIVING AREA j
SEALED: UNSEALED: i
A
B
C
D
E
MANY
SOME
FEW
NONE
UNKNOWN
69
6 'o."9
iww J
-------
HAC SYSTEMS, APPLIANCES, I. BYPASSES
HOUSE IDENTIFICATION CODE:
| PRIMARY SYSTEM:
FUEL:
FURNACE:
A - FORCED AIR A - GAS E - ELECTRIC A
B - HOT WATER B - OIL F - SOLAR E
C - ELECTRIC RADIANT C - COAL 6 - KEROSENE C
D - WOOD OR COAL STOVE/FIREPLACE D - WOOD H - OTHER D
E - OTHER E
BASEMENT
1st FLOOF
CRAWL SPACE
DUCT STRIPS
OTHER
LOCATION OF DUCTS
SUPPLY: RETURN:
j A - BASEMENT C
1 E - SUBSLAB D
CRAWL SPACE E
LIVING AREA F
ATTIC
COMBO
ARE DUCTS
INSUuATED:
r
SIZE OF |
AIR |
I | HANDLER ;
A - .YES C - PART j j (CFM) : j
B - NO D - UNKNOWN I " :
j CENTRAL AC »T,F5:
J WINDOW AC UNITS (tt)
HEAT RECOVERY VENTILATOR
(HRV>:
RATED
CAPACITY
:
HRV
OPERATION
tHRs/D^i t j !
A - WALL
B - DUCTED
C — NONE
D - UNKNOWN
SUPPLEMENTARY HEAT
|FIRE-LAC
f#>
j WuOD/COAL STOVE:
|KEROSENE HEATER?
I (#) :
LOCATION US
V. FRESH AIR
FPl
CT'"?
FP3
ws i
KM 1
KH2
LOCATIONS
A - BASEMENT
B - 1st FLOOR
C - 2nd FLOOR
D - OTHER
USE (1
NONE j
1 Tj u<_: i
OVEP
Uir I
APPLIANCES
LOCATION
FUEL.
A - BASEMENT
A
— Gh~
B - 1st FLOOR
B
- EL EC
C - CRAWL SPACE
C
- PROP
D — BARABE
D
- OTHE
E - OTHER
IAPPL IANCE
I F'ANBE / OVEN
LOCATION
FUEL
•/. FRESH AIR
WATER HEATER
!CLOTHES DRYER
- 6 -9=3
70
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I Whole house FAN (T,F>: attic EXHAUST FAN \T,F>:
i WINDOW FANS - EXHAUST : WINDOW FANS SUPPLY <#>:
j RANGE HOOD EXHAUST FAN : BATHROOM EXHAUST FANS <#):
TYPE AIR CLEANING SYSTEM:
A - SIMPLE FILTER C - MICROPORE FILTER
B - ELECTROSTATIC D - NONE
THERMAL BYPASSES
CHIMNEY s
OPEN STAIR WAYS <#):
LAUNDRY CHUTES <4 > :
LOOSE FITTING ATTIC ACCESS DOORS (T,F):
ANY OTHER SIGNIFICANT BYPASSES ;
71
- 6 t3£3
-------
>/l
PRE!"11 TI GAT X 0!v BASELINE DATfi
HC'JSE I DENT IF I CAT ION CODE:
FREMITI BATION
j RADON < p L i / L)
PRESSURE FIELD
jLOCATION EXTENSION DATA (Y/N) AVERAGE MINIMUM MAXIMUM TEST DAI
|BASEMENT SLAB ' / /
j SLAE-ON-SRADE
t;
jBLOCK WALL N/A
I
i
I SOIL GAS N/A
PREM IT I GAT I UN BLuWER DuOR DATA
ACH © 50 Pa: . ELA (SO IN):
| FREMITI SAT I ON ME ASUREMEN"
i
I OF RADON IN WELL WATER
I < p C i / L> :
ARE THE FOLLOW INS RREMITIGATION DATA AVAILABLE?
FATHE R (STAt I fVj , l_ Ii*l ITEij, NONn.) :
DIFFERENTIAL PRESSURE (YES, NO) :
TRACER GAS MEASUREMENTS
-------
1//
POST MITIGATION SHORT-TERM PERFORMANCE r,4Ti
HOUSE IDEN • IFICr-iTION CGDE:
FCSTM I T I BAT 1ON
!
(LOCATION
FRESSURE FIELD
EXTENSION DATA (Y/N5
RADON
AVERAGE MINIMUM MAXIMUM
TEST DATE
jBASEMENT SLAB
/
f
1SLAB-ON-SRADE
/
|BLOCK WALL
N/A
|£iJlL GAB N/A
i
i
r
F'OSTMIGAT ION BLOWER DOOR DATA [ |F'OSTMITI8ATI ON MEASUREMENT
I
I 'II
| ftCH
-------
-0N3—TERM RADON DATA FOR FINAL INSTALLATIONS
'/
MEASL'REMEN
NUMBER
RADON
pC' i / L)
START
DATE
STOP
DATE
TEST LOCATION
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APPENDIX D
ALPHA SCINTILLATION CELL SUB-SLAB RADON "SNIFFS"
PURPOSE
Sub-slab radon "sniffs" are used to identify the location and relative
strength of potential sources of radon.
METHODOLOGY
1. A visual inspection of the house is made to identify and tag locations for
obtaining radon "sniffs". Sub-slab Communication Test holes should be
among the sample points identified.
As in other limited sample point diagnostics, good engineering judgment
must be used to select a strategic representative and manageable number of
sampling locations.
2. Sample point communication test holes should be closed off to prevent
infiltration of ambient air into the space being sampled. This isolation
of the sampling space may be done by plugging gaps around sampling lines
with rope caulk or using plastic sheet and tape on flat surfaces such as
walls and floors.
3. "Sniffs" are taken under normal representative house conditions, that is,
as influenced by existing environmental conditions such as wind,
precipitation, and temperatures and existing house operating conditions,
such as during the operation of the heating and air conditioning systems
or other household appliances.
4. The following equipment is used:
Alpha scintillation (flow through) cells, 100-200 ml
Air or Nitrogen compressed gas cylinder
Portable photomultiplier tube scintillation counter
Small diameter flexible tubing
0.8 nm filter assembly
Small hand or battery pump
5. Prior to use, the scintillation cells are purged with aged compressed gas
(air or nitrogen) and a 2-minute background count is performed with a
portable photomultiplier tube scintillation counter. Data for each cell
should be entered on a Background Log as attached. Cells with background
counts greater than 10 counts per 2 minutes should not be used.
6. "Sniffs" are taken from sample points through a sample train made up of a
sample probe consisting of the minimum length of small diameter tubing,
followed by a 0.8 /im filter, the scintillation cell, and a small hand-
operated or battery-operated pump. The pump is used to draw sample air
through the-scintillation cell.
75
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7. Scintillation cell samples are counted during collection.
Scintillation cells sampling and counting periods should be selected to
reflect the source activities measured. Counting times should be in the
range of 30 seconds to 1 minute.
NOTE: To avoid counting spurious scintillations as produced by
exposing cell walls to bright ambient light, allow a 1 minute
delay after the cell is placed in the counter before commencing
sampling and counting.
8. After sampling, cells should be purged with aged air to minimize buildup
of the cell background.
9. If a high source of radon is detected, then the cell should be purged
immediately with outside air. If the counts do not reduce sufficiently, a
fresh cell should be used. For this reason, the suspected higher
concentration areas (sub-slab holes) are usually sampled last.
OUTPUT
Counting data is recorded for each scintillation cell sample on a form as
attached ("Sniffer" Data Sheet).
INTERPRETATION
"Sniffer" results are usually expressed as counts per minute as they are
more qualitative results than precise quantitative measures. The information
derived from the radon "sniff" is obtained by looking at the difference in
source strengths and location of those sources.
Elevated and large differences in subslab radon soil gas concentrations,
(e.g., greater than 3X) are important to note and should influence not only the
kind of mitigation but also the specific design of the mitigation system
appropriate for the house under investigation.
76
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"Sniffer" Data Sheet
Bouse ID: _______ Date/Time: / Technicians
Sample Number Scintillation Sample Length Counting Comments
(Mark on Floor Cell Location of Instrument
Plan and Tape} Number Interval
77
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APPENDIX E
Differencial Pressure Measurement
PURPOSE
Pressure differencials across Che house shell induced by environinencal (wind
or temperature) faccors, house appliances (heating/cooling system air handler or
exhausc) and occupant effects are the primary driving forces which draw radon
into a house.
METHODOLOGY
1. A visual inspection of the house is made to identify and
tag locations for making house shell differential pressure
measurements.
NOTE Possible entry points identified as part of the House Survey
diagnostic and Sub-slab Communication Test holes should be
among the measurement points identified.
Points should be identified in the vicinity of potentially
house depressurizing appliances.
NOTE: During the Air Infiltration (Blower Door) Leakage Area test
differential pressure measurements between upstairs and downstairs
floors and outdoors could be made using the blower door system
under both normal and induced conditions.
2.
3.
Measurement points oust be able to be tenqjorarily sealed
off around the non-reference point probe, e.g., sealing
the space around the probe into a wall.
Multiple instantaneous measurements using an inclined manometer
or electronic manometer capable of measuring 1-60 Pa + 0.6 Pa
should be taken over a 2 minute period and recorded on the
attached form.
4. Differential pressure measurements should be made under
house conditions subject to normal (non-extreme) environmental
conditions with major depressurizing appliances off and then
with appliances on.
OUTPUT
Subslab and wall differential pressure measurements made as part of the
Subs lab Comounication Test should be coordinated and recorded and/or cross
referenced.
INTERPRETATION
Short term differential pressure measurements can be used as an indicator of
the magnitude and range convective driving force for (1) above grade infiltration
(2) below grade soil gas entry, (3) soil gas and infiltration air flow within
house shell structural members, and (4) interzonal flows between house compartments,
e.g. basement to first floor due to weather, occupancy, and major depressurizing
appliance effects.
78
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DIFFERENTIAL
PRESSURE MEASUREMENT LOG
Occupant Name
House ID #
Technician
Date
Instrument
DIFFERENTIAL PRESSURE MEASUREMENTS
Measurement Number
Type of Measurement
Location
Measurement Condition
I 2 3
Date/Time
Measurements
Measurement Number
4
5
6
Type of Measurement
Location
Date/Time
Measurements
Measurement Number
7
8
9
Type of Measurement
Location
Date/Time
Measurements
79
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Type of Measurement Indoor Co Ambient Air
Indoor Co Subs lab
Indoor to Blockwall/Wall
Basement of Upstairs
Basement to Crawlspace
Specify others (Reference to ?)
Measurement Conditions Specify salient environmental, house
appliance, and/or occupant induced
house conditions which may affect
measurement. Where possible cross
reference, concurrent quantitative
test conditions, e.g. blower door
induced conditions.
Measurement Readings 4 or 5 measurements should be read
over a 2 minute interval. Record
measurements to nearest 0.25 Pa or
0.001 in UC
80
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APPENDIX F
Subslab Communication Test
PURPOSE
Quantitative characterization of the potential for airflow and pressure
field extensions along all house shell surfaces in contact with soil can be
accomplished by inducing subslab depressurization. The results of this test
will provide a basis for determining 1) the applicability of a subslab
depressurization system to a particular house and 2) an indication of the
engineering design features for an effective subslab system.
METHODOLOGY
1. A visual inspection of the house substructure is made noting the area
of below grade and on grade floor slabs and walls and their
distribution in the house layout. Note this information on a sketch
of the house.
2. From the above assessment with consideration given to subslab system
requirements and the degree of wall and floor finish and the existing
use of house space determine the location for (1) suction test holes
and (2) pressure and air velocity sample holes. Suction test holes
should not be located closer than about 10 meters (30 ft) one to
another and should be located so as to maximize the potential floor
and floor/wall joint area coverage within 5 meters (15 ft) radius of
the suction hole.
3. Pressure and air velocity (F&V) sample holes should be located, as
available, at radial distances of lm, 3m, and 5 meters from suction
test holes. P&V sample holes should be located in 2 or 3 directions
from the suction test hole.
4. Industrial vacuum cleaner, 170 m3h-J, 100 cfmg 80 in WC
Micromanometer, 0-5000 Pa, ±1% @ 1 Pa
Device to measure flow through slab and wall holes
Hot wire anemometer, 30 ft/min, ± 2%
Device to measure flow & pressures at vacuum cleaner inlet
Pitot tube or electronic anemometer or calibrated orifice(s)
Smoke bottle
Speed control for vacuum
3/8" variable speed hand drill
3/8" or 1/2" hammer drill masonary and impact drill bits
5. A (scaling baseline) pressure sample hole should be located about
300 mm (12 in.) from each suction test hole.
6. 32 or 38mm (1.25 or 1.5 in.) suction test holes are drilled through
designated slab and/or wall locations and temporarily sealed with a
rope caulk (e.g. Mortite)
81
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7. A subset of pressure and velocity sample holes (10 or 12.7 mm 0.375
or 0.5 In.), including the baseline P&V sample hole, are drilled
through designated slab and/or wall locations and temporarily sealed
with rope caulk (e.g. Mortite)
NOTE: At this stage in the communication test procedure subslab and wall
grab air samples could be taken to map radon concentrations at points
in the house shell under normal house operating conditions, i.e.,
depressurizing appliances off or on or under induced
depressurization, blower door conditions. Differential pressure
measurement may also be made at this point under normal or induced
depressurization conditions. See Radon Grab Sampling, Infiltration-
Leakage Area Tests and House Differential Pressure Measurements.
8. The.industrial (variable speed) vacuum cleaner is connected with an
air tight seal to the suction test hole and operated at the baseline
hole pressures of 0.5, 2.0, and 5.0 kPA while measuring the induced
flow from the suction hole and the pressures and flows at the sample
holes.
9. After measurements have been made through holes drilled just through
the slabs, the holes should be drilled to the full extent of the bits
being used and the same measurements made again.
OUTPUT
Test results are recorded on a form similar to the attached.
INTERPRETATION
If the results of the subslab communication test show that a depressurized
condition 0.25-1.0 Pa can be extended to all slab surfaces and walls in contact
with substructure soil this indicates a high confidence that a subslab
depressurization system can be installed to remediate the entry of soil gas
borne radon.
82
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APPENDIX G
Radon Durability Diagnostics - I
HOUSE NO. Date
location
Homeowner Questionnaire
1. Has the system been running steadily during these past months Y[ ] No[ ]
If not, what period has it been off? . Why is it turned off?
2. Has there been noise when the mitigation system operates? Y[ ] ]
If yes, describe the noise; when does it occur?
3. Has there been any moisture present along the mitigation system pipe
work or at the point of exhaust? Y[ ] ]
If yes, describe problems:
4. Has there been any events in the house that may have influenced radon
mitigation operation? Y[ ] N[ ]
If yes, please describe:
5. Have you observed any evidence of settling in the house, for example,
new wall or floor cracks, etc? Y[ J N[ ]
If yes, please describe:
6. Is there any other feature of the mitigation system you have questions
about?
83
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Radon Durability Dlagnosci.es - II
HOUSE NO. Date
location
Diapnostle Procedures
1. Observe basement for any new cracks or where old sealing joints may have
opened. Note areas of concern.
2. Use stethoscope to check for noise problems from fan, bearings,
vibration of piping, etc. Note status.
3. Check airflow in mitigation system piping:
Location Present previous ( )
1)
2)
3)
A) __
4. Check pressure differentials:
Basement/Subslab (S)
Basement to mitigation pipe (M)
Location Present Previous ( )
1)
2>
3)
4)
5. General Observations: (continue comments on reverse side)
84
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TECHNICAL REPORT DATA
(Please read Instructions on die reverse be/ore compter
1. REPORT NO. 12.
EPA-600/8-90-063 |
3.
4. TITLE AND SUBTITLE
Engineering Design Criteria for Sub-slab Depressuri-
zation Systems in Low-permeability Soils
5. REPORT DATE
.August 1990
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
C. S. Fowler, A. D. Williamson, B. E. Pyle, F. E.
Belzer, and E, N. Coker
8. PERFORMING ORGANIZATION REPORT NO.
SRI-ENV-89-911-6411-070
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Southern Research Institute
P. C. Box 55305
Birmingham, Alabama 35255-5305
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO,
CR 814621-01-0
12. SPONSORING AGENCY NAME AND ADORESS
EPA, Office of Research and Development
Air and Energy Engineering Research Laboratory
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final: 3/89 - 4/90
14. SPONSORING AGENCY COOE
EPA/600/13
is.supplementary notes AEERL project officer is David C. Sanchez, Mail Drop 54, 919/
541-2979.
is. abstractreport describes the development of engineering design criteria for the
successful design, installation, and operation of sub-slab depressurization systems,
based on radon (Rn) mitigation experience on 14 slab-on-grade houses in South Cen-
tral Florida. The Florida houses are characterized as being hard to mitigate because
of low sub-slab permeabilities. Premitigation indoor Rn concentrations ranged from
10 to 100 pCi/L. Mitigation experience and results have been combined into tables
and graphs that can be used to determine recommended numbers and placement cri-
teria for suction holes. Fan and exhaust pipe size selection is assisted by other tab-
ulated and derived information. Guidance for installation of the sub-slab system to
enhance the system's operation and effectiveness is also provided. This guidance is
reported in the form of a design manual for use by mitigators when they are dealing
with houses similar to these.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COS ATI Field/Group
Pollution Slabs
Radon Fans
Engineering
Design Criteria
Soils
Residential Buildings
Pollution Control
Stationary Sources
Depressurization
Indoor Air
13 B 13 C
07B 13 A
14 F
14G
08G.08M
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
93
20. SECURITY CLASS {Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 |9-73)
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