v>EPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
Air and Energy Engineering
Research Laboratory
Research Triangle Park,
NC 27711
Research and Development
EPA/625/5-86/019
Radon Reduction Techniques
for Detached Houses
Technical Guidance
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EPA/625/5-86/019
June 1986
Radon Reduction Techniques
for Detached Houses
Technical Guidance
Air and Energy Engineering Research Laboratory
Office of Environmental Engineering and Technology
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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EPA REVIEW NOTICE
This report has been reviewed by the U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the contents necessarily
reflect the views and policy of the Agency, nor does mention of firms, trade names,
or commercial products constitute endorsement or recommendation for use.
This document is availble to the public through the Center for Environmental
Research Information, Distribution, 26 W. St. Clair, Cincinnati, OH 45268.
A brief overview of the material contained in this document is available in the book-
let, "Radon Reduction Methods: A Homeowner's Guide," (OPA-86-005). For infor-
mation on how to obtain a copy, check with your State radiological health program
office (see Chapter 3 of this document).
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FOREWORD
This document is intended to supply State radiological health officials, State envi-
ronmental officials, and building contractors (and the concerned homeowners who
seek their assistance) with information on how to modify houses to reduce indoor
radon. This guidance is based on the results of documented tests by many research
groups, with emphasis on the soil-gas removal techniques EPA tested in the Read-
ing Prong (Pennsylvania). ,
Although radon mitigation is a new field, one fact is already clear: no two houses are
alike. Because of subtle differences in house construction and radon source mate-
rial, seemingly identical houses may require quite different approaches to control-
ling indoor radon.
Homeowners are cautioned against attempting installations themselves except in
cases of low indoor radon levels (controllable with inexpensive methods). Much
expense can be incurred before the inadequacy of a technique is evident. Thus, the
services of a mitigation contractor, knowledgeable in house construction and the
principles of radon entry, are usually required. Homeowners, or their contractors,
may also find it advisable to seek the assistance of their State radiological health
official (or environmental official, in some States) in interpreting the information
presented here.
EPA's Office of Research and Development is widening the scope of its house test-
ing as well as seeking more information on techniques that other research groups
have used successfully. This publication will be revised as new information be-
comes available.
in
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CONTENTS
Page
Foreword .Hi
Figures , —...., vi
Tables .• ., vi
Acknowledgments '. vii
Glossary ..... viii
Metric Equivalents ;.. xi
1. Introduction ...;.. 1
1.1 Purpose 1
1.2 Scope and Content '....... 1
1.3 Radon and its Sources :................ 1
2. Indoor Radon Reduction Approaches • 5
2.1 Overview of Radon Reduction Methods 5
2.2 Natural and Forced Air Ventilation : 10
2.3 Forced Air Ventilation With Heat Recovery 11
2.4 Active Avoidance of House Depressurization 12
2.5 Sealing Major Radon Sources 13
2.6 Sealing Radon Entry Routes : 13
2.7 Drain Tile Soil Ventilation ......... 15
2.8 Active Ventilation of Hollow-Block Basement Walls 19
2.9 Ventilation of Sub-Slab 32
3. Available Technical Assistance 43
3.1 State Radiological Health Program Office Contacts 43
3.2 U.S. Environmental Protection Agency Program
Responsibilities 47
4. References * 49
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FIGURES
Number Page
1 Major radon entry routes into detached houses 4
2 Effect of ventilation on indoor radon concentrations 5
3 Drain tile ventilation where tile drains to sump 14
4 Drain tile ventilation where tile drains to soakaway 18
5 Wall ventilation with individual suction points in each wall 23
6 Closing top void when a fair amount of the void is exposed 24
7 One option for closing top void when little of the void is exposed ... 25
8 Closing top void and veneer gap when exterior brick veneer is present . 25
9 Wall ventilation with baseboard duct 29
10 Sub-slab ventilation using individual suction point approach 34
11 Sub-slab ventilation using individual suction point approach 35
(option with horizontal run under slab)
12 Sub-slab piping network suggested for new houses (Central Mortgage
and Housing Corp. of Canada) 38
13 Sub-slab piping network around perimeter of slab 39
TABLES
Number Page
1 Representative Exposures to Radon-222 Progeny 2
2 A Comparison of Health Risks and Percentage Reductions in Measured
Concentrations Needed to Reach 0.02 WL 3
3 Summary of Radon Reduction Techniques 7
4 Soil-gas-borne Radon Entry Routes 15
5 Results Obtained With Drain Tile Systems in Three Test Houses 16
6 Results Obtained With Wall Ventilation in Three Test Houses 21
VI
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A CKNO WLEDGMENTS
Many individuals contributed to the preparation and review of this manual. The
authors are David C. Sanchez and D. Bruce Henschel of the Air and Energy Engi-
neering Research Laboratory (AEERL), Research Triangle Park, North Carolina.
Sharron E. Rogers of PEI Associates, Inc., Durham, North Carolina, provided tech-
nical editing. Virginia Hathaway and Jo-Anne Hockemeier of JACA Corporation,
Fort Washington, Pennsylvania, provided production and graphics support. Judy
Cook of AEERL served as task project officer and managed document preparation.
Norman Kulujian of EPA's Center for Environmental Research Information, Cincin-
nati, Ohio, served as editorial and graphics advisor, and contract administrator.
This document was submitted for comment to a broad range of technical and policy
reviewers, including: Radiological health/environmental officials in the States of
Colorado, Florida, Idaho, Illinois, Kentucky, Maine, Maryland, Minnesota, Missis-
sippi, Missouri, Montana, New Jersey, New Mexico, New York, Ohio, Pennsylva-
nia, South Carolina, Virginia, and Washington; the Department of Energy and its
San Francisco Operations Office and the Lawrence Berkeley Laboratory; the Ra-
dionuclides Task Group of the American Society for Testing and Measurement;
EPA's Science Advisory Board; all EPA Regional Offices; EPA's Radon Manage-
ment Committee and the Radon Working Group; EPA's Offices of Radiation Pro-
grams, Drinking Water, Emergency and Remedial Response, Pesticides and Toxic
Substances, Program Planning and Evaluation, General Counsel, and External Af-
fairs; and EPA's Center for Environmental Research Information.
We are particularly indebted to the following persons who provided important tech-
nical documentation as well as technical reviews: William Belanger, EPA Region 3;
Terry Brennan, Camroden Associates; William Brodhead, Buffalo Homes; Joe Co-
truvo, EPA Office of Drinking Water; Henry D. May, EPA Region 6; Arthur Scott,
American ATCON; Richard Sextro, Lawrence Berkeley Laboratory; J. Tell Tappan,
Arix Sciences, Inc.; and Bede Wellford, Airxchange.
We are indebted to the States of Maine, Minnesota, New Jersey, New York, Penn-
sylvania, and Washington, and to EPA Regions 2, 3, and 6 for their valuable com-
ments.
VII
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Glossary
Air changes per hour (ach)—The movement of a
volume of air in a given period of time; if a
house has 1 air change per hour, it means that
all of the air in the house will be replaced in a
1-hour period. Air changes also may be ex-
pressed in cubic feet per minute.
Alpha particle—A positively charged subatomic
particle emitted during radioactive decay, indis-
tinguishable from a helium atom nucleus and
consisting of two protons and two neutrons.
Back-drafting—A condition where the normal di-
rection of air flow through a pipe is reversed
due to abnormal pressure changes at one end
of the pipe. Examples include the reversal of
smoke down rather than up a fireplace chimney
when strong winds create a down draft, or a
similar condition that may occur in a furnace
(or other combustion appliance) stack or vent
when the inside of a room or house becomes
temporarily depressurized. Such depressuriza-
tion may result in increased radon-containing
soil gas being drawn into the indoor air space
in response to the lowered pressure.
Barrier coating(s)—A layer of a material that acts
to obstruct or prevent passage of something
through a surface that is to be protected. More
specifically, grout, caulk, or various sealing
compounds, perhaps used with polyurethane
membranes to prevent soil-gas-borne radon
from moving through walls, cracks, or joints in
a house.
Baseboard duct—A continuous system of sheetme-
tal or plastic channel ducts that is sealed over
the joint between the wall and floor around the
entire perimeter of the basement. Holes drilled
into hollow blocks in the wall allow suction to
be drawn on the walls and joint to remove ra-
don through the ducts to a release point away
from the inside of the house.
Confidence—The degree of trust one can have that
a method will achieve the radon reduction esti-
mated.
Contractor—A building trades professional who
would work for profit to correct radon prob-
lems; a remediation expert. At the present
time, training programs are underway to pro-
vide working professionals with the knowledge
and experience necessary to control radon ex-
posure problems. State radiological health of-
fices will haye lists of qualified professionals.
Crawl space —An area beneath some types of
houses which are constructed so that the floor.
is raised slightly above the ground, leaving a
crawl space between the two to allow access
to utilities and other services. In contrast to
slab-on-grade or basement construction
houses.
Cubic feet per minute (cfm)—A measure of the
volume of a substance flowing within a fixed
period of time. With indoor air refers to the
amount of air in cubic feet that is exchanged
with outdoor air in a minute's time, or an air
exchange rate.
Depressurization—A condition that occurs when
the air pressure inside a house is lower than the
air pressure outside. Normally houses are under
slightly positive pressure. Depressurization can
occur when household appliances that con-
sume or exhaust house air, such as fireplaces
or furnaces, are not supplied with enough
makeup air. Radon-containing soil gas may be
drawn into a house more rapidly under the de-
pressurized condition.
Detached houses —Single family dwellings as op-
posed to apartments, duplexes, townhomes, or
condominiums. Those dwellings which are typi-
cally occupied by one family unit and which do
not share foundations and/or walls with other
family dwellings.
Duct work —Any enclosed channel(s) or tubular
passage(s), normally hidden above the ceiling,
behind the walls, or under the floor for the pas-
sage of wiring or hot or cold air.
Footing(s)—A concrete or stone base which sup-
ports a foundation wall and which is used to
distribute the weight of the house over the soil
or subgrade underlying the house.
French drain (also channel drain)—A water drain-
age technique installed in basements of some
houses during initial construction. If present,
typically consists of a 1- or 2-in. gap between
the basement block wall and the concrete floor
slab around the entire perimeter inside the
basement.
VIII
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Grade (above or below)—The term by which the
level of the ground surrounding a house is
known. In construction typically refers to the
surface of the ground. Things can be located at
grade, below grade, or above grade relative to
the surface of the ground.
Header joist—Also called header plate or band joist.
A board (typically 2 x 8 in.) that rests (on its 2-
in. dimension) on top of the sill plate around
the perimeter of the house. The ends of the
floor joists are nailed into the header joist that
serves to maintain spacing between the floor
joists.
Heat exchanger—A device used to transfer heat
from one medium to another. Also called air-to-
air heat recovery ventilators or heat recovery
ventilators.
Heat recovery ventilators—Also known as air-to-
air heat exchangers or heat exchangers.
Hollow-block walls. Block walls—A wall built of
hollow rectangular masonry units arranged to
provide an air space within the wall between
the facing and backing tiers of the individual
blocks. Typical construction for concrete block
or cinder block foundations in detached
houses.
House air—Synonymous with indoor air. That part
of the atmosphere that occupies tr^ space
within the interior of a house.
Indoor air—That part of the atmosphere or air that
occupies the space within the interior of a
house or other building. Researchers have
found that the quality of indoor air is affected
by the construction materials (and other indoor
activities) that make up the house, the location
of the house, and the ventilation characteristics
of the space. >
Ionizing radiation—Any type of radiation capable
of producing ionization in materials it contacts;
includes high energy charged particles such as
alpha and beta rays and nonparticulate radia-
tion such as neutrons arid X-rays. In contrast to
wave radiation, such as visible light and radio
waves, which do not ionize adjacent atoms as
they move.
Joist—Any of the parallel horizontal beams set from
wall to wall to support the boards of a floor or
.ceiling.
Makeup air—Air which is supplied directly by a
small pipe to the vicinity of a combustion appli-
ance, such as a furnace, clothes dryer, or fire-
place, to replace the air that is used up in con>
bustion or that rises out a vent due to the heat
of combustion. Provision for makeup air can
prevent the conditions of back-drafting and de-
pressurization and thus prevent increased radon
entry to the house. -
Picocurie (pCi)—A unit of measurement of radioac-
tivity. A curie is the amount of any radionu-
clide that undergoes exactly 3.7 x IP10 radioac-
tive disintegrations per second. Pico indicates
an amount equal to one trillionth (1Q-12) of the
unit of-measure. .
Radionuclide—Any naturally occurring or artifically
produced radioactive element or isotope.
Radon—A colorless, naturally occurring, radioac-
tive, inert gaseous element formed by radioac-
tive decay of radium atoms. Chemical symbol is
Rn, atomic weight 222, half-life 3.82 days.
Radon progeny. Radon daughters —A term used
to refer collectively to the intermediate prod-
ucts in the radon decay chain. Each "daugh-
ter" is an ultrafine radioactive particle that de-
cays into another radioactive "daughter" until
finally a stable nonradioactive lead molecule is
formed and.no further radioactivity is pro-
duced.
Riser, Trap and Riser—A riser is a vertical pipe,
including pipes which allow warm air to flow
from a furnace to second-story rooms or to al-
low sewer gas to exhaust from sewer systems
to the outside air; typically not under pressure
or with minimum fan (forced air) pressure. A
trap is a bend (often S-shaped) in a water or
ventilation system that holds water to form a
barrier to gases which might otherwise rise up
into the house. A trap and riser together are
used to capture gas and route it to a chosen
release point.
Sill plate —A horizontal band (typically 2x6 in.)
that rests on top of a block or poured concrete
foundation wall and extends around the entire
perimeter of the house. The ends of the floor
joists which support the floor above the foun-
dation wall rest upon the sill plate.
Slab, Slab-construction —A term used to describe
a flat bed of concrete on which a house is built
in some types of construction. Such houses
typically do not have basements or crawl
spaces.
Soakaway—A drainage device that allows water to
slowly be absorbed into the soil or to drain
away from the foundation of a house. The
drainage water may be carried some distance
away from the house to the soakaway through
a pipe.
Soil gas—Those gaseous elements and compounds
that occur in the small spaces between parti--
cles of the earth or. soil. Rock can contain gas
IX
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also. Such gases can move through or leave
the soil or rock depending on changes in pres-
sure. Radon is a gas which forms in the soil
wherever radioactive decay of radium occurs.
Source strength—The intensity, power, or concen-
tration of a chemical or action from its point of
origin. In this report, refers to the general in-
tensity of radon evolution from a specific soil-
or rock-type beneath a house.
Stack effect—In houses and other buildings, the
tendency toward displacement (caused by the
difference in temperature) of internal heated air
by unheated outside air due to the difference in
density of outside and inside air. Similar to the
air and gas in a duct, flue, or chimney rising
when heated due to its lower density compared
with that of surrounding air or gas.
Sump, Sump pump—A pit or hole in a basement
designed to collect water, and from which such
water is drained by means of a vertical-lift or
sump pump.
Top voids. Block voids. Voids—Air space(s) cre-
ated within masonry walls made of concrete
block or cinder block. Top void specifically re-
fers to the air space in the first course of such
walls; that is, the course of block to which the
sill plate is attached and on which the walls of
the house rest.
Veneer, Brick veneer—A single layer or tier of ma-
sonry or similar materials securely attached to a
wall for the purposes of providing ornamenta-
tion, protection, or insulation, but not bonded
or attached to intentionally exert common
action under load.
Ventilation/Suction—Ventilation is the act of ad-
mitting fresh air into a space in order to replace
stale or contaminated air, achieved by blowing
air into the space. Similarly, suction represents
the admission of fresh air into an interior space;
however, the process is accomplished by lower-
ing the pressure outside of the space thereby
drawing the contaminated air outward.
Working level (WLJ—A unit of measure of the ex-
posure rate to radon and radon progeny de-
fined as the quantity of short-lived progeny that
will result in 1.3 x 105 MeV of potential alpha
energy per liter of air. Exposures are measured
in working level months (WLM); e.g., an expo-
sure to 1 WL for 1 working month (173 hours)
is 1 WLM. These units were developed origi-
nally to measure cumulative work place expo-
sure of underground uranium miners to radon
and continue to be used today as a measure-
ment of human exposure to radon and radon
progeny.
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METRIC EQUIVALENTS
Although it is EPA's policy to use metric units in its documents, nonmetric units are
used in this report for the reader's convenience. Readers more accustomed to the
metric system may use the following factors to convert to that system.
Nonmetric
°F
ft
ft2
ft3
in.
Times
5/9(°F-32)
30.48
0.09
28.32
2.54
Yields metric
°C
cm
m2
L
cm
X!
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Section 1
Introduction
1.1 Purpose
This document provides a general review of potential
indoor radon concerns and presents technical infor-
mation to support the choice of techniques to re-
duce indoor radon concentrations where unaccepta-
ble levels are found.
1.2 Scope and Content
This technical guidance document is based on many
existing sources of information and on recent U.S.
Environmental Protection Agency (EPA) research ex-
perience. Used in conjunction with selected re-
ferenced reports, it provides building trade profes-
sionals and homeowners with the basis for an
understanding of: ,
(1) The source and nature of radon emissions
(2) Common radon entry routes into houses
(3) Methods for preventing or reducing indoor ra-
don concentrations.
Radon levels in houses can be reduced by four
methods: 1) preventing the entry of radon gas into the
house, 2) ventilating the air containing radon and
its decay products from the structure, 3) removing
the source of the radon,'and 4) removing radon and/
or its decay products from the indoor air. This guid-
ance concentrates on the first two methods as they
relate to radon entry from soil gas.
This document does not address the fourth
method —removing radon and/or its decay products
from indoor air—due to incomplete data on the
effectiveness of air cleaners in reducing the amount
of radiation exposure to the lung. EPA, the Depart-
ment of Energy, and radiation protection groups in
several countries are currently conducting research
on this topic. Although air cleaners have been
shown to decrease the concentrations of airborne
particulates and the radon decay products attached
to those particulates, the devices may not, decrease
the concentration of unattached decay products.
Since several studies indicate that the unattached
decay products result in a higher absorbed radiation
dose to the lung, the overall effectiveness of air
cleaners in reducing the lung dose is uncertain, and
is likely to be less than the effectiveness of air clean-
ers in reducing particulate levels. Results of further
research on this topic will be reported to the private
sector and the public.
Information on the risks of exposure to radon and
why radon levels should be reduced in houses can
be obtained from "A Citizen's Guide to Radon"
(ORP86a), prepared by EPA's Office of Radiation
Programs. More information about sampling and
measuring levels of radon in houses can be found in
EPA's "Interim Indoor Radon and Radon Decay
Product Measurement Protocols" (ORP86b). A brief
review of radon mitigation approaches can be found
in "Radon Reduction Methods: A Homeowner's
Guide" (ORD86), prepared by EPA's Office of Re-
search and Development.
This document does not cover methods of dealing
with radon in water, nor does it cover methods of
handling building materials that emit radon, or sites
contaminated with radon-emitting materials. .Some
of the methods described here, however, are appli-
cable to any radon source. Programs conducted as a
result of the Uranium Mill Tailing Radiation Control
Act of 1978, and the Comprehensive Environmental
Response, Compensation and Liability Act (Super-
fund) of 1980 have provided guidance on deal-
ing with radon-emitting materials and contaminated
sites. ,
To assist the reader in understanding the material
presented here, this document contains a table sum-
marizing salient information about each technique,
detailed drawings where appropriate, ~ a glossary of
terms used in the document, and a list of State and
Federal representatives who can provide assistance.
1.3 Radon and Its Sources
Sources and Natural Background Levels
Radon gas is a naturally occurring radioactive ele-
ment, a radionuclide gas, found in soils and rocks
that make up the earth's crust. Radon gas comes
"from the natural breakdown or decay of radium. Be-
cause radon is a gas, it can travel over considerable
distances and through narrow passages before it also
goes through radioactive decay. Thus, radon as a
gas can move through the soil and water and into
the atmosphere.
Technically, radon-222 is derived from the emission
of alpha radiation from the decay of radium-226, as a
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step in the natural radioactive uranium-238 decay
chain. As part of this decay chain, radon also even-
tually decays by releasing alpha radiation and is
transformed into polonium-218, which decays further
into lead-214; that is followed by a decay into bis-
muth-214 and then to polonium-214. A final decay
and the end of this decay chain occurs when lead-
210 decays into a stable, nonradioactive lead-206
molecule. These intermediate products in the radon
decay chain are referred to collectively as radon de-
cay products, radon progeny, or radon daughters.
The significance of this radioactive decay process is
that the decay of radon and its progeny (polonium-
218, lead-214, bismuth-214, and polonium-214) oc-
curs within a relatively short period of time and
results in the release of potentially harmful ionizing
radiation. Radon, the only gaseous member of the
decay chain, is highly mobile in the environment;
therefore, it has the potential to increase human ex-
posure to natural radiation. It is emphasized that the
above process (generation of radon) is continually
occurring wherever uranium-containing source mate-
rial is found. Uranium-238 activity concentrations in
soil are known to vary from background levels of
around 0.6 pCi per gram (six-tenths of a picocurie
per gram) to hundreds of pCi per gram in uranium
ore bodies (NAS81). The curie is a measure of radio-
activity; pico means one-trillionth (O.Q00000000001).
Where radon gas and its progeny, which are ultra-
fine particles, stay in soil and rock or are liberated to
the outside air and diluted, their release does not
have the health significance that they have when
confined in indoor environments. Outdoor concentra-
tions of radon are reported to average around 0.25
pCi per liter, and concentrations in areas with exten-
sive mineralization are reported to be around 0.75
pCi per liter (Br83). The importance and extent of
outside air dilution of radon emissions become ap-
parent when one realizes that monitoring of radon
activity in undiluted soil gas has revealed radon con-
centrations ranging from a few hundred to several
thousand pCi per liter (Br83). Dilution with outside
air, thus, is seen to produce 1,000- to 10,000-fold
reductions in radon concentrations, in breathable out-
side air.
Health Effects of Exposure to Radon
Much of our knowledge of the health significance of
radon and its progeny is based on analysis of the
effects of high exposures to radon and its progeny
on underground miners (NAS81). Table 1, adapted
from the National Academy of Science report, pro-
vides a comparison of representative exposures to
radon and its progeny (NAS81). Major relevant find-
ings from health studies emphasize that (NAS81):
(1) There is-no doubt that sufficient doses of ra-
don and its progeny can produce lung cancer
in humans.
(2) It is generally believed that radon and radon
progeny are responsible for most of the lung
cancer risk to the general nonsmoking public.
(3) The cumulative: exposures at which human
cancer has been observed are generally 10
times higher than those characteristic of the
normal indoor environment.
(4) Excess incidence of cancer has been asso-
ciated with exposures that were 2 to 3 orders
of magnitude (100 to 1000 times) greater than
those found in normal indoor environments.
(5) The linear dose-response function relating can-
cer incidence to radiation exposure is the only
generally accepted means of assessing the
health significance of measured radon and ra-
don progeny concentrations for radiation pro-
tection purposes.
Based on the preceding information, researchers be-
lieve that the longer one lives in a high radon envi-
ronment and the higher the radon level in that envi-
ronment, the greater the risk of developing cancer.
Indoor Levels of Radon
Based on our current knowledge, radon and its prog-
eny are believed to be harmful at all exposure levels,
with the risk of cancer increasing with increasing ex-
posures. Thus, EPA guidance for homeowners calls
for homeowners to take increasingly expeditious
action to reduce exposure to proportionately higher
levels of indoor radon concentrations (ORP86a).
Beginning in the late 1970s, as interest increased in
energy conservation in both new and existing build-
ings, many researchers started studies to determine
how increasingly popular weatherization and house
tightening techniques affect indoor air quality. Some
of these studies established indoor air quality bases-
line (starting) conditions before installing energy-sav-
ing measures. Some studies found significant infor-
mation about radon concentrations in the indoor air
Table 1. Representative Exposures to Radon-222 Progeny
Location Working Level, WLa>b
Pre-1960 Mines
Outdoors
Indoors
1 to 20
00.001
00.01
aWorking level (WL) is a measure of exposure rate to radon prog-
eny defined as the quantity of short-lived progeny that will
result in 1.3 x 105 MeV of potential alpha energy per liter of air.
Exposures are measured in working level months (WLM); e.g.,
an exposure to 1 WLfoM working month (173 hrs) is 1 WLM.
bWorking level measurements measure the activity of radon-222
progeny. Under equilibrium conditions of radon and its prog-
eny, 1 WL equalsthe activity of 100 pCi per liter ofair. Atthe
characteristic equilibrium (50%) found in most indoor environ-
ments 1 WL equals 200 pCi per liter.
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of certain houses. Studies showed radon concentra-
tions in residences significantly above those found in
the outdoor environment. Recent monitoring of
houses in the Reading Prong (Pennsylvania) area of
the United States revealed concentrations ranging
from 0.1 to 10 WL in a number of houses.
Table 2 presents a comparison of the health risks
and the calculated reductions needed to lower these
health risks to a level associated with a 0.02 WL
concentration of radon.
Reported incidences of high radon and radon prog-
eny concentrations in houses have focused attention
on the need to identify, in a short time frame, effec-
tive approaches to reducing indoor radon concentra-
tions to the minimum levels practically obtainable.
Table 2. A Comparison of Health Risks and Percentage
Reductions in Measured Concentrations Needed
To Reach 0.02 WL
Percentage
.Reduction in
Risk of Death Measured
Measured from Lung Cancer Concentration
Concentrations, at Measured Needed to Attain
WL Concentrations 0.02 WL
10.0
1.0
0.2
0.1
0.02
> 75 times normal3
75 times normal
30 times normal
15 times normal
3 times normal
99.8
98
90
80
0
"Normal = national average lung cancer incidence for non-
smokers.
Methods for Measuring Radon Levels
The homeowner who wishes to know definitely
whether a particular house contains unacceptable
levels of radon gas and its radioactive progeny must
either monitor the house personally or have it moni-
tored professionally. Expert guidance by health and
radiation officials can be particularly valuable before
any monitoring program is conducted.
Radon measurements should be taken as part of a
well-planned mitigation program (ORP86a). Indoor
house conditions should be stabilized with the house
closed arid after sufficient time has been allowed for
the radon concentrations to stabilize. Ventilation
rates should be as low as possible throughout the
house; i.e., exhaust fans and air conditioners should
be turned off, and windows, doors, and basement or
crawl space openings should remain closed. No mat-
ter which of several available types of instruments
are to be used, the instrument(s) should be placed in
the area of the house closest to the underlying soil.
Relatively simple-to-use and inexpensive measure-
ment devices are available to determine indoor radon
levels; these include the charcoal canister and the al-
pha track-etch detector. These devices are typically
deployed for 3 days and 1 to 3 months, respectively;
and thus, they provide integrated radon concentra-
tion measurements (integrated over time). Longer
averaging time measurements have the advantage of
being more representative of annual radon exposures
and more applicable to evaluating overall per-
formance of installed radon control techniques.
Longer term measurements have the disadvantage,
for screening purposes, of delaying identification of
possibly unacceptable living area radon levels.
Professional public or private services can measure
radon and radon progeny concentrations by using a
variety of highly instrumental methods. Examples of
two such approaches include use of the Continuous
Working Level Monitor (CWLM) and the Radon
Progeny Integrating Sampling Unit (RPISU). These
instruments have recommended minimum sampling
times of 24 hours and 72 hours, respectively
(ORP86b). Professional services can provide en-
hanced accuracy and precision of results, but with
higher costs typically.
A homeowner may wish to select an inexpensive and
rapid method for an initial or screening measure-
ment, using a method such as the charcoal detector.
When a measurement reported from such a screen-
ing test results in a value far above or far below the
range of concern, decisions can be made with regard
to the need to develop a plan for mitigation. Obvi-
ously, a very low measurement can relieve the
homeowner's concern, while a very high measure-
ment can indicate the need for expeditious action. If
a screening measurement indicates an intermediate
level or a level near the target level for action, the
homeowner may wish to obtain more extensive and
sophisticated measurements for better determination
of the actual radon levels in the house and for help
in deciding upon remedial action.
For the homeowner contemplating remedial action,
accurate, reproducible, and representative results are
important to provide a basis for appropriate method
selection for mitigation. Comparable quality mea-
surements also are needed to confirm the degree of
success of any mitigation action taken. ,
Radon Entry and Buildup in House Air
For the Nation as a whole, measured radon and ra-
don progeny concentrations vary from house to
house by a factor of several thousand. For example,
radon progeny concentrations vary from 0.0007 to
greater than 10 WL. This variation in radon levels
found nationally also is found on a local scale, which
shows that indoor radon concentrations in ap-
parently similar houses in proximity to one another
can be quite different.'
The physical relationship between the major sources
of radon and the indoor structure of a house is illus-
trated in Figure 1. Common entry routes for radon
gas into the house are shown. Principal entry points
-------
for radon into the house include: 1) so/7 and rock
surrounding the house, Routes A-H; 2) potable
(drinking water), Route J; and 3) natural building
materials used in the house. Route I. The soil is gen-
erally believed to be the most important contributor
of indoor radon in typical detached houses, followed
by outdoor air, potable (drinking) water, and building
materials.
Figure 1. Major radon entry routes into detached houses.
Key to Major Radon Entry Routes
Soil Gas
A Cracks in concrete slab
B Cracks between poured concrete (slab) and blocks
C Pores and cracks in concrete blocks
D Slab-footing joints
E Exposed soil, as in sump
F Weeping tile
G Mortar joints
H Loose fitting pipes
Building Materials
I Granite
D -.'.: :•• ".••>.;:.• :.:- :'.".:'
-------
Section 2
Indoor Radon Reduction Approaches
2.1 Overview of Radon Reduction
Methods
When radon is known to have entered a house and
to have accumulated in unacceptable concentrations,
a homeowner may take effective action to reduce
concentration levels. Indoor radon exposure to occu-
pants of a house may be reduced by 1) preventing or
reducing radon entry into the house or 2) removing
the radon after it has entered the house.
With reference to Figure 1, examples of principal
methods of preventing radon entry into a house are:
(1) Sealing and closing of all pores, voids, open
joints, and exposed earth that permit soil-gas-
borne radon to enter a house. Entry routes A
through H in Figure 1 illustrate cases where
sealing would be an essential first step in re-
ducing radon entry.
(2) Reversing the predominant direction of soil-
gas-borne radon flows so that air movement is
from the house to the soil and outside air. This
could be accomplished by locating a uniformly
exhausting ventilation system around a
house's perimeter or under a basement slab.
The main cause of radon entry from soils is
pressure-driven air flows. Because houses are
generally at slightly lower pressures, especially
in the winter season, than the soils surround-
ing or underneath them, radon/soil gas flows
will be from the soil to the house. Thus, re-
versing this pressure-driven flow requires con-
trol techniques that lower the soil air pressure
relative to that of the house or raise the house
pressure relative to that of the soil.
(3) Avoiding use of water supplies containing ra-
don or removing radon from potable water
supplies through the use of aeration or carbon
adsorption removal techniques.
(4) Avoiding use of building materials that may
contain radium and release radon.
Currently, the only effective method for removing ra-
don after it has entered a house is by ventilating the
affected living space. Ventilation entails bringing out-
side air into the living areas, basements, or crawl
spaces to displace and replace an equal volume of
indoor air and to mix with undisplaced indoor air
(thus diluting radon concentrations). Where outside
air radon concentrations are much lower than indoor
concentrations (as they generally are by up to a fac-
tor of 1000), indoor radon can be reduced substan-
tially by increasing normal house ventilation rates.
The effect of increasing ventilation rates for houses
over a typical range of 0.2 to 2.0 air changes per
hour (ach) is shown in Figure 2. This figure shows
four important characteristics associated with the
use of ventilation for radon removal:
(1) The utility of ventilation to reduce indoor ra-
don levels decreases with increasing ventila-
tion rates. This means that ventilation is more
cost-effective for tight houses (i.e., low air
change —less than 0.5 ach).
Figure 2. Effect of ventilation on indoor radon concen-
trations.
50% reduction in
radon concentration
results from a twofold
increase (0.25 to 0.5
ach) in ventilation.
E
K5
§•
c
-------
(2) Increasing ventilation rates from 0.25 to 2.0
ach can yield about 90 percent reductions in
indoor radon levels.
(3) Use of ventilation, even at very high air
change rates, will not effectively reduce indoor
radon levels below a finite level determined by
the radon source strength and entry rates.
(4) While in theory ventilation can be used to ef-
fectively and efficiently reduce indoor radon
concentrations, practical field experience has
identified such implementation problems as
difficulty in operating ventilation systems so
that they do not further reduce indoor air pres-
sure and induce pressure-driven radon entry.
Table 3 summarizes radon reduction methods that
can effectively reduce indoor radon concentrations in
houses. The points summarized in this table are de-
scribed in more detail and specific applications are
discussed in the remainder of this section. Each
method for radon level reduction makes use of either
house ventilation/air exchange (e.g., forced air ven-
tilation with heat recovery) or control of radon at its
source (e.g., collection and exhausting of soil gas).
Table 3 shows that house ventilation control tech-
niques generally can reduce indoor radon concentra-
tion by as much as 90 percent on an annual basis
(Natural Ventilation, Forced Air Ventilation, and
Forced Air Ventilation with Heat Recovery). The ta-
ble also indicates that climatic conditions typical of
much of the country are such that these techniques
may pose significant comfort or economic cost pen-
alties. Significant energy (and, therefore, operating
cost) savings can be achieved by use of forced air
ventilation with heat recovery (as indicated by com-
parison of heating costs of forced air ventilation with
and without heat recovery).
Methods that prevent radon entry into the house by
collection of soil-gas-borne radon at its source have
been demonstrated to produce reductions from 98 to
99+ percent. These methods include Drain Tile Soil
Ventilation, Active Ventilation of Hollow-block Base-
ment Walls, and Ventilation of Sub-slab. Achieving
these kinds of radon reductions depends on house
design and technical limitations posed by the instal-
lation and operation of a complete soil-gas collection
system.
The method for Active Avoidance of House Depres-
surization addresses the need to avoid worsening an
existing radon entry problem by providing a supply
of outside air to home appliances that use and ex-
haust indoor air or by supplying natural or forced air
considering the air balance. Because such appliances
(e.g., furnaces, fireplaces, dryers, and exhaust fans)
are used only intermittently (sometimes only season-
ally), expected annual average reductions are esti-
mated to be 10 percent. However, during the actual
time-of-use of the appliance (e.g., use of a fireplace
for 12 hours), radon concentration may be reduced
as much as 50 percent by avoiding house depressuri-
zation effects.
With the exception of the sealing techniques all the
methods represented in Table 3 are judged to have
moderate to high confidence levels. The basis for the
estimated reductions is supported by some field ex-
perience and is consistent with control theory. The
operating conditions and applicability of the methods
are derived from actual experience reported in the
technical literature on radon control.
Natural and Forced Air Ventilation without heat re-
covery are limited in a very practical way by consid-
erations of human comfort and the potential energy
penalties for heating and air conditioning costs
needed to maintain comfort. These methods are very
climate and weather dependent. House occupants
must actively manage ventilation systems on a daily
basis. Even with active management, short-term
fluctuations in the effectiveness of these systems
should be expected. Nevertheless, a conscientious
homeowner can achieve significant reductions of ra-
don levels by these ventilation methods. These tech-
niques are particularly effective in one time situations
(e.g., clearing radon from a temporarily or seasonally
closed, uninhabited house).
Where possible, estimates of installation and annual
operating costs for the methods were taken from
specific radon control studies. Estimated increases in
the cost of house heating with the ventilation tech-
niques are based on the assumption that heating
costs will increase in direct relationship to increased
ventilation (air exchange rates). Installation costs in-
clude both equipment purchase costs and, where
necessary, contractor installation. It is presumed that
all methods described should be installed by profes-
sional contractors trained in radon mitigation to en-
sure that the installed systems will operate with max-
imum effectiveness, although some preliminary
actions are suited to do-it-yourself installation by
knowledgeable homeowners. A homeowner consid-
ering installation of any of the techniques described
in this document is encouraged to solicit several in-
dependent technical opinions as to the design spe-
cifics of any method and its applicability to the situa-
tion in his/her specific house.
The reader is cautioned not to interpret the separate
discussions of seemingly independent radon reduc-
tion techniques to mean that the techniques cannot
or should not be used in combination. Indeed, where
large reductions in indoor radon levels need to be
accomplished and this must be done in the most ec-
onomical way, simultaneous application of two or
three radon reduction techniques may be appropriate
and should be considered.
-------
Table 3. Summary of Radon Reduction Techniques
- Confi-
House Estimated dence Operating
Principle Types Annual Avg. in Conditions
of Appli- Concentration Effec- and
Method Operation cable Reduction, % tiveness Applicability
Natural
ventilation
Forced air
ventilation
Forced air
ventilation
with heat
recovery
Active
avoidance
of house
depressuri-
zation
Air exchange All8
causing re-
placement , ,
and dilution
of indoor
air with
outdoor air
by uniformly
opening
windows and
vents
Air exchange All
causing re-
placement
and dilution
of indoor
air with
outdoor air
by the use
of fans
located in
windows or
vent open-
ings
Air exchange All
causing re-
placement
and dilution
of indoor air
with outdoor
air by the
use of a fan
powered ven-
tilation
system
Provide All
clean
makeup air
to house-
hold appli-
ances which
exhaust or
consume
indoor air
90b Moderate Open windows
and air vents
uniformly
around house
Air exchange
rates up to 2
ach may be
attained
May require
energy and
comfort penalties
and/or loss of
living space use
90b Moderate Continuous op-
eration of a
central fan with
fresh air
makeup, win-
dow fans, or
local exhaust
fans
Forced air venti-
lation can be
used to in-
crease air
exchange rates
rates up to 2 ach
May require
energy and
comfort penal-
ties and/or
loss of living
space use
96d Moderate Continuous op-
tohigh eration of units
rated at 25-240
cubic feet per
minute (cfm)
Air exchange in-
creased from
0.25 to 2 ach
In cold climates
units can re-
cover up to 70%
of heat that
would be lost
through house
ventilation
without heat
recovery
0-1 Oe. : Moderate' Provide outside
makeup air to
appliances such
as furnaces,
fireplaces,
clothes dryers,
and room ex-
haust fans
Estimated
Installation
and Annual
Operating costs
No installation
cost
Operating costs for
additional heating
are estimated to
range up to a 3.4-
fold increase from
normal (0.25 ach)
ventilation condi-
tions0
Installation costs
range up to $150
Operating costs
range up to $100
for fan energy and
up to a 3.4-fold
increase in
normal (0.25 ach)
heating energy
costs0
Installation costs
range from $400 to
$1500 for 25-240
cfm units
Operating costs
range up to $100
for fan energy
plus up to 1.4-
fold increase in
heating costs
assuming a 70%
efficient heat
rscovsrv
Installation costs
of small dampered
duct work should
be minimal
Operating benefits
may result from
using outdoor air .
for combustion
sources
Sources
of
Information
Be84; •
ASHRAE85,
DOC82
Be84,
Go83,
Be84,
CR86,
NYSERDA85,
Na81,
We86b
Na85
-------
Table 3. (Continued)
House
Principle Types
of Appli-
Method Operation cable
Sealing
major
radon
sources
Sealing
radon
entry
routes
Drain tile
soil ven-
tilation
Active ven-
tilation of
hollow-
block
basement
walls
Use gas- All
proof barri-
ers to close
off and
exhaust
ventilate
sources of
soil-gas-
borne radon
Use gas- All
proof
sealants to
prevent soil-
gas-borne
radon entry
Continuously BB
collect, PCB
dilute, and S
exhaust soil-
gas-borne
radon from
the footing
perimeter of
houses
Continually BB
collect,
dilute, and
exhaust soil-
gas-borne
radon from
hollow-block
basement
walls
Confi-
Estimated dence Operating
Annual Avg. in Conditions
Concentration Effec- and
Reduction, % tiveness Applicability
Local ex- Extremely Areas of major
haustofthe case soil-gas entry
source may specific such as cold
produce sig- rooms, exposed
nificant earth, sumps, or
house-wide basement
reductions • drains may be
sealed and
ventilated by
exhausting
collected air
to the outside
30-90 Extremely All noticeable
case interior cracks,
Specific cold joints,
openings
around
services, and
pores in base-
ment walls and
floors should
be sealed with
appropriate
materials
Up to 98 Moderate9 Continuous col-
lection of soil-
gas-borne
radon using
a 160 cfm fan to
exhaust a
perimeter drain
tile
Applicable to
houses with a
complete perim-
eter footing
level drain
tile system
and with no
interior block
walls resting on
sub-slab foot-
ings
Up to 99+ Moderate Continuous col-
tohigh lection of soil-
gas-borne radon
using one 250
cfm fan to ex-
haust all hol-
low-block perim-
eter basement
walls
Baseboard wall
collection and
exhaust system
used in houses
with French
(channel) drains
Estimated
Installation Sources
and Annual of
Operating costs Information
Most jobs could be Sc85b,
accomplished for Na85,
less than $1 00 NYSERDA85
Operating costs for
a small fan would
be minimal
Installation costs NYSERDA85,
range between Sc83
$300 and $500
Installation cost He86
is $1200 by con-
tractor
Operating costs
are $15 for fan
energy and up to
$125 for supple-
mental heating
Installation costs He86
for a single suc-
tion and exhaust
point system is
$2500 (contractor
installed in un-
finished basement)
Installation cost
for a baseboard
wall collection
system is $5000
(contractor in-
stalled in un-
finished basement)
Operating costs
are $15 for fan
energy and up to
$125 for supple-
mental heating
-------
Table 3. (Continued)
Principle
of
Method Operation
Sub-slab Continually
soil collect and
ventilation exhaust
soil-gas-
borne radon
from the
aggregate or
soil under ..
the concrete
slab
--.
Confi-
House Estimated dence
Types Annual Ayg. in
Appli- Concentration Effec-
cable Reduction,% tiveness
BB 80-90, Moderate
PCB as high to high
S as 99
IT? in some
; cases
Operating
Conditions
and
Applicability
Continuous col-
lection of soil-
gas-borne radon
using one fan
(~100cfm,
a0.4in.;H2O
suction) to ex-
haust aggregate
or soil under
slab
For individual
suction point
approach,
roughly one
suction point
per 500 sq ft
of slab area
Piping network
under slab is
another ap-
proach, might
permit adequate
ventilation
without power-
driven fan
Estimated
Installation Sources
and Annual of
Operating costs Information
Installation cost Er84,
for individual sue- Br86b,
tion point ap- NYSERDA85,
proach is about Sa84,
$2000 (contractor He86,
installed) Sc86
Installation costs
for retrofit sub-
slab piping net-
work would be
over $5000
(contractor
installed)
Operating costs
are $15 for fan
energy (if used)
and up to $125
for supplemental
heating
aBB (Block basement) houses with hollow-block (concrete block or cinder block) basement or partial basement, finished or unf in-
ishsd
PCB (Poured concrete basement) houses with full or partial, finished or unfinished poured-concrete walls
C (Crawl space) houses built on a crawl space
S (Slab, or slab-on-grade) houses built on concrete slabs.
bField studies have validated the calculated effectiveness of fourfold to eightfold increases in air exchange rates to produce up to
90 percent reductions in indoor radon.
"Operating costs are ascribed to increases in heating costs based on ventilating at 2 ach the randon source level; as an example,
the basement with 1) no supplementary heating or 2) supplementary heating to the comfort range. It is assumed the basement re-
quires 40 percent of the heating load and if not heated would through leakage still increase whole house energy requirements by
20 percent. Operating costs are based on fan sizes needed to produce up to 2 ach of a 30x30x8 ft (7200 cu ft) basement or an eight-
fold increase in ventilation rate.
dRecent radon mitigation studies of 10 inlet/outlet balanced mechanical ventilation systems have reported radon reduction up to
96 percent in basements. These studies indicate air exchange rates were increased from 0.25 to 1.3 ach.
eTnis estimate assumes that depressurizing appliances (i.e., local exhaust fans, clothes dryers, furnaces, and fireplaces) are used
no more than 20 percent of the time over a year. This suggests that during the heating season use of furnaces and fireplaces with
provision of makeup air may reduce indoor radon levels by up to 50 percent.
'Studies indicate that significant entry of soil-gas-borne radon is induced by pressure differences between the soil and indoor envi-
ronment. Specific radon entry effects of specific pressurization and depressurization are also dependent on source strengths, soil
conditions, the completeness of house sealing against radon, and baseline house ventilation rates.
9Ongoing studies indicate that where a house's drain tile collection system is complete (i.e., it goes around the whole house perim-
eter) and the house has no interior hollow-block walls resting on sub-slab footings, high radon entry reduction can be achieved.
-------
Application of the techniques addressed in this docu-
ment to a specific house should be discussed with
knowledgeable State or Federal government person-
nel to obtain the benefit of the most up-to-date in-
formation with regard to the performance of cur-
rently available radon reduction techniques or
systems (combinations of techniques).
2.2 Natural and Forced Air Ventilation
Principle of Operation
Natural ventilation refers to the exchange of indoor
air for outdoor air that occurs in response to and is
driven by natural forces. The major forces driving
natural ventilation are winds and pressure and tem-
perature differences between the indoor and outdoor
atmospheres. Natural ventilation in a house takes
place through all passageways, however small, that
connect the inside air to the outdoors. Thus some
exchange of indoor air with outdoor air occurs even
when doors and windows are closed. This baseline
ventilation, present in all buildings, is called infiltra-
tion.
Forced air or mechanical ventilation relies on the use
of fans to force an increase in house air exchange
rates by 1) blowing in outside air or 2) exhausting
indoor air with the assurance that it will be replaced
by cleaner air from the outside.
In most American houses in normal use, the annual
average ventilation rate is about 1.0 air change per
hour (ach). Newer houses, built with a concern for
reducing heating and cooling energy costs, may
have air exchange rates as low as 0.1 ach (one-tenth
of an air change per hour), and older houses may
have air exchange rates as high as 2.0 ach. Houses
with high air exchange rates probably would not be
suitable for the ventilation approach to radon mitiga-
tion.
The ventilation approach relies on achieving reduc-
tions in indoor radon levels from a constantly emit-
ting radon source that are in direct proportion to in-
creases in ventilation rates. This reduction is due to
both the removal of radon-laden air and the dilution
of the total indoor volume with the clean incoming
air. This relationship is shown in Figure 2. Over the
typical house ventilation rates of 0.25 to 2.0 ach,
each doubling of the ventilation rate reduces indoor
radon concentrations by a factor of 2. For example,
if energy and human comfort cost penalties were not
a consideration, ventilation could be used to reduce
a 0.1 WL indoor concentration to about 0.02 WL by
increasing house ventilation rates from 0.25 to 1.0
ach, or to about 0.01 WL by increasing the house
ventilation rate to 2.0 ach.
Applicability
In practice the application of ventilation, whether
natural or forced air, to reduce indoor radon concen-
10
tration is limited by the energy penalty imposed by
the need to maintain human comfort conditions at
potentially high ventilation rates, especially in the
winter. Human comfort is a somewhat subjective
determination, but temperatures between 68° and
78°F* with relative humidities between 30 and 70
percent are generally comfortable to most people
(ASHRAE85). Considering only the temperature cri-
terion and data on heating and cooling, degree days
(DOC82), it is estimated that nationally (and in the
Mid-Atlantic States of New York, Pennsylvania, and
New Jersey in particular) natural or forced air venti-
lation could be used to reduce indoor radon con-
centrations up to 4 months per year with little or no
comfort penalty.
If a homeowner were willing to 1) accept a comfort
penalty, 2) offset this comfort penalty by closing off
and limiting use of a ventilated radon source area
such as a basement, or 3) incur a supplemental heat-
ing or cooling cost, greater application of ventilation
as a technique for reducing indoor radon levels
would be possible. Current experience with the use
of ventilation (in pressure-balanced, heat-recovery
systems) suggests that ventilation can effectively re-
duce moderately high basement radon levels (up to
20 pCi per liter) to levels below 4 pCi per liter (NY-
SERDA85, We86a).
Confidence
Ventilation as a technique for reducing airborne
concentration has a proven performance (and thus a
high confidence level) under controlled ventilation;
that is, where ventilating air can be distributed or
mixed with indoor air at controlled and quantifiable
rates (ASHRAE81). ,
Forced air ventilation with the proper placement of
fans, or with inlet and exhausting forced air duct
work, can be expected to meet controlled ventilation
conditions; therefore, the confidence level in its per-
formance is high.
The radon-reduction effectiveness of natural ventila-
tion has a low to moderate confidence level if for no
other reason than it varies with the weather and its
only control is by opening or closing windows.
Installation, Operation, and Maintenance
The ability of any radon-reduction technique to pro-
vide reliable performance depends greatly on a sys-
tematic and understandable definition of the operat-
ing conditions required.
The effectiveness of natural ventilation is dependent
on ensuring uniform ventilation throughout all por-
tions of the house with elevated radon concentra-
tions; for example, as found in crawl spaces or base-
ments. Thus, the space to be ventilated should have
"Readers more familiar with metric units may use the conversion factors in
the front matter of this report.
_
-------
windows and vents completely around it, and they
all should be opened to-the same degree.
Although natural ventilation clearly depends on and
varies with weather conditions, its minimum per-
formance level, which is unique to each house,
should be demonstrated and quantified to ensure
that natural ventilation is not relied upon, even tem-
porarily, to reduce radon concentrations to levels be-
yond its capability.
The air distribution and ventilation rates of forced air
ventilation of a basement or larger space can be con-
trolled by the size and location of fans and the use
of louvered air deflectors. Extrapolations from and
experience with small chambers and room-sized
spaces suggest the need for two or three fans rated
at twice the air-moving dapacity nominally desired.
The design, implementation, or operation of a con-
trol strategy based on ventilation requires an under-
standing of the dynamics of radon entry into a
house, as well as the dynamics of air distribution
within the house. For example, adding ventilation
that creates a negative pressure on a basement area
actually may increase the entry rate of soil-gas-borne
radon and cause increased radon concentrations in
areas remote from the basement. Both natural and
forced air ventilation can produce this unwanted ef-
fect if the inlets and outlets are improperly located
(e.g., opening the upstairs windows or using an attic
fan may be a mistake in some situations).
Estimate of Costs
No installation cost is assumed with natural ventila-
tion in its simplest application. Minor costs, how-
ever, could occur in securing house windows in
fixed, open positions. The need for acquiring addi-
tional protective devices for occupants of a house
with open windows can result in specific environ-
ments where security, insect pests, or cold tempera-
tures are at issue. Relocation of services in areas
which are closed off to adequately heated spaces
may also be required.
Operating costs for the natural ventilation method
can run from none (if the technique is" used only
when outdoor temperatures and humidities are
within comfort criteria or the homeowner is willing to
accept comfort penalties or to close off parts of the
house) to a range of from 1.2- to 3.4-fold increases
in heating costs incurred by, for example, ventilating
a basement space year-round and supplementing
heat loss from the upper floor or increasing base-
ment air heating to maintain comfortable conditions
in the basement. These estimates for supplementary
heating are based on increasing basement ventilation
rates eightfold with a basement that normally incurs
40 percent of the house heating load.
Forced air installation costs were estimated to be no
more than $150 for the purchase of fans with an air-
moving capacity of approximately 240 cfm. If new
wiring, duct work, dampers, filters, or automatic
smoke alarm cutoffs are desired, installation costs in-
crease substantially. Annual operating costs for the
forced air ventilation technique were estimated to be
$100 for fan energy (Be84) and from none (if the
technique is used only when outdoor temperatures
and humidities are within comfort criteria or the
homeowner is willing to accept comfort penalties) to
a range of 1.2- to 3.4-fold increases in heating costs
incurred by ventilating a basement space year-round
and supplementing heat lost from the upper floor or
increasing basement air heating to maintain comfort
criteria conditions.
2.3 Forced Air Ventilation with Heat
Recovery
Principle of Operation
Forced air ventilation with heat recovery is a tech-
nique for bringing outside air into a house, exhaust-
ing radon-contaminated indoor air, and transferring
or recovering the heat from the exhaust air to the
cleaner incoming air. Fans provide controlled steady
flows of ventilating and exhaust air.
As explained in Section 2.2 indoor radon concen-
trations are reduced by replacing the indoor air with
clean outside air. Mixing of the clean outside air with
the indoor air that is not exhausted dilutes the indoor
radon concentrations. As the rates of air exchange
(air changes per hour) are increased indoor radon
concentrations are decreased, as shown earlier in
Figure 2.
Section 2.2 also addresses the practical consider-
ations of comfort and the cost of providing supple-
mental heating to offset loss of comfort during the
use of ventilation. Heat recovery between exhaust
and inlet ventilating air thus - becomes an important
feature in extending the applicability of ventilation.
Heat recovery basically entails the transfer of heat
energy from warm sources to cold sources. The rate
of heat transfer is related to the temperature differ-
ence of the two sources. The incoming colder clean
air is heated by contact with a heat transfer surface
that has been warmed by the exhausting warm in-
door air. The greater the temperature difference is
between the ventilating air -and the exhausting air,
the more effective the heat transfer.
Applicability
The application of forced air ventilation with heat re-
covery has its greatest potential in low-ventilation-
rate (tight) houses in cold climates. These conditions
maximize the effectiveness of the ventilation and
heat recovery mechanisms. For the most part, this
11
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approach has been used in houses with moderately
elevated radon levels (less than 0.1 WL) (We86,
Na85). Ventilating capacities of commercially availa-
ble "heat-recovery ventilators" identified by Con-
sumer Reports (CR86) vary from about 25 to 240
cfm, and heat recoveries range from 15 to 70 per-
cent at 5° and 45°F, respectively.
Confidence
Forced air ventilation with heat recovery is a proven
technique for reducing indoor air pollutant concen-
trations in direct relation to the ventilating rates.
Heat recoveries up to 70 percent are possible. Confi-
dence in the effectiveness of this technique should
be high.
Installation, Operation, and Maintenance
Commercially available forced air ventilation systems
with heat recovery vary in size from room or window
units to systems that ventilate the whole house. For
the purpose of radon reduction, the whole-house
systems probably would be placed in basements and
run automatically. These systems require their own
duct work for collection and distribution of outdoor
air and the collection and exhausting of indoor air.
Generally, existing windows can be used for air in-
take and exhaust purposes.
The particular heating and ventilating system de-
cided upon and information regarding the source
strength and radon entry path into the house will
dictate the precise location, size, and configuration
of the ventilation system duct work.
Estimate of Costs
Installation costs will vary with the size (ventilating
capacity) and complexity of the system to be in-
stalled. Estimates indicate that costs of commercial
units can range from $400 to $1500 for rated air-
moving capacities of 25 to 240 cfm. A 240-cfm ca-
pacity would be needed, for example, to ventilate a
30 x 30 x 8 ft (7200 cu ft) basement at a rate of 2
ach. If the basement's original ventilation rate was
0.25 ach, this increased ventilation could reduce ra-
don levels by approximately 90 percent.
The operating cost of a 240-cfm system is estimated
to be $100 per year for fan energy. If the basement
is just ventilated with the system (no makeup heat
added), whole-house heating costs could still in-
crease by 20 percent because of the heat loss to the
ventilated basement. In cold climates, this would
limit the use of the basement and can require the
insulation of utility services. If makeup or supple-
mental heat is added to the basement, whole-house
heating costs could increase 1.4-fold; i.e., about 40
percent.
12
2.4 Active Avoidance of House
Depressurization
Principle of Operation
The house living space may be depressurized when
certain household appliances that use and exhaust
house air to the outside are used and when unbal-
anced natural or forced air ventilation is applied. De-
pressurization of a house occurs naturally in the win-
ter as a result of the rising of heated indoor air and
its loss or exfiltration to the outdoors. This is called
the "stack (as in smoke-stack) effect." The winter
stack effect or depressurization in houses is believed
to be the main cause of increased soil-borne radon
entry.
Any additional cause of depressurization, especially
in the radon source entry spaces (e.g., basements or
rooms abutting or directly on soil), can also contrib-
ute to increased radon entry. Thus, if additional de-
pressurization activities can be limited or modified by
the direct provision of outside makeup (combustion
or exhaust) air, increased radon entry can be
avoided.
Applicability
The American Society of Heating, Refrigerating, and
Air-Conditioning Engineers (ASHRAE81) has recom-
mended the provision of outside makeup air for com-
bustion appliances, such as furnaces and water
heaters, since 1981. They believe that outside
makeup air is necessary to ensure the effective and
controlled ventilation needed for acceptable indoor
air quality. Other appliances affecting indoor air ven-
tilation (e.g., intermittently used local exhaust fans)
are not mentioned by ASHRAE and are clearly not
as important as combustion appliances in effecting
ventilation or house depressurization. Where depres-
surization and ventilation effects have been docu-
mented, it was during the use of combustion appli-
ances (Na85, Sc85a).
Confidence
The major consequence of providing makeup or
combustion air to household appliances is to prevent
additional house depressurization and hence to pre-
vent increasing pressure-driven flows of soil-gas-
borne radon into the house. While there is high con-
fidence that the pressure-driven flow of
soil-gas-borne radon into the house is the major ra-
don entry mechanism, quantitative evidence of the
radon-reduction benefit of avoiding appliance de-
pressurization effects is variable, 0 to 50 percent
(Na85). The variability probably reflects the specific
appliance's operating conditions, varying indoor con-
ditions, and differences in radon source strength.
Installation, Operation, and Maintenance
Because of the potential for significant seasonal ra-
don reduction benefits and improvements in the
-------
quality of the whole-house ventilation performance,
installation of homeowner- or, contractor-installed
duct work for supplying outside air to major indoor
combustion appliances is encouraged. Additional
guidance in this area can be found in U.S. Depart-
ment of Energy report DOE/CE/15095 (DOE86).
Estimate of Costs „,
Installation costs will be""a$sbc'iated with providing
small dampered duct work systems for indoor air
consuming appliances, such as furnaces, fireplaces,
and (perhaps) clothes dryers.
2.5 Sealing Major Radon Sources
Principle of Operation
Exposed soil and rock'under, around, or within a
house can be a major source and entry route for ra-
don into the living area of a house. These areas
should be closed, sealed, and (if necessary) exhaust-
ventilated to the outdoors to prevent soil-gas-borne
radon entry into the house.
Applicability
Exposed earth, as in basement cold rooms or water
drainage sump areas, is a prime target for 1) excava-
tion of fill and replacement with a concrete cap; or
2) at least capping of those areas with an imperme-
able covering such as aluminum sheet metal, sealing
of all cover joints, and forced air exhausting of any
below-grade air space (such as that found in a sump
pump cavity).
Confidence
Theoretically, locating, capping, and sealing major
potential sources of soil-gas-borne radon entry
should have significant radon reduction benefits.
Several studies indicate that pressure-driven soil-gas-
borne radon entry into a tightly sealed energy effi-
cient house is effectively prohibited or significantly
reduced in houses with radon levels of 30 to 70 pCi
per liter by sealing of all visible cracks and gaps be-
tween floor, walls, and service pipes entering a base-
ment (Ho85, NYSERDA85). Most researchers in the
radon research community, however, would proba-
bly caution that, while better barriers, sealants, and
construction techniques can have a significant effect
on radon entry rates, this beneficial effect will be
limited in degree and in duration of control. Even im-
perceptible movements of a house's understructure
can create small imperfections that appear to be ade-
quate pathways for the entry of soil-gas-borne radon
(Ne85).
If a moderate to high confidence level is to be as-
signed to the control of radon entry through loca-
lized major soil gas sources, such confidence will be
attributable to a system that effectively caps and
seals the source and uses a small-capacity fan to ex-
haust the capped source space. The potential benefit
of exhausting a capped sump has been demon-
strated in studies where variations in concentrations
at a sump pump cover corresponded to variations in
average house concentrations for the same time per-
iod (Na85, NYSERDA85).
Installation, Operation, and Maintenance
Figure 3 shows a possible sump ventilation arrange-
ment. A tight-fitting cover is placed over the sump,
and the sump is exhausted to the outside by a small
fan. Although the immediate purpose is to exhaust
the radon that enters the sump from the surrounding
soil, Figure 3 shows that the fan suction produced in
the sump may be transmitted through the attached
weeping tile drainage system and diminish the radon
soil gas concentration for some distance from the
sump.
Estimate of Costs
Such a sump ventilation system should cost less
than $100 (Sc85b); however, variations of this sys-
tem with increased soil gas removal capacities can
cost up to $1200. See Section 2.7.
2.6 Sealing Radon Entry Routes
Principle of Operation
Radon entry with soil gas can be prevented by seal-
ing all cracks, openings, or other voids in the house
structure that provide pathways for gas flows from
the soil to the house interior. Sealing of potential
soil-gas-borne radon entry routes is often considered
as an initial radon reduction approach, especially in
houses with marginal problems. It is often imple-
mented in conjunction with other radon-reduction
strategies.
The discussion of sealing is limited to the closing off
of small soil-gas entry routes. Major entry routes
(e.g., sumps, drains, or soil outcroppings in cold
rooms) are addressed in Section 2.5. Sump and
channel or French drains are also discussed in Sec-
tion 2.8.
Applicability
The practical applicability of sealing is generally lim-
ited by the knowledge of and access to all small soil
gas entry routes. In existing houses, limited access is
a major impediment to complete sealing without sig-
nificant expense.
Confidence
Current experience dictates that only a low confi-
dence level can be assigned to the use of sealing in
existing houses for the prevention of soil-gas-borne
radon entry. A homeowner should not expect sealing
of all noticeable cracks or openings to eliminate an
indoor radon problem. The potential effectiveness of
13
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Figure 3. Drain tile ventilation where tile drains to sump.
Drainpipe
Existing drain tile
circling the house
14
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sealing as a means of significantly reducing indoor
radon concentration has been demonstrated in the
30 to 90 percent range (NYSERDA85, Sc83). These
studies emphasize the uncertainty of successful con-
trol with comparable sealing efforts in apparently
similar house situations.
Installation, Operation, and Maintenance
Table 4 is a checklist of soil-gas-borne radon entry
routes through walls and floors into the house.
The method most commonly used to seal floor and
wall cracks and utility openings involves enlarging
the existing crack or opening to dimensions suffic-
ient to allow filling with a grout, caulk, or sealant.
These compounds must be compatible, gas-proof,
and nonshrinking. Wall and floor joints are sealed by
a variety of methods. The most common are a po-
lyurethane membrane sealant and protective coyer or
a nonshrink grout with a protective concrete cap.
Radon flow through porous walls, especially block
walls, and floors can be reduced by the use of inte-
rior and exterior barrier coatings. In general, sealants
cannot be applied to exterior wall surfaces of exist-
ing houses inexpensively. Thus, walls are usually
sealed by applying epoxy sealants or waterproof
paints to interior surfaces. Proper sealing of these
entry points generally requires meticulous surface
preparation and quality control in the application of
appropriate sealants.
Table 4. Soil-Gas-Borne Radon Entry Routes
Category
Description
Block or concrete
wall
Concrete floor
Pores in block
Mortar joint cracks between blocks
Openings in top course of block
Utility openings through walls
Cracks in wall
Gaps between block and brickwork
surrounding basement fireplaces
Cold joints in poured floor
Cracks in floor slab
Wall and floor joints on footings
Utility openings .
Estimate of Costs
Many sealing jobs can be accomplished for a materi-
als cost of less than $100. Comprehensive, whole-
house efforts have cost up to $500 (Sc83).
2.7 Drain Tile Soil Ventilation
Principle of Operation
Perforated drain tiles surround part or all of some
houses in the vicinity of the footings to drain mois-
ture away from the foundation. The water collected
in the drain tiles is generally routed either to an
above-grade soakaway remote from the house or to
a sump in the basement. It is believed that a signifi-
cant amount of the radon-containing soil gas enter-
ing a house may be gaining access through openings
in the vicinity of the footings; e.g...through the exte-
rior mortar joint between the block and the footings,
through other mortar joint cracks, through block
pores in the exterior face of block wall near the foot-
ings, or through the crack between the interior face
of the blocks and the concrete slab. Drain tile
ventilation involves drawing suction on the drain tiles
by use of a fan in an effort to draw soil gas away
from these potential entry routes. Depending on the
permeability of the soil and of the aggregate beneath
the slab, drain tile ventilation can also ventilate por-
tions (or all) of the area underneath the slab and the
soil well above the level of the footings.
The advantage of drain tile ventilation is that it is the
least expensive and least obtrusive active soil ventila-
tion approach potentially capable of significantly re-
ducing radon levels. Its disadvantage is its limited
applicability, as discussed in the following subsec-
tion. , -; •
Applicability
It would be fairly expensive to install drain tiles
around a house that did not have them installed dur-
ing construction; therefore, the practical application
of drain tile ventilation may be limited to houses al-
ready having drain tiles in place. Data acquired by
EPA in testing this technique on seven houses sug-
gest that the technique offers reasonable potential
for substantial, year-round reductions in radon only
when the drain tiles are known to extend around the
entire perimeter of the house and to be basically
open and connected. This is necessary to ensure
that the ventilation is treating the entire footing re-
gion. If some portion of the perimeter does not in-
clude drain tiles —or if the tiles are damaged or
blocked with silt—that portion of the perimeter will
not be effectively treated. Another potential problem
concerns houses having interior block walls in the
basement that rest on footings underneath the con-
crete slab (e.g., walls that divide the basement into
sections or separate the basement from an attached
garage). Such "interior" footings generally do not
include drain tiles; only the exterior perimeter foot-
ings do. Thus, such interior footings provide a po-
tential access route for soil gas into the house, an
entry route that cannot be treated reliably with
house perimeter drain tile ventilation. EPA's data
do show, however, that as long as the perimeter
drain tile system is complete, drain tile ventilation
can sometimes produce significant reductions of in-
door radon on houses with interior block walls.
Thes_e interior walls would, however, increase the
risk of reduced performance. Drain tile ventilation
would be an especially logical choice in houses with
"finished" basements, as the practicality of installing
control measures inside the house is reduced.
15
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To date testing of the drain tile ventilation technique
has focused primarily on houses with concrete block
basements. In view of the principle of operation,
however, this technique may also offer reasonable
potential for reducing radon in houses of other sub-
structure types.
In summary, drain tile ventilation would be most ap-
plicable to 1) houses known to have a complete
drain tile system in place, and 2) preferably (al-
though not necessarily) houses that do not have in-
terior basement walls that penetrate the slab to rest
on footings.
If a homeowner is uncertain as to whether the drain
tile system is complete or might be blocked by silt,
drain tile ventilation may not be a wise approach.
The fact that the technique is sufficiently attractive
(i.e., has the potential to produce significant radon
reductions at fairly low cost with an unobtrusive in-
stallation) may lead some homeowners who believe
their drain tiles are reasonably likely to form a com-
plete loop to try this approach before attempting a
more expensive one.
Confidence
To date, EPA has tested drain tile ventilation in
seven houses all of which have concrete block base-
ments (He86). In all cases, the tiles drained to an
above-grade soakaway. Three of these houses are
known to have drain tile systems that completely
surround the house. The results obtained at these
three houses are shown in Table 5.
Table 5. Results Obtained With Drain Tile Systems
in Three Test Houses
Concentration before
technique installed,
WL
Concentration after
technique installed,
WL
House
No.
10
12
15
Early
1985
1.1-3.1
0.22
0.17
July/
Aug. 1985
0.46-1.5
0.03-0.10
0.02-0.50
July/
Aug. 1985
0.02-0.04
0.005-0.01
0.01-0.02
Nov./
Dec. 1985
0.005-0.03
0.01-0.03
0.01-0.03
These radon level ranges are generally based on 1 to
2 days of continuous radon monitoring by EPA dur-
ing the months indicated. The exception is the
column presenting early 1985 data before mitigation
technique installation; these results are based on 5-
minute grab samples (and sometimes on longer-term
integrated measurements) by the Pennsylvania De-
partment of Environmental Resources. House No.
10, which has an interior block wall, illustrates that
the technique can, at least in some cases, provide
reasonable reductions even under these conditions.
The good performance in House No. 10 suggests
16
that the ventilation effect of the drain tile system in
this case must have extended under much or all of
the slab. These data indicate that, under favorable
conditions, the drain tile ventilation technique can
provide reasonably high levels of radon reduction
and that these reductions can be sustained during
the winter when the natural stack effect created in
the house gives the control technique its greatest
challenge. '•'• •*••'-' f;
Levels of radon in House No. 10 peaked to 0.05 WL
when the clothes washer and dryer in the basement
were used. This reflects either the effects of base-
ment depressurization caused by the dryer or the
contribution of additional radon from the 35,000-pCi
per liter well water used in the washer. Radon levels
in House No. 12 peaked to 0.05 WL when the fire-
place was operating (which caused depressurization
of the basement). These results suggest that drain
tile ventilation may be somewhat vulnerable to in-
creases in soil gas influx when the house is depres-
surized.
At the other four houses on which EPA tested drain
tile ventilation, the drain tiles were known not to ex-
tend around the full perimeter. In these four houses,
reductions of 74 to 98 percent were observed during
the summer (based on a comparison of EPA's sum-
mer premitigation data and summer post-mitigation
data); summer premitigation levels of 0.12 to 1.6 WL
were reduced to 0.01 to 0.08 WL. With the onset of
cold weather, however, the levels began to increase
(0.06 to 1.0 WL), which indicates that the technique
cannot maintain reasonably low levels year-round in
houses that do not have complete drain tile systems.
Although EPA's testing in the three houses having
complete drain tile loops draining to a soakaway
showed consistently significant reductions in radon
levels, further tests on additional houses (including
more houses with interior walls) would be necessary
before a high statistical confidence level of success
could be established in a variety of houses with com-
plete drain tile systems. Further, EPA's measure-
ments in the three houses where this approach was
successful were relatively short-term (1 to 2 days of
continuous monitoring on two occasions). Longer-
term (2-month) monitoring and observation of sys-
tem performance for a full year or longer are needed
for better confirmation of performance.
Other investigations have tested drain tile ventilation
in situations where the tiles drain to a sump inside
the basement (Na85). Of three houses with a footing
drain/sump ventilation system, one had a poured
concrete basement, one had a concrete block base-
ment, and one had a combination block basement
plus crawl space. The drain tiles for the last house
were known not to extend entirely around the perim-
eter; however, how far the tiles extended in the
other two houses was not reported. Drain tile/sump
_
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ventilation was applied to each house in combination
with crack sealing and closure, of major wall open-
ings. In the partial crawl space house, the crawl
space was also isolated and vented. Radon reduc-
tions of from 70 to over 95 percent were observed in
these three houses. The radon levels remained sub-
ject to peaks during basement depressurization un-
less major cracks and openings in the walls and floor
(including the wall/floor joint) were sealed (Na85).
In another study, 80 percent radon reduction was
achieved by the use of suction on a partial drain tile
system draining to a soakaway in a house with
poured concrete walls (Sa84).
Based on the aforementioned considerations, the
confidence level in the performance of the drain tile
ventilation approach is considered to be "moderate."
Design and Installation
Figure 4 shows a drain tile ventilation system (where
the tiles drain to an above-grade soakaway). The
drain tile, including the line running to the soak-
away, must be already in place. The ventilation sys-
tem in Figure 4 consists of the water trap and riser(s)
(which are in the existing line to the soakaway) and
the fan. The water trap ensures that the fan. effec-
tively draws suction on the drain tiles. Without the
trap, the fan would simply draw outside air up from
the soakaway and have no significant radon reduc-
tion impact. Most of EPA's experience to date has
been with houses where the tiles drain to a soak-
away. If the tiles drain instead to an inside sump, the
drain tiles can be ventilated by covering and drawing
suction on the sump. One sump ventilation approach
is illustrated in Figure 3: Other sump ventilation con-
figurations have been tested by other investigators
(e.g., flat rather than raised cover, fan inside the
house with exhaust piping leading outside).
Locating Line to Soakaway
The following general description of the ventilation
design features focuses on the soakaway system
(Figure 4). In preparation for installation of a soak-
away system, the contractor must first locate the po-
sition of the drain line to the soakaway and then dig
down to expose the line at the point where the trap
and riser are to be installed (Figure 4). A complete
drain tile system consists of a continuous loop
around the perimeter of the house (at footing level)
with a discharge drain tile line tapping out of the
loop at some point to run to the soakaway; it is in
this drain line (not in the loop itself) that the vent
system should be installed. The position of the dis-
charge line can initially be estimated by locating the
point at which the line comes above grade at the
soakaway and then visually tracing the.likely path of
the line from the point back to the house.
The ventilation system can be installed at any point
in the drain line. The advantages of installing the
system at a point remote from the house are re-
duced fan noises in the house, a more aesthetically
appealing installation, and less digging because the
line may be closer to grade level at a remote point.
In addition, the release of the fan exhaust, which
could contain high levels of radon, would be remote
from the house. On the other hand, the long length
of drain tile required between the fan and the loop
around the house could result in a potentially signifi-
cant pressure drop which would make the fan less
effective in maintaining suction in the loop around
the house and thus reduce the system's perform-
ance. Also, a long length of electric cable would be
required to supply the fan motor with power from
the house. Further, the trap must be at a point suffi-
ciently deep underground to keep the water in the
trap from freezing and prevent proper drainage dur-
ing winter months. Based on these considerations,
the ventilation system should be installed at some
reasonable distance from the house—perhaps up to
20 ft.
Trap and Riser(s) Installation
To install the trap and riser(s) after the proper point
in the drain tile line is exposed, the contractor must
sever the tile and remove a section so that the trap/
riser assembly can be inserted. In the EPA testing,
the trap and riser(s) consisted of 4-in. Schedule 40
plastic sewer pipe. The trap itself can be purchased
as a unit or assembled from elbows and tees ce-
mented together. Details on how the trap is fabri-
cated are not crucial as long as it serves the purpose
of preventing outside air from being drawn up from
the soakaway. Where the plastic trap connects to
the existing drain tile on either side of the trap, the
plastic pipe and the drain tile must be firmly con-
nected (e.g., by a clamp over a rubber sleeve) so
that there is no break that permits silting or other-
wise prevents effective suction from being drawn on
the drain tile loop.
The riser to support the fan must be on the house
side of the trap. It should protrude some distance
(perhaps 2 to 3 ft) above grade level to provide rea-
sonable clearance for the fan and to permit proper
condensation of moisture during the winter. The soil
gas contains moisture and is relatively warm com-
pared with winter air temperatures; thus, moisture
can condense and freeze up the fan unless much of
it is condensed in the riser.
Although the riser shown on the opposite side of the
trap from the fan is optional, it would ensure that
the trap always contains water, even in prolonged
dry weather. Were the trap ever to dry out, the ven-
tilation system would become ineffective. This se-
cond riser should extend above ground only far
enough for convenient access and should always be
17
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Rgure 4. Drain tile ventilation where tile drains to soakaway.
Protective box
Exhaust
Riser connecting
drain tile to fan
Condensate
Capped riser to add
water to trap
Soakaway
Existing drain tile circling the house
• Water trap to prevent air from
being drawn up from soakaway
18
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capped except when being used to inspect the water
level or to add water. After the trap and risers are
installed, the hole, should be filled in to cover the
trap and the tiles.
Fan Selection and Mounting
The fan needed to draw suction on the drain tiles is
fairly small (relative to a central furnace fan). Al-
though a wide variety of fans can be considered, the
fans used in the EPA testing were 0.03-hp (25-W),
160-cfm centrifugal fans (maximum capacity) capable
of drawing up to 1 in. of water suction before stall-
ing. These fans actually operated at about 80. cfm
and 0.2 in. of water during the EPA study. The fan
must be large enough (both in terms of flow rate
and suction capability) to draw reasonable suction
on the drain tiles. Fans of this type can cost be-
tween $40 and $100. :; •;_-,-•.
The fan must be mounted to draw suction on the
drain tiles (i.e., not mounted in the reverse direction
to blow air down into the tiles). The preferred
mounting is directly on the pipe. In some of EPA's
initial Installations, the fan was in a protective box
that stood on the ground near the riser and was con-
nected to the riser by flexible ducting; however, this
configuration resulted in increased pressure drops
(and, consequently, less effective suction on the
drain tiles) as well as condensate buildup and plug-
ging in low sections of the flexible ducting in cold
weather. Figure 4 shows the fan mounted directly on
top of the riser and enclosed within a protective box.
This configuration minimizes pressure drop in the
riser/fan connection .arrangement by eliminating all
bends in the pipe and ducting. Some fans can be
purchased with a protective enclosure similar to that
shown in Figure 4. Such a protective box also can
be fabricated separately. The exhaust should be cov-
ered with a screen to prevent children and pets from
reaching the blades and to keep out debris. Electrical
"connections to the fan should be wired according to
code to avoid electrical hazards.
The fan .should be mounted tightly on the riser. Any
gaps in the connections between the fan and the
pipe should be caulked or otherwise .sealed. If the
fitting is not airtight, the fan will simply draw outside
air through itself and will not draw effective suction
on the drain tiles. :
Operation and Maintenance
The operating and maintenance requirements for the
drain tile ventilation system consist of regular inspec-
tions by the homeowner to ensure that 1) the fan is
operating properly (e.g., is not iced up or broken),
2) the trap is full of water, and 3) any seals are still
intact (e.g., where the fan is mounted onto the
riser). Maintenance would include routine mainte-
nance to the fan motor (e.g., oiling), replacement of
the fan as needed, addition of water to the trap, and
the repair of any broken seals.-
Estimate of Costs
Based on EPA's experience in installing drain tile
ventilation systems in seven houses, it is estimated
that a private homeowner might have to pay about
$1200 to have a contractor install a system. This esti-
mate assumes that the house and drain tile installa-
tion present no unusual difficulties and that the job
is completed without the added expense of a "radon
mitigation expert" to oversee the contractor's work.
The estimate includes both materials and labor. Most
of the cost is the manual labor required for digging
down to expose part of the discharge line..
Some homeowners may be able to install the drain
tile ventilation system themselves. This approach
would limit the cost to materials; i.e., the fan, the
sewer pipe, and some incidentals. The material cost
alone should not exceed $300.
Operating costs would include the electricity to run
the fan and possibly a heating penalty because of
the increased ventilation in the house (assuming that
the gas drawn out of the drain tiles by the fan is
made up partly by house air that has been drawn out
through the block walls near the footings). Occa-
sional replacement of the fan would also be an oper-
ation and maintenance cost. The cost of electricity
to run a 0.03-hp (25-W) fan 365 days per year would
be about $15. Assuming that the system increases
house ventilation by roughly 50 cfm, the cost of
heating 50 cfm of outside air to house temperature
throughout the winter would be about $125. Thus,
the total operating cost would be about $140 per
year. Experience to date is insufficient to estimate
how often the fan might have to be replaced; a new
fan would likely cost between $40 and $100.
2.8 Active Ventilation of Hollow-Block
Basement Walls
Principle of Operation
The centers of concrete blocks used to construct
many basement walls contain voids. These., voids
generally are interconnected both vertically and hor-
izontally within a wall. Soil gas that enters the wall
through mortar joint cracks or pores in the exterior
face can travel through the wall by means of these
interconnected voids, and can enter the basement
through the voids in the top course-of block or
through holes, mortar joint cracks, and pores in the
interior face of the blocks. The principle of block
wall ventilation is to sweep the soil gas out of these
voids by drawing suction on (or by blowing air into)
this void network. When the wall ventilation system
operates to draw suction, the void network within
the block wall is maintained at a pressure lowerthan
that in the basement; hence, the flow of any radon-
containing soil gas that has leaked through the block
pores or through other inaccessible and unsealed
openings will be outward with the basement air
rather than into the basement.
19
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Two approaches have been considered for imple-
menting block wall ventilation. In one approach, one
or two pipes are inserted into the void network in
each wall to be treated and are connected to fans
that draw suction on or ventilate the wall (pipe-wall
ventilation approach). In the second approach, a
sheet metal "baseboard" is installed around the en-
tire perimeter of the basement (including interior
block walls), and covers the joint between the floor
and the wall. Holes are drilled through the interior
face of the block at intervals inside this baseboard,
and the wall is ventilated by depressurizing or pres-
surizing the baseboard duct with fans (baseboard
duct approach). The baseboard duct approach pro-
duces a more uniform ventilation of the walls, and
may be more aesthetic in some cases, but it is
approximately twice as expensive as ventilation
achieved by using single suction points in each wall.
Regardless of which of these approaches is used it is
crucial that all big openings in the walls be closed.
These openings include voids in the top course of
block, the gap between the interior block and any
exterior brick veneer, and large unsealed holes
around utility penetrations through the walls. In prin-
ciple, small fans have sufficient capacity to handle
the relatively small air leakage that will occur
through small cracks, block pores, etc. In fact, the
whole premise of active wall ventilation is that these
little cracks and openings are probably too numerous
and inaccessible to seal completely with caulk, ep-
oxy, or mortar, so a fan is used to ensure that soil
gas will not flow into the basement through these
routes. The fans that can realistically be considered
for these two approaches are too small to handle the
air flows that could enter the walls through big
openings. If the big openings are left unclosed, the
entire fan capacity would be consumed in drawing
house air (or outside air) through the big openings,
and the fan would not be able to maintain adequate
suction on the entire void network. Thus, radon re-
duction could be quite limited.
Applicability
Obviously, this technique applies only to houses with
basements constructed with hollow-block walls (con-
crete block or cinder block). The data obtained by
EPA during the testing of wall ventilation on eight
houses have shown that this technique produces
consistently high reductions in radon only when ma-
jor openings in the blocks can be effectively closed;
otherwise, the technique cannot properly ventilate
the wall. In some houses, such effective wall closure
is very difficult to achieve; in these houses, the ex-
pense involved in trying to accomplish such closure
could be prohibitive.
The baseboard duct approach to wall ventilation is
particularly applicable in block basements having
French drains (also called channel drains) with a 1-
or 2-in. gap between the block wall and the concrete
slab around the perimeter inside the basement for
water drainage purposes. In these houses^ the base-
board duct (which Would cover the drain) would
ventilate not only the wall voids (via the holes drilled
into the walls), but also the aggregate underneath
the slab. This gap in the slab is a potentially impor-
tant entry route for soil gas into the basement; thus,
the baseboard duct apprdach is particularly appropri-
ate as it addresses this entry route.
To draw suction on or pressurize the wall void
network effectively requires that the major openings
in the wall be closed. If large openings (such as the
voids in the top course of block) are left open, a fan
used for suction would simply draw basement air
into the openings close to the fan and exhaust it; the
fan probably would not effectively draw soil gas out
of the wall. In other words, any fan of reasonable
capacity would be unable to maintain the wall void
network at a lower pressure than the basement, par-
ticularly during winter, if there were major openings
through which large quantities of house (indoor) or
outdoor air could leak into the network. Some
houses are constructed in a manner that limits major
openings to those that can be closed fairly readily.
An example of a house that is particularly suitable
for the wall ventilation system is one where:
(1) All concrete block walls (including any interior
walls that penetrate the floor slab and rest on
footings as well as perimeter walls) have a top
course with the voids reasonably accessible for
being mortared and closed
(2) There is no exterior brick veneer
(3) There is no fireplace or chimney structure
within any block wall.
By comparison, effective closure of voids could be
difficult in houses where the top voids are rendered
inaccessible by a sill plate. In houses with exterior
veneer on one or more walls, a gap is usually
present between the exterior veneer and the interior
sheathing or block that connects to the wall voids
but is inaccessible for effective closure. Fireplace
structures can contain accessible but totally con-
cealed openings at points within the wall.
EPA's testing of three houses considered suitable by
the above definition showed very high levels of sus-
tained radon reduction. Testing in several less suit-
able houses (i.e., houses having one or more of the
difficulties discussed in the previous paragraph) dem-
onstrated that reasonably high levels of reduction
were generally achieved in the summer, but these re-
ductions were lost again with the onset of cold
weather. EPA is currently working to define ap-
proaches for achieving good year-round performance
with wall ventilation on houses in which effective
20
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closure is more difficult to achieve. Currently, how-
ever, high sustained levels of reduction can be confi-
dently expected dilly on suitable houses.
In summary, wall ventilation would be most applica-
ble to:
(1) Concrete block basement houses that have
reasonably accessible top voids, no exterior
brick veneer, and no fireplace structure within
a blbek Wall
(2) Houses fitting the above description, but with
French drains (in which case the baseboard
duct variation is particularly appropriate).
The wall ventilation system (whether the pipe-wall
ventilation approach or the baseboard duct approach
is selected) can be designed and operated with suc-
tion or ventilation on the hollow-block wall voids. If
the wall ventilation system operates by suction, the
void network is maintained at a pressure lower than
both the basement and the surrounding soil. Any soil
gas that penetrates into the wall (through cracks and
pores in the exterior face) is drawn out by the fan. If
there are small unsealed cracks or holes in the in-
terior face of the basement wall (e.g., small mortar
joint cracks), the gas flow will consist of basement
air flowing into the cracks (and out through the fan)
rather than soil gas flowing into the basement. The
gas flow through the pores of the blocks also will be
in the direction of basement air entering the blocks,
and thus keep radon out of the basement.
Based on EPA's experience, the subsequent discus-
sions on maintaining hollow-block wall ventilation for
radon reduction focus on the operation of the sys-
tem under suction. As mentioned earlier the system
Could be operated to blow into the walls and thus
maintain the hollow-block wall voids under pressure.
In this case, the voids would be at a pressure higher
than the surrounding soil gas. Any air flow across
the exterior face of the block would be clean outside
air (from the fan) flowing out into the soil rather
than radon-containing soil gas entering the block
voids. Essentially all of the subsequent discussion of
wall ventilation design would be equally applicable to
depressurization or pressurization of the void
network.
Confidence
EPA has tested wall ventilation in eight concrete
block basement houses to date: six use pipe-wall
ventilation and the other two use baseboard ducts
(He86). In all of this testing, the fans were operated
to draw suction on the walls (not to pressurize the
walls). Three of the six single-pipe wall ventilation
houses lent themselves to effective closure (although
a portion of one wall of House No. 14A has veneer).
Testing results on these three houses are shown in
Table 6.
Table 8. Results Obtained With Wall Ventilation In Three
Test Houses
House
No.
Concentration before
technique installed,
WL
Early July/
1985 Aug. 1985
Concentration after
technique installed,
WL
July/ Nov./
Aug. 1985 Dec. 1985
3A 1.7 - 3.0 4.2 - 7.4 0.005 - 0.01 0.005 - 0.01
8 0.13-1.7 0.26-0.80 0.005-0.02 0.01-0.02
14A 0.12 - 0.42 0.26 - 0.34 Not available 0.005
Except for the early 1985 premitigation values, these
values are each based on 1 or 2 days of continuous
radon monitoring by EPA during the months indi-
cated; the early 1985 results are based on both grab
sampling and longer-term integrated measurements
by the Pennsylvania Department of Environmental
Resources (PDER85). These data demonstrate that
very high radon reductions can be achieved and sus-
tained into the cold weather months if effective clo-
sure of major wall openings is achieved.
In the remaining five houses, which were less suit-
able for effective closure, the wall ventilation installa-
tions were able to achieve reductions of between 81
and 99 percent during the summer months but were
unable to maintain this performance into the cold
weather months. The premitigation levels measured
by EPA in July and August (0.14 to 2.4 WL) in these
five houses were reduced to 0.005 to 0.06 WL in the
summer after the technique was installed, but the
levels increased to 0.05 to 1.0 WL when followup
measurements were made in November and Decem-
ber. Each of these five houses had significant un-
closed openings in the block walls (three of them
had brick veneer on three or four walls). EPA is cur-
rently exploring effective ways of applying wall venti-
lation to these more complex houses. Technique
modifications under study include additional fan ca-
pacity, redesigned ducting, and ways of sealing inac-
cessible wall openings.
EPA's testing in the three houses that were suitable
for effective wall closure demonstrated that very
high radon reductions can be achieved and main-
tained in such houses. Nonetheless,-demonstrations
are needed on a variety of additional suitable houses
to increase confidence in the reliability of the tech-
nique and to identify other house design features
that could result in sufficient inaccessible wall open-
ings to reduce wall ventilation performance. Further-
more, EPA's measurements in the three houses
where this approach was successful have been rela-
tively short-term (1 to 2 days of continuous monitor-
ing); longer-term (2-month) monitoring and observa-
tion of system performance for a year or longer are
needed to confirm these results. Based on these
considerations, it is believed that there can be mod-
erate to high confidence that suitable houses can be
21
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identified for the successful application of wall venti-
lation for the reduction of indoor radon levels.
Even in less suitable houses with inaccessible top
voids, exterior veneer and/or a fireplace structure, it
is still possible that wall ventilation can work suc-
cessfully (e.g., through increased fan capacity and/
or special closure efforts); however, EPA has not yet
demonstrated consistently high radon reductions in
such houses. Thus, the confidence in the per-
formance of wall ventilation in these houses must be
considered low to moderate at present.
Some question exists as to how well wall ventilation
ventilates the aggregate under the concrete slab at
points remote from the wall. The ability of wall venti-
lation to provide such sub-slab ventilation depends
on the effectiveness of communication between the
bottom course of block and the sub-slab (i.e., the
nature of the mortaring and slab-pouring when the
house was built), the condition of the aggregate, the
extent of slab cracks, and the size of the ventilation
fan. The baseboard duct approach may provide a
greater potential for simultaneous ventilation of the
sub-slab, especially when the duct is laid over a
French drain.
Design and Installation (Pipe-Wall Ventilation
Approach)
A wall ventilation system using the pipe-wall ventila-
tion method is shown in Figure 5. In this system,
generally one pipe (sometimes two) would be em-
bedded in each wall to ventilate the void network.
Figure 5 depicts the system as drawing suction on
the wall.
In the design of a pipe-wall ventilation system, every
block wall that rests on footings should have at least
one vent pipe. This would, of course, include each
of the exterior perimeter walls (even if one or more
of those walls is not below grade). In addition, any
interior block walls that penetrate the slab and rest
on footings should be vented. These include walls
dividing the basement into living areas, walls sepa-
rating the basement from an attached garage, and
walls separating the basement from an adjoining
crawl space. If the crawl space is heated (i.e., is es-
sentially open to the basement or to other parts of
the home), the block walls around the crawl space
also must be vented. The concern with above-grade
and interior walls arises because the mortar joint be-
tween the bottom course of block and the footings
appears to be a major- entry route for soil gas into
the void network; thus, any block wall that contacts
footings can serve as a chimney for soil gas to flow
into the home, even if the exterior face of the block
does not appear to contact the soil.
Number and Location of Wall Suction Points
In the three houses where EPA experienced the
greatest success with wall ventilation, one suction
22
point per wall was generally adequate. At least one
suction point per wall is necessary because there is
no guarantee that effective communication has been
maintained between the voids in turning a corner.
The mason who laid the block during construction
might have applied the mortar and laid the block in a
manner that would prevent suction on one wall from
being effectively transmitted to the adjoining wall. If
there is reason to believe that a particular wall could
be subject to greater leakage of baserffent or outside
air (e.g., due to the presence of brick veneer on the
exterior of that wall) and thus the pipe into the wall
could be handling a larger than average air flow, a
second suction point would probably be advisable! If
a segment of a particular wall is offset from the re-
mainder of that wall (e.g., by a pair of right-angle
turns in the block), that offset segment probably
should have a suction point of its own, again be-
cause the suction in the main part of the wall might
not effectively turn the corner.
It appears reasonable to locate a single suction point
approximately in the linear center of the wall (or the
segment of wall) that it is meant to treat. A rule of
thumb applied in the EPA testing was to use one
suction point for each 24 ft of wall length (i.e., 12 ft
on either side of the suction point). Vyhen the wall
was longer than 24 ft, two suction points were pro-
vided. If multiple points are used in a given wall/log-
ical placement would be approximately one-quarter
of the wall length from each end of the wall. In
terms of height, it is generally advantageous to place
the suction points as close to the floor as possible in
order to sweep the top courses of voids with clean
air entering through any leaks (rather than drawing
soil gas up into the void network). Often practicality
or aesthetics may prohibit placement of the suction
points near the floor; in this case, it is acceptable to
place them higher. In a house where effective clo-
sure of wall openings is possible, the height of the
points should not be important.
The suction points may be located either inside or
outside the basement. Figure 5 shows them inside
the basement and connected to an outdoor fan. In-
side installation is generally more simple and mini-
mizes the piping visible outside the house. When a
basement is finished (or for aesthetic purposes even
in an unfinished basement), penetration of the
blocks from outside the house may be preferred to
avoid making holes in wallboard or panelling and
putting a piping network inside the living area. If a
basement wall is partially above grade, access to the
block voids from outdoors should not be a problem.
Outside installation would simply involve drilling half-
way into the blocks from the outside rather than the
inside and mounting the pipe outside. When a base-
ment is largely below grade, outside mounting would
require the digging of a small well against the ex-
terior basement wall, similar to a basement win-
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Figure 5. Wall ventilation with individual suction points in each wall.
.Brick veneer
Close top voids2
Top void
Connections to other walls
1. Closing the veneer gap may
be important in some cases.
2. If top voids are not closed,
there will be some leakage
of house air into the void
network.
3. Closing major slab openings
may be important.
House air through block pores,
unclosed cracks, and holes
Soil gas
Concrete block
Close major mortar cracks and holes in wall
Utility pipe
Aggregate
23
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dow well, to provide access. If desired, such a well
could be filled in after the piping was mounted and
brought above grade. For interior walls, of course,
the only option is to make the penetration inside the
basement. The least obtrusive approach for making
this penetration (and installing the piping) is a house-
specific decision.
Closing Major Wall Openings—Top Voids
The voids in the top course of block interconnect
with all of the other voids inside the wall and must
be adequately closed; otherwise, the wall ventilation
system will be unable to maintain the void network
reliably at a pressure lower than the basement. In
cases where these top voids were capped with solid
block during construction, an effective closure is al-
most ensured. This situation did not occur, however,
in most of the houses that EPA inspected in eastern
Pennsylvania.
In some houses the top voids are sufficiently acces-
sible for a person to reach down into the voids. This
situation can occur when 12-in.-wide blocks have
been used and the sill plate is sufficiently small that
much of the void is exposed (see Figure 6). Voids
Rgure 6. Closing top void when a fair amount of the
void is exposed.
•Siding
•Sheathing
Concrete block
Mortar/foam
to close void
Crushed
newspaper support
Top void
that are thus exposed on one or more of the walls
can be effectively closed, and the house may be par-
ticularly suitable for wall ventilation. The best ap-
proach is to force crumpled newspaper (or some
other suitable support) down into every void in the
wall and then to fill the entire void carefully with
mortar to a depth of at least 2 in., as shown in Fig-
ure 6. It is crucial that the mortar be forced all the
way to the far face of the void under the sill plate;
mortaring only the exposed part of the void would
greatly reduce the effectiveness of the seal. Closing
every void in the wall is a slow and difficult process,
but it will pay high dividends in improved system
performance.
In some houses, where the voids were fairly accessi-
ble but space was somewhat more limited, EPA used
a single-component urethane foam that could be ex-
truded through a hose-and-nozzle assembly. Some
of the foams are available in aerosol cans for house-
hold use and some are available for commercial ap-
plications. Even with the use of foam, it was still
necessary to force a crumpled newspaper support
down into each void; however, the use of the hose
and the expanding foam eliminated the need for the
void opening to be large enough to accommodate
part of a person's hand. Thus, where the void ac-
cess is not large enough to permit mortaring but is
large enough to force newspaper through, the use of
a foam can be considered.
In other houses, the top voids may be entirely
blocked by the sill plate. This can occur where 8-in.-
wide blocks are used, and the sill plate is so large
that it essentially covers the top of the block (see
Figure 7). The successful application of wall ventila-
tion is still possible in these houses. Two of the
three houses where EPA had the greatest success
with wall ventilation had one wall, or a portion of
one wall, where the voids were inaccessible in this
manner. If literally none of the void is visible under
the sill plate, an attempt can be made to use the sill
plate to close the void by caulking the seam between
the sill plate and the top blocks with silicone caulk.
When a fraction of an inch of void was exposed —
too small to force crumpled newspaper and a foam
nozzle through, but possibly too large to close with
caulk—EPA used one approach that involved coating
two sides of a strip of wood with caulk or some
other suitable sealant (e.g., tar) and nailing this strip
tightly in place over the void, and pressed against
the sill plate and the block (Figure 7).
Figures 6 and 7 depict a house without exterior brick
veneer. When walls are covered with veneer, often
few or none of the top voids are exposed inside the
basement because the veneer will displace the sill
plate toward the inside face of the block. Thus, mor-
taring or foaming the block voids shut generally will
not be feasible. Instead, the use of caulk (or the tar-
covered wood strip approach) is required.
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Figure 7. One option for closing top void when little of
the void is exposed.
Siding
Sheathing
Wallboard
Floor
Header joist
Coated wood strip
to close void
Sill plate
Top void
Concrete block
It is reemphasized that the top voids must be closed
in all walls— including interior block walls that rest
on footings as well as exterior perimeter walls.
Closing Major Wall Openings—Holes and
Cracks in Walls
Any other visible holes or major cracks in basement
walls should also be closed. Holes in the wall around
utility penetrations should be closed by mortaring
around the pipe or duct. Major mortar joint cracks
should be sealed with caulk or some other appropri-
ate type of sealant.
Although the pores inherently present in concrete
blocks permit air leakage, they generally do not allow
enough air to penetrate to overwhelm the capacity
of the fan. Hence^ no special effort is required to
seal concrete blocks as part of a wall ventilation in-
stallation. When houses are constructed of cinder
block,,however, the far more porous block makes it
difficult to maintain adequate Suction. If wall .ventila-
tion is to be attempted in a cinder block basement,
consideration probably should be given to sealing the
pores in some manner. One approach that EPA has
used successfully is coating the inside of the entire
basement wall with a latex waterproofing paint con-
taining Portland cement. Some other (higher-cost)
options include epoxy paints and other coatings or
waterproofing membranes (e.g., polymers).
Closing Major Wall Openings —Gaps Created
by Brick Veneer
In houses with exterior brick veneer, a gap occurs
between the veneer and the sheathing and block be-
hind the veneer. This gap is depicted in Figure 8.
Depending on how the bricks were laid and the size
of the gap, this inaccessible gap could prevent effec-
tive suction from being drawn on the block voids.
The fan intended to ventilate the walls could simply
be drawing outside air (or house air) down through
that gap into the voids.
EPA has not yet demonstrated very high sustained
radon reductions by using wall ventilation in houses
with brick veneer on more than a portion of one
wall. Nor has the Agency yet confirmed that this in-
accessible veneer gap is a major cause of this lack of
Figure 8. Closing top void and veneer gap when exterior
brick veneer is present.
Veneer gap
Sheathing
Brick veneer
Wallboard
Header joist
Floor
Drilled access hole
Closure plate
Coated wood strip
to close void
Sill plate
Foam to close
veneer gap
Concrete block
25
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success. Measurements in some veneered houses
suggest that this gap may not be a major source of
air leakage and that additional fan capacity should
improve radon control. EPA has attempted to close
this gap by drilling through the header joist and us-
ing a hose-and-nozzle assembly to extrude urethane
foam into the gap (Figure 8), but the effectiveness of
this closure or the best way to accomplish it have
not been confirmed. Further assessment is needed in
this area.
In view of the current lack of a successful demon-
stration in houses with one or more complete veneer
walls, such houses are currently considered less suit-
able for application of the wall ventilation technique.
Until further testing is completed, anyone attempting
to install a wall ventilation system in a veneered
house should plan initially on doubling the fan ca-
pacity. If effective performance is still not achieved,
attempts should be made to seal the veneer gap as
illustrated in Figure 8.
Closing Major Wall Openings—Fireplace
Structures
Fireplace structures incorporated into block walls of-
fer the potential for numerous invisible, inaccessible
openings between the structure and the surrounding
wall, between the structure and the outdoors, or be-
tween the structure and the upper levels of the
house. Thus, attempts to draw suction on the sur-
rounding wall may be difficult or impossible—even
when the top voids in the wall itself are well
sealed—because air from outside or upstairs can leak
into the wall through the fireplace structure. Such
leakage points probably cannot be located, much
less closed, except by tearing down the surrounding
wall and/or the fireplace/chimney structure. Be-
cause the latter is expensive, EPA is testing an ap-
proach that involves increasing fan capacity in an ef-
fort to maintain adequate suction despite this
leakage. Although its success has not yet been dem-
onstrated suitable increases in fan capacity may
solve the problem of fireplace structure leakage in
many houses.
Closing Slab Openings
Although closing openings in the concrete slab is
usually unnecessary for effective suction on the wall,
large openings in the slab can be an important
source of soil gas flow into the home, and such
openings should be closed. Wall suction will not al-
ways treat all of the slab-related entry routes for soil
gas; thus, it is important to address at least the ma-
jor slab-related routes in conjunction with the instal-
lation of any wall suction system. Large holes and
cold joints should be mortared shut or otherwise
closed, as discussed in Section 2.6. In particular, for
the purposes of wall ventilation, any large cracks vis-
ible in the wall/floor joint should be sealed. Such
large cracks, which represent defects when the con-
26
crete slab was poured, could serve as a source of air
leakage into the wall and reduce the effectiveness of
maintaining the wall under suction. If the wall/floor
joint consists of a French drain, this gap should not
be mortared shut; rather, the homeowner should
take advantage of the drain by selecting the base-
board duct approach for wall ventilation.
Open sumps in the basement should be covered and
possibly ventilated, as discussed in Section 2.5.
Floor drains that drain to a septic tank and thus con-
tain a trap beneath the slab should be checked to
ensure that the trap is full of water. Otherwise, soil
gas (and odors) from the septic tank may come up
the drain line and enter the home through the floor
drain. If a floor drain contains a cleanout plug be-
yond the trap, this plug must be in place to prevent
septic tank or sewer gas from entering the house
even though the trap is full of water. A floor drain
that connects directly to drain tiles may not be
equipped with a trap. Such untrapped floor drains
can be important sources of soil gas and must be
plugged in some manner. Removable stoppers can
be fabricated or purchased commercially. If the floor
drain is ever needed (e.g., because a clothes washer
or water heater in the basement overflows), the
stopper can be removed temporarily. The only alter-
native to this stopper approach is to install a trap in
the drain line, which would likely require tearing up
part of the slab around the drain. With the slight de-
pressurization of the. basement that can take place
when wall suction systems are in operation, failure
to address these other soil gas entry routes not asso-
ciated with the walls can become increasingly impor-
tant.
Piping Network Design
Pipes must be mounted and sealed into each wall
suction point and connected to one or more fans.
This can be designed in several ways, the most satis-
factory method determined largely by the preference
of the individual homeowner.
EPA used Schedule 40 plastic sewer pipe in the test
houses because this pipe seemed to be the easiest
for a homeowner to work with. Other piping could
be chosen for some parts of the piping network;
e.g., metal air ducting. In general, 4-in. plastic sewer
pipe should be used. Smaller pipe could be consid-
ered and may be more aesthetic in some installa-
tions. In general, however, the larger diameter piping
is better. Since significant pressure drops can occur
through the piping, the larger the diameter of the
pipe, the lower the flow velocity, and thus the lower
the pressure drop. A high pressure drop can cause
the fan(s) to consume much of their suction capabil-
ity in moving the gas through the pipes; therefore,
less capacity will be available for drawing suction on
the walls. Also, numerous bends in the piping in-
crease the pressure drop. Therefore, the use, of
-------
larger diameter pipe with as few bends as possible
will increase the effectiveness with which a given fan
ventilates the walls.
At the selected suction points in each wall, a hole
should be drilled or chiseled through the near face of
the-block wall to expose the interior voids, but it
should not penetrate all the way through the far face
of the block. Logically the hole would be drilled into
a void in one of the blocks (i.e., at a point midway
between the end and the middle of the block). The
hole dimensions should be as close as possible to
those of the piping being used; e.g., a circle roughly
4 in. in diameter if 4-in. sewer pipe is being used.
After the piping is mounted in this hole, any gap be-
tween the block and pipe must be sealed tightly so
that air cannot leak into the block through the space
around the pipe. Such leakage could reduce the ef-
fectiveness of the ventilation system in the same
manner as that from other major unclosed openings
in the wall. In the EPA testing, an asphaltic caulk
was generally used to seal the gap between the pipe
and the block.
If the penetration into the block is from the outside
of the house/the fan can be mounted directly on the
short, straight section of pipe that is embedded in
the wall. In this design, a fan would be mounted
onto the outside foundation wall at each suction
point. If the wall is below grade at a given suction
point, the fan would have to be mounted in a small
well (similar to a window well) dug for this purpose
or an elbow could be installed to bring the pipe
above grade before mounting the fan. Although this
design would ensure the least pressure loss through
the piping network, it would probably result in more
fans than would really be necessary (one per suction
point, at least four per house). Another possibility
might be to mount one fan at the rear of the house
or perhaps one fan near each of the two rear corners
and to tee the piping from each exterior suction
point into a central collection pipe that runs around
the perimeter of the house and back to the fans. If
there are two fans, logically there would be two col-
lector pipes, one around each side of the house. One
configuration for such a system could include 6-in.
pipe to serve as the central collector, with 4-in.
diameter legs tapping off from the collector to pene-
trate the walls at the selected suction points. These
pipe sizes should reduce the pressure loss in the
pipe. For aesthetic purposes, some of this piping
could be buried, especially in front of the house.
If the penetration into the block is from inside the
basement, it would be generally reasonable to use
elbows to bring the pipe legs from each suction
point up to the floor joists, where they could be
tapped into a central collection pipe. This central
collector could conveniently run near the ceiling, up
between the floor joists, and penetrate the wall at a
convenient point to connect to a fan mounted on
the collector pipe just outside the house. An alterna-
tive would be to have the collector exit the house
through a window. Penetrating the wall would be a
more permanent installation, however, and would fa-
cilitate mounting of the fan (as the fan could then be
attached directly to the plastic pipe on the exterior
wall), tf more than one fan were used, it-would be
logical to have an additional collector for each fan.
In this design, a fan would be attached to the side of
the house at each point where a collector penetrates
a wall. Again, a reasonable choice (to reduce pres-
sure drops In the pipe) would include 4-in.-diameter
legs from each suction point that tap into 6-in. col-
lectors.
The preceding discussion assumes that the fan is
mounted outside the house; however, the fan could
be mounted inside'the house with the fan exhaust
pipe penetrating the wall so that the soil gas is ex-
hausted outdoors. This design would avoid problems
with freeze-up during.the winter, but it results in fan
noise indoors. Also, any leaks in the exhaust system
would allow soil gas to be released inside the house.
Logistic considerations for each house probably will
play some role in determining where the fans are lo-
cated; however, locating them away from windows
and bedroom walls.would be generally desirable to
reduce the inconvenience of fan noise. Positioning
them away from windows also will reduce the risk of
prevailing winds carrying fan exhaust with.an ele=-
vated radon-level into open windows. As mentioned
earlier, some homeowners may wish to locate the
fans remote from the house by running a length of
pipe some distance into the back yard. This would
reduce fan noise and the risk of backwash, but the
resulting increase in pressure .drop could necessitate
additional fan capacity to maintain effective suction
on the walls. ,
Selection and Mounting of Fans
The fans used most commonly in the EPA testing of
wall ventilation were 250 cfm centrifugal fans capa-
ble of drawing about 1/4-in. of water suction. In
some cases, 160 cfm centrifugal fans (capable of 1
in. of water suction) were used. In the three houses
where radon reduction was deemed successful, a
single fan was sufficient. In two of these houses, a
single 250-cfm fan was used; in the third, a single
160-cfm fan was used.
In houses where the closing of potentially major wall
openings is difficult, more fans may be necessary to
accommodate the increased leakage of basement air
or outside,air into the walls. Testing has not yet con-
firmed exactly how much fan capacity is required un-
der various circumstances where effective sealing is
difficult. For houses that include a wall with exterior
brick _veneer or with a fireplace structure, however,
the use of at least two fans is suggested.
27
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Caution must be applied if several fans are used to
try to compensate for air leakage through inaccessi-
ble openings in a wall. Under these conditions, the
fans could depressurize the basement sufficiently to
cause back-drafting of combustion appliances (fur-
naces, fireplaces, etc.). If this occurred, the prod-
ucts of combustion from these appliances could be
drawn out into the room instead of being drawn nat-
urally up the flue. Such a depressurized condition
could result in carbon monoxide poisoning. Where
the threat of back-drafting exists, it would be advisa-
ble to consider reversing the fans so that they pres-
surize the walls rather than drawing suction. This
avoids the back-draft threat. Currently, however,
EPA has no data on the performance of wall ventila-
tion systems operating under pressure.
The fans should be tightly clamped to the collector
pipes. Any gaps in the connection between the fan
and the pipe should be caulked or otherwise sealed
to ensure an airtight fitting. If the fan is mounted
outdoors, some reasonable weather protection for
the fan should be provided. The 250-cfm fans used
in the EPA tests were intended for exterior roof or
wall mounting and thus came from the supplier with
a protective aluminum housing. For unprotected
fans, a protective housing would have to be fabri-
cated. If the fans are mounted at a point outside the
house that is lower than the suction points in the
walls, the fan and motor should be protected from
condensed moisture during the winter. If the fans
are mounted inside the house, extreme care should
be taken to ensure that the exhaust pipe is tightly
mounted onto the fan outlet and that there are no
leaks between the fan and the point where the ex-
haust pipe ends outdoors.
Fans can be made to draw suction on the wall or to
pressurize the wall, either of which would likely re-
duce radon levels. To date, all of EPA's testing has
been with the fans in suction because of the concern
that cold outside air blown into the walls during win-
ter months could cause condensation of moisture on
the wall inside the basement. As discussed earlier,
operation under pressure might be advisable where
major unclosed wall openings exist and pose a threat
of basement depressurization and back-drafting.
Testing Wall Ventilation Effectiveness
When the fans are turned on for the first time, and
periodically thereafter, the homeowner would be well
advised to test how well the fans are maintaining
suction on the wall. A simple way to do this is to
use a smoke-generating device such as an incense
stick. As the smoke generator is passed over the sur-
face of the wall, along the top of the wall, and along
the wall/floor joint, the smoke should consistently
be drawn into the block pores and the cracks around
the total perimeter. If the smoke is blown outward at
28
any point, soil gas may be entering the house at that
point because adequate suction is not being main-
tained.
Design and Installation (Baseboard Duct
Approach)
Wall ventilation with baseboard ducts is illustrated in
Figure 9. In this approach, hollow-wall ventilation is
provided by a sheet metal duct that is sealed over
the wall/floor joint around the entire perimeter of the
basement and on any interior block walls that pene-
trate the basement slab to rest on footings under the
slab. Holes are drilled into each void within the base-
board duct to permit ventilation of the void network.
(In some houses, the wall/floor joint consists of a
French drain.) Baseboard ducts offer more uniform
distribution of the ventilation than does the individ-
ual pipe-wall method because the baseboard holes
into the void network are drilled along the entire li-
near distance of block wall, rather than being placed
all at one point. Also, because the baseboard ventila-
tion holes are at the bottom of the wall, baseboard
ventilation could provide a more effective "sweep-
ing" of the upper courses of block. Clean air leaking
in near the top of the fan offers greater potential for
keeping the voids in the upper courses relatively free
of soil gas.
Selection of Walls To Be Ventilated
A baseboard duct must be installed on every block
wall in the basement that rests on footings, including
both interior and exterior walls. For an interior wall
on which both faces of the wall are accessible, in-
stalling the baseboard duct on just one face might
be sufficient. If the interior wall separates a finished
portion of the basement from an unfinished store-
room, the duct might conveniently be mounted on
the unfinished side of the wall for the sake of ap-
pearance. The baseboard duct should be installed on
the entire linear distance of the wall/floor joint
around the total basement perimeter. Some interrup-
tions in the duct could be considered at particularly
inaccessible locations (e.g., behind a furnace or
stairwell that is essentially against the wall). All seg-
ments of a French drain must be covered or mor-
tared shut if really inaccessible for the duct. If a sig-
nificant crack is evident along the wall/floor joint on
the untreated face of the interior wall, this crack
should be closed.
Closing Major Wall Openings
All major wall openings—the top voids, large holes
and cracks, the brick veneer gap, and openings as-
sociated with fireplace structures—must be closed.
Any major openings in the concrete slab should also
be closed, as discussed previously, except cracks as-
sociated with the wall/floor joint. These do not have
to be sealed because the baseboard duct treats this
_
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Figure 9. Wall ventilation with baseboard duct.
Brick veneer
Notes:
1. Closing the veneer gap may
be important in some cases.
2. If top voids are not closed,
there will be some leakage
of house air into the void
network.
3. Closing major slab openings
may be important.
Close major mortar cracks and holes in wall
House air through block pores,
unclosed cracks, and holes
Close top voids*
Top void
Sheet metal baseboard duct tightly
sealed against floor and wall
Utility pipe
29
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joint. Such cracks actually may be helpful, as they
can improve communication between the duct and
the wall voids or sub-slab aggregate.
Design of Baseboard Duct System
As indicated previously, the duct should cover the
wall/floor joint everywhere around the entire base-
ment perimeter, and on at least one face of every
interior wall. If the duct must be interrupted at any
point because the joint becomes inaccessible, the
end of the duct must be capped off so that proper
suction is maintained. All lengths of French drain
must be covered by the duct. Any inaccessible seg-
ment of the drain should be mortared shut, not only
because it would be an untreated source of soil gas
into the house, but because it could serve as a
source of basement air leakage into the adjacent
duct.
Before the duct is mounted, holes must be drilled
through the wall near the floor in the region that will
be covered by the duct. These holes permit the ven-
tilation system to draw the necessary suction on the
void network uniformly around the perimeter of the
basement. In the EPA testing, these holes were
made with a 1/2-in. drill into each void in every
block around the perimeter.
The baseboard ducts can be fabricated out of sheet
metal, or they can be created with internal channel
drains that are sold commercially. EPA has tested
both materials and found that sheet metal offers
greater flexibility for selecting duct size and fitting to
the contours of the basement perimeter. This duct
must be attached and sealed tightly to the wall and
to the slab around the entire perimeter to form ah
airtight seal over the wall/floor joint and over the
holes that have been drilled in the wall. In the EPA
testing, the duct was anchored to the wall and floor
with masonry screws and sealed against the wall and
the slab by a continuous bead of asphaltic caulk. It
is crucial that the connection against the wall and
the slab be airtight; otherwise, basement air will leak
into the duct and prevent the system from being ef-
fective. Masonry screws alone will not ensure an ad-
equate seal.
Wherever the duct must be interrupted, the open
end of the duct must be sealed, preferably with
sheet metal, and a sealant must be applied over re-
sidual seams. Particular care must be made where
the duct "turns corners." The seam between the
legs joined at the corner must be carefully sealed..
When the slab is not perfectly flat, special care is
required and additional caulking is needed to ensure
that a good seal is maintained.
Figure 9 illustrates a duct with a rectangular cross
section; triangular cross sections also were used in
the EPA testing. The exact shape of the cross sec-
tion is not important, and selection can be based on
a homeowner's particular preferences or on any
unique features of a specific basement. The size of
the duct is important. Of course it would be large
enough to cover the holes drilled in the wall and any
French drain that exists. Beyond that, it also must
be large enough to reduce the pressure drop created
by the air and soil gas flowing through it. If the duct
is too small, a large pressure drop will occur and
much of the fan's suction capacity will be consumed
in moving gas through the duct, which leaves less
for maintaining suction on the walls. If a lot of air
leakage is expected into the walls (e.g., due to a
brick veneer gap or to a fireplace structure), a larger
duct will be required.
In recent testing in one house with such potential
sources of air leakage through unsealed wall open-
ings, EPA used a triangular sheet metal duct config-
uration that covered (in cross section) an area of the
wall from the floor to 8 in. above the floor and ex-
tended up to 3 in. away from the wall. In a second
house, where even larger leakage was expected a
rectangular duct was used covering an area of the
wall to 12 in. above the floor, and extending 3 in.
away from the wall (Figure 9). Smaller ducts might
be considered in houses that have no major inacces-
sible wall openings, or when the homeowner wants
to use a larger number of fans.
Unlike the pipe-wall ventilation method, the base-
board approach requires that ventilation points, be in-
stalled inside the basement. In finished basements,
this entails extra effort to install the duct behind the
wallboard or panelling, or to cut off the bottom of
the wall finishing to accommodate the duct.
The installed duct must be connected to one or
more fans. This can be done in a number of ways,
but the method typically used in the EPA testing was
to tap plastic sewer pipe (typically 2 in. diameter) or
metal ducting into the baseboard duct at one or
more locations and then to lead each pipe through a
window or through the wall to connect to a fan out-
side. As an alternative, the fan could be mounted
inside the house with the exhaust pipe leading out-
doors. If more than one segment of duct has been
used (i.e., if the duct has had to be interrupted and
does not form a continuous loop), each segment
must have a tap that connects to a fan. Places
where the plastic pipe taps into the sheet metal
baseboard duct must be effectively sealed with caulk
or an asphaltic sealant. The same considerations ap-
ply to positioning the fans as those discussed for the
pipe-wall ventilation method. In general, if more than
one fan is used, it seems reasonable to locate them
at opposite ends of the house to help ensure effec-
tive suction around the total perimeter.
Selection and Mounting of Fans
In the baseboard duct installations tested to date by
EPA either 250-cfm centrifugal fans (1/4-in. of water
30
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suction) or 160-cfm centrifugal fans (1 in. of water
suction) were used. In one house, only one fan was
used; however, more commonly, two fans were
used, typically mounted at the two rear corners of
the house. In houses with inaccessible openings in
the wall, such as a brick veneer gap or a fireplace,
more than one fan should be used. Testing has not
yet confirmed exactly how much fan capacity is re-
quired under various circumstances-where effective
sealing is difficult. As discussed previously, the ven-
tilation system can be operated to pressurize the
walls rather than to draw suction if back-drafting is a
threat. Fan-mounting considerations are the same as
those discussed previously for the pipe-wall venti-
lation approach.
Testing Wall Ventilation Effectiveness
Periodic testing is suggested to determine how well
the fans are maintaining suction on the wall by using
the smoke technique described previously. With the
pipe-wall ventilation approach, smoke tracer results
suggest that there is sufficient communication in
some houses between the bottom course of blocks
and the aggregate underneath the slab to achieve
ventilation of the wall/floor joint and thus prevent
soil gas from entering via that joint. (Baseboard
ducts enclose and ventilate the joints directly.)
Operation and Maintenance
The operation and maintenance requirements for
either wall ventilation system include regular inspec-
tions by the homeowner to ensure that the fan(s) are
operating properly (e.g., are not iced up or broken);
all seals are still intact (e.g., where the top voids and
other wall openings have been sealed, where the
pipes penetrate the wall, where the baseboard duct
attaches to the wall and the slab, where sections of
pipe join together, and where the fan is mounted
onto the pipe); and adequate suction is being drawn
on the walls (e.g., by use of smoke testing). If the
fan is mounted indoors, the exhaust system should
be inspected regularly for leaks.
Fan maintenance should be performed routinely, and
fans should be replaced as needed. Any seals show-
ing signs of cracking should be repaired with as-
phaltic sealant or silicone caulk. The integrity of
these seals must be maintained to permit the system
to provide proper wall ventilation. If smoke testing
indicates that the system is no longer properly main-
taining suction on some portion of the wall, seals
should be checked for failure and the duct/piping
leading to the fan should be checked for blockage. If
the inadequate suction persists, consideration should
be given to adding a suction point and/or a fan to
improve the ventilation of that portion of wall.
The homeowner should be alert to any signs of
back-drafting of fireplaces and combustion appli-
ances in the basement. Odors and smoke inside the
basement are signs of back-drafting when a fireplace
is operating in the house. Oil-fired burners also may
produce such telltale signs.
Estimate of Costs
The installed cost of a wall ventilation system can
vary significantly, depending on the approach se-
lected and the amount of effort required for effec-
tively sealing the major wall openings.
If the pipe-wall ventilation method is installed in a
house that lends itself well to effective closure of
major wall openings—i.e., top voids are reasonably
accessible, has no exterior veneer, contains no fire-
place structure—EPA's experience suggests that a
private homeowner may have to pay about $2500 to
have such a system installed by a contractor. This
estimate assumes that the house does not have a
finished basement and that the job is completed
without the added expense of a "radon mitigation
expert" to oversee the contractor's work. The cost
estimate includes both materials and labor.
In a house where effective wall closure is more diffi-
cult to achieve—possibly one requiring additional ef-
fort to close the top voids, having a veneer gap,
built with porous cinder block, etc.—the costs could
be significantly higher. Also, if the house has a com-
pletely finished basement, additional cost (associated
with partial dismantling of the paneling, etc.) would
be encountered in gaining access to the top voids
and other major openings requiring closure. If the
pipes are to be installed inside a finished basement,
some additional cost would be associated with the
modification of the paneling/wallboard, etc., to
accommodate the pipes when paneling is replaced.
With the baseboard duct ventilation method, costs
for installation by a contractor would be higher than
for the pipe-wall ventilation approach because more
labor is required to attach the duct to the wall and
floor. Based on EPA's experience in two houses, the
installed cost in a suitable house could run $5000,
based on using the same assumptions as those for
the pipe-wall ventilation estimate. Again, a less suit-
able house or a house with a finished basement
could significantly increase costs.
Although installing wall ventilation would not be an
easy do-it-yourself job, some homeowners might be
willing to try it. In that case, the installation cost
would be limited to the cost of materials—probably
about $100 to $500 for the fans, piping, sheet metal,
and incidentials, depending upon the number of fans
required and the size of the basement.
Operating costs would include electricity to run the
fan(s) and possibly some heating penalty due to in-
creased ventilation of the house (some of the gas
drawn out of the walls by the fan includes house air
that has been drawn through the block pores and
31
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cracks). Occasional replacement of the fan would
also be an operational/maintenance.cost. The cost
of electricity to run a single 0.03-hp (25-W) fan 365
days per year would be about $15. Assuming that
the system increases house ventilation by roughly 50
cfm, the cost of heating 50 cfm of outside air to
house temperature throughout the winter would be
about $125. Thus, the total operating cost would be
about $140 per year. This would increase somewhat
with each additional fan. Experience is too limited to
predict how often each fan might have to be re-
placed, but a new fan would cost between $40 and
$100.
2.9 Ventilation of Sub-Slab
Principle of Operation
Soil gas accumulates in the soil and the aggregate
(the crushed rock) that underlies the concrete slab in
a basement or a slab-on-grade house. The gas can
then enter the house through any opening in the
slab; e.g., the wall/floor joint, settling cracks and
cold joints, or openings around utility penetrations.
In some extreme cases in eastern Pennsylvania, sub-
slab soil-gas radon concentrations as high as 10,000
pCi per liter (50 WL) have been measured. The in-
tent of active sub-slab ventilation is to use a fan to
sweep the soil gas out of the aggregate before it can
enter the house. A frequently employed approach in-
volves using the fan to draw suction on the aggre-
gate and thereby maintaining a pressure lower than
that inside the house. With this system, any gas
flow consists of cleaner house air flowing outward
into the aggregate through the openings in the slab
rather than soil gas flowing up into the house.
Two variations of the sub-slab ventilation system
have been tested by various researchers: 1) the indi-
vidual pipe variation, in which two (or more) nonper-
forated pipes are installed vertically down through
the slab and into the aggregate and all ventilation is
achieved by drawing suction on (or blowing air into)
these pipes; and 2) the perforated piping network
variation, in which a more extensive network of hori-
zontal perforated pipe is laid under the slab and suc-
tion is drawn on this network. The first approach re-
lies on a good layer of aggregate (or a fairly
permeable soil under the slab), so that the effects of
the one or two ventilation points can radiate under-
neath the entire slab. The second approach is less
dependent on the uniformity of the aggregate and
ensures -better ventilation under the total slab; how-
ever, this approach could entail considerable effort in
cutting channels through an existing slab to place
the perforated pipe and could be expensive. In prac-
tice this variation has most commonly been used
either in new construction or in existing houses
where the slab has had to be torn out to remove
contaminated soil from under the house (e.g., ura-
nium mill tailings) or when the existing slab has had
to be replaced for structural reasons. In these cases,
the perforated piping network is then relatively easy
to install before a new slab is poured.
Some houses have perforated pipe that was laid un-
der the slab during construction for water drainage
purposes. This pipe typically drains into a sump
within the house footings. By drawing suction on
the sump in such houses, the sub-slab can be venti-
lated by using this in-place perforated piping
network.
An extensive sub-slab piping network sometimes will
provide adequate ventilation in a passive mode, with-
out power-driven fans, by connection of the network
to a stack which penetrates up through the roof.
The suction created by this stack is low (it results
from natural thermal effects in the stack and a re-
duced pressure at the roofline caused by wind move-
ment). The flow resistance through the aggregate,
however, sometimes may be sufficiently low so that,
with an extensive piping network, this low suction
might be adequate.
Applicability
Sub-slab ventilation, by itself, would be most
applicable in houses where 1) the concrete slab is
expected to contain the major soil gas entry routes
(e.g., cracks and other openings), and 2) a reason-
ably uniform layer of crushed aggregate is known to
underlie the entire slab or where soil permeabilities
are moderate to high. The slab might be expected to
contain the major radon entry routes in slab-on-
grade houses and often is in houses with poured
concrete basement walls. In concrete block base-
ment houses, the wall void network probably will al-
ways contain major radon entry routes. Based on
EPA's data, sub-slab ventilation by itself may not al-
ways do an adequate job in treating the wall-related
entry routes unless major wall openings are effec-
tively sealed, and unless there is good connection
between the sub-slab aggregate and the wall voids,
so that the sub-slab ventilation system can draw ad-
equate suction on the wall void network. In some
concrete block basement houses, effective applica-
tion of sub-slab suction may require that either a
number of individual suction points be installed, or
that an extensive network of perforated suction pipe
be laid under the existing slab to ensure good sub-
slab suction near the wall/floor joint. The use of
sub-slab ventilation in conjunction with wall ventila-
tion can effectively treat important slab-related entry
routes that may not be adequately addressed by wall
ventilation (e.g., slab cracks remote from the walls).
A reasonably good, uniform layer of aggregate (or a
permeable soil) is necessary to ensure that suction
from the sub-slab system extends effectively under-
neath the total slab. If the aggregate is thin or non-
existent under sections of the slab, then these sec-
32
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tions may not be adequately treated. .If uncertain
about the nature of the aggregate underneath a par-
ticular slab, a homeowner should be prepared to in-
stall a larger number of individual suction points in
the event that, for example, two points per slab
prove to be inadequate. An initial test of aggregate
permeability discussed in the Design and Installation
subsection may provide a preliminary check on the
condition of the aggregate. In some houses, a more
extensive (and more expensive) network of per-
forated pipe under the slab may ultimately have to
be considered to ensure that the ventilation is
adequately distributed.
The sub-slab variation involving a network of per-
forated pipe under the slab is most applicable in
new construction or in houses where the slab must
be torn out anyway to remove contaminated material
from under the house (or to replace a structurally
unacceptable slab). It can also be applicable in
houses that already have in place sub-slab drain pip-
ing connected to a sump. The extent of the existing
sub-slab network in these houses, however, is not
always known, and radon reductions achievable by
drawing suction on the sump may not be adequate.
Confidence
Variations of the sub-slab ventilation technique have
been tested by a number of organizations in the
United States, Canada, and Sweden. The perform-
ance achieved in these tests has varied, depending
on the form of the technique being tested, the de-
sign of the particular installation, and the type of
substructure a house has. With the individual-pipe
variation in houses with poured concrete basements,
investigators in all three countries have reported re-
ductions of 80 to 90 percent in the indoor radon con-
centrations (Er84, Na85, Sc86). In some cases, re-
ductions of 90 to 95 percent have been reported
(Br86a). These results cover 39 houses in Sweden,
several in the United States, and several in Canada.
EPA's testing of the individual-pipe variation in con-
crete block basement houses has shown reductions
between 58 and 86 percent during summer months,
based on hourly measurements of 24 to 48 hour du-
ration before and after the fan was turned on; how-
ever, performance deteriorated substantially during
cold weather (He86). Other investigators have re-
ported higher reductions with sub-slab suction in
concrete block basement houses, up to 96 to 99 per-
cent, with the use of higher-suction fans (Br86b).
The radon measurements in these houses, however,
were based on several grab samples, and it is not
known whether the reported high levels of reduction
were sustained through the winter months. None of
the individual-pipe sub-slab ventilation .tests to date
in block basement houses appear to have involved
extensive efforts to close major openings in the walls
in an effort to improve suction on the wall voids.
Such closure efforts may improve performance.
Testing of the sub-slab network variation in both
poured concrete basements and concrete block
basements in Canada and the United States has
yielded highly variable results (Ar82). The variations
are caused by differences in the extent and configu-
ration of the perforated piping network beneath the
slab; whether or not a fan was utilized to draw suc-
tion on the network (in some cases, the systems
were passive, and did not include a fan); and the
extent of other remedial steps taken in conjunction
with the sub-slab installation. Many of these network
installations were part of a remedial program in exist-
ing houses built over contaminated soil (e.g., ura-
nium mill tailings) or were incorporated into new
construction in these locations. A power-driven fan
often was not employed because the higher levels of
reduction provided by an active fan were not re-
quired to reduce the radon levels in the houses be-
low the target level. Thus, the optimum performance
available by retrofitting one of these systems into a
house having a very high natural radon level, has not
been demonstrated consistently. Reductions up to 95
percent and higher were realized in existing houses
where such networks have been installed even with-
out a power-driven fan, but it is not entirely clear
what fraction of the reduction can be attributed to
the sub-slab system and what fraction to other reme-
dial steps that were implemented simultaneously
(e.g., removal of contaminated material from under-
neath the slab).
The radon levels in one concrete block basement
house were reduced by greater than 99 percent on a
sustained basis by use of a passive sub-slab system
in combination with other mitigation steps (i.e., seal-
ing of block walls, replacing the slab, placement of
good aggregate, and placing a polymer liner under
the new slab) (Ta85). In another house with a piping
network (of unknown extent) already in place under-
neath the slab, suction on the sump into which the
pipe drained produced radon reductions in excess of
90 percent (Sa84).
The confidence level of the sub-slab ventilation sys-
tem is believed to be as follows:
• Individual-pipe variation in houses with poured
concrete basement walls and in slab-on-grade
houses—moderate. The major uncertainties are
the nature of the aggregate (and/or the permea-
bility of the soil) beneath the slab, and the ef-
fectiveness with which separate radon reduction
steps are implemented to address soil gas entry
routes associated with the concrete basement
walls (e.g., closing of cracks and holes).
• Individual-pipe .variation in concrete block base-
ment houses —low. This rating is based on
EPA's experience to date and the limited nature
of the data from other sources. This confidence
level might be increased through the use of
33
-------
1) higher-suction fans, 2) more effective wall
closure in conjunction with subTslab ventilation,
3) an increased number of sub-slab suction
points near the walls, or 4) the perforated
pipe network variation.
The perforated pipe network variation in poured
concrete basement and slab-on-grade houses-
moderate to high. The nature of the aggregate
under the slab becomes less of,an uncertainty,
and good distribution of suction underneath the
slab is more ensured.
The network variation in concrete block base-
ment houses—low to moderate. The potential
for effective treatment of the wall voids is im-
Figure 10. Sub-slab ventilation using individual suction point approach.
Close top voids
Close major mortar
cracks and holes in
wall
Note:
1. Closing of major slab openings
(e.g., major settling cracks, utility
penetrations, gaps at the wall/
floor joint) is important.
Restored concrete
House air through unclosed
settling cracks,cold joints,
utility openings1
Connection
to other
suction point
~C*v*::$£'&X:?'W
» 0 "-."'.'•:\:-''':V:-^VsoiigaV.::;v>V-;-v^r.Linerunder
On0 .; .-'•••' '.'•'•''•••' •'.: - •••• •'.'.'• '••.'•/'.:.'.'restored concrete
34
-------
proved by the network design. For an improved
confidence-level, major wall openings must be
closed, r..---'
Design and Installation (Individual-pipe
Variation)
The schematic diagram of a potential individual-pipe
sub-slab ventilation system, where the suction pipe
terminates just below the slab (Figure 10), shows,the
system as having--two-ventilation points in the slab
both connected to a single fan operated to draw
suction. Figure 10 represents a typical installation;
variations are possible.
In a variation, such as Figure 11, the suction pipe
has a horizontal run underneath the slab so that the
Figure 11. Sub-slab ventilation using individual suction point approach (option with horizontal run under slab).
Close top voids
Connection to other suction point
Note:
1. Closing of major slab openings
(e.g., major settling cracks, utility
penetrations, gaps at the wall/
floor joint) is important.
Close major mortar
cracks and holes in wall
House air through unclosed
settling cracks, cold joints,
utility openings1
Utility pipe
Boundary
restored
concrete1
•. /. : • ' ••• TTW^- •. r ..... /.. . .- .• ;. •-.;.••..
,.: .-';••' '.'•'•'•••'.•'-':•; Soil gas .•..'.'••'•'-.'-1-.' '• .'•"•••;'
35
-------
vertical riser can be at a remote location in the room,
out of the traffic pattern. The steps involved in the
design and installation of this type of sub-slab venti-
lation system are described below.
Closing Major Openings in Slab
The sub-slab suction system will not be able to
maintain adequate suction underneath the total slab
if there are major openings in the slab; e.g., holes,
large cold joints, openings around utility penetra-
tions, significant settling cracks, or large openings at
the wall/floor joint. House air drawn into these large
openings can prevent adequate suction at points be-
yond the opening. Soil gas also could enter the
house via these openings, depending on the pres-
sures in the house and the soil. Such major openings
should be sealed with mortar or, if sufficiently small,
asphaltic sealant, caulk, or other suitable material.
If the major opening is a French drain, it would be
advisable not to close this opening, but rather to uti-
lize a baseboard duct approach (similar to that de-
scribed in Section 2.8) to draw suction on this gap
(and potentially on the sub-slab). This approach is
discussed further later.
Other slab-related entry routes (specifically, sumps
and untrapped floor drains which connect to the soil)
also should be addressed, as discussed in earlier sec-
tions, as they can be major sources of soil gas enter-
ing the house. This soil gas can be generated by soil
outside the zone being treated by soil ventilation sys-
tems. Sumps and floor drains should be addressed
as part of any radon reduction strategy.
Closing Major Openings in Basement Walls
If sub-slab suction is being installed in a block wall
basement house, major openings in the block wall
should be closed. Not only would this aid the sub-
slab system in maintaining suction on the void
network, but also would increase the possibility that
the sub-slab systems can address the wall-related en-
try routes. Such wall openings can be a major route
for soil gas entry, and their closure should be part of
any radon reduction strategy in any event.
If the sub-slab suction system is being installed in a
house with poured concrete basement walls, any sig-
nificant openings in the concrete walls should be
sealed in order to reduce or eliminate wall-related
soil gas entry routes. Such openings may include
significant settling cracks and the seam where the
basement wall joins the slab of an adjoining slab-on-
grade.
Selection of Number and Location of Suction
Points in Slab
The number and location of suction points is de-
signed to ensure effective treatment of the total
slab. If a reasonably uniform crushed aggregate (or
reasonably permeable soil) underlies the slab, two
suction points should be sufficient for a typical slab.
A guideline used by one Swedish firm is to place
one suction point for every 300 to 500 ft2 of slab
floor area. EPA's test results have been mostly at the
upper end of the range. Houses where the nature of
the aggregate is unknown may require additional
suction points to control the entire area under the
slab.
The suction points generally should be placed at ap-
proximately equal distances from each other and
from the end walls. Ideally (in an effort to achieve
adequate suction on the walls and the wall/floor
joint) no point in the perimeter wall/floor joint
should be much more than about 15 ft from a suc-
tion point. Often the suction point will involve a
plastic pipe embedded straight down through the
slab, terminating just below the slab. With this de-
sign a vertical pipe will protrude up through the slab
at each suction point (Figure 10). In practice, the
suction points would likely be positioned so that the
vertical pipe is located in a central location yet out of
the traffic pattern in the room; e.g., near an existing
vertical load-bearing post. Another possibility (shown
in Figure 11) is to locate the vertical pipe penetration
into the slab at a point near a perimeter wall so that
it is out of the way and then to run the pipe horizon-
tally under the slab so that suction is drawn at a
more central location. The disadvantage of this ap-
proach is that it requires cutting a channel (up to 15
ft long) in the slab, thus increasing the installation
cost. A third possibility is to install four (or more)
suction points of the type shown in Figure 10. At
least one suction point should be near each of the
walls. This arrangement supports adequate suction
at each wall/floor joint while the risers are placed
away from the traffic flow. Generally, each of the
four suction points should be placed midway along
the wall with each far enough away from the wall so
as not to be over the footings.
If the house has a French drain, the logical approach
would be to use the existing French drain opening to
gain access to the sub-slab. In this situation a base-
board duct system (Figure 9) should achieve reason-
able suction on the sub-slab through communication
between the drain and the aggregate under the slab.
In houses with block basement walls, the baseboard
duct approach has the added advantage of facilitat-
ing simultaneous suction on the wall void network
(Section 2.8).
Testing Permeability of Sub-slab Aggregate
A preliminary check of the condition of the aggre-
gate beneath the slab is advisable before final system
design and installation is begun. One approach for
doing this is cutting or core drilling a hole (perhaps 4
in. in diameter) in the slab at one of the points
where a suction pipe is to be installed. This will re-
veal the aggregate at that point under the slab and
36
-------
give the first visual clue regarding its condition.
Ideally, the aggregate should be coarse crushed
stone or clean, washed gravel, preferably at least 2
in. deep. If the aggregate looks reasonably good at
that point, the condition of the surrounding aggre-
gate can be tested by mounting a temporary fan in-
side the house over the hole in the slab to draw suc-
tion. The fan can be mounted either on a length of
4-iri. pipe which would fit into the hole or on a sheet
of plywood that covers the hole and temporarily
sealed by caulking around the edges resting on the
slab.. With the fan in operation, smoke tracer tests
can be conducted at cracks and joints remote from
the fan to determine to what distance the suction is
extending under the slab. If smoke is drawn down
into the remote cracks with the fan operating, the
suction is extending to that point. As an alternative
test, small holes can be drilled in the slab" at several
remote points and smoke tracer testing conducted. If
the equipment is available, pressure probes can be
inserted into the small holes to measure sub-slab
pressures with the fan on and off. If results indicate
that the fan is clearly depressurizing the slab, there
is reason to believe that the aggregate is a reason-
able approach for radon control.
Installation of Suction Pipes into Slab
Holes must be made in the slab at the points where
the suction pipes are to be installed. This usually re-
quires the use of a jackhammer. Electrically driven
hammers can be rented by a homeowner, but these
are not always powerful enough to break through
the concrete. More powerful compressed-air ham-
mers, operated by experienced operators, may be
needed.
If the pipes are to be embedded straight down into
the aggregate (Figure 10) the hole will typically be
about 1.5 ft square at each suction point. Soil
should be dug out of the hole and the bedrock
should be hammered out (if necessary) to create an
excavation perhaps 1 to 2 ft deep and, if possible, its
horizontal dimension should be larger than the hole
through the slab. After being filled with crushed rock
up to the level of the underside of the slab, the ex-
cavation will serve as a collector for soil gas. The
vertical plastic suction pipe should be embedded in
this gravel base, extending at least 6 in. down into
the gravel. The open end of the pipe should be cov-
ered with a hardware cloth screen. To prevent plug-
ging the aggregate with cement or sealant when the
slab hole is repaired, some material (e.g., building
felt) should be placed over the top of the gravel be-
fore cementing the hole. All seams should be coated
liberally with an appropriate sealant (e.g., asphaltic
sealant), so that house air will not be drawn down
through cracks, decreasing the system's effective-
ness. Seams to be sealed include the circular seam
between the PVC pipe and the building felt and the
square seam between the felt and the side of the
hole in the concrete. Some investigators further pro-
pose that the surface of the broken concrete be
cleaned and coated with an epoxy adhesive. Before
the adhesive has dried, the hole is then filled with
concrete and leveled to match the existing floor.
Some investigators have reported success without
the large hole and the excavation described in the
previous paragraphs. In this simpler case, a hole is
drilled through the slab just large enough to accom-
modate a riser (typically 4 in. in diameter) that is em-
bedded and sealed directly in the smaller hole.
If the pipes are to have a horizontal run under the
slab (Figure 11), it will be necessary to cut a trench
through the slab to permit the horizontal section to
be laid. The initial cut in the concrete slab, outlining
the dimensions of the trench, can be made with a
concrete saw. The bulk of the concrete demolition
and removal will still be done by using a jackham-
mer. The exposed trench should be partially exca-
vated and filled to the underside of the slab with
gravel; the region around the end of the pipe should
be excavated to a greater depth as described previ-
ously for the vertical-pipe approach. The suction
pipe is buried in the gravel. In this design, the
gravel-filled trench serves as an enlarged soil gas col-
lector. The exposed area in the trench should be
covered (e.g., with building felt), sealed, and rece-
mented. .
Design of Piping Network
The verticalpiping coming up out of the slab must
be connected to one or more fans. This can be done
by various methods. The piping used in the EPA
sub-slab testing has been 4-in.-diameter plastic
sewer pipe. Other investigators have used pipe of
similar size. In view of the relatively low gas flows
achieved by using sub-slab suction, this diameter en-
sures a relatively low pressure drop through the pipe;
i.e.,- the suction capacity of a given fan will be util-
ized primarily in drawing suction on the sub-slab,
rather than moving gas through the pipe. Where gas
flows are sufficiently low, smaller pipe diameters can
be considered (e.g., 2 in.). Workers in Sweden have
used 2-in. pipes. The larger the pipe that can be tol-
erated aesthetically, however, the more effective a
given fan will be in ventilating the sub-slab.
Perhaps the most common piping design configura-
tion for sub-slab systems with two suction points in
basements is to extend the vertical pipes protruding
from the slab up to the level of the floor joists at the
basement ceiling, and then running the piping later-
ally between the joists from one of the points to a
location where it can be teed into the pipe from the
other suction point. The single horizontal pipe leav-
ing this T then penetrates the basement wall at some
convenient location to connect to a fan outdoors.
(As an alternative, the fan could be placed indoors
with the exhaust pipe penetrating the wall.) Thus/a
37
-------
single fan would draw suction on the two sub-slab
suction points. Each pipe also could penetrate the
wall separately and connect with a separate fan.
Workers in houses with poured concrete basements
report good results with just a single fan, even when
more than two suction points are connected to it.
However, in cases where the permeability under the
slab is not good (and in block wall houses, where
the sub-slab system is designed to treat the wall
voids as well) multiple fans may be required. In any
piping system an effort should be made to reduce
the number of bends in the piping. Each elbow cre-
ates a pressure drop and reduces the effectiveness
of the fan's suction.
In slab-on-grade houses with a finished ceiling rather
than exposed floor joists overhead, running the lat-
eral pipe across or above the ceiling could be desir-
able, but it could also be run at floor level. Another
option is to run the pipe up through the ceiling and
the attic, mounting the fan on the roof. In order to
reduce fan noise and back-wash it is advisable to
penetrate the exterior house wall and to place the
fan(s) away from windows and bedroom walls. Plac-
ing the fan exhaust above head level will prevent in-
advertent exposure of individuals to high radon lev-
els in the exhaust.
The sub-slab variation just discussed is the config-
uration most commonly tested; however, some limited
testing has also been conducted on the following
configurations: 1) one point operating to pressurize
the sub-slab by blowing air under the slab, with a
second point serving simply as a vent; and 2) all
points operating to pressurize beneath the slab. In-
sufficient data have been collected on the perform-
ance of these configurations to warrant comment.
One concern with pressurization is possible freezing
around the footings in cold climates. In addition, in
low permeability soils, pressurization could force soil
gas from the sub-slab into the house through un-
sealed cracks and openings in the slab.
Selection and Mounting of Fans
The fans used in the EPA testing of sub-slab suction
were single 250 cfm fans (maximum capacity) capa-
ble of drawing about 1/4-in. of water suction at low
flows. Other researchers have typically used smaller,
higher-suction fans ranging in maximum capacity
from 60 to 150 cfm and capable of suctions between
3/8-in. and 1.2 in. of water. In view of the relatively
low flows typical in sub-slab suction systems, a
lower-capacity fan capable of drawing greater suc-
tion appears to be a reasonable choice. The fan se-
lected should be as quiet as possible.
Figure 12. Sub-slab piping network suggested for new houses (Central Mortgage and Housing Corp. of Canada).
i— rerror.
A on 2 ft
Perforated pipe 4 in. dia.
centers
Fan
Exhaust-
€
Vent to roof ^
(optional) I
-Vertical vent
- PVC manifold
6 in. dia.
in
PVC vent stack
—.
Perforated pipes,
4 in. dia. capped
"at each end.
Aggregate
Top view — network laid under slab
38
Section A-A
-------
The considerations in mounting, the fan(s) on the
pipe(s) outside the house or in mounting the fan(s)
inside the house are the same as those discussed
previously in connection with wall ventilation (Sec-
tion 2.8).
Testing of Sub-slab Suction Effectiveness
After the fan has been turned on for the first time,
and periodically thereafter, the homeowner would be
well advised to test how well the fan is maintaining
suction underneath the slab. The testing method
was described in Section 2.8.
Design and Installation (Perforated Pipe
Network Variation)
The primary question in the design of this sub-slab
ventilation variation is the extent and configuration
of the perforated piping network to be installed un-
der the slab.
Closing Major Openings in Slab and Walls
Major openings in the slab and walls should be
closed as discussed in connection with the individ-
ual-pipe sub-slab suction approach.
Design of the Sub-slab Perforated Piping
Network
Several configurations have been considered for the
perforated piping network. One configuration speci-
fied in guidelines for new houses is illustrated in Fig-
ure 12_(Ch79). In .this configuration, a single 6-in.-
diameter PVC pipe is laid horizontally underneath the
slab in the middle of the house, from front to back.
This PVC pipe would serve as a manifold for 4-in.-
diameter perforated pipes, which would be laid at
right angles to the manifold pipe on 2-ft centers,
from one side of the house^to the other, and capped
at both ends. A vertical pipe, tapped into the mani-
fold pipe, comes up through the slab in the center of
the house. This design would ensure effective vent-
ing of the sub-slab, but could not be installed with-
out totally, removing the original slab. Thus, a
network this comprehensive should be considered
only for hew construction (or for existing houses
where the original slab must be torn out for removal
of contaminated material underneath).
Another possible configuration for a subfloor
network is illustrated in Figure 13 (PDER85, Ta83). In
this case, the 4-in. perforated pipe is laid underneath
Figure 13. Sub-slab piping network around perimeter of slab.
Perforated pipe
4 in. dia., beside footings •
Concrete footing •
I I
Riser-
«;• i
A
I
Fan
Vent to roof
(optional)
Exhaust •
Perforated pipe,
4 in. diameter around
perimeter of the slab
Liner under
restored concrete
Top view — network around perimeter of slab
Section A-A
39
-------
the slab around the entire interior perimeter of the
footing about 18 in. in from the wall. Other
configurations are also possible.
Because of the difficulties involved in installing a
system such as this in existing houses, only a partial
system (or maybe a couple of partial systems) could
realistically be considered for an existing house. For
example, one segment of perforated pipe can be
placed around one part of the perimeter, and a sec-
ond segment around another part, to keep interior
walls or other obstructions from preventing clear ac-
cess to the slab (Figure 13).
Installation of Perforated Pipe Under Slab
The channels in the slab where the pipe is to be laid
would initially be outlined with cuts about 2 in. deep
into the slab with a concrete saw. The remainder of
the concrete demolition would be completed with a
jackhammer. The exposed channel would be exca-
vated to a depth of about 1 to 2 ft and filled to the
underside of the slab with crushed aggregate. The 4-
in.-diameter perforated pipe would be laid in the
middle of this gravel bed, and each end would be
capped to ensure effective collection. Each segment
of perforated pipe must be connected to a vertical
plastic pipe through which the suction on the system
will be drawn. As described in the previous section
on the individual-pipe sub-slab suction approach, the
aggregate in the entire trench must be covered with
some suitable material (so that the new concrete
does not plug the aggregate). All seams between the
cover, the sides of the trench, and the vertical riser
should be coated with asphaltic sealant, and the
rough sides of the trench may require coating with
epoxy adhesive. Fresh cement is then poured to re-
store the slab.
Design of Piping Network
The PVC pipe risers coming up through the slab
from each of the perforated piping segments can be
connected in the manner described for the individ-
ual-pipe variation. The riser from one segment
should be extended by using additional PVC pipe up
to the overhead floor joists and then running the
pipe horizontally between the joists to the point
where it can be teed into the riser(s) from the other
segment(s). The resulting single pipe would pene-
trate the exterior wall at a convenient point, and a
fan would be mounted outside. Alternatively, the ris-
ers from each segment could penetrate the wall sep-
arately and be provided with separate fans, or the
fan(s) could be mounted inside the house with the
fan exhaust pipe penetrating the wall to the out-
doors.
PVC pipe (4-in. diameter) would be a reasonable se-
lection for this piping network, as long as a power-
driven fan is used to draw suction on the perforated
pipe. Smaller pipe can be used if a low pressure
drop can be maintained.
40
If the perforated piping network is extensive enough,
a passive system (with no power-driven fan) may
provide adequate radon reductions. In this case, the
PVC risers coming up through the slab would be
connected to 6-in.-diameter piping that would be
brought up vertically through the living area and the
attic of the house and terminated 1.5 to 4 ft above
the roof. The 6-in. pipe is needed to reduce the pres-
sure drop through the piping, as the suction drawn
by the natural stack effect in the pipe and by the
wind movement over the roof will be low. A power-
driven fan may be required in this stack if the pas-
sive ventilation proves insufficient. Maintenance of
the natural thermal stack effect may require insula-
tion of the riser through an unheated attic. Unless
the installed perforated piping network is substantial,
houses with high initial radon levels would best be
served by going directly to the power-driven fan.
Selection and Mounting of Fans
As discussed previously for the individual-pipe ap-
proach, one or more fans (possibly 60 to 100 cfm)
capable of reasonably high suction (0.3 to 1 in. of
water) with low noise would appear to be a reason-
able choice.
Operation and Maintenance
The operation and maintenance requirements for the
sub-slab system consist of regular inspections by the
homeowner to ensure that the fan is operating prop-
erly (e.g., is not iced up or broken); the seals where
the suction pipes penetrate the floor and the new
cement remain intact; and adequate suction is being
drawn on the sub-slab (determined by smoke test-
ing). If the fan is mounted inside the house, the ex-
haust system should be inspected for leaks.
Routine fan maintenance should be performed as
necessary. The fan should be replaced as needed. If
the new concrete develops cracks where it contacts
the pipe or the original slab, these cracks should be
sealed (e.g., with asphaltic sealant, caulk, or some
more extensive procedures). Any new cracks/open-
ings that appear in the slab or wall should be sealed.
If smoke testing indicates that the system is no
longer properly maintaining suction on some portion
of the slab, the fan and the piping leading to the fan
should be checked to ensure that the piping is not
blocked. If inadequate suction persists, consideration
should be given to adding a suction point to improve
the ventilation of that portion of the slab.
Estimate of Costs
If the individual suction point variation of sub-slab
suction is installed in a house where no special effort
is required to close major openings in the walls, a
homeowner might have to pay approximately $1000
to $2500 to have such a system installed by a con-
struction contractor based on EPA's experience. This
estimate assumes that the house presents no un-
-------
usual difficulties and that the job is completed without
the added expense of a "radon mitigation expert" to
oversee the contractor's work. The cost estimate in-
cludes both materials and labor. If significant labor
time must be spent in closing major wall openings
(so that the sub-slab system will adequately treat the
walls), costs would be significantly higher.
For the piping network approach, costs will increase
as a result of the labor required to make the chan-
nels in the slab. Costs would vary depending upon
the extent of the network installed. A rough estimate
for installation by a contractor is $2000 to $7500.
Installation of a sub-slab suction system is not an
easy "do-nt-yourself" job, but parts of the installation
may be completed by some homeowners. In that
case, the installation cost would be limited to the
cost of materials (about $100 to $500) and the cost
of hiring a jackhammer operator or renting an elec-
tric hammer.
Operating costs would include electricity to run the
fan(s) and possibly some heating penalty due to in-
creased ventilation of the house. Occasional replace-
ment of the fan would also be an operational/main-
tenance cost. The cost of electricity to run a single
0.03-hp (25-W) fan for a year would be about $15.
Assuming that the system increases house ventila-
tion by about 50 cfm, the cost of additional heating
would be approximately $125 per year (in houses
with basements, this estimate assumes that the
basement is heated to the same temperature as the
remainder of the house). Thus, the total operating
cost would be approximately $140 per year, which
increases somewhat with each additional fan. A new
fan would likely cost between' $40 and $100 when
replacement is needed.
41
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-------
Section 3
Available Technical Assistance
Government at all levels recognizes the need to pro-
vide points of contact within their organizations
where the concerned public can obtain the most re-
cent technical information with regard to indoor ra-
don. The following lists of State (Section 3.1) and
U.S. Environmental Protection Agency (Section 3.2)
offices were compiled to address this need.
3.1 State Radiological Health Program
Office Contacts (RAD85)
Homeowners and contractors should first contact
their State official, listed below, if they require as-
sistance in interpreting the material in this manual or
for further support in resolving indoor radon prob-
lems.
Alabama
Alaska
Arizona
Arkansas
California
Godwin, Aubrey V., Director
Division of Radiological Health
State Department of Public
Health
State Office Building
Montgomery, Alabama 36130
Business: 205/261-5315
Heidersdorf, Sidney D., Chief
Radiological Health Program
Department of Health & Social
Service
Pouch H-06F
Juneau, Alaska 99811-9976
Business: 907/465-3019
Tedford, Charles F., Director
Arizona Radiation Regulatory
Agency
925 South 52nd Street, Suite 2
Tempe, Arizona 85281
Business: 602/255-4845
Wilson, E. Frank, Director
Division of Radiation Control &
Emergency Management
Department of Health
4815 West Markham Street
Little Rock, Arkansas 72201
Business: 501/661-2301
Ward, Joseph O., Chief
Radiological Health Branch
Colorado
Connecticut
Delaware
District of
Columbia
Florida
State Department of Health
Services
714 P Street, Office Bldg. 8,
Sacramento, California 95814
Business: 916/322-2073
Hazle, A. J., Director
Radiation Control Division
Department of Health
4210 East 11th Avenue
Denver, Colorado 80220
Business: 303/320-8333, Ext.
6246
McCarthy, Kevin T.A., Director
Radiation Control Unit
Department of Environmental
Protection
State Office Building
165 Capital Avenue
Hartford, Connecticut 06106
Business: 203/566-5668
Tapert, Allan C., Program
Administrator
Office of Radiation Control
Division of Public Health
Department of Health & Social
Services
Cooper Building, Cooper Square
Post Office Box 637
Dover, Delaware 19901
Business: 302/736-4731
Bowie, Frances A., Administrator
Department of Consumer &
Regulatory Affairs
Service Facility Regulation
Administration
614 H Street, N.W., Room 1014
Washington, D. C. 20004
Business: 202/727-7190
Jerrett, Lyle E., Director
Office of Radiation Control
Department of Health &
Rehabilitative Services
1317 Winewood Boulevard
Tallahassee, Florida 32301
Business: 904/487-1004
43
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Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Maryland
Rutledge, Bobby G., Director Louisiana
Radiological Health Section
Department of Human Resources
878 Peachtree Street, Room 600
Atlanta, Georgia 30309
Business: 404/894-5795
Anamizu, Thomas, Chief
Noise and Radiation Branch
Environmental Protection and
Health Services Division
Department of Health Maine
591 Ala Moana Boulevard
Honolulu, Hawaii 96813
Business: 808/547-4383
Funderburg, Robert, Program
Manager
Radiation Control Section
Department of Health and
Welfare
Statehouse Mail
Boise, Idaho 83720
Business: 208/334-4107
Cooper, John, Manager
Office of Environmental Safety
Department of Nuclear Safety
1035 Outer Park Drive
Springfield, Illinois 62704
Business: 217/546-8100
800/672-3380 (Toll Free In State)
Stocks, Hal S., Chief
Radiological Health Section
State Board of Health
1330 West Michigan Street
Post Office Box 1964
Indianapolis, Indiana 46206
Business: 317/633-0152 Michigan
Eure, John A., Director
Environmental Health Section
Iowa Department of Health
Lucas State Office Building
Des Moines, Iowa 50319
Business: 515/281-4928
Romano, David J., Manager
Bureau of Air Quality and
Radiation Control
Department of Health and
Environment
Forbes Field, Building 740
Topeka, Kansas 66620
Business: 913/862-9360
Hughes, Donald R., Manager
Radiation Control Branch
Cabinet for Human Resources Mississippi
275 East Main Street
Frankfort, Kentucky 40621
Business: 502/564-3700
Massachusetts
Minnesota
Spell, William H., Administrator
Nuclear Energy Division
Office of Air Quality and
Nuclear Energy
Department of Environmental
Quality
Post Office Box 14690
Baton Rouge, Louisiana
70898-4690
Business: 504/925-4518
Hinckley, Wallace, Assistant
Director
Division of Health Engineering
157 Capitol Street
Augusta, Maine 04333
Mailing Address: State House,
Station 10
Augusta, Maine 04333
Business: 207/289-3826
Resh, David L., Administrator
Community Health Management
Program
Department of Health and
Mental Hygiene
O'Conor Office Building
201 West Preston Street
Baltimore, Maryland 21201
Business: 301/225-6031
Hallisey, Robert M., Director
Radiation Control Program
Department of Public Health
150 Tremont Street, 7th Floor,
Boston, Massachusetts 02111
Business: 617/727-6214
Bruchmann, George W., Chief
Division of Radiological Health
Bureau of Environmental and
Occupational Health
Department of Public Health
3500 North Logan Street
Post Office Box 30035
Lansing, Michigan 48909
Business: 517/373-1578
Hennigan, Alice T. Dolezal, Chief
Section of Radiation Control
Environmental Health Division
Minnesota Department of Health
717 Delaware Street, S.E.
Post Office Box 9441
Minneapolis, Minnesota 55440
Business: 612/623-5323
Fuente, Eddie S., Director
Division of. Radiological Health
State Department of Health
3150 Lawson Street
44
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Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
North
Carolina
North Dakota
Ohio
Post Office Box 1700 New York ,
Jackson, Mississippi 39215-1700
Business: 601/354-6657
Miller, Kenneth V., Chief
Bureau of Radiological Health •
1730 East Elm Plaza ,
Post Office Box 570
Jefferson City, Missouri 65102
Business: 314/751-8208
Lloyd, Larry L., Chief
Occupational Health Bureau
Department of Health and
Environmental Sciences
Cogswell Building
Helena, Montana 59620
Business: 406/444-3671
Borchert, Harold R., Director
Division of Radiological Health
Department of Health
301 Centennial Mall, S.
Post Office Box 95007
Lincoln, Nebraska 68509
Business: 402/471-2168
Vaden, John D., Supervisor
Radiological Health Section,
Health Division
Department of Human Resources
505 East King Street
Carson City, Nevada 89710
Business: 702/885-5394
800/992-0900 (Toll Free In State)
Tefft, Diane E., Program
Manager
Radiological Health Program Oklahoma
Post Office Box 148
Concord, New Hampshire 03301
Business: 603/271-4588
Nicholls, Gerald P., Acting Chief
Bureau of Radiation Protection
Division of Environmental Quality
Department of Environmental Oregon
Protection
380 Scotch Road
Trenton, New Jersey 08628
Business: 609/530-4000
800/648-0394 (Toll Free In State)
Brown, Michael F., Acting Chief
Radiation Protection Bureau
Environmental Improvement
Division
Department of Health and
Environment , Pennsylvania
Post Office Box 968
Santa Fe,* New Mexico
87504-0968
Business: 505/827-2948
Rimawi, Karim, Director
Bureau of Environmental
"Radiation Protection
State Health Department
Empire State Plaza, Corning
Tower
Albany, New York 12237
Business: 518/473-3613
Brown, Dayne H., Chief
Radiation Protection Section
Division of Facility Services
Department of Human Resources
Post Office Box 12200
Raleigh, North Carolina
27605-2200
Business: 919/733-4283
Mount, Dana K., Director
Division of Environmental
Engineering
Department of Health
Missouri Off ice-Building
1200 Missouri Avenue
Bismarck, North Dakota 58501
Business: 701/224-2348
Quillin, Robert M., C.H.P.,
Director
Radiological Health Program
Department of Health
246 North High Street
Post Office Box 118
Columbus, Ohio 43216
Business:. 614/466-1380
800/523-4439 (Toll Free In State)
McHard, J. Dale, Chief
Radiation & Special Hazards
Service
State Department of Health
Post Office Box 53551
Oklahoma City, Oklahoma 73152
Business: 405/271-5221
Paris, Ray D., Manager
Radiation Control Section
State Health Division
Department of Human Resources
1400 Southwest Fifth Avenue
Portland, Oregon 97201
Mailing Address:
State Health Division
Post Office Box 231
Portland, Oregon 97207
Business: 503/229-5797
Gerusky, Thomas M., Director
Bureau of Radiation Protection
Department of Environmental
Resources
Fulton Building, 16th Floor
45
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Puerto Rico
Rhode Island
South
Carolina
South Dakota
Tennessee
Texas
Utah
Third and Locust Street Vermont
Harrisburg, Pennsylvania 17120
Mailing Address:
Post Office Box 2063
Harrisburg, Pennsylvania 17120
Business: 717/787-2480
800/237-2366 (Toll Free In State)
Saldana, David, Director
Radiological Health Division
G.P.O. Call Box 70184
Rio Piedras, Puerto Rico 00936
Business: 809/767-3563
Hickey, James E., Chief
Division of Occupational Health
and Radiation Control
Department of Health
Cannon Building, Davis Street
Providence, Rhode Island 02908
Business: 401/277-2438
Shealy, Heyward G., Chief
Bureau of Radiological Health
South Carolina Department of
Health and Environmental
Control
2600 Bull Street
Columbia, South Carolina 29201
Business: 803/758-8354
Virginia
Washington
West Virginia
Glawe, Joyce E.
Radiation Safety Specialist
Licensure and Certification
Program
State Department of Health Wisconsin
Joe Foss Office Building
523 East Capital
Pierre, South Dakota 57501
Business: 605/773-3364
Mobley, Michael H., Director
Division of Radiological Health
TERRA Building
150 9th Avenue, N. Wyoming
Nashville, Tennessee 37203
Business: 615/741-7812
Lacker, David K., Chief
Bureau of Radiation Control
Department of Health
1100 West 49th Street
Austin, Texas 78756-3189
Business: 512/835-7000
Anderson, Larry, Director
Bureau of Radiation Control
State Department of Health
State Office Building, Box 45500
Salt Lake City, Utah 84145
Business: 801/538-6734
McCandless, Raymond N.,
Director
Division of Occupational and
Radiological Health
Department of Health
Administration Building
10 Baldwin Street
Montpelier, Vermont 05602
Business: 802/828-2886
Price, Charles R., Director
Bureau of Radiological Health
Division of Health Hazard
Control
Department of Health
109 Governor Street
Richmond, Virginia 23219
Business: 804/786-5932
Strong, T. R., Chief
Office of Radiation Protection
Department of Social & Health
Services
Mail Stop LE-13
Olympia, Washington 98504
Business: 206/753-3468
Aaroe, William H., Director
Industrial Hygiene Division
151 11th Avenue
South Charleston, West Virginia
25303
Business: 304/348-3526
McDonnell, Lawrence J., Chief
Radiation Protection Section
Division of Health
Department of Health & Social
Services
Post Office Box 309
Madison, Wisconsin 53701
Business: 608/273-5181
Haes, Julius E., Jr., Chief
Radiological Health Services
Division of Health & Medical
Services
Hathaway Building
Cheyenne, Wyoming 82002-0710
Business: 307/777-7956
46
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3.2 U.S. Environmental Protection
Agency Program Responsibilities
Guimond, Richard J., Director
Criteria and Standards Division
Office of Radiation Programs (ANR-460)
Environmental Protection Agency
401 M Street, S.W. ,
Washington, D. C. 20460
FTS: 557-9710
Commercial: 703/557-9710
Bliss, Wayne A., Director
ORP Las Vegas Facility
Environmental Protection Agency
Post Off ice Box 18416
Las Vegas, Nevada 89114
FTS: 545-2476
Commercial: 702/798-2476
Porter, Charles R., Director
Eastern Environmental Radiation Facility
Environmental Protection Agency
1890 Federal Way
Montgomery, Alabama 36109
FTS: 534-7615
Commercial: 205/272-3402
Craig, A. B., Deputy Director
Air & Energy Engineering Research
Laboratory (MD-60)
Environmental Protection Agency
Research Triangle Park, North Carolina 27711
FTS: 629-2821
Commercial: 919/541-2821
Cotruvo, Joseph A., Director
Criteria and Standards Division
Office of Drinking Water (WH5500)
Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
FTS: 382-7575
Commercial: 202/382-7575
Keene, Bryon E., Chief
Radiation and Noise Branch
Environmental Protection Agency, Region 1
John F. Kennedy Federal Building
Boston, Massachusetts 02203
FTS: 223-4845
Commercial: 617/223-4845
Giardina, Paul A.
Environmental Protection Agency
Region 2 (2AIR:RAD)
26 Federal Plaza
New York, New York 10278
FTS: 264-4418
Commercial: 212/264-4418
Health effects, measurement protocols, contractor proficiency pro-
gram action level guidance, quality assurance
Sampling and analysis field evaluation
Sampling and analysis field evaluation
Radon mitigation research program (new and existing houses)
Radon and radiation in drinking water
EPA Regional Representative for Connecticut, Maine, Massachu-
setts, New Hampshire, Rhode Island, and Vermont
EPA Regional Representative for New Jersey, New York, Puerto
Rico, and the Virgin Islands
47
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Belanger, William
Environmental Protection Agency
Region 3 (3AH14)
6th and Walnut Streets
Philadelphia, Pennsylvania 19106
FTS: 597-9800
Commercial: 215/597-9800
Payne H. Richard
Environmental Assessment Branch
Environmental Protection Agency, Region 4
345 Courtland Street, N.E.
Atlanta, Georgia 30365
FTS: 257-3776
Commercial: 404/347-3776
Tedeschi, Pete
Environmental Protection Agency
Region 5 (5AHWM)
230 South Dearborn Street
Chicago, Illinois 60604
FTS: 353-2654
Commercial: 312/353-2654
May, Henry D.
Environmental Protection Agency
Region 6 (6T-AS)
1200 Elm Street, Suite 2800
Dallas, Texas 75270
FTS: 729-5319
Commercial: 214/767-5319
Brinck, William L.
Environmental Protection Agency, Region 7
726 Minnesota Avenue
Kansas City, Missouri 66101
FTS: 757-2893
Commercial: 913/236-2893
Lammering, Milt
Environmental Protection Agency
Region 8 (8AH-NR)
1860 Lincoln Street
Denver, Colorado 80295
FTS: 564-1710
Commercial: 303/293-1700
Duncan, David L.
Environmental Protection Agency
Region 9 (A-3)
215 Fremont Street
San Francisco, California 94105
FTS: 454-8378
Commercial: 415/974-8378
Cowan, J. Edward
Environmental Protection Agency
Region 10 (Mail Stop 532)
1200 Sixth Avenue
Seattle, Washington 98101
FTS: 399-7660
Commercial: 206/442-7660
EPA Regional Representative for Delaware, District of Columbia,
Maryland, Pennsylvania, Virginia, and West Virginia
EPA Regional Representative for Alabama, Florida, Georgia, Ken-
tucky, Mississippi, North Carolina, South Carolina, and Tennessee
EPA Regional Representative for Illinois, Indiana, Michigan, Minne-
sota, Ohio, and Wisconsin
EPA Regional Representative for Arkansas, Louisiana, New Mexico,
Oklahoma, and Texas
EPA Regional Representative for Iowa, Kansas, Missouri, and Ne-
braska
EPA Regional Representative for Colorado, Montana, North Da-
kota, South Dakota, Utah, and Wyoming
EPA Regional Representative for American Samoa,
Arizona, California, Guam, Hawaii, and Nevada.
EPA Regional Representative for Alaska, Idaho, Oregon, and Wash-
ington
48
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Section 4
References
Ar82 — Arix Corporation, Planning and Design for a
Radiation Reduction Demonstration Project,
Butte, MT, Report to the Montana Department of
Health and Environmental Sciences, Appendix C,
January 1982.
ASHRAE81 — American Society of Heating, Refrig-
erating, and Air-Conditioning Engineers, Inc.,
Ventilation for Acceptable Indoor Air Quality,
ASHRAE Standard 62-1981, Atlanta, GA, 1981.
ASHRAE85 — American Society of Heating, Refrig--
erating, and Air-Conditioning Engineers, Inc.,
ASHRAE Handbook 1985 Fundamentals, Atlanta,
GA, 1985.
Be84 — Becker A. P. and Lachajczk. T. M., Evalua-
tion of Waterborne Radon Impact on Indoor Air
Quality and Assessment of Control Options, Office
of Research and Development, U.S. Environmen-
tal Protection Agency, EPA-600/7-84-093 (NTIS
PB84-246404), Research Triangle Park, NC, Sep-
tember 1984.
Br83 — Bruno R. C., Sources of Indoor Radon in
Houses: A Review, JAPCA 33(2): 105-109, 1983.
Br86a — Brennan T., U.S. Department of Energy,
Washington, D.C. Personal Communication re-
garding DOE/CE/15095, 1986.
Br86b — Brodhead W., Buffalo Homes, Riegelsville,
PA, Sub-slab Ventilation Results, February 1986.
Ch79 — Chakravatti J. L., Control of Radon-222/
WL in New Construction at Elliot Lake, Presented
at Workshop on Radon and Radon Daughters in
Urban Communities Associated with Uranium
Mining and Processing, Bancroft, Ontario, March
12-14, 1979.
CR86 — Consumer Reports, 1986 Buying Guide Is-
sue, Mount Vernon, NY, December 1985.
DOC82 — U.S. Department of Commerce, Statisti-
cal Abstract of the United States 1982-83, Bureau
of the/Census, Washington, D.C., 1982.
DOE86 — U.S. Department of Energy, Introducing
Supplemental Combustion Air to Gas-Fired House
Appliances. (DOE/CE/15095) Washington, D.C.,
December 1983.
Er84 — Ericson S. O., Schmied H., and Clavensjo
B., Modified Technology in New Construction,
and Cost Effective Remedial Action in Existing
Structures, to Prevent Infiltration of Soil Gas Car-
rying Radon, in Proceedings of the 3rd Interna-
tional Conference on Indoor Air Quality and Cli-
mate, Stockholm, Sweden, Vol. 5, pp 153-158,
August 20-24, 1984.
Go83 — Goldsmith W. A., Poston J. W.y Perdue P.
T., and Gibson M. O., Radon-222 and Progeny
Measurements in "Typical" East Tennessee Resi-
dences, Health Physics 45(1)81-88, 1983.
He86 - Henschel D. B. and Scott A. G. The EPA
.Program to Demonstrate Mitigation Measures for
Indoor Radon: Initial Results, Presented at APCA
International Specialty Conference on Indoor Ra-
don, Philadelphia, PA, February 25-26, 1986.
Ho85 - Holub R. F., Droullard R. F,, Borak T. B.,
Inkret W. C., Morse J. ,G., and Baxter J. F., Ra-
don-222 and 222 Rn Progeny Concentration Mea-
sured in an Energy-Efficient House Equipped with
a Heat Exchanger, Health Physics 49(2) 267-277,
1985.
Na81 - Nazaroff W. W., Boegel M. L., Hollowell C.
D., and Roseme G. D., The Use of Mechanical
Ventilation with Heat Recovery for Controlling Ra-
don and Radon Daughter Concentration in
Houses, Atmospheric Environment, 15:263-270,
1981.
Na85 - Nazaroff W. W., Feustal H., Nero A. V.,
Revzan K. L., and Grimsrud D. T., Radon Trans-
port into a Detached One-Story House with a
Basement. Atmospheric Environment, 19(1) 31-46,
1985.
1MAS81 — National Academy of Sciences, Indoor
Pollutants, National Academy Press, Washington,
D.C.,. 1981.
Ne85 — Nero A. V., What We Know About Indoor
Radon, Testimony Presented at Hearings on Ra-
don Contamination: Risk Assessment and Mitiga-
tion Research, before Subcommittee on Natural
Resources, Agriculture and Environment, Commit-
tee on Science and Technology, U.S. House of
Representatives, October 10, 1985.
49
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NYSERDA85 — New York State Energy Research
and Development Authority, Indoor Air Quality,
Infiltration and Ventilation in Residential Buildings,
NYSERDA Report 85-10, New York, NY, March
1985.
ORD86 — Office of Research and Development,
U.S. Environmental Protection Agency, Radon
Reduction Methods: A Homeowner's Guide.
(OPA-86-005) Washington, D.C., July 1986.
ORP86a — Office of Radiation Programs, U.S. Envi-
ronmental Protection Agency, A Citizen's Guide
to Radon. Washington, D.C., July 1986.
ORP86b — Office of Radiation Programs, U.S. Envi-
ronmental Protection Agency, Interim Indoor Ra-
don and Radon Decay Product Measurement Pro-
tocols, EPA-52071-86-04, Washington, D.C., April
1986.
PDER85 — Pennsylvania Department of Environ-
mental Resources, General Remedial Action De-
tails for Radon Gas Mitigation, May 1985.
RAD85 — Conference of Radiation Control Program
Directors, Inc., Directory of Personnel Responsi-
ble for Radiological Health Programs, Conference
Publication 85-1, Frankfort, KY, January 1985.
Sa84 — Sachs H. M. and Hernandez T. L, Residen-
tial Radon Control by Subslab Ventilation, Pre-
sented at 77th Annual Meeting of the Air Pollution
Control Association, San Francisco, CA, June 24-
29, 1984.
Sc83 — Scott A. G. and Findlay W. 0., Demonstra-
tion of Remedial Techniques Against Radon in
Houses on Florida Phosphate Lands, Office of Ra-
diation Programs, U.S. Environmental Protection
Agency, EPA-52075-83-009 (NTIS PB84-156157),
Washington, D.C., 1983.
Sc85a — Scott A. G., American ATCON, Wilming-
ton, DE, Personal Communication, 1985.
Sc85b — Scott A. G., A Review of Potential Low-
Cost Mitigation Measures for Soil Generated Ra-
don, Report No. 1401/1334, American ATCON,
April 22, 1985.
Sc86 — Scott A. G., American ATCON, Wilming-
ton, DE, Personal Communication, February 26,
1986.
Ta83 — Tappan J. T., Mitigation Methods for Natu-
ral Radioactivity Associated with Energy Efficient
Structures, Presented at National Conference on
Environmental Engineering, Boulder, CO, July
1983.
Ta85 — Tappan J. T., Radon Mitigation Remedial
Action Demonstration at the Watras Residence,
Report to Philadelphia Electric Co. by Arix Corp.,
June 1985.
We86a — Wellford B. W., Mitigation of Indoor Ra-
don Using Balanced Heat Recovery Ventilation
Systems, Presented at APCA International Spe-
cialty Conference on Radon, Philadelphia, PA,
February 25-26, 1986.
We86b — Wellford B. W., Airxchange, Inc.,
Hingham, MA, Personal Communication, March
3, 1986.
50
U.S. GOVERNMENT PRINTING OFFICE: 1986- 6 "* 6- 1 1 6/ 40650
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