United States
Environmental Protection
Agency
Office of
Research and
Development
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
EPA/600/9-90/048 Dec. 1990 .
&EPA
Radon Mitigation Update
Introduction
This update summarizes the Air and Energy
Engineering Research Laboratory's
(AEERL's)radonmitigationresearchprogram
objectives and updates recent Radon Miti-
gation Branch (RMB) activities. A listing of
recent AEERL publications and EPA docu-
ments relating to radon mitigation is included
as a reference for obtaining additional infor-
mation.
The technical portions of this update are
intended to provide timely and useful in-
formation to the radon mitigation industry. It
should benoted that this information may be
based on regional and/or preliminary findings
and should be viewed as such. As research
programs progress, AEERL will publish de-
tails of its findings as technical reports.
For additional information on specific re-
search activities or programs, you may con-
tact the specific RMB project officer either by
phone (see below) or mail at MD-54, U.S.
EPA, Research Triangle Park, NC 27711.
Mike Osborne, Branch Chief
(919) 541-4113
- EPA radon mitigation
research and development program
Kelly Leovic
(919)541-7717
• radon mitigation in schools
A.B. "Chick" Craig
(919)541-2824
• Senior Physical Scientist •
Radon
Tim Dyess
(919)541-2802
- radon resistant new
construction
. Bruce Harris
(919) 541-7807
- radon diagnostics and
; measurement technology
• John Ruppersberger
(919)541-2432
- radon barriers and
block permeability
Bruce Herischel
(919)541-4112
- radon mitigation in existing houses
Ron Mosley
(919)541-7865
- radon data analysis
David Sanchez
(919)541-2979
• mechanisms of radon entry
AEERL Radon Mitigation Research Objectives for 1990 and Beyond
In late 1988, Congress enacted the Indoor
Radon Abatement Act (IR AA). The Act sets a
long-term goal of reducing indoor radon levels
to the point that air within buildings is as free
of radon as is the ambient air outdoors (about
0.2-0.7 pCi/L). AEERL will focus its research
programs toward developing and demonstrat-
ing technologies necessary to reduce indoor
radon levels toward this goal.
Existing House programs will research the
application of subslab depressurization and
other radon reduction approaches in different
house types, soils, and geographic regions;
evaluate the durability and long-term perfor-
mance of radon reduction techniques and ma-
terials; and study the effects of natural venti-
lation, air cleaners, and block wall coatings.
Radon Resistant New Construction House
programs will focus on determining the most
effective radon resistant construction tech-
niques. Radon resistant features in previously
constructed houses will be removed or deac-
tivated to determine their impact on indoor
radon levels. Soil and house characteristics for
slab-on-grade, basement, and crawl space
houses constructed on both sandy and expan-
sive clay soils will be studied to determine
interactions. Research will continue on the
radon resistant properties of concrete blocks
and block wall coatings.
School programs will include demonstrating
the regional application of subslab depressur-
ization systems, initiating an effort to investi-
gate reduction strategies for difficult to miti-
gate schools, and quantifying school charac-
teristics throughout the country in order to
better focus school research projects.
AEERL Research Programs
Schools
AL MD NC NY TN VA
New Construction Houses
CO FL MD NJ NY VA
Existing Houses
AL CO FL MD NJ NM NY OH PA TN
AEERL has conducted radon mitigation research and demonstration programs in each of the states
identified. Locations were chosen to represent diverse geological conditions and building construction
practices.
i
Printed on Recycled Paper
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Recent Research Findings
Existing Houses
Slab-On-Grade and Basement Houses
Subslab Dcpressurization (SSD) has been shown to be the most
effective mitigation strategy for slab-on-grade'(SOG)-and basement,
houses. SSD works best when there is clean coarse aggregate under-
neath the slab which facilitates air movement (communication)
throughout the subslab area. When good communication exists, SSD
with only one or two suction pipes has been shown to provide
substantial radon reduction even when there are forced air heating or
cooling supply ducts under the slab. Large slabs (greater than 1000 sq
ft) are more likely to require two suction points.
Excavating pits 1 to 2 ft in diameter underneath the slab/suction pipe
interfacehas proven effective in increasing the area of subslab depres-
surization.
Research has also shown that suction pipes inserted through the
foundation from outdoors are often as effective as interior suction
pipes, that houses with poured concrete stem walls generally per-
formed better than those with block stem walls, and that suction fans
could generally be slowed to 15-40% of full capacity and still provide
«dequatereductions(althoughfansgenerallyprovidebetterreductions
when operated at full capacity).
Crawl Space Houses
Sub-Membrane Depressurization (SMD)—where suction is applied
to the soil underneath a plastic liner—has demonstrated significantly
better radon reductions than any crawl space ventilation technique.
By depressurizing the soil underneath a membrane, SMD (like SSD)
causes a reversal of pressure differentials and typical air movement
patterns. Radon-laden soil gases, along with small quantities of crawl-
space air, are drawn from beneath the membrane and vented outdoors.
Research in four crawl space houses in Ohio has shown that 90%+
reductions can sometimes be achieved when perforated drain tile is
used in conjunction with 8-10 ft membranes extending from all sides
of a crawl space, even when the center of the crawl space is left
Uncovered. This indicates that it may not always be necessary to cover
entire areas when using SMD mitigation strategies.
An alternative to SMD is ventilation of the entire crawl space. SMD is
commonlymoreeffective,asshowninthetablebelow,butcrawlspace
ventilation may be sufficient in some cases. Forced exhaust (blowing
crawl space air out with a fan) consistently provides better reductions
than natural and forced supply ventilation. Even though forced exhaust
may increase crawl space radon levels by drawing more radon from the
soil, it inhibits crawl space air from entering the living spaces by
dcpressurizing the crawl space. Forced exhaust is less likely to contrib-
ute to cold floors and increased indoor humidity than forced supply or
natural ventilation.
New Construction
It is generally less expensive to build radon resistant features into new
houses than it is to mitigate existing houses. The average cost of
building passiveradonresistantfeatures into anew house is about$300
to $400, but this will vary depending on local building practices and
availability of materials. To activate the SSD system with an electric
fan may cost an additional $220 to $300.
Research in Maryland and Virginia has shown that SSD with passive
stacks can sometimes provide considerableradonreductionif properly
installed under the folio wing conditions: the stack is routed through the
warm part of the house up to the roof line; there is ait least 4 in. of clean
coarse aggregate'under the slab; care is taken to seal openings in the
house shell; and activities which depressurize the building are avoided
(e.g., use of air-consuming appliances). It should be noted, however,
that all 16 SSD systems studied provided better and more reliable
reductions when activated by a fan.
Schools
Important factors contributing to elevated radon levels in schools and
influencing the mitigation approach are the design, installation, and
operation of the heating, ventilating, and air conditioning (HVAC)
system. The complexity of these systems and their potential to depres-
surize buildings present problems not encountered in house mitigation
research.
Experience to date indicates that SSD in schools typically requires
greater fan capacities (typically 300 cfm) and suction pipe diameters
(4-6 in.) than does mitigation in. houses, but can usually overcome
negative pressures induced by HVAC operations if there is a layer of
clean coarse aggregate under the slab and no subslab return air ducts.
In fact, SSD has been applied successfully in a school with only one
suction point depressurizing an area of 15,000 sq ft However, if
interior walls extend through the aggregate creating subslab barriers or
compartments, a suction point will likely be heeded for each subslab
area surrounded by walls that penetrate the slab.
Pressurization through continuous or modified operation of HVAC
systems may also provide effective radon reductions in some schools.
The use of these techniques in a particular school will depend on
HVAC system design, capacity, and potential for modified operation.
Long-term feasibility will depend on proper operation and mainte-
nanceof the system throughout the lifeof the building, and the school's
ability to afford the additional operational cost.
As with houses, radon resistant features can be cost effectively built
into new schools. When 4-6 in. of clean coarse aggregate is placed
under slabs and subslab barriers are limited, one SSD suction point
should be roughed in for each major area defined by footings and block
walls dividing the aggregate. Roughing in roof vents during construc-
tion will facilitate post-construction mitigation by avoiding additional
roof penetrations.
Radon Reentrainment Into Buildings
Exhaust of high levels of radon-laden soil gas from soil depressuriza-
tion systems near the walls or below the eave lines of buildings may
increase indoor radon levels. Research has shown the potential for
radon exhaust to reenter (reentrain into) buildings around the band joist
and through other air infiltration points in walls. The potential for
reentrainment is increased when down-turn (dryer) vents which push
exhausting soil gas toward or parallel to the building are used.
EPA recommends above-eave exhaust to minimize reentrainment.
However, studies suggest that exhausting below the eave line may not
be a problem when low radon-containing soil gases (less than 1,000
pCi/L) are vented through the band joist or wall, but directly away from
the building. The potential for exhausting other soil gas contaminants
or pesticides/termiticides should also be considered when selecting
exhaust locations. Further research is underway.
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Block Wall Coatings
Laboratory testing indicates that light weight concrete blocks gener-
ally allow greater air flow than heavy weight blocks. However, air
permeability consistently varies directly with the surface roughness of
the block. Both light and heavy weight blocks allow substantial soil
gas infiltration if notproperly coated and capped with solid materials.
Tests of six paints and coatings demonstrated that all were effective in
reducing air movement through block walls. Brushed-on cementitious
coatings gave the best reduction per unit cost with single coat applica-
tions reducing air flows by up to 99.7%. A two-part water-based epoxy
was the best performing paint with reductions of 96.2% after a single
coat and 99.9% after a second coat. This indicates that a second coat
may not be required in low radon buildings.
Important considerations for selecting and applying coatings include
existing water problems, mildew, hairline cracks, and other factors
which may affect the life and performance of the coating.
Mitigation Durability and Long Term Performance
AEERL has evaluated the long-term perfor-
mance of 34 SSD systems installed 2-4 years
ago as partof its Pennsylvaniademonstration
project. Most but not all of the 34 fans were
Kanalflakt models. Five of the fans have lost
suction due to capacitor failure in the fan
motor. All five were Kanalflakt fans (four T-
2 models and one T-l model).
If the fan is operating when the capacitor fails,
it may continue to operate for up to 1 year, but
at greatly reduced suction and flow capacities
(see graph).
System Performance Cannot Be Judged By
Fan Noise Alone. These findings underscore
the need for an air flow or pressure sensitive
alarm to alert building owners to system fail-
ures. A simple test for capacitor failure is to
turn the system off, allow the fan to stop, and
then turn it back on. Systems with failed
capacitors will not restart.
Effect of capacitor failure on Kanalflakt fans.
I
600
500
400
8 300
a.
200
roo
With New Capacitor
20 30 40 50 60
Fan Flow (Usec)
I
70
80
90
100
State Code Development
AEERL is serving as technical managers of
the state of Florida's research activities fo-
cused on understanding radon generation and
movement in soils, entry into buildings, and
distribution throughout buildings. Results of
this research will be used in the development
of Florida's radon codes and standards which
are slated for release in February 1992.
Output from this cooperative research will
assist both Florida and AEERL in developing
recommendations and specifications for fill
materials, SSD systems, improved slab/floor
radon barriers, slab/superstructure tightness,
and mechanical air moving systems.
Research Notes
B asement pressurization has worked success-
fully in some houses in Tennessee but has not
been applicable in others. The ability to seal
the basement from the first floor appears to be
the limiting factor. Pressurization is extremely
difficult if the house has forced air heating or
air conditioning.
Preliminary studies of natural ventilation in
one New Jersey house indicate that opening
basementwindowscanreducetheradonlevels
by a factor of 8 while increasing the air ex-
change rate by only a factor of 2.
Radon measurements in two areas of Ala-
bama resulted in summer radon levels which
were consistently higher than winter radon
levels.
Sealing of radon entry routes enhanced the
effectiveness of subslab suction depressuriza-
tion techniques. However, when sealing was
used alone, it often failed to reduce radon
levels below 4 pCi/L, with typical reductions
ranging from 50 to 70%.
In slab-on-grade houses in Florida, it was
difficult to create suction under the entire slab
area using only one suction hole because
tightly packed soil (and lack of aggregate)
inhibited the flow of ah- under the slab. The
most effective means of increasing system
performance in these geological conditions
was the installation of additional suction holes
where the air flow was inhibited.
Research in existing Maryland houses shows
that passive subslab systems (i.e., systems
without fans) were generally not adequate and
required activation with fans to lower radon
levels below 4 pCi/L.
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Recent Technical Information
Journal Articles
Some Results from the Demonstration of Indoor Radon Reduction
Measures in Block Basement Houses. Environ International, 15:265-
270,1989, Henschel, DJB. and A. G. Scott.
Radon Mitigation in Schools - Part 1. American Society of Heating,
Refrigerating and Air-Conditioning Engineers (ASHRAE) Journal,
Vol. 32, No. 1, pp. 40-45, January 1990. Leovic, K. W., et al.
Radon Mitigation in Schools - Part 2. American Society of Heating,
Refrigerating and Air-Conditioning Engineers (ASHRAE) Journal,
Vol. 32, No. 2, pp. 20-25, February 1990, Saum, D. W., et al.
Symposium Presentations
New Construction Techniques and HVAC Over-pressurization for
Radon Reduction in Schools. In: Proceedings of the ASHRAE Con-
ference IAQ '88, Atlanta, 1988. pp. 69-76. Witter (Leovic), K., et al.
Fan Door Testing on Crawl Space Buildings. In: Proceedings of the
ASTM Symposium on Air Change Rate and Air Tightness in
Buildings, Atlanta, April 17-18, 1989, Brennan, T., et al. (M.C.
Osbome, Project Officer)
The Influences of HVAC Design and Operation on Radon Mitigation
of Existing School Buildings, In: Proceedings of the IAQ '89. The
Human Equation: Health and Comfort. Leovic, K.W., et al.
Technical Issues Related to Emission Releases from Subslab Radon
Mitigation Systems, In: Proceedings of the 1989NationalConference
on Environmental Engineering, American Society of Civil Engineers,
Austin, July 1989, Sanchez, D. C.
Occupational and Environmental Exposures to Radon: A Perspective
for Mitigators, In: Proceedings of the 1989 National Conference on
Environmental Engineering, Austin, July 10-12, Sanchez, D.C. et al.
Reports
Testing of Indoor Radon Reduction Techniques in Central Ohio
Houses: Phase 1 (Winter 1987-1988). EPA-600/8-89-071, (NTIS PB
89-219984), 1989, Findlay, W.O., et al. (D. B. Henschel, Project
Officer).
Testing of Indoor Radon Reduction Techniques in Central Ohio
Houses: Phase 2 (Winter 1988-1989). EPA-600/8-90-050, (NTIS PB
90-222704), 1990, Findlay, W.O., et al. (D. B. Henschel, Project
Officer).
1990 International Symposium on Radon and Radon Reduction Technology,
Atlanta, February 1990
Approximately 600 federal, state, and private sector personnel met
February 19th-23rd in Atlanta, Georgia, to discuss radon and radon
reduction technology. Some of the major findings of the symposium
included:
• Less than5% of homeowners are measuring for radon and most
of those measurements are motivated by real estate or reloca-
tion activities.
• Most people who test do not follow up with mitigation, and
sometimes those who do mitigate receive substandard work
from mitigators.
Many SSD systems are stable after 2-4 years. A SSD system
with a passive stack is a judicious first step for new construc-
tion in radon prone areas.
• A majority of participants favored testing schools during the
school year with the HVAC systems turned off.
• Many schools are proceeding with testing and mitigation.
The next symposium is planned for April 2-5,1991, in Philadelphia,
PA. '
AEERL Research Presented at the 1990 International Symposium
"Evaluation of Radon Resistant New Con-
struction Techniques." Brennan, T., et al.
"Energy Penalties Associated with the Use
of Sub-slab Depressurization System."
Clarion, M., et aL
"Radon Diagnostics and Mitigation in Two
Public Schools in Nashville, Tennessee."
Craig, A.B.,etal.
"Engineering Design Criteria for Sub-slab
Depressurization Systems in Low Perme-
ability Soils." Fowler, C. S., et al.
"Evaluation of Sub-slab Ventilation for In-
door Radon Reduction in Slab-on-Grade
Houses." Henschel, D. B., et al.
"Radon Mitigation Experience in Difficult-
to-Mitigate Schools." Leovic, K. W., et al.
"RadonMitigation Experience in Houses with
Basements and Adjoining Crawl Spaces."
Messing, M. and B. Henschel.
"Radon Mitigation Techniques for Basement
Houses with Poor Sub-slab Communica-
tion." Pyle, B. E. andM. Osborne.
"The Florida Radon Research Program: Sys-
tematic DevelopmentofaBasis for Statewide
Standards." Sanchez, D. C., et al.
"Radon Mitigation Performance of Passive
Stacks in Residential New Construction."
Saum, D. W. and M. Osborne.
"The Effects of HVAC System Design and
Operation on Radon Entry Into School
Buildings." Turner, W. et al.
"Electret Ion Chambers for Radon Measure-
ments in Schools During Occupied and Unoc-
cupied Periods." Wiggers, K., et al.
"Sub-slab Suction System for Low Perme-
ability Soils." Hintenlang, D. and R. Furman.
'Temporal Patterns of Indoor Radon in North
Central Florida and Comparison of Short-
term Monitoring to Long-term Averages."
Roessler, C., et al.
"A Simplified Modeling Approach and Field
Verification of Airflow Dynamics in SSD
Radon Mitigation Systems." Gadsby, K., et
al.
"Benchmark and Application of the
RAETRAD Model." Rogers, V. and K.
Nielson.
"Long Term Durability and Performance of
Radon Mitigation Subslab Depressurization
Systems." Harrje, D., et al.
(Continued on p. 5)
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"The Use of Coatings andBlock Specification
to Reduce Radon Inflow Through Block
Basement Walls." Ruppersberger, J.
"Study on the Reliability of Short-term Mea-
surements to Predict Long-term Basement
Levels in a Residence. Hull, D. andT. Reddy.
'Time Series Linear Regressionof Half-hourly
Radon Levels in a Residence." Hull, D.
"One-year Follow-up Study of Performance
of Radon Mitigation Systems Installed in
Tennessee Valley Houses." Dudney, C., et al.
"Long-term Performance and Durability of
Active Radon Mitigation Systems in Eastern
Pennsylvania Homes." Scott, A. and A.
Robertson.
Copies of the 1990 Symposium Proceedings are expected to be available in the fall of 1990 by contacting the National Technical Information
Service (NTIS), at 5285 Port Royal Road, Springfield, Virginia 22161, or by calling (800) 336-4700. (Virginia residents call (703) 487-4650.)
Recent EPA Publications/Manuals on Radon and Radon Reduction Technology
These publications/manuals were developed
to provide technical information to individu-
als and radon industry professionals. Radon
Reduction Methods - A Homeowner's Guide
contains an overview of the basic radon re-
duction strategies.Theothermaterials contain
more specific and detailed technical informa-
tion. As ongoing research provides new in-
formation, these materials will be updated and
new manuals published. When requesting in-
formation or copies of these materials, indi-
viduals should ask if these materials have
been updated or superseded.
Radon Reduction Techniques for Detached
Houses, Technical Guidance, (2nd edition)
EPA/625/5-87/019 (NTIS PB 88-184908)
1988
Application of Radon Reduction Methods,
EPA/625/5-88/024 (NTIS PB 89-122162)
1988
Radon-resistant Residential New Construc-
tion, EPA/600/8-88/087,1988
Radon Reduction Techniques in Schools -
Interim Technical Guidance, EPA-520/1-89/
020 (NTIS PB 90-160086) 1989
Radon Reduction Methods - A Homeowner's
Guide (third edition) 1989
Application of Radon Reduction Methods
(Revised), EPA/625/5-88-024 (NTIS PB 89-
205975)1989
Copies of these materials may be obtained by writing to NTIS or by contacting your EPA Regional Office.
Other Sources of Information
If yon would like further information on these publications or expla-
nations concerning information contained in them, you should contact
your state radiation protection office or homebuilders association.
EPA Regional Offices
If you have difficulty locating these offices, you may call your EPA
Regional Office listed below. They will be happy to provide you with
the names, addresses, and phone numbers of these contacts.
Region 1
JFK Federal Building
Boston, MA 02203
(617) 565-4502
Region 2
26 Federal Plaza
New York, NY 10278
(212) 264-4418
State - EPA Region
Alabama-4
Alaska-10
Arizona-9
Arkansas-6
California-9
Colorado-8
Connecticut-1
Delaware-3
District of Columbia-3
Florida-4
Georgia-4
Hawaii-9
Idaho-10
Region 3
841 Chestnut Street
Philadelphia, PA 19107
(215) 597-8320
Region 4
345 Courfland St N.E.
Atlanta, GA 30365
(404) 347-8257
Region 5
230 South Dearborn St.
Chicago, IL 60604
From IN, MI, OH, and WI
(800)621-8431
Dlinois-5
Lidiana-5
Iowa-7
Kansas-7
Kentucky-4
Louisiana-6
Maine-1
Maryland-3
Massachusetts-1
Michigan-5
Minnesota-5
Mississippi-4
Missouri-7
Region 6
1445 Ross Avenue
Dallas, TX 75202
(214) 655-7223
Region 7
726 Minnesota Avenue
Kansas City, KS 66101
(913) 551-7020
Region 8
999 18th Street
Denver Place, Suite 500
Denver, CO 80202
(303) 293-1709
Montana-8 .
Nebraska-7
Nevada-9
New Hampshire-1
New Jersey-2
New Mexico-6
New York-2
North Carolina-4
North Dakota-8
Ohio-5
Oklahoma-6
Oregon-10
Pennsylvania-3
Region 9
1235 Mission Street
San Francisco, CA 94103
(415) 556-5285
Region 10
1200 Sixth Avenue
Seattle, WA 98101
(206)442-7660
EPA Headquarters
401 M Street S.W.
Washington, D.C. 20460
(202)475-9605
Rhode Island-1
South Carolina-4
South Dakota-8
Termessee-4
Texas-6
Utah-8
Vermont-1
Virginia-3
Washington-10
West Virginia-3
Wisconsin-5
Wyoming-8
•frll.S. GOVERNMENT PRINTING OFFICE: 1991 - 548-187/20532
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Environmental Protection
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Center for Environmental Research
Information
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