Schools and Other
Large Buildings
Research

Estimated Costs of Radon
Diagnostics and Mitigation in
Schools

To date, school facility managers with
responsibility for radon mitigation have
had little information on the costs of ra-
don diagnostics and mitigation in school
buildings. The most common approaches
to radon mitigation in schools are ASD
and heating, ventilating, and air condi-
tioning (HVAC) system control. The costs
of HVAC control are very school-s;
cific, depending on the design cap:
ties of the existing HVAC system in the
building. To provide guidelines that school
Officials can use to estimate the cost of
reducing radon levels with ASD systems,
seven radon mitigators with extensive
experience in schools were surveyed.
The mitigators were asked to provide
cost data for two scenarios of “typical”
school buildings with elevated radon lev-
els. The mitigators provided cost and
labor-hour estimates for five work ele-
ments associated with conducting radon
diagnostics and mitigation in these two
typical schools:

* reviewing construction plans;

* conducting diagnostic measure-
ments;

«designing an ASD system;

* — purchasing ASD materials; and
installing and checking out the
ASD system.

Based on the results of the survey, it is
estimated that radon diagnostics and miti-
gation in a typical school would cost
roughly $0.50 per square foot ($0.05 per
square m). It is estimated that about 20
percent of this cost is for diagnostics and
80 percent for materials and installation.
The cost would be higher in schools with
extensive subslab walls, very poor pres-
sure field extension (PFE), and building
code and/or asbestos complications.
Costs would be lower in simple schools
with very good PFE and no substab bar-
riers to communication. For additional
information, see Recent RMB Publica-
tions—Papers in Section 2.

Effect of Suction Pit Volume
on Pressure Field Extension

Research in a Kentucky school has
helped to quantify the effect of suction
pit size on subslab depressurization. Fig-
ure 4 shows the average subslab differ-
ential pressure in the school with no
suction pit and with three pits with in-

Average Differential Pressure (- Inches WC)

creasing size. Subslab differential pres-
sure measurements under these four
conditions were grouped into four dis-
tance ranges from the suction point: less
than 100 feet (30.5 m), 100 to 149 feet
(45.4 m), 150 to 200 feet (45.7 to 61.0
m), and over 200 feet. For all four ranges,
the negative pressure under the slab
increased with increased suction pit vol-
ume. Based on the results of this experi-
ment and on other research, EPA rec-
ommends that a suction pit 3 feet (0.9 m)
in diameter and 1 foot (0.3 m) deep be
used for maximum PFE in schools. PFE
measurements in the school showed that
one ASD point depressurized the entire
50,000-square-foot (4645-square-m)
slab, the greatest PFE coverage yet mea-
sured by RMB in an existing building.
The construction characteristics of this
school were “ideal” for installation of an
ASD system: post and beam construc-
tion, no internal barriers to subslab com-
munication, and 4 inches (10 cm) of
coarse aggregate under the slab.

HVAC Systems in Schools

A report describing the various types of
HVAC systems found in schools across
the country describes how each system
type operates, how the systems are con-
trolled, and how system operation should
affect building pressures, ventilation, and

0.4
Pez)
0.08
0.06
0.04 Ae
0.02
: J
0 z Z
100-149 150-200 >200
Distance from Suction Point (Feet)
Boxo txt) Ejexe Lfaxs
Pit Size (depth x diameter, feet )
1 inch = 2.54 centimeters
1 foot = 0.305 meters
Figure 4. Effect of suction pit size on PFE .



Region 1
(CT, ME, MA, NH, Fl, VT)
JFK Federal Building
Boston, MA 02203
(617) 585-4502
Raglon 2
(NY, NY)
26 Federal Plaza
New York, NY 10278
(212) 264-4418
Region 3
(DE, DC, MD, PA, VA, WV)
(218) 597-8320
Region 4
(AL, FL, GA, KY, MS, NC, SC, TN)
345 Courtland St. N.E.
Atlanta, GA 30365
(404) 347-3907

EPA Regional Offices
Ragion 5
(IL, IN, MI, MN, OH, WI)
230 South Dearborn St.
Chicago, IL 60604
From IN, Ml, MN, OH, and WI:

Region 6
(AR, LA, NM, OK, TX)
1445 Ross Avenue
Dallas, TX 75202
(214) 655-7223

Reglon 7
(IA, KS, MO, NE)

726 Minnesota Avenue
Kansas City, KS 66101
(918) 551-7020

Region 8
(CO, MT, ND, SD, UT, WY)
999 18th Street
Denver Place, Suite 500
Denver, CO 80202-2405
(803) 293-1708

Region 9
(AZ, CA, Hl, NV)
75 Hawthorne Street
San Francisco, CA 94105
(415) 744-1045

Region 10
(AK, ID, OR, WA)
1200 Sixth Avenue
Seattle, WA 98101
(208) 442-7660

1992 International Symposium

The 1992 International Symposium on
Radon and Radon Reduction Technol-
ogy will be held September 22-25, 1992,
at the Sheraton Park Place Hotel in Min-
neapolis, Minnesota [(800) 542-5566].
The purpose of this Symposium is to

provide a forum for exchanging technical
information on radon and radon reduc-
tion technology in the indoor environ-
ment. The major topics to be covered at
the Symposium are: experience in ap-
plying radon reduction and radon-resis-

tant construction techniques, measuring
radon and radon progeny, and assess-
ing radon-derived health impacts. For
information on the Symposium, contact
Tim Dyess at (919) 541-2802.

1992 Radon Symposium Information Card

Yes, | am interested in attending the 1992 International Symposium on Radon and Radon Reduction Technology to be held
September 22-25, 1992, in Minneapolis, Minnesota. Please send me a registration form.

Name.

Organization

Address,

City/State/Postal Code.

Country.

Telephone/Fax.

Type of Organization.

United States
Environmental Protection

Agency

Center for Environmental Research
Information
Cincinnati, OH 45268

Detach and return to:
Radon Symposium or contact Diana Fry
at CROPD:
cfo CRCPD
205 Capital Avenue
Frankfort, KY 40601 USA
Phone (502) 227-4543;
Fax (502) 227-7862

BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35

Official Business
Penalty for Private Use $300

EPA/600/N-92/009



firmly, use spatula to spread caulk
away from funnel along surface of
block to edges, evenly caulking
half the block, Repeat using sec-
ond funnel on other half of block.
Repeat entire process with re-
maining test blocks and funnels.

While caulk sets, assemble
aquarium pump and tubing. Cut 2
fest (0.6 m) of tubing; connect
one end to pump and other end to
tee arm. Cut 2-1/2 feet (0.8 m) of
tubing and connect one end to
tee leg. Shape this tubing into a
“U" with the open-ended leg
slightly shorter to allow for filling
with water in Step 9. To prevent
kinking, place the “circular form”
inside the bottom of the U tubing.
Tape the tubing together just
above the circular form and near
the tee so the arrangement lies
flat. Position the tee and U tubing
on the face of the spare block and
use silicone caulk to hold the tee,
circular form, and tubing to the
block. Leave the center 6 inches
(15 cm) of tubing free of caulk or
tape but flat against block.

While U tubing caulk sets, cut a 3-
inch (8 cm) length of tubing for
each funnel plus one extra. Apply
a generous bead of silicone caulk
1/2-inch (1 cm) from one end of a
piece of 3-inch tubing and insert
into tip of a funnel so about 2
inches (5 cm) of tubing extends
from tip. Be sure to use enough
caulk to completely seal tubing to
tip of funnel, spreading excess
caulk over top edge of funnel tip
and along tubing to ensure acom-
plete seal. Repeat with remaining
tubing and funnels.

Connect one end of the remain-
ing length of tubing (about 4 feet,
1.2 m, long) to the tee and insert
the nipple into the free end.

—~ Tee

7. Seal all connections at the tee,
the pump, and the nipple with sili-
cone caulk.

Allow time for all silicone caulk to
cure (at least 4 hours; preferably
overnight).

Lift the block with the attached U
tubing to a vertical position and fill
the U tubing half full with water
(coloring improves visibility), Mark
the center horizontal line (refer-
ence line) on a piece of graph
paper about 4 inches (10 cm)
square and slide it between the
center of the U tubing and block,

. Place the reserved 3-inch length
of tubing on the nipple.

. Turn on pump. Slide the graph
paper "reference line” to the water
level in the side of the U tubing
that is open at the top.

. Remove 3-inch tubing from nipple
(do not pinch tubing closed; this
may blow water out of U tube)
and insert nipple into the first block
funnel tubing. Wait 30 seconds.
Read amount of change in water
level in open side of U tubing.
Remove nipple from funnel and
replace 3-inch tubing. Check that
water level returns to reference
line. If not, repeat this step. Record
reading. Repeat with second fun-
nel on first block.

. Continue until all blocks are tested
and readings are recorded.

|. Review results, and select the
block with the highest U tubing
readings. Higher readings indicate
better resistance to air infiltration
(low air permeability). Generally,
blocks with the smoothest surface
texture have the best resistance.

. If all results are “low,” less than
0.1 to 0.2 inch (0.2 to 0.5 cm),
then you may want to consider
other sources of concrete block,
another material, or coating the

Aquarium

a Tubing

Tape

i Caulk

[| --- Graph Papor

surface of the constructed block
wall with a cementaceous block
filler/coating, or other durable coat-
ing that fills the pores of the block.

Feasibility Study of Basement
Pressurization Using a
Forced-Air Furnace

In a previous project, RMB demonstrated
that a typical forced-air furnace system
could be installed to pressurize a base-
ment to reduce radon entry. This re-
search project, in the same Pennsylva-
nia house, will determine the most effec-
tive configuration for this type of furnace
installation. EPA is collecting continuous
data on indoor conditions (temperature,
humidity, radon levels, pressure relation-
ships, and equipment operation) and out-
door conditions (temperature, humidity,
radon levels, wind speed and direction,
and barometric pressure) for each oper-
ating mode of the furnace system. The
system reduced radon levels from 19.3
to 1.5 pCi/L in summer (cooling) condi-
tions, and data are now being collected
under winter (heating) conditions. A re-
port should be available in the fall of
1992,

Application of Small Fans for
Active Soil Depressurization
in New Construction

EPA's proposed model standards for con-
trolling radon in new buildings include
placing a layer of aggregate and barrier
under the slab. By meeting these stan-
dards and sealing the slab, it may be
possible to use smaller ASD fans than
those now used for ASD systems in
existing houses. Smaller fans cost less
to install and operate, require less space,
and may be quieter. In addition, it might
be possible to power them with a simple
photovoltaic system. This project involves
an initial survey of at least 20 new slab-
on-grade or basement houses that meet
the requirements of the proposed model
standards. At each house, RMB will mea-
sure radon levels under three ASD oper-
ating conditions, conduct blower door
and tracer gas tests, and obtain data on
subslab aggregate size and depth, soil
permeability, and foundation size and
shape. RMB will use these data, together
with information on weather patterns, to
predict the fan size required and ASD

performance characteristics. Based on
these results, RMB will select about six
houses to study how well small ASD
fans actually perform.

"U Tube"
Tape

}— Caulk

|. Circular Form

Aquarium
Pump

Spare Block Test Block

Figure 3, Concrete block permeability test assembly.



radon concentrations. The report entitled
“A Study of HVAC Systems in the Cur-
rent Stock of U. S. K-12 Schools” is
scheduled for publication later this year.

School Program Peer Review

Areview of RMB’s School Research Pro-
gram took place in May in Research
Triangle Park, North Carolina. The pur-
pose of the review was to present school
tesearch results to a panel of four ex-
perts and obtain feedback for future re-
search. Research topics covered in-
cluded: ASD control, HVAC system con-
trol, comparison of ASD and HVAC con-
trol, radon reduction in crawl space
schools, and radon prevention in the
construction of schools and other large
buildings.

Innovative and
Supporting Research

A Simple Model for Describ-
Ing Radon Migration and
Eniry Into Houses

The relative importance of physical
mechanisms such as diffusion, dilution,
and radon decay may be helpful when
designing radon mitigation systems. This
model uses simplified assumptions about
the distribution of radon entry routes and
driving forces to relate indoor radon lev-
els to soil characteristics. Under these
assumptions the model shows that:

* soil permeability is the most im-
portant influence on indoor radon
concentrations because soil per-
meability varies naturally by five
to six orders of magnitude;

the area of the radon entry route
is not very important;

90 percent of the total soil gas
flow occurs in a band surrounding
the house with a width six times
the depth of the basement; and

because radon decays, only the
volume of soil within a band of
width about two times the base-
ment depth actually contributes to
indoor levels (this volume may be
much smaller at low permeabili-
ties).

The simplified model provides realistic

predictions of indoor radon_concentra-

tions for permeabilities higher than 107"
square meters. RMB plans to extend the
model to cover transport by both advec-
tive flow and diffusion. For additional
information on this model see Recent
RMB Publications in Section 2.

Modeling the Influence of
Active Subslab
Depressurization (ASD)
Systems on Airflows in
Subslab Aggregate Beds

When the total soil gas flow rate and the
average size, thickness, porosity, and
permeability of a subslab gravel bed are
known, this model predicts the pressure
in the aggregate bed as a function of
distance from a suction point. Mitigators
can use the model to design an ASD
mitigation system when pressure field
extension (PFE) measurements are not
available. Builders should find the model
helpful when designing a mitigation sys-
tem based on a specified gravel bed, as
well as selecting the type of fan needed
to provide a required flow rate, The model
is based on calculating the distances at
which the soil gas flow changes from
Darcian (lower velocities near the perim-
eter), through a “transition zone,” to tur-
bulent (higher velocities) near the center
of the bed. So far, results from the model
compare well with PFE measurements
in three basement houses and espe-
cially well with measurements made in
larger buildings. For additional informa-
tion on this model, see Recent RMB
Publications in Section 2.

Evaluation of Radon
Movement Through Soil and
Foundation Substructures

To design and install improved mitiga-
tion systems, EPA, mitigators, and build-
ers need detailed information on how
radon moves through soil and enters
buildings. RMB is currently conducting
pilot studies on radon movement using a
large steel chamber. This study will also
help complement the modeling work de-
scribed above. The chamber contains
21 cubic yards (16 cubic m) of elevated-
radium soil with known permeability,
moisture retention, density, and particle
distribution characteristics. The soil is
placed in the chamber to match typical

moisture and density conditions as
closely as possible. A central perforated
pipe under vacuum simulates a driving
force, and probes collect radon grab
samples at varying depths and distances
from the suction point. When the first
series of experiments are completed later
this year, part of a foundation wall and a
floor slab will be installed in the chamber
to measure convective and diffusive ra-
don entry characteristics. Final results
will be included in a future Update.

National Concrete Survey and
Assessment

This two-phase project is developing a
database on the radon transmission char-
acteristics of typical concrete used in
building slabs across the country. EPA
will use the results to support the devel-
opment of American Society for Testing
and Materials (ASTM) protocols for test-
ing concrete for permeability and diffu-
sivity. The nationwide survey will collect
and analyze 40 to 50 samples from dif-
ferent climatic and construction regions
to determine how widely they vary in
permeability and diffusivity. Results will
be included in a future Update.

Effects of Leakage
Distribution and Neutral
Pressure Level (NPL) on
Indoor Radon Concentrations

RMB is investigating the effect of leaks
in building envelopes (such as around
windows and through electrical outlets)
on differential pressures across the slab.
The effects of leakage distribution on the
NPL will be tested under a variety of
stack effect conditions. Results of this
study will help determine the best places
to seal the superstructure of a house to
reduce the driving forces for radon entry.
Studies are now underway in atest house
constructed on_radium-rich soils in
Bartow, Florida. RMB is collecting radon
data and measuring the pressure differ-
entials at floor level, across the slab, and
at various heights under both heating
and cooling conditions. The results will
be analyzed by Lawrence Berkeley Labo-
ratory and will help to validate newly
developed air infiltration models. A re-
port should be available in the fall of
1992.

Section 2: Additional Information

Recent RMB
Publications

This section lists RMB reports, manuals,
papers, journal publications, and sympo-
slum proceedings published since the

last Update. All publications with NTIS
numbers are available (prepaid) from the
National Technical Information Service,
5285 Port Royal Road, Springfield, VA
22161 [(703) 487-4650]. If you would
like more information on these publica-

6

tions or explanations concerning infor-
mation contained in them, you may con-
tact your EPA Regional Office (addresses
and phone numbers are given after the
publications) or the appropriate RMB
project officer.



United States

Environmental Protection

Agency

Office of
Research and Development
Washington, DC 20460

Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711

EPA/G00/N-92/009_ June_1992

& EPA Radon Mitigation Research Update

Introduction

The Radon Mitigation Research Update
is the fourth in a series of research sum-

maries intended to provide up-to-date
information on EPA’s Air and Energy

Contents

Section 1: Project Highlights
Existing House Research ...
+ Fiold Testing of a Now Pre-Mitigation
Diagnostic Approach for Subslab
Depressurization Systems
Effects of Natural and Forced Basement
Ventilation on Radon Levels in Single
Family Dwellings
ASD Exhaust Re-Entrainment Research
Durability of Radon Mitigation Systoms
Radon Mitigation in Attached Houses
Applied Research on Design of Sub-
Mombrane Depressurization Systems
for Crawl Space Houses
New House Construction Research ...
+ A Simple Procedure to Solect Low Air
Pormeability Concrete Blocks
Foasibility Study of Basoment Pressur-
ization Using a Forced-Air Furnace
+ Application of Small Fans for Active Soil
Doprossutization in New Construction
Schools and Other Large Buildings
Research...
Estimated Costs of Radon Diagnostics
and Mitigation in Schools
Effect of Suction Pit Volume on Pressure
Field Extension

HVAC Systems in Schools
+ School Program Poor Review
Innovative and Supporting Research .....
+ A Simple Model for Describing Radon
Migration and Entry Into Houses

Modeling the Influence of Active Subsiab
Dopressurization Systems on Airflows in
Subslab Aggragate Beds

+ Evaluation of Radon Movement Through
‘Soil and Foundation Substructures

+ National Concrete Survey and
Assessment

+ Effects of Leakage Distribution and
Noutral Pressure Level on Indoor
Radon Concentrations

essere

‘Section 2: Additional Information
Recent RMB Publications

EPA Regional Offices.
1992 International Symposium

Daan

Radon Mitigation
Research Contacts
A. B. “Chick” Craig (919) 541-2824
Senior physical scientist—

radon,

Radon-resistant large build-
ing construction

Tim Dyess (919) 541-2802
Chief, Radon Mitigation
Branch
Radon Symposium

Bruce Harris (919) 541-7807
Radon diagnostics and mea-
surement technology
Durability of mitigation sys-
tems

Bruce Henschel (919) 541-4112
Radon mitigation in existing
houses
Cost studies

Kelly Leovic (919) 541-7717
Radon mitigation in schools
Radon Mitigation Research
Update

Marc Menetrez (919) 541-7981
Innovative and supporting re-
search
Radon reduction in attached
housing

Ron Mosley (919) 541-7865
Radon data analysis
Radon modeling

John Ruppersberger (919) 541-2432
Radon barriers and block per-
meability
Safety issues
David Sanchez (919) 541-2979
Florida Radon Research Pro-

gram
Mechanisms of radon entry

1

Engineering Research Laboratory's
(AEERL’s) radon mitigation research pro-
grams. The Updates summarize recently
completed and ongoing research activi-
ties intended to achieve the Radon Miti-
gation Branch’s (RMB's) research objec-
tives. Research topics included in this
Update are listed in the table of con-
tents. If you would like more information
about specific research activities or pro-
grams, you may contact the appropriate
RMB project officer at the number listed
on this page.

The first two Updates, published in De-
cember 1990 and March 1991, summa-
rize RMB’s radon mitigation research
objectives and RMB’s strategic research
plan for meeting these objectives. The
projects described in the November 1991
Update reflect the strategic plan's em-
phasis on innovative and supporting re-
search and on reducing radon in schools
and other large buildings. Copies of these
Updates may be requested by writing to
RMB Research Updates, MD-54, U.S.
EPA, AEERL, Research Triangle Park,
NC 27711. AEERL plans to publish sub-
sequent Updates approximately twice a
year.

This Update has two main sections. The
first is Project Highlights, which contains
summaries of completed or ongoing re-
search projects. These summaries are
intended to provide the radon mitigation
industry with timely and useful informa-
tion in RMB's four research areas: Exist-
ing Houses, New House Construction,
Schools and Other Large Buildings, and
Innovative and Supporting Research
(covering research in the other three
areas). Some of this information is based
on regional or preliminary findings and
should be viewed as such. As research
programs progress, RMB will publish the
final results as technical reports, manu-
als, and papers. The second section in
this Update contains a list of RMB publi-
cations completed since the previous
Update, a list of the EPA Regional Of-
fices, and an announcement of the 1992
International Symposium on Radon and
Radon, Reduction Technology.

& Printed on Recycled Paper



EPA Reports:

Recommended Foundation Fill Materials Construction Stan-
dard of the Florida Radon Research Program. D. Sanchez
(project officer), EPA-600/8-91-206 (NTIS PB92-105865), Oc-
tober 1991.

Recommended Sub-slab Depressurization Systems Design
Standards of the Florida Radon Research Program. D. Sanchez
(project officer), EPA-600/8-91-208 (NTIS PB92-105626), Oc-
tober 1991.

Development of Alternate Performance Standard for Radon
Resistant Construction Based on Short-Term/Long-Term In-
door Radon Concentrations. Volume 1: Technical Report. D.
Sanchez (project officer), EPA-600/8-91-210a (NTIS PB92-
115211), October 1991.

Development of Alternate Performance Standard for Radon
Resistant Construction Based on Short-Term/Long-Term In-
door Radon Concentrations. Volume 2: Appendices. D. Sanchez
(project officer), EPA-600/8-91-210b (NTIS PB92-115229),
October 1991.

Standard Measurement Protocols: Florida Radon Research
Program. D. Sanchez (project officer), EPA-600/8-91-212 (NTIS
PB92-115294), November 1991.

Proceedings of the Workshop on Radon Potential Mapping:
Florida Radon Research Program. D. Sanchez (project offi-
cer), EPA-600/9-91 -044 (NTIS PB92-1 15278), November 1991.

Natural Basement Ventilation as a Radon Mitigation Tech-
nique. R. Mosley (project officer), EPA-600/R-92-059 (NTIS
PB92-166958), April 1992.

Manuals:

Durability of Performance of a Home Radon Reduction Sys-
tem - Sub-slab Depressurization Systems, Assessment Proto-
cols. D. Sanchez (project officer), EPA-625/6-91-032, April
1991.

Handbook: Sub-slab Depressurization for Low-permeability
Fill Materia\—Design and Installation of a Home Radon Re-
duction System. D. Sanchez (project officer), EPA-625/6-91-
029, July 1991.

The following two manuals are currently being prepared:

+ Radon Prevention in the Design and Construction of
Schools and Other Large Buildings. This manual will
provide designers, builders, and school officials with
information on how radon prevention techniques work
and how to incorporate them during the design and
construction stage at lower costs than retrofit systems.
Expected publication is summer 1992.

+ Radon Reduction Techniques for Existing Houses. The
existing version of this manual, the second edition, is
EPA-625/5-87-019 (NTIS PB88-1 84908). Expected pub-
lication of the third edition is fall 1992.

Papers:

Modeling the Influence of Active Subslab Depressurization
(ASD) Systems on Airflows in Subslab Aggregate Beds, EPA-
600/D-91-226 (NTIS PB91-242925). Mosley, R. B. Presented
at the Sth International Symposium on the Natural Radiation
Environment, Salzburg, Austria, September 1991.

The U.S. EPA Office of Research and Development Overview
of Current Radon Research, EPA-600/D-91-259 (NTIS PB92-
121250). Dyess, T. M., and M. C. Osborne. Presented at the
1991 Annual AARST National Fall Conference, Rockville, MD,
October 1991.

Update on Radon Mitigation Research in Schools, EPA-600/
D-91-229 (NTIS _PB91-242958), Leovic, K. W., A. B. Craig,
and D. B. Harris. Presented at the 1991 Annual AARST
National Fall Conference, Rockville, MD, October 1991.

The Florida Radon Research Program: Technical Support for
the Development of Radon Resistant Construction Standards,
EPA-600/D-91-235 (NTIS PB92-108109) Sanchez, D.C., R.
Dixon, and M. Madani. Presented at the 1991 Annual AARST
National Fall Conference, Rockville, MD, October 1991.

A Simple Model for Describing Radon Mitigation and Entry into
Houses, EPA-600/D-91-021 (NTIS PB91-176743). Mosley, R.
B. Presented at the 29th Hanford Symposium on Health and
the Environment, Richland, WA, October 1990.

Costs of Radon Diagnostics and Mitigation in Schoo! Build-
ings. Leovic, K. W., H. Rector, and N. Nagda. Presented at the
85th Annual AWMA Conference, Kansas City, MO, June 1992.

Journal Publications:

Cost Analysis of Soil Depressurization Techniques for Indoor
Radon Reduction. EPA-600/J-91-320 (NTIS PB92-120443),
Indoor Air, Vol. 1, No. 3, pp. 337-351, 1991. Henschel, D.B.

Radon Prevention in the Design and Construction of Schools
and Other Large Buildings. Architecture/Research, Vol. 1, No.
1, pp. 32-33, October 1991, Leovic, K. W., A. B. Craig, and D.
B. Harris.

Case Study of Radon Diagnostics and Mitigation in a New
York State School. indoor Air, Vol. 1, No. 4, 1991, pp. 531-538,
Leovic, K. W., D. B. Harris, M. Clarkin, and T. Brennan.

Symposium Publications:

Proceedings: The 1991 International Symposium on Radon
and Radon Reduction Technology. Volume 1. Symposium
Oral Papers (Opening Session and Technical Sessions I-V). T.
Dyess (project officer), EPA-600/9-91-037a (NTIS PB92-
115351), November 1991.

Proceedings: The 1991 International Symposium on Radon
and Radon Reduction Technology. Volume 2. Symposium
Oral Papers (Technical Sessions VI-X). T. Dyess (project
officer), EPA-600/9-91-037b (NTIS PB92-115369), November
1991.

Proceedings: The 1991 International Symposium on Radon
and Radon Reduction Technology. Volume 3. Symposium
Panel and Poster Papers (Technical Sessions I-V). T. Dyess
(project officer), EPA-600/9-91-037c (NTIS PB92-115377),
November 1991.

Proceedings: The 1991 International Symposium on Radon
and Radon Reduction Technology. Volume 4. Symposium
Poster Papers (Technical Sessions VI-X). T. Dyess (project
officer), EPA-600/9-91-037d (NTIS PB92-115385), November
1991.

“U.S. Government Printing Office: 1992 — 648-080/60029



Section 1: Project Highlights

Existing House
Research

Field Testing of a New
Pre-Mitigation Diagnostic
Approach for Subslab
Depressurization Systems
(SSD)

Recent field tests in six slab-on-grade
houses in New Mexico show that a new
diagnostic approach, the “radon entry
potential” method, can be useful when
designing SSD systems. Radon entry
potential testing involves depressurizing
the house (rather than just the subslab
region) by 0.004 to 0.12 inch (0.01 to
0.30 cm) water column (WC) with a
blower door and measuring the total flow
rate and radon concentration of the gas
flowing into the house through each test
hole drilled in the slab. Test holes with
the highest radon flow rate (total flow
rate times radon concentration) indicate
the slab areas with the highest radon
entry potential. SSD suction pipes should
be placed in these areas. Mitigators can
use these results, together with other
diagnostic information (especially pres-
sure field extension measurements), to
design effective SSD systems.

The SSD systems in the New Mexico
houses, designed using radon entry po-
tential as a diagnostic tool, performed
well. The entry potentials at the perim-
eter of the slabs were about 10 times
greater than the potentials at the central
portion (perimeters had lower radon con-
centrations but higher flows), suggesting
that suction pipes should be located near
the perimeter in the houses. In addition,
the soil beneath the slabs was much
more resistant to gas flow than the slab
itself, so once soil gas moved into the
area beneath the slab, it entered the
house relatively easily.

The radon levels in two of the New Mexico
research houses also turned out to in-
crease significantly while barometric pres-
sure was dropping, overwhelming the
SSD system. This effect has been ob-
served in a few other cases, and sug-
gests that more data are needed on
radon entry and control mechanisms.
The barometric pressure effect may also
Influence diagnostic measurements and
post-mitigation radon monitoring results.

RMB is continuing to analyze data from
this project and will soon publish a final
report. A paper was presented at the
1991 Symposium; other papers being
prepared will provide further detail.

Effects of Natural and Forced
Basement Ventilation on
Radon Levels in Single Family
Dwellings

EPA’s 2-year systematic study of three
Princeton University research houses
clearly demonstrates that radon entry
rates depend directly on basement de-
pressurization. The results also clarify
the role of natural ventilation in reducing
indoor radon concentrations. Natural ven-
tilation is a simple way to reduce indoor
radon levels, but, until now, there has
been no information on how much re-
duction to expect. This work demon-
strates that natural ventilation decreases
radon levels in two ways: (1) by simple
dilution; and (2) by providing a pressure
break (any opening in the building shell
that reduces the outdoor-to-indoor pres-
sure difference). The pressure break re-
duces both depressurization and radon
entry. Results from one of the research
houses are shown in Figures 1 and 2.
Figure 1 illustrates the dramatic drop in
basement radon levels when two base-
ment windows were opened (at point 0).
Figure 2 shows the corresponding drop
in differential pressure. For additional
information, see Recent RMB Publica-
tions in Section 2.

ASD Exhaust Re-Entrainment
Research

The “Radon Contractor Proficiency Pro-
gram Interim Radon Mitigation Stan-
dards” published by EPA’s Office of Ra-
diation Programs in December 1991 re-
quire the exhaust from active soil de-
pressurization (ASD) systems to meet a

200

“{0-foot rule"—to discharge at least 10
feet (3.05 m) above ground level, at
least 10 feet away from any opening in
the house or an adjacent building, and at
least 10 feet from any private or public
walkway. The purpose is to ensure that
people in or near houses with ASD sys-
tems are not exposed to elevated radon
levels from the ASD system exhaust.
These standards effectively require an
exhaust stack inside or outside the house.
This increases installation costs by about
$100, and owners may object to the
appearance of the stack. If stacks were
not needed under some conditions,
homeowners might be more willing to
install ASD systems.

RMB is working with Pennsylvania State
University to determine the conditions
under which grade-level ASD exhaust
may be appropriate. The study will ex-
perimentally examine re-entrainment (in-
door exposure) and dispersion (outdoor
exposure) in relation to exhaust location,
configuration, velocity, and wind condi-
tions. The study will also include math-
ematical modeling to determine whether
ASD exhausts increase deposits of ra-
don progeny (including lead-210) on soil
surrounding and buildings.

The study is using a “mock” exhaust
system (a fan and piping, not connected
to an ASD system) and a tracer gas as a
radon substitute. This approach allows
RMB to test many different exhaust loca-
tions and system configurations without
modifying a real ASD system or increas-
ing the amount of radon drawn into a
house by re-entrainment. For each test
condition, RMB will take gas samples
from 12 to 24 sampling points indoors

Radon (pCi/L)

je)

Figure 1.
2

T
89220
dulian Date

Effect of opening two basement windows (at point 0) on basement radon levels.



6
Aitic Fan AP Spike

5 4

44

34

24

1-4

0 T T T

89216 89218 89220 89222
Julian Date
Figure 2. Effect of opening two basement windows (at point 0) on basement/outdoor

differential pressures.

and around the exhaust point outdoors.
The samples will be analyzed for the
tracer gas by gas chromatography to
measure re-entrainment and dispersion.
The observed results will then be checked
with mathematical models that consider
jet effects.

Durability of Radon Mitigation
Systems

To determine how well radon mitigation
systems hold up, this study is measuring
radon levels in about 300 homes and
schools with radon mitigation systems
that have been installed for at least 18
months. Three-month (or longer) alpha
track detector (ATD) measurements will
be compared with pre- and post-mitiga-
tion charcoal canister measurements
made when the system was installed. If
the post-mitigation ATD measurements
are consistent with post-mitigation canis-
ter measurements, the system presum-
ably is operating properly. In addition,
EPA is physically checking some sys-
tems to determine how well they are
operating and to see if certain compo-
nents, such as seals or fans, consis-
tently fail. Results will be included in a
final report this fall.

Radon Mitigation in Attached
Houses

Because attached houses are common
in many areas of the country, blocks of
attached apartments located in Cortland,
New York, are being researched. RMB is
investigating techniques that can be used
to mitigate attached structures as well as
individual residential units. One focus is

on building components common to ad-
joining housing units, such as exhaust
stacks, furnace combustion air intakes,
and vacuum fields. Pre-mitigation mea-
surements included subslab communi-
cation and double blower-door tests of
each unit (individually and in conjunction
with adjacent apartments).Mitigation sys-
tems include ASD and encapsulation of
sump pits. A report on the research will
be available later this year.

Applied Research on Design
of Sub-Membrane Depressur-
ization (SMD) Systems for
Crawl Space Houses

This project will expand the database on
radon mitigation techniques for crawl-
space dwellings. Possible techniques in-
clude 1) SMD, 2) depressurizing the en-
tire crawl space, and 3) ventilating the
crawl space. SMD has a lower energy
penalty and is typically more effective
than the other techniques, but it also
costs more to install. This study should
anawer several questions pertaining to

+ How much membrane sealing is
required? What is the effect of
sealing on radon levels?

+ How should suction be distributed
beneath the membrane?

+ What portion of the crawl-space
floor needs to be covered?

+ When should crawl-space depres-
surization rather than SMD be
used?

Much of this testing will be conducted
using an existing crawl-space test house.
3

New House
Construction Research

A Simple Procedure to Select
Low Air Permeability Con-
crete Blocks

Air entering a building through concrete
blocks can contain radon, moisture, bio-
logical agents, and other contaminants
that threaten the health and comfort of
the occupants and the structure itself.
Tests show that the permeabilities be-
tween different types of concrete blocks
can vary by a factor of 50. The following
procedure may help determine the per-
meability differences between the types
of blocks available in an area, permitting
a more informed choice of concrete
blocks. A general conclusion is that
smooth-surfaced blocks may be less per-
meable than blocks with a rough-looking
surface: in short, “if it looks leaky, it
probably is leaky.”

Materials
* aquarium pump (“Whisper” 400 or
equivalent)
* concrete blocks to be tested, plus
a spare

* 9 feet (2.7 m) of clear aquarium
tubing plus 6 inches (15 cm) for
each test block, to fit pump

* one tee and one nipple to fit tub-
in

. one tube of silicone caulk (G. E.
"Silicone Clear Household Glue
and Seal” or equivalent)

* spatula, 1-1/2 inches (4 cm) wide

* “circular form” (3/8-inch, 1 cm,
cross section cut from bottom of
spent caulk cartridge)

+ clear tape
* sheet of graph paper (10 x 10 grid
preferred)

+ for each block to be tested, half a
cartridge of caulk (Red Devil “Life-
time” or equivalent)

+ for each block to be tested, two 3-
inch (7.6 cm) plastic funnels

Procedure (see Figure 3)

1. Label each type of block sample
and lay it on its side, 1 inch (3 cm)
or more apart.

2. Select two identical 3-inch (7.6
em) plastic funnels. Carefully trim
away any tabs. Center one funnel
directly on the surface above one
core (void) in first test block.

3. Hold funnel down firmly and apply
a generous (3/8-inch, 1 cm) bead
of cartridge caulk around rim of
funnel, touching both funnel and
block. Apply two more beads of
caulk to the block against first
bead. Continuing to hold funnel