Research on Central HVAC
Systems

During the winter of 1990-1991, a data log-
ger was installed in a Colorado school to
continuously monitor radon, differential pres-
sure, temperature, and the status of the out-
door air damper for the school’s central
HVAC system. The HVAC system supply
ducts are located under the slab, with the
corridor serving as the return air plenum.
From the hallway, the return air is ducted
into a subslab return-air tunnel that pulls the
air back to the single-fan air handler. Radon
levels in the school ranged from 6 to 13 pCi/
L.

Results indicate that the position of the HVAC
system outdoor air damper has a significant
influence on radon levels in the building.
With the damper closed, radon levels in the
school were elevated for two reasons: (a) the
fan was creating a large negative pressure in
the return air tunnel, increasing radon levels
in the tunnel, and (b) since minimal outdoor
air was entering the HVAC system, the ra-
don collected in the return air tunnel was
distributed throughout the building with mini-
mal dilution.

With the outdoor air damper opened to 100%,
the pressure differential was reduced, radon
levels were diluted, and average radon con-
centrations in the building were less than 1
pCY¥L. It appears that radon levels are re-
duced even when the outdoor air damper is
only partially open. Radon levels rise rapidly
when the damper is closed, indicating that
mitigation in this school will require con-
tinual monitoring of the outdoor air damper
to ensure that it is open while the building is
occupied. This project was conducted with
the assistance of the Western Regional Ra-
don Training Center in Fort Collins, Colo-
tado.

Comparison of Three Mitiga-
tion Techniques in Same Build-
Ing

Research in a Maine school, originally stud-
ied as part of EPA's Office of Radiation
Programs School Evaluation Program, was
initiated in the winter of 1990-1991. Because
the design and construction of each of the
three wings of the school are different and
the radon source strength is relatively uni-
form, the school provides an excellent op-
portunity to compare different mitigation
techniques within the same building.

Three mitigation techniques were evaluated —
ASD, unit ventilator pressurization/dilution,

and heat recovery ventilation (HRV)—inde-
pendently in each of the three wings during
the winter of 1990-91. Preliminary data indi-
cate that average radon levels in the ASD
wing are below 4 pCi/L, with most rooms
below 2 pCi/L. The HRV has also reduced
radon levels to below 2 pCi/L in the one
room where it is installed. However, the unit
ventilators have thus far proven ineffective
in consistently reducing radon levels to be-
low 4 pCi/L. As a result, an ASD system will
be installed in this wing for monitoring dur-
ing the winter of 1991-92.

Long-term Effectiveness of
ASD Systems

Radon levels were measured in February
1991 in two Tennessee schools that were
mitigated by RMB in 1989. Measurements
made during the first winter after the sys-
tems were installed (1989-90) indicated that
some ASD system modifications were
needed. Following these modifications, mea-
surements made this past winter (1990-91)
were all below 4 pCi/L in the mitigated areas
of the buildings. (Premitigation levels had
averaged 30 and 40 pCi/L in the two schools.)
RMB will continue to follow the long-term
effectiveness of the ASD systems installed
in these two schools.

Crawl Space Mitigation

Submembrane depressurization (SMD), crawl
space depressurization, craw! space pressur-
ization, and natural ventilation of the crawl
Space were compared in a Tennessee school.
SMD performed most effectively, reducing
radon levels from 9.7 pCi/L in the class
rooms above the crawl space to below 0.5
pCi/L in a matter of hours.

Craw] space depressurization worked as well
as SMD in reducing class room radon levels
(to 0.6 pCi/L), but increased the crawl space
levels by at least a factor of two during
depressurization. Natural ventilation failed
to reduce class room levels to below 4 pCi/L
and crawl space pressurization was found to
be even less effective than natural ventila-
tion.

The results from craw] space depressuriza-
tion demonstrate that ization may
be a cost effective alternative to SMD in
buildings where unused crawl spaces can be
easily isolated and depressurized. However,
its applicability may be limited in buildings
where there are utilities in the crawl space,
leaky wooden floors above the crawl space,

or any other doors or openings where radon
can move from the space to occupied rooms.
(For more information on crawl space schools
see “A Comparison of Radon Mitigation
Options for Crawl Space School Buildings,”
areprint from the 1991 International Sympo-
sium on Radon and Radon Reduction Tech-
nology.)

New Research Projects in Ex-
isting Schools

Radon diagnostics were conducted in four
Ohio schools during the spring of 1991. Data
loggers were installed in two of the schools
to determine if the HVAC systems can be
used to control radon levels and, if they can,
how the HVAC systems should be operated.
One of the schools has a two fan central
HVAC system with the retum air located in a
subslab tunnel. The other school has fan coil
units located in a subslab tunnel, and outdoor
air can be supplied to the fan coils in the
tunnel.

Radon diagnostics were also conducted in
eight South Dakota schools during the sum-
mer of 1991. One of the schools with unit
ventilators was selected for continuous moni-
toring with a data logger since it consistently
measured the highest radon levels. The open-
ing of the unit ventilator dampers will be
controlled to determine the units’ ability to
reduce radon levels in this cold climate. Pa-
rameters that will be monitored include: ra-
don levels, differential pressure, opening/
closing of the classroom-to-corridor door,
and weather. In the long-term, school offi-
cials plan to install an ASD system, and the
two techniques (ASD and HVAC system
control) will be compared.

Profile of School Building Char-
acteristics

To gain a better understanding of the physi-
cal characteristics of schools throughout the
U.S. and to help guide future school re-
search, RMB is conducting a profile of school
building characteristics using a subsample of
approximately 100 schools from ORP’s Na-
tional School Radon Survey. Detailed struc-
tural and HVAC system characteristics are
being collected, and results should provide
approximate percentages of various school
building characteristics in the U.S. The re-
sults of the profile will also be compared
with the RMB research schools in order to
identify any correlations between the research
schools and the random sample.


RMB manuals covering the five topics listed below are being up- - Handbook on Sub-Slab Depressurization for Low Permeability

dated and should be available in the near future: Fill Material Design and Installation of a Home Radon Reduc-
- Radon Reduction for Detached Houses (addresses soil depres- tion System
surization only) - Radon Reduction Techniques in Schools (includes more techni-
- Durability of Performance of a Home Radon Reduction Sys- cal details and results from recent school research)
tem—Subslab Depressurization Systems, Assessment Protocols - Radon Prevention in the Design and Construction of Schools
and Other Large Buildings

1992 Radon Symposium Information Card

‘Yes, I 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

Detach and return to:

Radon Symposium Or contact Diana Fry at CRCPD:
c/o CRCPD Phone (502) 227-4543

205 Capital Avenue Fax (502) 227-7862

Frankfort, KY 40601 USA

U.S, Environmental Protection Agency
Region 5. Library (PL-12J)

West Jackson Boulevard, 12th Floor
Chicago, IL 60604-3590

United States Center for Environmental Research BULK RATE
Environmental Protection Information POSTAGE & FEES PAID
Agency Cincinnati, OH 45268 EPA PERMIT NO. G-35

Official Business
Penalty for Private Use $300

EPA/600/9-91/038

PS Shi denna) Prctetion Agenay2?

DS, Eibra
i hi ace


Radon Mitigation Research in
Schools

RMB has conducted radon mitigation research in 47 schools in 12
states since 1988. Initial research focused on the application of ASD
techniques. More recent research has been directed at the ability and
limitations of using school HVAC systems to reduce radon levels. A
goal of future projects is to compare the effectiveness of the two
techniques in the same buildings.

School Structures and Subslab Pressure Field
Extension

Most of the 47 schools studied have slab-on-grade substructures
(91%), although some basement (19%) and crawl space (15%)
substructures have been studied. (Note that this distribution includes
combination substructures; for example, a school with both a base-
ment and slab-on-grade substructure would count as both.)

A rough analysis of pressure field extension (PFE) data collected in
72% of the 47 buildings shows an average PFE radius of about 40
feet (12.5 meters). This implies an average coverage of slightly more
than 5000 square feet (490 square meters) per suction point and
roughly equates to the area of seven 25-by-30-foot (8-by-9-meter)
classrooms. However, in addition to subslab permeability’s being a
determinant of PFE, it appears that subslab walls are also an impor-
tant limiting factor in PFE in a number of these schools. This is
important both in the mitigation of existing schools and in the design
of new buildings.

HVAC Systems and Indoor Air Quality

The types of HVAC systems found in the 47 RMB research schools
are relatively evenly distributed: 45% of the schools have central air
handling systems; 43% have unit ventilators; 30% have radiant heat;
and 11% have fan coil units. (Note that this distribution includes
schools with combination HVAC systems; for example, a school that
has both unit ventilators and radiant heat would count as both.) Of
the schools, 17% have only radiant heat (11%) or only fan coil units
(6%), indicating that the other 83% have been designed to provide
conditioned outdoor air. In practice, however, most of these 83% are
not designed or operated to supply at least 15 cfm (7 L/s) of outdoor

air to each occupant as recommended by current ASHRAE guide-
lines.

To illustrate the ventilation in a sample of schools, Figure 1 presents
the average carbon dioxide measurements made in 67 rooms in seven
schools. All seven schools use typical unit ventilators (UV in figure)
for HVAC. As seen in the figure, the average carbon dioxide levels in
all 67 classrooms is 1423 ppm. As would be expected, the average
carbon dioxide level in the 32 classrooms where the unit ventilators
were operating was lower than in the 35 classrooms where there was
No unit ventilator or where it was off, measuring 1118 and 1702 ppm,
respectively.

It is interesting to note that the average carbon dioxide levels in the
32 classrooms where the unit ventilators were operating still ex-
ceeded the ASHRAE guideline of 1000 ppm. This is not surprising
since the average carbon dioxide level in the unit ventilator air
supply in these 32 rooms is 933 ppm. These results are typical of
those found in many of the research schools, indicating that unit
ventilator outdoor air dampers are often closed, only bringing in
minimum outdoor air through leakage.

Current School Research Projects

AEERL currently has research projects in existing schools in Ken-
tucky, Maine, Ohio, and South Dakota, and projects were recently
completed in Colorado, Maryland, Virginia, and Washington State.
In addition to evaluating the regional applicability of ASD by
measuring PFE, these projects are typically designed to collect
continuous data on the effects of HVAC system operation on radon
levels to determine the conditions under which HVAC systems can.
be used to control radon levels. Data loggers are installed in selected
schools to continuously monitor parameters such as radon, differen-
tial pressure, HVAC system operation (e.g., amount of outdoor air
supplied), opening/closing of classroom-to-corridor doors, and
weather. Initial results indicate that HVAC system control of radon
levels is school (and sometimes room) specific.

The following subsections briefly discuss some results from a sample
of RMB school research projects. The details of these projects, along
with other RMB school research projects, will eventually be included
in an EPA report.

2
1.9
1.8
17
1.6
15
1.4
1.3
1.2
4

1
0.9
08
0.7
0.6
0.5
0.4
03
0.2
01

0

Litt yi

(Thousands)

Average Carbon Dioxide (ppm)

All rooms (67)

Rooms with UV on (32)

UV supply (32) Rooms with UV off (35)

Measurements in Seven Schools (# Rooms)

Figure 1. Average Carbon Dioxide Measurements in 67 Classrooms


Correction of Table in March 1991 Update

Please note that the “Time Door Closed” columns were reversed in the table in the March 1991 Update. Below is the corrected table.

Table 1. Average Radon Levels In Washington School During One Week

Normal Operation Test Operation
Average Radon Time Door Average Radon Time Door Subslab
Closed Closed Radon
Sniff, 8190

Location pCUL = (max) — (%) pCUL = (max) = (%) pCi
Room 139 26 (27) 76 12 qd?) 97 400
Room 140 53 (29) 4 32 (7) 92 500
Room 141 48 (32) 75 24 (25) 88 700
Average 42 (29) 75 22 (16) 92 533

Note that the classroom-to-hall doors had to be closed for the unit ventilators to reduce average radon levels to below
4 pCiL, although radon spikes (as high as 25 pCi/L) still occurred.

«1991 Innovative Radon Mitigation De-
sign Competition—RMB is providing
funding to the following participants in
the Innovative Design Competition
sponsored by EPA’s Office of Radia-
tion Programs and the Association of
Energy Engineers (AEE).

(a) Pacific Northwest Laboratories
(PNL)—1o study subslab sealing tech-
niques. Subslab sealing is proposed as a
novel new approach to radon preven-
tion and passive mitigation that is.appli-
cable to both new and existing build-
ings. PNL will conduct 2-D modeling
to facilitate experimental design and will
construct a bench-scale experimental
system to test various sealants includ-
ing epoxies, polyesters, polyurethanes,
and phenolics.

(b) Intermountain Radon Service—to
evaluate a solar fresh air ventilation
system for radon reduction in schools.
Two solar air collectors/heaters will be
constructed and installed in a western
U.S. school with elevated radon levels.
RMB will instrument the school for
radon and differential pressure moni-
toring. Studies will focus on evaluating
the solar collectors’ effectiveness at pro-
viding preheated outdoor air for school
ventilation and pressurization systems.

Research Notes

New Mexico Mitigation Field Testing—
Tracer gas measurements in six slab-
on-grade houses suggest that about 50%
(30-60%) of subslab depressurization
exhaust gas is air drawn from inside the
house. This is consistent with results
reported by other researchers. Fan power
measurements show that the 90-watt
mitigation fans, operated at full power,
are typically drawing 60-65 watts. This
will reduce EPA’s operating cost esti-
mates which assumed conservatively
that fans were operating at 90 watts.

ASD Exhaust Calculations—Model cal-
culations have been conducted to deter-
mine whether the installation of large
numbers of ASD systems in a commu-
nity might result in a significant raising
of the ambient radon level in the area.
Calculations show that for soil permea-
bilities below 2 x 10" m? (note that soil
permeabilities are normally presented
only in SI units) the increase in the total
radon emission rate is not significant
(less than 1%). Even for permeabilities
as large as 5 x 10'° m’, the total in-
crease in radon emission rate from a
mitigation system and its sphere of in-
fluence would probably not exceed 5%.
The increase in total emission rate is
‘small because the increase in emissions

6

is generally compensated for by a de-
crease in the rate of escape from the soil
surface,

*  Blockwall Research—Air entering
buildings through concrete block walls
can contain radon, moisture, biological
agents, and other contaminants that
threaten the health of the occupants and
the structure itself.

RMB studies of commercially available con-
crete blocks have demonstrated a variation
of over a factor of 50 in block air permeabili-
ties ranging from 0.63 to 35 standard liters
per minute/meter” at 0.012 inch WC (at 3
pascals). Additional studies have shown that
block wall air infiltration rates can be dra-
matically reduced by applying surface coat-
ings (see December 1990 Update).

Since the application of block coating may’
not always be practical and some coatings
may deteriorate over time, losing their effec-
tiveness, mitigators/designers may wish to
select blocks with lower air permeabilities as
part of a prevention strategy.

AEERL has developed an inexpensive test
procedure to assist in determining the rela-
tive air permeabilities of cement blocks. De-
tails will be provided in a subsequent Radon
Mitigation Update.


GEPA

Introduction

The Radon Mitigation Research Update is a
series of research summaries intended to pro-
vide information on EPA's Air and Energy
Engineering Research Laboratory (AEERL)
radon mitigation research programs. This up-
date is the third of the series and summarizes
recently completed or ongoing Radon Miti-
gation Branch (RMB) research activities fo-

Radon
Mike Osborne, Branch Chief,
(919) 541-4113
+ EPA radon mitigation research and devel-

opment program
* Planning/Management/Coordination

AB. “Chick” Craig, (919) 541-2824

* Senior Physical Scientist—Radon

+ Radon resistant large building construc-
tion

Tim Dyess, (919) 541-2802
« Radon resistant residential construction
+ Radon symposia

United States Oitice of Air and Energy Engineering
Environmental Protection Research and Research Laboratory
Agency Development Research Triangle Park, NC 27711

EPA/600/9-91/038/Nov. 1991

Radon Mitigation
Research Update

cused on achieving AEERL’s stated radon
mitigation research objectives. Research
projects summarized in this update are listed
in the table of contents below.

Radon Mitigation Research Updates pub-
lished in December 1990 and March 1991
provide summaries of AEERL’s radon miti-
gation research objectives and the RMB's
strategic research plan for meeting these ob-

be requested by writing RMB Research Up-
dates at the address below.

AEERL plans to publish subsequent updates
approximately two times a year. If you would
like more information about specific research
activities or programs, you may contact the
appropriate RMB project officer at MD-54,
U.S. EPA, AEERL, Research Triangle Park,
NC 27711, or at the number listed below.

jectives. Copies of these earlier Updates may

Mitigation Research Contacts

Bruce Harris, (919) 541-7807 John Ruppersberger, (919) 541-2432
+ Radon diagnostics and measurement tech- + Radon barriers and block permeability
nology + Safety issues
+ Durability of mitigation systems
David Sanchez, (919) 541-2979

Bruce Henschel, (919) 541-4112 * Florida Radon Research Program
* Radon mitigation in existing houses + Mechanisms of radon entry
* Cost studies

New Addition to RMB Team

Marc Menetrez, (919) 541-7981

+ Innovative and supporting research
* Radon reduction in attached housing

Kelly Leovic, (919) 541-7717

« Radon mitigation in schools

+ Radon Mitigation Research Update
Ron Mosley, (919) 541-7865

* Radon data analysis
* Radon modeling

U.S. Environmental Protection Agency

Region 5, Library (PL-12J)

77 West Jackson Boulevard, 12th Floor
60604-3590

Contents

Project Highlights csssesaseestsrsesetetststenenesseststneststntn wa
+ Radon Prevention in the Design and Construction of

Chicago, tte

Project Highlights

RMB project highlights are summaries of completed or ongoing
Tesearch projects intended to provide the radon mitigation industry
with timely and useful information. This information may be based
on regional or preliminary findings and should be viewed as such. As
research programs progress, RMB will publish details of its findings
as technical reports, manuals, and papers.

Large Buildings

+ Active Soll Depressurization Cost Analysts ++...
+ Innovative and Supporting Research .....
» Radon Mitigation Research in Schools ..

Radon Prevention in the Design and
Construction of Large Buildings
Based on research results over the past 3 years, RMB has begun

+ Research Notes
Recap of 1991 International Symposium

on Radon and Radon Reduction Technology .....ssssscessessessee7

incorporating radon control measures into the design and construc-
tion of new schools and other large buildings. The goal of the designs
is twofold: (1) to prevent elevated radon levels in the completed
building, and (2) to provide this protection at a fraction of the cost of

1992 International Symy m retrofit systems. A case study of one such installation is discussed
Announcement and Call For Papers sssssesesessesesssssssesesveeseessene 7 .

below, and a summary of the recommended radon prevention steps
Update of RMB Publications we erizammentat-Protec ranldgency

Region 5, Library (PL-12J) !
77 West Jackson Boulevard, 12th Floor

& Printed on Recycled Paper

Chicago, IL 60604-3590


Recap of 1991

International Symposium on

Radon and Radon Reduction Technology

The 1991 International Symposium on Radon and Radon Reduction
Technology, “A New Decade of Progress,” was held April 2-5, 1991,
in Philadelphia, Pennsylvania. The Symposium’s technical presenta-
tions and discussions were well received and provided an excellent
opportunity for the scientific and commercial communities to meet
and exchange research findings and ideas.

Over 400 people representing 15 countries attended this year’s
Symposium, which was sponsored by AEERL, EPA’s Office of
Radiation Programs (Radon Division), and the Conference of Radia-
tion Control Program Directors (CRCPD), Inc. Among those in
attendance were radiation control program directors of 33 states.

Tn all, 119 papers relating to state and federal government policies,
health effects, radon surveys, measurement methods, and mitigation
strategies were presented during the week. Included among them was
a Swedish paper that reported a 70% increase in the risk of cancer
among those subjects who lived in houses with more than 4 pCi/L of
radon.

A number of presenters added continued support/evidence for the
use of ASD for effective radon mitigation. Papers also addressed
pressurization and ventilation of buildings using HVAC systems to
prevent radon entry, finding it important for indoor air quality
purposes, though sometimes a less reliable and less effective method
for radon control.

Several presentations encouraged treatment of buildings as systems,
incorporating an approach which integrates radon mitigation, energy
conservation, and indoor air quality issues.

A total of 16 oral and poster presentations covering radon measure-
ment methods, radon mitigation methods, radon entry dynamics,
radon prevention in new construction, and radon in schools were
delivered by RMB Project Officers and contractors. A brief descrip-
tion of each paper was presented in the March 1991 Update.

Peer reviewed proceedings, available from the National Technical
Information Service (NTIS) in late 1991, are not available from any
other source at this time.

1992 International Symposium
Announcement and Call for Papers

The 1992 International Symposium on Ra-_ study results. However, theoretical discus-
sion of concepts and mechanisms will also

don and Radon Reduction Technology will
be held September 22-25, 1992, at the
Sheraton Park Place Hotel in Minneapolis,
Minnesota. [(800) 542-5566]

Call for Papers—Abstracts should convey
in 150 words or less the essence of the
intended paper, clearly indicating the contri-
bution it will make. Papers should provide

be considered.

Abstracts will be accepted through Novem-
ber 30, 1991, and should be submitted to:

Abstracts
c/o Timothy M. Dyess
U.S. Environmental Protection Agency

AEERL, MD-54

Research Triangle Park, NC 27711
Symposium Registration—To obtain a reg-
istration form, detach and retum the infor-
mation card on the last page of this Update.

Update of RMB Publications

All publications with NTIS numbers are available (prepaid) from the
National Technical Information Service, 5285 Port Royal Road,
Springfield, VA 22161 (phone 703/487-4650).

Reports:

Follow-Up Durability Measurements and Mitigation Performance
Improvement Tests in 38 Eastern Pennsylvania Houses Having

Indoor Radon Reduction Systems. D. B. Henschel (project officer),
EPA-600/8-91-010 (NTIS PB91-171389), March 1991.

Correlation of Florida Soil-Gas Permeabilities with Grain Size,
Moisture, and Porosity. D. Sanchez (project officer), EPA-600/8-91-
039 (NTIS PB91-211904), June 1991.

Feasibility and Approach for Mapping Radon Potentials in Florida.
D. Sanchez (project officer), EPA-600/8-91-046 (NTIS PB91-
217372), July 1991.

An Assessment of Soil-Gas Measurement Technologies. D. Sanchez
(project officer), EPA-600/8-9 1-050 (NTIS PB91 -219568), July 1991.
Parametric Analysis of the Installation and Operating Costs of Ac-
tive Soil Depressurization Systems for Residential Radon Mitiga-
tion. B. Henschel, EPA-600/8-91-200, October 1991.

Papers:

Cost and Effectiveness of Radon Resistant Features in New School
Buildings. A.B. Craig, K.W. Leovic, and D.W. Saum. Presented at
the American Society of Heating, Ventilating and Air-Conditioning
Engineers (ASHRAE) IAQ’91, Washington, DC, September 1991.

7

Design of New Schools and Other Large Buildings Which Are
Radon Resistant and Easy to Mitigate. A.B. Craig, K.W. Leovic, and
D.B. Harris. Presented at the Fifth International Symposium on the
Natural Radiation Environment, Salzburg, Austria, September 1991.
Modeling the Influence of Active Subslab Depressurization (ASD)
Systems on Airflows in Subslab Aggregate Beds. R. B. Mosley,
Presented at the Fifth International Symposium on the Natural Ra-
diation Environment, Salzburg, Austria, September 1991.

Cost Analysis of Soil Depressurization Techniques for Indoor Radon
Reduction, Indoor Air, September 1991.

Symposia Publications:
PROCEEDINGS: THE 1990 INTERNATIONAL SYMPOSIUM
ON RADON AND RADON REDUCTION TECHNOLOGY

Volume 1: Symposium Oral Papers (Sessions I - IV)
EPA-600/9-91-026a (NTIS PB91-234443), July 1991.

Volume 2; Symposium Oral Papers (Sessions V - IX)
EPA-600/9-91-026b (NTIS PB91-234450), July 1991.

Volume 3: Symposium Poster Papers
EPA-600/9-91-026c (NTIS PB91-234468), July 1991.

Manual Updates:

“Radon Resistant Construction Techniques for New Residential
Construction (Technical Guidance)”; M. C. Osbome (project offi-
cer), EPA-625/2-91-032, February 1991.

U.S. GOVERNMENT PRINTING OFFICE: 1991 - 648-003/40665


Case Study of Radon Prevention in Tennessee Hospital

A single-point active soil depressurization (ASD) system has suc-
cessfully depressurized under a 60,000 square foot (5580 square
meter) slab in a new Tennessee hospital for less than $0.10 per
square foot (or about $1.00 per square meter). In fact, the results
indicate that the system, as designed, would be able to depressurize a
much larger space. The incremental cost for the ASD system com-
pares favorably with a sample from eight northeast U. S. schools
where radon prevention systems were installed during construction.
In this sample, estimated installation costs ranged from about $0.30
to $1.00 per square foot (about $3.00 to $11.00 per square meter).
(Refer to Update of RMB Publications on page 7, “Cost and Effec-
tiveness of Radon Resistant Features in New School Buildings.”

The hospital was constructed in a radon-prone area where the soil is
highly impermeable. The building is post and beam construction,
with no subslab barriers to communication. The slab was poured
over a vapor barrier that was underlain with a continuous 4 inch (10
centimeter) layer of crushed aggregate. The slab, exterior walls, and
footings were poured monolithically, and no expansion joints were
used. This resulted in a relatively “tight” area between the soil and
the slab.

After RMB review of the building plans, the following recommenda-
tions were made to the architect for radon prevention purposes: 1)
good compaction of the clay layer under the aggregate, 2) minimum
of 4 inches (10 centimeters) of crushed aggregate (ASTM #5)
carefully placed so as not to include any fine-grained soil, 3) sealing
of all control saw and pour joints and slab penetrations with polyure-
thane caulking, 4) installation of a centrally located ASD system
with a suction pit, 6 inch (15 centimeter) diameter piping, and a
suction fan rated at 300 cubic feet per minute, cfm (141 liters per
second, L/s) at 1 inch water column, WC (248 pascals), and 5)

Summary of Recommended Radon Prevention Features

continuous operation of the heating, ventilating, and air-conditioning
(HVAC) fans to pressurize the building.

The incremental costs of these additional features were covered by
four change orders, and the total capital cost was $5,300. These costs
included installation of the suction pit and radon vent pipe to the
roof, sealing (as specified above), and installation of the suction fan
and failure-warning system. The aggregate was already specified in
the plans, and the HVAC system was intended to operate coritinu-
ously because of the hospital occupancy pattems.

Radon measurements were first made with both the ASD and HVAC
systems off, and radon levels as high as 50 pCi/L were measured.
‘The measurements were then repeated with the ASD system fan off
and the HVAC system on: the highest level measured was 16 pCi/L.
This indicates that, because of the radon source strength (measured
to be about 1800 pCi/L under the slab), continuous operation of the
HVAC system (which includes exhaust fans) did not reduce radon
levels below the current EPA guideline of 4 pCi/L. The final set of
measurements was made with both the ASD and HVAC systems
operating: all 30 rooms measured were below 0.5 pCi/L.

Pressure field extension measurements showed a negative pressure
of 0.45 inch WC (112 pascals) in the suction pit and 0.18 inch WC
(45 pascals) at the farthest comer of the building—185 feet (56
meters) away. Extrapolation of these data suggests that properly
designed and installed single point ASD systems can effectively
contro] radon levels in buildings with much larger footprints,

A more detailed description of these research findings is found in the
paper listed in the Update of RMB Publications on page 7, “Design
of New Schools and Other Large Buildings Which Are Radon
Resistant and Easy To Mitigate.”

Active Soil
Depressurization Cost

RMB research to date has shown the follow-
ing features to be most important in cost
effective radon prevention in the construc-
tion of schools and other large buildings:

1) Subslab Aggregate—A 4- to 6-inch
(10- to 15-centimeter) layer of clean,
coarse aggregate (ASTM #5 is preferred)
should be evenly placed under the slab
with care taken not to include any soil.

2) Barriers to Subslab Commupica-
tion—Interal barriers to subslab com-
munication—such as subslab walls—
should be avoided. If subslab walls must
be used, they should be minimized and
openings through them to all slab areas
should be included.

3) Suction Pit and Radon Vent Pipe—
The radon vent pipe should extend be-
neath the slab into a suction pit that is
open to the aggregate. The suction pit
should have an exposed aggregate sur-
face area of 5 to 7 square feet (about 0.5
to 0.7 square meter). Six inch diameter
polyvinyl chloride (PVC) vent pipes are
typically used.

4) Major Radon Entry Routes—Sealing
of major radon entry routes during con-
struction (such as utility penetrations

and expansion joints) will help to in-
crease ASD effectiveness.

5) Suction Fan—If elevated levels of ra-
don are measured in the building, a
suction fan should be attached to the
radon vent pipe outside the building.
Typical fans used in these installations
are rated at about 400 cfm (188 L/s) at 1
inch WC (248 pascals).

6) HVAC System—The HVAC system
should be designed and operated in ac-
cordance with ASHRAE Standard 62-
1989, “Ventilation for Acceptable In-
door Air Quality.” Proper operation of
the HVAC system will help to reduce
radon levels and maintain indoor air
quality through both pressurization and
dilution.

Note: Applications of the radon prevention

techniques above are currently being studied

in other buildings in the U.S. RMB is search-
ing for additional schools and other large
buildings where the effectiveness of these
features can be further evaluated. For more
information on the application of these fea-
tures in large footprint buildings being con-
structed in radon-prone areas, please contact
AB. Craig.

Analysis

Cost analyses of active soil depressurization
(ASD) systems suggest that low-cost mitiga-
tion technology other than ASD will be re-
quired if lung cancer deaths due to radon are
to be reduced by more than about 14 to 22%.
An in-house parametric cost analysis has
been completed to determine the importance
of various system design and operating vari-
ables on the installation and operating cost
of ASD systems in houses. The analysis
found a potential ASD installation savings
several times larger than the potential opera-
tions savings, indicating that innovative de-
sign research should be given a higher prior-
ity.

The analysis indicated that various modifica-
tions to ASD system designs offer potential
for reducing installation cost by up to several
hundred dollars but would not reduce total
installed cost much below $800 to $1000.
Reductions of this magnitude would prob-
ably not be sufficient to dramatically in-
crease voluntary use of ASD technology in
houses with premitigation levels below 4
pCi/L.

See Analysis, p.3.


Analysis, continued from p. 2

Since the only way to reduce annual lung about 14 to 22% is to motivate people with proach other than ASD would appear to be

cancer deaths due to radon by more than

houses at or below 4 pCyL to mitigate, some
innovative and inexpensive mitigation ap-

necessary.

Innovative and Supporting Research

AEERL’s Strategic Research Plan places in-
creased emphasis on Innovative and Sup-
porting Research (ISR) projects directed at
accelerating improvements in mitigation tech-
nologies, lowering the cost of these tech-
nologies, and facilitating their delivery to
larger and broader audiences. ISR projects/
concepts developed through bench or pilot
scale efforts which show promise will ulti-
mately be demonstrated in research build-
ings and the findings incorporated into tech-
nical guidance documents.

AEERL's ISR Work Group (headed by David
Sanchez and staffed by Bruce Harris, Tim
Dyess, Ron Mosley, John Ruppersberger,
and Marc Menetrez) has identified and se-
lected several projects for work plan devel-
opment and peer review. The projects to be
conducted by RMB personnel include:

Bench-Scale Task Area
Projects:

Testing of concrete for diffusive and convec-
tive radon transpor!—The objectives of this
study are to provide an initial analysis of the
permeability and the diffusivity of typical
Florida concrete and to relate these mea-
sured parameters to the physical properties
of the concrete. Tests will be conducted by
exposing various concretes to both pressur-
ized and static radon environments and mea-
suring radon transport through the materials.
Parameters to be evaluated include cement/
water ratios, types and amounts of sand,
cement, and aggregate used, and how the
concrete is mixed, poured, and finished.
Testing and evaluation of radon transport
blocking substrates—This project is designed
to evaluate and recommend one or more
subslab barrier materials which would limit
soil radon transport when used in innovative
building foundation preparations. The mate-
tials to be tested for radon retardation poten-
tial include numerous zeolites, Indian red
pottery clay, bentonite clay, synthetic silica,
and barium sulfate. Each material will be
exposed in radon test chambers and its radon
blocking capability and adsorption coeffi-
cient evaluated.

Testing and development of performance
curves for small fans—Many fans installed
in radon mitigation systems are being re-
quired to operate beyond the manufacturer’s

recommended range. This research effort will
evaluate the durability of a number of typi-
cally used small fans and develop perfor-
mance curves for each. A test procedure has
been established to measure the stator tem-
perature (a common cause of motor winding
failure is overheating) as a function of static
head against the fan. The data obtained will
be used to establish maximum operational
head settings for each fan.

Testing of atmospheric radon monitoring
equipment—Atmospheric levels of radon are
typically less than 1 pCi/L. However, atmo-
spheric levels can be higher and may need to
be evaluated as part of a radon mitigation
strategy. Phase one of this project will in-
clude identifying, calibrating, and bench test-
ing a field monitoring device which is ca-
pable of reliably measuring radon levels as
low as 0.1 pCi/L. Phase two will include
constructing an in-house test chamber and
protocols for evaluating this and other EPA
owned atmospheric monitoring devices.

Pilot-Scale Task Area
Projects:

Radon transport and entry studies—The long
term objective of this project is to acquire
fundamental knowledge of radon transport
and entry through pilot scale studies. A pilot
test unit will be designed and constructed
this year. Data resulting from subsequent
studies of radon transport through soils and
entry into building substructures will be used
to construct new and/or validate existing ra-
don transport and entry models.

Florida Radon Research Program—The

FRRP is a joint effort between the Florida

Department of Community Affairs and

AEERL, where AEERL consults and assists

in managing ongoing state-supported research

projects. The second year of the FRRP began

March 15, 1991, and covers radon research

in the following areas:

+ Development of a geological and litho-
logical data base and correlations of
such data with indoor radon for use in
radon potential mapping algorithms,

+ Completion of an 80-house short-term
and long-term indoor radon monitoring
study and development of statistical cor-
relations of short-term (24 hours) to
long-term (up to 1 year) indoor mea-

3

surements for selected monitoring de-
vices,

+ Provision of laboratory analyses and
the construction of a data base of (a) the
soil properties affecting the strength and
radon availability of soils, and (b) the
radiometric and radon transport proper-
ties of concrete and its aggregates.

+ Development of integrated research
house studies in three distinct geographic
(Florida) regions for the purpose of (a)
developing and validating radon con-
trol i and construction prac-
tices to (1) limit radon emanation, trans-
port, and availability at building sites,
(2) provide enhanced substructure ra-
don barriers, (3) provide guidance for
the design and operation of residential
central forced air heating and cooling
systems, and (4) provide guidance on
superstructure infiltration effects on ra-
don entry, and (b) developing an inte-
grated model and algorithm of the house
system for evaluation of the interactive
effects of (1) through (4) above on ra-
don entry and accumulation in resi-
dences.

Full-Scale Task Area Projects:

Determining the effects of the vertical distri-
bution of building shell openings on soil gas
driving forces—The objective of this project
is to determine the effect of leaks in building
envelopes on floor/slab level pressures under
given stack effect conditions. Research will
be carried out largely by EPA personnel in
an existing FRRP test house constructed on
radium-tich soils in Bartow, Florida. Data
will be collected for both heating and cool-
ing situations and will be used to construct
new and/or validate existing house dynamics
models.

Modeling of interior house dynamics—The
long-term objective of this project is to de-
velop and verify a simplified physical model
to predict radon concentrations in residences.
The model will be based on measurable/
estimatable parameters and is ultimately in-
tended to cover crawl space, slab-on-grade,
and basement houses.

Model variables will include convective soil-
gas entry, diffusion from soils and materials,
air infiltration, natural ventilation, and me-
chanical system dynamics.