United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park^ NC 27711
Research and Development
EPA/600/SR-93/225 February 1994
EPA Project Summary
Case Studies of Radon
Reduction Research in
13 School Buildings
Bobby E. Pyle and Ashley D. Williamson
This report details 13 case studies
covering radon mitigation research in
school buildings from 1990 to 1992.
The 13 schools are in Colorado, Maine,
Minnesota, Ohio, South Dakota, Ten-
nessee, and Washington state. Diag-
nostics were carried out in all of these
schools, and suggested mitigation
plans were developed for each based
on the diagnostic measurements. Miti-
gation systems were installed in 5 of
the 13 schools as part of the research
project.
The major objective of these research
projects was to better understand the
conditions under which heating, venti-
lating, and air-conditioning (HVAC) sys-
tems in existing school buildings could
be used for effective radon reduction.
Criteria used to evaluate system effec-
tiveness included: radon reduction;
long-term reliability of operation; instal-
lation, maintenance, and operating
costs; and impact on the indoor air
quality in the school. An additional ob-
jective, studied in three of the schools,
was to compare the effectiveness of
HVAC system control of radon with ac-
tive subslab depressurization control
in the same building.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Tri-
angle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
The purpose of the Environmental Pro-
tection Agency's (EPA's) Air and Energy
Engineering Research Laboratory's
(AEERL's) school radon research program
is to develop and demonstrate low-cost
radon mitigation options for existing and
new schools and other large buildings.
These mitigation options must address the
unique features of these structures (i.e.,
large size, different types of heating, ven-
tilating, and air-conditioning (HVAC) sys-
tems, and varying occupancy patterns)
because these features can affect radon
entry routes and building pressure differ-
entials.
Since 1988 AEERL's Radon Mitigation
Branch has conducted radon mitigation
research in 50 school buildings in 13
states. Initially, AEERL's radon mitigation
research in schools focussed on active
subslab depressurization (ASD), the most
successful radon control technique in resi-
dential houses. Because of complicated
subslab structures and subslab fill mate-
rial that sometimes make ASD systems
expensive to install in large buildings, and
because of indoor air quality concerns,
AEERL has concentrated part of its re-
cent research efforts in schools on the
use of HVAC systems for radon reduc-
tion. Using the HVAC system to control
radon can be beneficial in schools where
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ASD is not applicable, and can also be
used as a supplemental radon reduction
technique in schools where ASD systems
are installed to further reduce radon lev-
els. In addition, the HVAC system can
also provide improved indoor air quality in
addition to radon reduction through the
introduction of additional outdoor air.
This report details case studies of ra-
don mitigation research in 13 school build-
ings. The research was conducted by
AEERL's Radon Mitigation Branch from
1990 to 1992. The 13 schools are in
Colorado (two), Maine (two), Minnesota
(one), Ohio (four), South Dakota (one),
Tennessee (one), and Washington state
(two). The schools were selected based
on a number of parameters including ra-
don levels, type of HVAC system, building
substructure type, and location. Measure-
ments to diagnose the radon problem were'
made in all of these schools, and sug-
gested mitigation plans were developed
based on the diagnostic measurements.
Mitigation systems were then installed in
5 of the 13 schools as part of the re-
search. In addition, continuous
dataloggers were installed in a number of
the schools to monitor several parameters
simultaneously.
Objectives
The major objective of this research'
was to better understand the conditions
under which HVAC systems in existing
school buildings can be used for effective
radon reduction. Use of the HVAC sys-
tem as a radon control technique depends
on the specific building, but in general, it
may be considered in any school that has
a HVAC system that supplies outdoor air.
However, restrictions on the use of the
existing HVAC system may apply where
the HVAC system does not consistently
supply outdoor air during all seasons, and
radon control/indoor air quality concerns
in the school system are overridden by
energy cost concerns. The criteria used
to evaluate the HVAC system's effective-
ness for radon control included: degree of
radon reduction; long-term reliability of
operation; installation, maintenance, and
operating costs; and impact on the indoor
air quality in the school.
An additional objective, studied in three
of the schools, was to compare the effec-
tiveness of HVAC system control of radon
with ASD control in the same building.
The objective was addressed because
school facility managers may sometimes
be faced with a decision to use either
ASD, HVAC control, or a combination of
the two techniques for radon reduction.
This report also presents results from
the first wide scale use of continuous
dataloggers to study the interactions of
various radon mitigation systems with
school operation and use. Dataloggers
were installed in seven of these research
schools to continuously monitor relevant
parameters including: radon concentration,
differential pressure, differential tempera-
ture, percent open of outdoor air damper,
operation of exhaust fans, opening and
closing of doors in the building, and car-
bon dioxide levels.
Radon Diagnostic
Measurements
The radon diagnostic procedures used
in the schools discussed in this report
include: a review of all radon screening
and confirmatory measurements; a review
of all available building plans and specifi-
cations including structural; mechanical,
and electrical; a thorough building investi-
gation to assess potential radon entry
routes and to confirm and supplement in-
formation cited in the building plans; an
analysis of the HVAC system design and
operation and its influence on pressure
differentials and radon levels; and mea-
surements of pressure field extension
(PFE) to assess the potential of an ASD
system. Depending on the objectives of
each project, varying levels of diagnostics
were performed in the 13 schools dis-
cussed in this report.
Conclusions
Several conclusions can be drawn from
the radon mitigation research in schools
conducted in the case studies discussed
in this report:
• If PFE measurements indicate that
an ASD system will be effective, this
would be the preferred system for
consistent, trouble-free,, and economi-
cal radon control.
• If in addition, improvement in indoor
air quality or further radon reduction
is desired, the amount of outdoor air
supplied through the HVAC system
should be increased. Increasing the
amount of outdoor air will help to ap-
proach the long-term national goal of
ambient radon levels in buildings es-
tablished in the 1988 Indoor Radon
Abatement Act.
• Some existing central HVAC systems
are not designed to supply conditioned
outdoor air and hence are not suit-
able for use as year-round radon miti-
gation systems because of energy
cost and/or comfort concerns.
• Since it appears that unit ventilators
(UVs) reduce radon levels more by
dilution than by preventing radon en-
try, their successful use as mitigation
systems is generally restricted to build-
- ings with initial levels in the 4 to--1-0-
pCi/L of air range.
• For schools constructed over crawl
spaces with exposed soil, the most
successful mitigation system is a
variation of ASD—submembrane de-
pressurization—which depressurizes
the area under a plastic membrane
covering the soil. Crawl space de-
pressurization was also effective in
reducing radon levels in the building;
however, this technique increased ra-
don levels in the crawl space.
• Where central HVAC or UV systems
are used for radon mitigation, careful
attention must be given to the opera-
tion of these units in setback mode at
night and over the weekend. They
must be turned on early enough to
lower the radon levels before the
building is occupied. In some of the
research schools, HVAC system start-
up at 7 am did not reduce the radon
levels to below 4 pCi/L limits until
after 12 noon.
• Carbon dioxide levels (an indicator of
indoor air quality) were well above
the American Society of Heating, Re-
frigeration, and Air Conditioning
Engineer's (ASHRAE's) guidelines of
10OOppm in most of the schools where
levels were measured. Typical car-
bon dioxide levels during school oc-
cupancy averaged from 1000 ppm
to 1700 ppm.
£l).S. GOVERNMENT PRINTING OFFICE: MM - S50-M7/80ZOO
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B. Pyle and A. Williamson are with Southern Research Institute, P.O. Box 55305,
Birmingham, AL 35255-5305.
Kelly W. Leovlc is the EPA Project Officer (see below).
The complete report, entitled "Case Studies of Radon Reduction Research in 13
School Buildings, "(Order No. PB94-130010/AS; Cost: $36.50; subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Off her can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
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