United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S8-90/072 Dec. 1990
& EPA Project Summary
Summary of EPA's Radon
Reduction Research in Schools
During 1989-90
Kelly W. Leovic
This report details EPA's radon miti-
gation research in schools during 1989
and part of 1990. The major objective
was to evaluate the potential of active
subslab depressurization (ASD) in vari-
ous geologic and climatic regions. The
different geographic regions also pre-
sented a variety of construction types
and heating, ventilating, and air-condi-
tioning (HVAC) system designs that are
encountered in radon mitigation of
school buildings. A secondary objective
was to initiate research in difficult-to-
mitigate schools. Depending on the
school, various levels of diagnostics
and mitigation were performed in the
schools discussed in the report.
In the Maryland, New York, and two of
the Tennessee schools, the mitigation
systems were generally installed by the
joint efforts of the EPA Contractor, EPA
personnel, and school personnel fol-
lowing diagnostics and mitigation sys-
tem design by EPA and/or its contractor.
In the Alabama schools and in four of the
Tennessee schools, recommended
mitigation system designs were provided
to the schools for installation by school
personnel. This report is organized into
sections by state, and each of the 13
schools is discussed separately.
This research led to the following ma-
jor conclusions on radon diagnostics
and mitigation in schools: (1) Schools
have many physical characteristics that
typically make their mitigation more
complex than house mitigation. These
characteristics—which can influence
radon levels in the building since they
affect radon entry routes, building pres-
sure differentials, and radon mitigation
approach—include building size and
substructure, subslab barriers, HVAC
systems, and locations of utility lines.
(2) Important school diagnostic proce-
dures and measurements include re-
view of radon measurements and build-
ing plans, investigation of the building
to assess potential radon entry routes
and confirm information in the building
plans, analysis of the HVAC system and
its influence on pressure differentials
and radon levels, and measurement of
subslab pressure field extension to de-
termine the potential applicability of
ASD. (3) ASD can be applied success-
fully in schools where the slab is under-
lain with a clean coarse layer of aggre-
gate if subslab communication barriers
are limited. (4) If all block walls sur-
rounding the classrooms extend to foot-
ings that create subslab barriers, a mini-
mum of one ASD point for every two
rooms will probably be necessary.
ccccplf the walls between rooms are
thickened slab footings, rather than be-
low-grade wails, ASD from one point wil I
extend underthe thickened slab If aggre-
gate is continuous. (5) ASD systems in
schools typically require greater fan ca-
pacities and suction pipe diametersthan
those in houses.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that Is fully docu-
mented In a separate report of the same
title (see Project Report ordering Infor-
mation at back).
OyD Printed on Recycled Paper
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Introduction
The U.S. EPA initially became involved
with the radon problem in schools by as-
sisting three counties in Maryland and Vir-
ginia !n reducing elevated levels of radon in
1988. Active subslab depressurization
(ASD)—a technique which had been dem-
onstrated successfully in existing
houses—was modified and installed in these
schools. Where design permitted, heating,
ventilating, and air-conditioning (HVAC)
systems were also used to pressurize some
of the school buildings to control radon
levels prior to installing the ASD system.
These initial efforts are detailed as case
studies in an earlier document.
In 1989 and early 1990, EPA's Radon
Reduction Research/Development/Dem-
onstration Program in schools was ex-
panded to include projects in Alabama, New
York, and Tennessee, and research in some
of the Maryland schools continued. The
major objective of this research was to
apply ASD In varied geologic and climatic
regions. The different geographic regions
also presented a range of construction types
and HVAC system designs. A secondary
objective was to initiate research efforts in
difficult-to-mitigate schools. Three schools
that had been identified in the initial re-
search efforts in Maryland in 1988 were
selected for additional research. Charac-
teristics addressed included schools with
very poor subslab communication (limiting
the application of ASD), schools with return-
air ductwork located under the slab, schools
with utility tunnels, and schools constructed
over crawl spaces.
Three schools in Alabama, three in Mary-
land, one in New York, and six in Tennes-
see were selected for these research
projects. Depending onthe objectives of the
project, various levels of diagnostics and
mitigation were performed in the different
schools. In the Maryland, New York, and
two Tennessee schools, the mitigation
systems weregenerally installed bythe joint
efforts of the EPA Contractor, EPA per-
sonnel, and school personnel following di-
agnostics and mitigation system design
by EPA personnel and/ortheircontractor. In
the Alabama schools and in four of the
Tennessee schools, mitigation system de-
signs were provided to the schools based
on diagnostic measurements. System in-
stallation was up to the school personnel.
The diagnostics and mitigation for each
of the 13 schools are discussed separately
and organized into sections by state. As
applicable, discussion of each school is
organized into 13 sub-sections: (1) Back-
ground Information, (2) Building Descrip-
tion, (3) Pre-Mitigation Radon Measure-
ments, (4) Building Investigation, (5) HVAC
System, (6) Diagnostic Measurements, (7)
Mitigation Strategy, (8) ASD System De-
tails, (9) Results of Initial Mitigation System,
(10) Additional Phases of Diagnostics/Miti-
gation, (11) Final Radon Levels, (12) Esti-
mated Cost, and (13) Summary. The state
and general location of each school are
provided in the report.
Diagnostic Measurement
Techniques
School buildings have a number of
physical characteristics that make them dif-
ferent, and typically more complex, than
residential houses. These characteristics
include building size, substructure, subslab
barriers, HVAC system design and opera-
tion, and locations of utility lines. These
physical characteristics can influence ra-
don levels in the building since they affect
radon entry routes, building pressure dif-
ferentials, and radon mitigation approach.
The radon diagnostic procedures and
measurements for the schools discussed in
this report generally included: a review of all
radon screening and confirmatory mea-
surements; a review of all available building
plans and specifications including struc-
tural, mechanical, and electrical; a thor-
ough building investigation to assess po-
tential radon entry routes and to confirm and
to supplement information cited in the
building plans; an analysis of the HVAC
system design and operation and its influ-
ence on pressure differentials and radon
levels; measurement of subslab radon lev-
els; and measurement of subslab Pressure
Field Extension (PFE) to assess the potential
for ASD. Depending on the objectives of
each project, varying levels of diagnostics
were performed in the schools discussed.
Summary and Conclusions
The radon diagnostics and mitigation
conducted in 13 schools; in Alabama, Mary-
land, New York, and Tennessee, led to the
following conclusions on radon diagnostics
and mitigation in schools: (1) School build-
ings have a number of physical character-
istics that make their mitigation different,
and typically more complex, than houses.
These characteristics include: building size
and substructure, subslab barriers, HVAC
systems, and locations of utility lines. These
physical characteristics can influence radon
levels in the building since they affect radon
entry routes, building pressure differentials,
and radon mitigation approach. (2) Radon
measurements in schools can vary dramati-
cally over time (seasonally and diurnally),
and this variation must be considered when
conducting radon diagnostics and design-
ing mitigation systems. (3) Radon mitiga-
tion research in schools has shown that the
following diagnostics procedures and mea-
surements are important in understanding a
school's radon problem and potential solu-
tion: review of radon measurements; review
of building plans including structural, me-
chanical, plumbing, and electrical; investi-
gation of the school building to assess po-
tential radon entry routes and confirm in-
formation cited in the building plans; analy-
sis of the HVAC system and its influence on
pressure differentials and radon levels; and
performance of subslab PFE measure-
ments. (4) ASD can be applied successfully
in schools where the slab is underlain with
a clean coarse layer of aggregate of narrow
particle size range as long as subslab bar-
riers to communication are limited. (5) ASD
in schools typically requires greater fan
capacities and suction pipe diameters than
does ASD in houses. The capacities of the
fans used (or recommended) in these
schools were typically around 310 dm (at
0.75 in. WC)* compared to capacities of
about 150 dm (at 0.75 in. WC) for fans
commonly installed in house ASD systems.
In schools where the slab was underlain
with at least a 4 in. layer of clean, coarse
aggregate enhancing subslab air fbw, fan
capacities of about 470 of m (at 0.75 in. WC)
were often installed. Suction pipe diameters
used (or recommended) in these ASD
systems were typically 4 in. or greater,
compared to 4 in. or less in typical house
ASD systems. (6) If all block walls sur-
rounding the classrooms extend to footings
that create subslab barriers (or compart-
ments), it is necessary to have one ASD
point for every two rooms and, in many
cases, one point for each room. If the walls
between rooms are set on thickened slab
footings rather than on below-grade walls,
ASD from one point will extend under the
thickened slab especially if the aggregate is
continuous underneath. PFE measurements
will provide essential data on the nature and
extent of subsfab barriers and implications
for ASD system design. (7) In general, the
correlation between classroom radon con-
centrations and subslab radon "sniffs" was
not particularly good. (8) Most of the schools
studied so far include slab-on-grade sub-
structures, although portions of some of the
schools had basements and/or crawl
spaces. (9) HVAC systems in the schools
studied so far include unit ventilators, fan
coil units, radiant heat, and central-air han-
dling systems. Many of the schools are not
designed to deliver conditioned outdoor air
to the occupied space. As a result, radon
* For readers more familiar with metric units: 1 cfm >
0.00047 m'/s; 1.0 in. WC - 248.8 Pa; and 1 in..
2.54cm.
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control using the existing HVAC system
was often not a mitigation option. Increas-
ing the outdoor air supply in schools could
reduce the driving force for radon entry.
(10)The utility lines of many slab-on-grado
schools are in subslab utility tunnels. It may
be possible to reduce radon levels by de-
pressurizing these tunnels; however, many
of them contain asbestos, limiting the feasi-
bility of this approach.
U. S. GOVERNMENT PRINTING OFFICE: 1991/548-028/20159
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Kelly W. Leovlc (also the EPA Project Officer, see below) is with Air and Energy
Engineering Research Laboratory, Research Triangle Park, NC 27711.
The complete report, entitled "Summary ofEPA's Radon Reduction Research in
Schools During 1989-90," (Order No. PB91-102 038/AS; Cost: $39.00, 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 Officer 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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EPA/600/S8-90/072
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