United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/S8-88/087 Sept. 1988
SEPA Project Summary
Radon-Resistant Residential
New Construction
Michael C. Osborne
The purpose of this manual is to
provide builders and potential new
house buyers with a broader
selection and explanation of
techniques that are expected to be
effective in reducing the potential for
elevated radon levels in the house. In
addition, legislators, regulators, and
residential code writers may choose
to evaluate these radon-resistant
construction technologies for
potential application to or
modification of existing regulations
or codes applicable to residential
construction.
Three approaches to resolving the
radon problem in the construction of
new houses are to 1) prevent radon
entry by using barrier methods, 2)
reduce the radon entry driving
forces, and 3) divert the radon from
the house through sub-slab
ventilation. Radon entry routes of
concern in new construction are the
same as those that have previously
been identified for existing houses.
Figures provided in the report depict
the major radon entry routes for
simple basement, slab-on-grade,
and crawl-space houses.
Expensive control measures may
be justified if they serve multiple
purposes, such as combining radon
control with water control or
eliminating the need for constantly
operating a mechanical control
system through a high initial cost.
Sealing of obvious openings, a
moderate effort to maintain slab
integrity, and preparatory work for
sub-slab suction may be the most
cost-effective approach to radon-
resistant new construction.
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 documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Growing publicity about the dangers of
radon, a radioactive gas found in varying
amounts in all houses, has underscored
the need for dependable radon-resistant
residential construction techniques. In
recent years, the U.S. Environmental
Protection Agency (EPA) has developed
and demonstrated a variety of methods
that have been used to reduce radon
levels in existing houses. Many of these
methods should be easier and less
expensive to apply during construction
than after the house is built. One EPA
report,, Radon Reduction Techniques for
Detached Houses, gives details on
modifying existing houses. Another,
Radon Reduction in New Construction,
An Interim Guide, is based on experience
gained in mitigating radon problems in
existing houses.
The purpose of this manual is to
provide builders and potential new house
buyers with a broader selection and
explanation of techniques that are
expected to be effective in reducing the
potential for elevated radon levels in the
house. In addition, legislators, regulators,
and residential code writers may choose
to evaluate these radon-resistant
construction technologies for potential
application to or modification of existing
regulations or codes applicable to
residential construction.
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Adequate supporting data on the
effectiveness of the radon-resistant
construction techniques mentioned in
Sections 3 and 4 have NOT yet been
fully demonstrated in new houses;
therefore, readers should consider the
techniques identified in Sections 3 and 4
as only developmental and WOT as
proven technology for preventing radon
problems in new houses. The soil
ventilation techniques described in
Section 5 have good potential for
application in new construction based on
extensive testing in existing houses and
are, therefore, more strongly recom-
mended.
Builder Reaction
Already, many builders in widely
scattered sections of the country
recognize the word "radon" and have
some idea of what it is. Few, however,
have dealt with radon as a problem.
Fortunately, some homebuilders in
identified problem areas are, on their
own initiative, educating themselves
about the mechanisms of radon entry.
Traditional construction details
developed for such purposes as moisture
control, energy conservation, and
structural integrity are being evaluated
and modified to take radon control into
account in new house construction.
Some builders are keeping abreast of
research developments and are
intentionally modifying construction
practices, while others are waiting for
regulatory guidance and attempting to
limit liability with standard disclaimers.
Regulatory Influences
Factors that influence residential
construction practice in the United States
include: building codes, environmental
regulations, zoning ordinances, new
house warranty performance standards,
generally accepted standards and
technical recommendations emanating
from trade associations, and the standard
practices and cost competition typical
among builders within a given geo-
graphic area.
State-level government has the
constitutional power to regulate
residential construction practice unless
the state chooses to delegate that power
to local jurisdictions. Many states have
adopted residential building codes. In
some cases, these codes are presented
to municipalities as preemptive; in
others, the codes express minimum
standards open to only those local
amendments which increase their
restrictiveness. At the other end of the
spectrum, some states adopt building
codes that appear to serve as mere
suggestions, while others have no state-
level involvement in residential building
construction.
Local government has traditionally
been responsible for the administra-
tion and enforcement of zoning
ordinances. These ordinances may
dictate, among other things, drainage
requirements and construction practices
that may be applicable to specific
geographic subareas of the community
or to the municipality as a whole. Even in
states with preemptive, mandatory
building codes, municipalities may be
allowed to exercise some local autonomy
by designating "radon-prone" regions,
comparable to flood zones or other
environmentally sensitive areas.
National Variability of Standard
Construction Practice
Current interest in radon-resistant
construction is generally focussed on
large-scale projects, whereas a
considerable amount of residential
construction activity is dispersed among
small contractors. Differences in
residential construction details and
practices currently being used in various
regions of the country may have resulted
from on-the-job training as much as
from formal regulations or written
guidelines.
Regional construction practice and
locally available materials have an
important influence on residential
construction. Florida, for example,
constructs few houses with basements
due to its high water table. Gravel or
crushed stone is not available in most
areas of Florida for use as a sub-slab
aggregate; therefore, sand is used
instead. Both of these construction
features affect radon entry into typical
Florida houses and limit mitigation
options. In Texas it is reported that
expansive soils make aggregate beneath
the slab undesirable because of potential
water problems.
Identification of Radon-Prone
Sites
Although radon in water and radon
emissions from building materials do
account for a minor share of the radon
problems found in the United States, the
overwhelming majority of residential
radon problems occur from radon
emanating from the soil. The radon gas
found in soils is a product of the decay of
uranium-226, a radioactive chemical
element that is ubiquitous in nature and
present in trace levels in most soils and
in many types of rock. Uranium decays
through a chain of radioactive elements,
releasing radioactive particles and
electromagnetic radiation in the process.
Each element in the chain is a solid
except radon-222 (radon), which is a
gas. The amount of radon gas that enters
the house is a function of how much
radon gas or radon parent compounds
are found in the soil beneath the house,
the permeability of the soil, the presence
of faults and fissures in underlying and
nearby rock, openings between the
house and soil, and the driving forces
that move soil gas (containing radon)
along these pathways into the house. To
have a radon problem requires radium
nearby, a pathway for the gas to move
through the soil or rock, a driving force,
and openings in the foundation.
In the siting of new residential
construction, builders would like to be
able to predict the potential for radon
problems associated with each building
site. Unfortunately, at present there are
no reliable methods for correlating the
results of radon soil tests at a building
site with subsequent indoor radon levels
in a house built on that site. Houses vary
significantly in their ability to resist radon
entry. This is true even among houses
where controlling radon entry was not
considered during construction.
Radon-Resistant Construction
Techniques
Three approaches to resolving the
radon problem in the construction of new
houses are to 1) prevent radon entry by
using barrier methods, 2) reduce the
radon entry driving forces, and 3) diven
the radon from the house through sub-
slab ventilation. Section 3 addresses the
barrier approach.
Radon entry routes of concern in nev
construction are the same as those tha
have previously been identified foi
existing houses. Figures provided in the
report depict the major radon entn
routes for simple basement, slab-on
grade, and crawl-space houses, House:
that are combinations of the abovi
substructures often provide additione
entry routes at the interface between tru
two substructures. Section 3 of the repoi
addresses each of the potential rado
entry routes and suggests alternativ
radon-resistant construction technique
relative to the specific entry routes
Sometimes these alternatives includ
barriers that can be used to block rado
entry while continuing to use th
traditional construction methods; other
may require significant alternativ
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construction methods that avoid creating
the potential radon entry route.
When possible, comments on specific
radon-resistant construction techniques
have been obtained from builders
claiming to build radon-resistant
houses. Builders providing input to the
report are identified in Appendix A. Also,
building material average retail prices are
quoted when available. These prices are
always in 1988 dollars. THE EPA DOES
NOT ENDORSE ANY OF THE
COMPANIES OR PRODUCTS REFER-
ENCED IN THE REPORT.
Cost of Radon-Resistant
Construction
The costs of many radon-resistant
construction materials and practices have
been presented throughout the text. In
some cases, however, the substitution of
a radon-resistant material involves a
change in application procedure that
makes cost difficult to estimate. For
example, the labor and cost of parging
may be deducted when a waterproof
membrane is used on a masonry wall;
however, most masons do not break out
the cost of parging when they quote
prices on building a wall.
Homebuilders are mindful of the final
cost of their product as they evaluate
new materials and techniques.
Innovations that can be shown to reduce
labor or material cost gain easier
acceptance than those that increase cost.
Changes that will increase the final cost
of the house must be justified on the
basis of increased consumer appeal or
decreased liability. Construction
practices vary according to the market
for which the house is intended.
Energy-conserving housing insulated
beyond code requirements could be sold
at a premium because of projected
savings in operating costs. Radon-
resistant construction techniques may
evolve to fit market slots as well.
Standard houses might be set up for
active mitigation if radon levels dictate
the need, while passive designs requiring
more expensive preparation may be
reserved for custom and luxury houses.
Expensive control measures may be
justified if they serve multiple purposes,
such as combining radon control with
water control or eliminating the need for
constantly operating a mechanical
control system through a high initial cost.
Unless barrier systems can achieve
passive radon control when installed by
commercial enterprises as well as
research teams, then the value of
investing in the relatively expensive
materials necessary for this approach is
questionable. It may be that perfect
barriers are impossible and imperfect
barriers are ineffective. If that is the case,
then sealing of obvious openings, a
moderate effort to maintain slab integrity,
and preparatory work for sub-slab
suction may be the most cost-effective
approach to radon-resistant new
construction.
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Michael C. Osborne (also the EPA Project Officer) is with the Air and Energy
Engineering Research Laboratory, Research Triangle Park, NC 27711.
The complete report, entitled "Radon-Resistant Residential New
Construction," will be available only from:
ORD Publications
USEPA - CERI
26 W. Martin Luther King Drive
Cincinnati, OH 45268
Telephone: 513-569-7562
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
Official Business
Penalty for Private Use $300
EPA/600/S8-88/087
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