Resource Information on Radon
& Radon-Resistant Construction
This resource guide was prepared
to provide architects, builders, code
officials, contractors and other bi ild-
ing professionals with general and
technical information on radon ,md
radon-resistant construction.
Radon's proven link to lung
cancer, combined with its prevalence
throughout the United States, has
increased public demand recently for
radon-free home environments.
In turn, consumers are seeking
building professionals for advice and
expertise in dealing with radon und
radon-protection systems.
Radon is a known human carcin-
ogen, and the nation's second
leading cause of lung cancer after.
smoking. It is believed responsible
for some 15,000 deaths every your.
This colorless, odorless radio-
active gas occurs from the natjral
breakdown of uranium found in soil
and rocks, and can seep into hones
through foundation cracks and other
openings.
Scientists estimate that nearly
one of every 15 homes in the nation
has elevated indoor radon levels. In
addition, mapping studies suggest
that more than one-third of all U.S.
counties are potentially at risk for
high indoor radon readings.
Radon's carcinogenicity and the
need for protecting home dwel.ers
from its health risks have baen
recognized by scores of scientific,
medical, government and consumer
groups, including the U.S. Surgoon
General, Consumer Federation of
America, National Medical Associa-
tion, American Lung Association,
National Association of Counties,
Environmental Law Institute, and the
National Safety Counca.
Nation* Problem
The dangers of radon were first
publicized in the early 1980s, wtten
extremely high indoor levels were
found in parts of Pennsylvania, New
Jersey and New York.
By 1988, Congress had passed
the indoor Radon Abatement Act,
which called for efforts to eventually
ensure that indoor building air would
be made "as free of radon as the
ambient air outside of buildings."
Cooperative Effort
Since that time, hundreds of
experts in both the public and private
sectors have worked to lay the
groundwork for a radon-protected
housing stock in the United States.
Several of these advances will
have a long-lasting impact on the
U.S. housing industry and its allied
professions:
•The Environmental Protection
Agency (EPA) and the U.S. Geo-
logical Survey have developed
extensive maps and information
outlining the potential radon levels of
every county in the nation.
•Recognized health and medical
institutions in the U.S. and abroad
have carried out additional studies of
radon to develop more accurate
knowledge of "how" radon induces
lung cancer and to develop updated
risk assessments.
•Commercial testing laboratories,
in cooperation with government and
research organizations, have devel-
oped improved testing devices and
monitoring methods.
•Radon offices have been estab-
lished in every state to provide
consumers, as well as building
professionals, with general and local
information on radon and radon-
resistant construction techniques.
•Model radon-resistant building
standards, methods and techniques
have been developed and/or adopt-
ed for use by the EPA, the National
Association of Home Builders, the
American Society for Testing and
Materials, the Council of American
Building Officials, and many others.
•State and federal certification
programs have been developed to
ensure that contractors providing
radon testing and radon reduction
for existing homes have the
necessary knowledge and expertise
to carry out radon work competently.
•State and local officials have
begun to adopt a variety of radon-
protection laws, including radon
testing for all residential real estate
transactions, mandatory radon test-
ing of schools and the adoption of
radon-resistant building codes.
All of the above subjects and
more are discussed in greater detail
on the following pages.
INSIDE
**»
Radon Zone Map
and discussion of zone
classifications 2
Radon and Cancer,
a look at the radioactive
decay process 3
Building Methods
for radon-resistant
construction 4
Testing Procedures
and how to best obtain
reliable results 6
Radon Legislation,
a quick review of laws
regarding radon 7
StateRadon Offices
for obtaining local help
and information 8
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EPA Maps, Studies Offer In-Depth Radon Data
Because it is impossible to know
in advance if a building site will
produce hfgn radon readings, EPA
radon maps and their accompanying
studies provide excellent predictive
information and guidance for build-
ing professionals.
In the late 1980s, Congress
directed EPA to identify areas of the
United States with the potential for
producing elevated levels of radon.
In response, the EPA, U.S. Geo-
logical Survey and the Association of
American State Geologists began
developing a detailed map that
would target those areas of the
country with the potential for
elevated indoor radon levels.
The result, known simply as the
Map of Radon Zones, classifies the
radon potential of all 3,141 counties
in the United Slates.
To foster lay interpretation of the
underlying technical data, counties
were given one of three possible
ratings: Zone 1, Zone 2, or Zone 3.
Zone 1 counties have the highest
potential for elevated radon levels,
with predicted indoor readings that
match or exceed the lake action"
level of 4.0 picocuries per liter of air
(pCM).
By comparison, Zone 2 areas
have predicted readings of 2.0 to 4.0
pCl/l. Zone 3 areas have the lowest
potential for elevated radon, with
predicted indoor readings of 2.0
pCly) or less.
Generally speaking, the bulk of
the nation's Zone 1 counties are
found in the northern half of the
United States, in a broad arc that
begins in the Northeast and moves
down along the Appalachians,
spreads across the Central and
Northern Plains, and sweeps up the
RocWes to the Canadian border.
Each county's zone designation
was determined by in-depth analysis
of the region's geology, aerial
radioactivity, soil parameters, sample
indoor radon measurements, and
foundation types.
While the Map of Radon Zones is
a targeting tool for characterizing an
An EPA map breaks the nation's 3,141 counties into radon zones. Zone 1 areas have
predicted potential radon levels of 4.0 picocuries per liter of air (pCi/l) or greater. Zone 2
predicted readings are between 2.0 and 4.0pCi/l. Zone 3 readings are predicted at 2.0 or less.
area's likely radon potential, it should
never be considered a verification
document; only in-structure testing
can accurately provide indoor radon
measurements.
Instead, it is designed for use by
building professionals as a starting
point for gaining general knowledge
of an area's radon potential, after
which a state-specific radon zone
map and its accompanying booklet
should be studied.
Even then, it is important to
remember that in order to give a
county a specific zone classification,
data has to be extrapolated from a
geological area to the often artificial
boundaries of a county.
In the process, significant highs
and lews within a county may be
masked. In addition, "hot spots" can
and do occur in any zone, and radon
readings can vary dramatically from
one home to the next in the same
neighborhood.
Because of the vagaries of accu-
rately predicting indoor radon levels,
building professionals may wish to
install a radon-reduction system as
"basic health insurance" for a home,
regardless of the area's radon zone
classification.
To the iaft are details of bedrock and
soil-type maps from the Vermont study
document for EPA's map of radon
zones. Similar in-depth, radon zone
study documents are available for
every slate.
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; =•
Area's Geologly
Is Key Factor i
In Radon Levels
Certain Rock, Soil Types
Likely Radon Candidates
Because radon is a byproduct of
uranium, the geology of an area's
rock and soil can prove invaluable in
predicting the potential for elevated
indoor radon levels. ':
Although such variables as soil
permeability, moisture, barometric
pressure and temperature can
significantly affect radon concentra-
tions, certain rock types are more
likely to cause elevated indoor radon
readings.
Rock types likely to be associated
with elevated radon readings include
the carbonaceous black shales,
glauconite-bearing sandstones* and
certain fluvial sandstones, chalk,
phosphorites, and karst-prodi icing
carbonate rocks. ':
Certain glacial deposits, bauxite,
uranium-rich granite, metamcrphic
granite, silica-rich volcanic rbcks,
some coals and contact meUimor-
phosed rocks, as well as numerous
types of sheared or faulted Pocks
should also be included as likely
candidates. '
Of special note are fault and sheer
zones associated with localized
uranium concentrations. To date, the
highest known indoor radon levels
have been found in Boyertown, Pa.,
and Clinton, N.J. - sites of sheared
fault zones with localized uranium
concentrations.
Geologists say that the rocks least
likely to cause radon problems
include marine quartz sands, non-
carbonaceous shales and siltstones,
certain days, silica-poor metamcrphic
and igneous rocks, and basalts.
Localized uranium deposits in any
of these rocks, however, significantly
increases the probability of elevated
radon readings.
Thorium 234
Uranium 238
Protactinium 234
Uranium 234
The uranium-238 decay series
and their modes of decay.
Radioactive Decay Process Defines
Nature of Radon's Carcinogenicity
Radon-Resistant Ceasti-aetiion;
Tecbniqw for the
Within the world's scientific and
medical communities, the link
between radon and lung cancer is
well understood.
But for most people, the thought
of an invisible gas bringing cancer
into their home has a hard-to-believe
science-fiction quality to it.
Unfortunately, radon's health risks
are all too real. Radon gas is a Class
A carcinogen, accounting for an
estimated 15,000 deaths every year.
A recent study released by the
National Cancer Institute now pegs
one in every ten lung cancers to
indoor radon exposure.
How does radon gas trigger lung
cancer, and why is it most commonly
found in the home? The answers
begin with an understanding of
radon's role in the radioactive decay
of uranium.
Radon's genesis is uranium, and
uranium is ubiquitous to the earth's
soil and rock. As uranium begins its
natural radioactive decay, it produces
thorium, which in turn produces
radium. . .
Radium then decays into radon.
Unlike thorium and radium, which are
solids that remain in the earth, radon
is a gas that moves up through soil
and rock to areas of lower pressure.
When radon gas reaches the
atmosphere unimpeded, it diffuses
quickly and harmlessly into the
outdoor air.
But when radon's escape from
soil or rock is impeded by a building,
it frequently seeps into that
structure, usually through small
foundation cracks and openings,
where it remains unless diverted by
some means to the outside.
Once inside a building, radon's
radioactive decay continues in the
form of microscopic solids or
particles. These decay products
carry an electrostatic charge that
allows them to easily attach to dust or
other particles in the air.
When radon's radioactive decay
products are inhaled, they may be
deposited in the lungs before they
can be naturally cleared out by the
mucus of the bronchi. As the decay
process continues within the lungs,
high-energy alpha particles are
produced.
These alpha products give off
massive jolts of electron energy,
which can kill sensitive cells and/or
transform cell DMA. Once a cell has
been transformed in this manner, it
has a significant potential for devel-
oping into lung cancer.
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A Primer on Radon-Resistant Construction T
When the simplicity and minor
costs of Installing a radon-control
system are compared to the health
risks and prevalence of radon, it's
easy to see why many experts
believe radon-reduction techniques
will soon be standard to a large
percentage of new U.S. residential
construction.
The vast majority of today's radon-
reduction techniques, whether for
new or retrofit installations, achieve
their effectiveness through soil
suction or depressurization.
Because the air pressure inside a
building is generally lower than that
of the soil around and beneath a
structure, the pressure difference
wiM cause a building to act like a
vacuum deaner.
This means that soil ar (as weH as
radon) will be dragged up into a
building through any foundation
cracks or other small openings that
mayexfet
Understanding the Bask*
The use of radon-resistant con-
struction techniques prevents this
by (1) creating a physical barrier to
the Indiscriminate entry of gas into a
structure, and (2) providing a con-
trolled means of tunneling and
redirecting the gas to the outdoors.
Currently, the EPA estimates the
average cost of installing a passive
radon system for new residential
construction between $350 and
$500. However, many builders who
are already using similar methods for
moisture control and drainage report
a substantially lower figure.
Although methods vary by locale
and foundation type, most radon-
resistant techniques employ the
following basb steps (see Rgure 1):
• Before concrete slabs or other
floor systems that directly contact the
ground are put into place, a uniform
and gas-permeable layer of dean
aggregate or sand is put down. This
layer of aggregate/sand should be at
least 4 inches thick.
* A minimum 6-mit (or 3-mi! cross
laminated) polyethylene sheet or
equivalent sheeting materials is then
placed on top of the aggregate layer.
*A PVC or other gas-tight venting
pipe is embedded vertically into the
sub-slab aggregate. This venting or
suction pipe should be at least 3
inches in diameter, and secured with
a T" fitting or similar support.
•The venting pipe is extended
vertically through the building floors,
terminating at least one foot above
the surface of the roof, and at least
10 feet away from any window or
opening. The venting pipe serves to
direct the radon from under the
foundation, up through the house
and to the outdoors, where it
dissipates quickly and harmlessly.
•All openings in and around the
foundation are sealed and caulked,
and an electrical junction box is
roughed in, should a venting fan be
needed in the future.
While the above steps are
generally applicable to new homes
with slab foundations, passive radon
systems for crawlspace foundations
employ similar techniques.
One difference is that instead of
using a layer of aggregate, the
polyethylene sheeting is placed
directly on the ground.
Lengths of perforated drain pipe
are then placed beneath the
sheeting around the foundation
perimeter and connected to the
venting pipe. The sheeting is then
sealed to all foundation walls and
piers (see Figure 2).
Passive vs. Active
The only difference between a
"passive" and an "active" radon-
control system is whether a venting
fan is in operation. When a fan is not
used, the system is considered
passive; use of the fan makes the
system active. In many cases, a
passive system is all that is needed
Figure 1
Passive Radon System
For New Construction
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-------
hniques for Building Professionals
to effectively reduce radon levels.
However, all new homes should
be tested after a passive system has
been installed to ensure that" the
indoor radon level is below 4.0 pCi/1.
If not, a fan should be installed- and
operated continuously to actively
draw radon from the soil and into the
venting pipe (see Figure 3).
Retrofitting
Retrofit installation of radon-
control systems generally use the
same concepts as new-construction
systems, although most are active
rather than passive in design.
For slab foundation retrofits, sub-
slab, drain-tile or sump-hole suction
techniques are the most frequently
used. Sub-slab suction calls for the
venting pipe to be inserted through
the floor slab into the aggregate or
soil below and then actively vented
to the outside air. *
For slab foundations with drain
tiles in place, suction on the tiles can
often effectively reduce elevated
indoor radon levels. With sump-hole
depressurization, the sump can be
capped to serve as the location for a
radon suction pipe.
For crawl space-type retrofits, a
common solution is sub-membrane
depressurization with suction pipes
as well as additional venting of the
crawl space area.
As to be expected, retrofitting is
more costly than installing a new-
home radon control system. In fact,
retrofit systems generally run from
$500 to $2,500, depending on the
size of the home, its foundation type
and the reduction method chosen.
Increasing Use
Because radon systems are far
more simple and inexpensive to
install during the construction phase,
the EPA is encouraging building
professionals to routinely include
them as a basic new-home feature.
The National Association of Home
Builders already recommends pass-
ive radon systems for all new
residential construction in Zone 1
areas. Also, the Council of American
Building Officials recently adopted
radon-reduction techniques for use
in high-radon areas.
Model building standards for
radon-resistant construction in new
homes are available from the EPA as
well as the American Society for
Testing and Materials (ASTM).
Building professionals living in
areas where soil conditions or local
building practices appear to preclude
the use of these model building
standards are encouraged to contact
their State Radon Offices for infor-
mation on practical alternatives.
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Components for Activating
A Passive Radon System
-------
Testing: Sole Method for Measuring Indoor Radon
Modern radon testing devices are popular, accurate, inexpensive
In-structure testing is the only
known method for measuring indoor
radon levels.
Fortunately, the technology for
monitoring radiation has progressed
to the point that accurate radon tests
are easily obtained at relatively little
cost.
Radon testing is recommended
for al existing homes and is often
required for the dosing of residential
real estate transactions.
In addition, testing is generally
needed to verify the effectiveness of
a radon-resistant system installed
during construction of a new home.
Testing can be conducted with
do-rt-yourself kits or by an EPA or
state-certified radon tester. While
hiring a certified tester is generally
more expensive, test results may be
obtained more quickly or prove more
reliable, depending on the type of
device used.
Length of Testing
Radon tests are classified as
either short term (2-90 days) or long
term (more than 90 days). Practically
speaking, most short-term tests
require two to seven days; long-term
tests are usually measured at dose
to 90 days.
Short-term tests generally have
one- to two-week waiting periods to
receive lab results; long-term tests
take two to four weeks for results.
Many companies offer results by
phone or fax, which can shorten the
wailing period.
Short-term test kits are the most
popular, given their abbreviated time
frames. However, long-term kits
"smooth out" daily and seasonal
radon fluctuations to yield a better
measure of the average year-round
radon reading.
Types of Device*
All radon testing devices, whether
short-term or long-term, are dassified
as passive or active.
By definition, passive testing de-
vices do not require a power source.
Common passive testing devices in-
dude charcoal canisters, alpha-track
detectors, charcoal liquid scintillation
devices, and electret ion chamber
detectors.
With the exception of the latter,
which often are available only
through laboratories, passive test
devices are readily available in
hardware and building supply stores
for $10 to $25.
By comparison, active testing
devices require a power source. In
addition, they require operation by a
trained technidan.
Active testing devices will monitor
the indoor air continuously, and can
usually record unusual swings in
radon levels. Many detect testing
interference, making them popular
for use in real estate transactions.
Common Passive Testing Devices
Charcoal canisters are popular short-
term passive testing devices; most
take 48-hour readings. A lab then
measures the number of radon particles
absorbed by the activated charcoal.
Alpha-track detectors are often used
for long-term passive testing. Radon
decay or alpha particles strike a special
plastic dish at the base of the device.
A lab then counts the "strike" spots.
In all of these testing scenarios,
the threshold measurement at which
action should be taken to reduce the
indoor radon level is 4.0 picocuries
per Iter (pCi/l) or greater.
Recommendations
The EPA generally recommends
that in the case of short-term tests
using passive devices, two tests
should be taken and the results
averaged.
The two tests can be conducted
simultaneously or repeated 48 hours
apart. If an active device is employed,
only one short-term reading is
considered necessary.
When results are dose to the 4.0
threshold, another round of short-
term tests or a long-term reading
may be advisable.
In all cases, testing devices
should be placed at least 20 inches
above the floor in the basement or
lowest level of the home suitable for
occupancy.
The kit or device should also be
placed in an area where it will not be
disturbed, away from drafts, exterior
walls and areas of high temperature
or humidity. Testing should be
avoided during severe storms.
In addition, short-term tests
require "closed-house" conditions at
least 12 hours prior to and during the
testing period.
If testing is being conducted in a
home with an active radon-reduction
system in place, the fan should be in
operation at least 24 hours prior to
and during the testing period.
Consumer Reports
Rates Radon Kits
Consumer Reports magazine, in
its July 1995 issue, tested and rated
a variety of short-term and long-term
passive testing devices.
For the most part, the magazine
found the majority of the kits to be
accurate and widely available.
The report also discusses what
consumers should know and do if
they obtain test results at the lake
action" level of 4.0 pCi/l or greater.
6
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States Continue to Pass Radon-Protection Laws
During the past ten years, law-
makers around the country have
passed a significant number of radon
protection laws.
Many of the earliest radon laws
focused on developing certification
programs for contractors providing
radon mediation services.
This was followed by a wave of
legislation to inform individuals of
any potential indoor radon problems
before purchasing a home.
Much of the radon legislation
currently under consideration is
centered on introducing radon-
reducing features into the nation's
new housing stock.
Red Estate
State laws requiring indoor radon
measurements be disclosed to the
buyer as part of a real estate sale or
transfer probably affect the greatest
number of Americans every year.
At least 15 states currently have
radon-disclosure real estate laws in
place, and similar legislation has
been introduced in several more.
In many areas of the country
where radon levels are generally
high, but radon testing is not
required by law, home inspection
firms routinely recommend radon
testing prior to closing.
Between these voluntary and
mandated radon disclosures, an
estimated 16 percent of the nation's
annual real estate transactions now
involve a radon test
Certification
To protect consumers requesting
radon testing and mitigation, many
states also have developed pro-
grams to register, license and certify
radon testing professionals and
mitigation service providers. The
EPA also certifies such individuals
through its own Radon Proficiency
Program or RPP.
Types of Radon Legislation Enacted by States
Certification R.E. Disclosure
Under the RPP program, con-
tractors must take a rigorous exam
and follow specific standards in
carrying out mitigation work.
RPP contractors are certified as
qualified to review testing results, to
evaluate radon problems and to
provide detailed remediation pro-
posals.
In addition, they are qualified to
design and install radon reduction
systems, and to ensure that the
installed system effectively reduces
elevated radon levels. Most state
radon certification programs are
similar to that of the EPA.
Code Changes
In recent years, some states have
added radon-resistant construction
provisions to their building codes.
Most of these code changes are
patterned after the EPA model
standards for controlling radon in
new residential buildings.
In addition, the Council of Ameri-
can Building Officials (CABO) has
adopted radon-resistant techniques
for use in all new homes located in
high-radon areas.
CABO is a nationally recognized
model-code organization. Because
many cities and other municipalities
automatically adopt CABO code
modifications into their own building
codes, the number of new homes
featuring radon-resistant construc-
tion should increase dramatically in
the future.
FmADDTTIONAL INFORMATION
The Environmental Protection AgencyCoffers tou8dlng professionals complete information on radon and radon-resistant
construction, including model standards and architectural drawings, at no charge. To obtain these or other documents:
PHONE 1-800-SS-RADON
-------
State Radon Offices
** f f
Every state radon office can provide building professionals with complete information on radon in general, regional radon
studies, and radon-resistant construction techniques. Please note that the "800" numbers are for in-state use only.
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
DtslofCol
Rorida
Georgia
Hswal
Idaho
Knots
Sndtana
owa
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