United States
Environmental Protection
Agency
September 1987
OPA-87-010
oEPA
Research and Development
Radon Reduction
Methods
A Homeowner's
Guide
(Second Edition)
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The U.S. Environmental Protection Agency strives to provide accurate,
complete, and useful information. However, neither EPA, nor any other
person contributing to or assisting in the preparation of this booklet—nor
any person acting on the behalf of any of these parties—makes any
warranty, guarantee, or representation [express or implied] with respect
to the usefulness or effectiveness of any information, method, or process
disclosed in this material or assumes any liability for the use of—or for
damages arising from the use of—any information, methods, or process
disclosed in this material.
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EPA Study
The U.S. Environmental Protection
Agency (EPA) is studying the
effectiveness of various ways to reduce
high concentrations of radon in houses.
While our work is far from complete,
we have gained some information
which may be of immediate use to
homeowners. We are publishing this
booklet to share what we have learned
with those whose radon problems
demand prompt action.
The booklet describes methods that
have been tested successfully—by EPA
and/or other research groups—on
houses with high indoor radon levels.
The information presented here is
concerned primarily with radon which
enters a house from the underlying soil.
Additional information will be
published as it becomes available.
Unique Problems
The first lesson to learn about radon
reduction is this: No two houses are
alike. Even houses that look the same
have small differences in existing
conditions that can affect radon entry
and the design and effectiveness of
reduction techniques. Underlying soils
also vary greatly, even among houses
which sit close together. These
differences will affect the results
obtainable from using the radon
reduction methods described here.
General Information
This booklet is intended primarily for
homeowners who already have had
their homes tested for radon and have
decided that they need to take some
action to reduce radon levels. If you
are uncertain of the meaning of such
test results, or if you need general
information about radon in houses,
read the EPA booklet, A Citizen's
Guide to Radon: What It Is And What
To Do About It (OPA-86-004). To get
a copy, contact your state radon
program, office (see list at the end of
this booklet).
Performing screening and follow-up
measurements prior to a decision to
mitigate (that is, to reduce radon
levels), is strongly encouraged. The
results of follow-up measurements will
enable the homeowner to make a
well-informed decision about health
risks and the need for remedial action.
As mitigation often entails spending a
significant amount of money, follow-up
measurements should be reliable
estimators of the actual maximum
potential exposures of the occupants.
Using Contractors
Many radon remedies require the
skilled services of a professional
contractor who is experienced in radon
reduction procedures. (EPA and the
states are currently working to increase
the number of experienced contractors.)
Due to the skills required, do-it-yourself
efforts are recommended only for
homeowners with these special skills.
This booklet does not attempt to give
the homeowner detailed instructions
for corrective action. But, the
information here should help you make
informed decisions on what type of
remedy is needed, and may assist you
in evaluating proposals from
contractors.
We cannot overemphasize the
importance of carefully selecting a
contractor and reviewing any proposal
for radon reduction work at your house.
Asking for business references and
checking with your local Better
Business Bureau or Chamber of
Commerce will help'you ensure that a
contractor is reputable. Many states
will provide lists of contractors doing
radon mitigation work, and some states
have certification programs for radon
measurement and mitigation.
Getting a second opinion from
another contractor or from one of your
state's radiological health officials can
help you decide if a proposal is
reasonable. You should be certain to get
a written estimate of costs which
stipulates the work to be done. Because
radon reduction work is so new, most
contractors will not guarantee a
reduction in radon levels.
A few contractors may be willing to
guarantee a radon concentration of less
than 4 pCi/L (picocuries per liter);
1
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however, for a contractor to make this
promise he should first thoroughly
evaluate the potential for radon
reduction methods to work in your
home.
Technical Information
Those homeowners who are confident
they have the tools, equipment, and
skills to do the job themselves may
want to read EPA's more detailed
manual, Radon Reduction Techniques
for Detached Houses: Technical
Guidance [EPA/625/5-86/019]. Single
copies can be obtained by writing:
U.S. EPA
Center for Environmental Research
Information
26 West St. Clair Street
Cincinnati, Ohio 45268
Methods
This booklet describes various methods
which may reduce the level of radon in
your house—either by preventing its
entry or by replacing contaminated
indoor air. Some of the methods are
simple, some are complex, and some
are much more expensive than others.
The effectiveness of any one method
will depend upon the unique
characteristics of each house, the level
of radon, the routes of radon entry, and
how thoroughly a job is done. No one
can guarantee that these methods will
work as they did in the test houses.
Sometimes a single method may be
sufficient, but often—especially where
levels are high—several methods will
need to be combined to achieve
acceptable results.
Mitigation Follow-up
Once an action (or combination of
actions) has been performed, it is
important that you have further testing
done to determine the level to which
radon has been reduced. Some states
provide this service. If the radon levels
have not been satisfactorily lowered,
additional mitigation steps may be
taken, and the testing process repeated.
All tests should be performed in
exactly the same manner as the test
which confirmed the high radon levels
in your house.
Due to the many factors affecting the
performance of any reduction
technique, a trial-and-error approach
often will be necessary to achieve
lasting radon reductions. If short-term
testing indicates that radon has been
reduced to an acceptable level, you
may wish to test on a long-term basis.
Before Choosing a Radon
Reduction Method
The selection of appropriate and
cost-effective radon reduction
techniques for a specific house depends
on how well the source of the indoor
radon problem is understood, how
house characteristics affect radon entry
rates, and how candidate radon
reduction systems influence the radon
entry process. Definition of these
factors is possible through a series of
diagnostic observations and
measurements made before, during, and
after radon reduction systems are
installed.
Diagnostics begin with a house
survey. This involves visual inspection
to identify possible radon entry routes
and any construction features which
could influence the design of later
radon reduction techniques. Diagnostics
should also include an evaluation of
the ease of soil gas movement
underneath the concrete slab if sub-slab
soil ventilation is a potential control
option. If ventilation techniques are to
be considered, the natural air
infiltration rate also should be
measured. The measurement of radon
levels in well water is a good way to
learn whether water is an important
contributor to the airborne radon level.
Similarly, measuring gamma levels
inside and outside the house can help
identify the possibility of building
materials as a radon source.
As with radon reduction techniques,
the skills needed to perform radon
diagnostics are beyond the capabilities
of most homeowners. Diagnostic
methods are mentioned here only as
supplemental information to assist
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homeowners when working with radon
diagnosticians and mitigators.
New Construction
If you are planning to build a new
home and are concerned about the
potential for elevated indoor radon
levels, you should consider measures to
prevent radon entry into the house. It is
typically less expensive to build a
home that resists radon entry than to
reduce a radon problem after
construction.
A recent EPA document, Radon
Reduction in New Construction: An
Interim Guide (OPA-87-009), is
available to assist home builders and
others interested in potential radon
prevention alternatives in new
construction. The suggestions contained
in this guide represent current
knowledge and experience gained
primarily from radon reduction tests
and demonstrations on existing houses.
Until some of these techniques have
actually been applied during the
construction of new homes, the
applicability, cost-effectiveness,
radon-prevention effectiveness, and
durability of the techniques cannot be
fairly assessed. Ongoing
EPA-sponsored field testing of radon
prevention techniques in new
construction should provide a better
evaluation of radon prevention
alternatives. The results of these studies
will be published in future technical
guidance documents.
Radon in Water
The potential concern with radon in
water is the airborne radon released
when water is used. The amount of
radon that is given off from water
depends on the amount in the water
initially. The amount given off will
increase as the temperature of the water
increases and as the surface area
exposed to air increases.
In the home, activities and
appliances that spray or agitate heated
water (showers, dishwashers, and
clothes washers) create the largest
release of waterborne radon. However,
the level of radon in household water
must be very high to significantly
influence the overall level in the air
within a house. As a rule of thumb,
10,000 pCi/L of radon in the incoming
household water is equivalent to
1 pCi/L of radon in the indoor air.
In some areas, especially in the
northeast and west, water from private
wells or small community water
systems can contain sufficient radon to
contribute significantly to elevated
levels within a house. Water from large
community water supplies releases
most of its radon before it reaches
individual houses.
Two techniques can be considered to
remove radon from water. The first
requires either spraying water into a
contained air space, introducing air
bubbles into the water, or storing water
in a tank until the radon has decayed.
The second uses granular activated
carbon (GAG) to remove radon from the
water. The GAG method has been more
widely tested and is more commonly
used in individual homes. Radiation
buildup in the unit itself may cause
exposure and disposal problems.
For more detailed information on
radon in water see the recent EPA
booklet, Removal of Radon From
Household Water (OPA-87-011).
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Air Cleaners
The radon reduction methods discussed
in this booklet concentrate on methods
of removing radon gas or preventing
radon gas from even entering the house.
Since the radon health hazard is
associated with the products of radon
decay (which are chemically active),
and not the radon itself (which is an
inert gas), it is appropriate to ask
whether it is feasible to remove the
radon decay products without removing
the radon gas itself.
Air cleaners are devices which either
filter or electrostatically remove
particles—such as dust or radon decay
products—from the air. Air cleaners are
commonly used to condition indoor air
for a variety of health and comfort
reasons, and there have been attempts
to market air cleaners to reduce radon
decay products. At this time, EPA does
not endorse the use of air cleaners as a
method of reducing radon decay
products in indoor air because this
technology has not been demonstrated
to be effective in reducing the health
risks associated with radon.
Although air cleaners will remove
some of the radon decay products,
many questions remain concerning the
relative health effects of the decay
products that are not removed and the
potential impacts of the undiminished
source of radon decay products. Until
more is known, EPA believes that the
available data do not warrant
discontinuing the use of air cleaners
already installed, nor can we suggest
installing air cleaners to reduce your
risk of exposure to radon and its decay
products.
Some people also ask whether the
radon gas itself can be removed from
the indoor air. While some limited
research has been done on using
charcoal to filter the air, it appears that
extremely large quantities of charcoal
would be required. This is not yet a
demonstrated or even clearly feasible
approach.
Method
Natural
Ventilation
How It Works
Replaces radon-laden indoor air with
outdoor air and neutralizes pressure.
This is most often achieved by opening
windows.
Some natural ventilation occurs in
every house as air is drawn through
tiny cracks and openings by
temperature and pressure differences
between indoor and outdoor air. In the
average American house, outside air
equal in volume to the inside air
infiltrates about once every hour. In
technical terms, this is called 1.0 ach
(air changes per hour). Newer houses,
which are generally "tighter," may have
air exchange rates as low as 0.1 ach
(one-tenth that of the average house).
The rate in older houses, on the other
hand, may be more than twice the
average (2.0 ach).
Cost
There are no installation costs unless
devices must be purchased to hold
windows or vents in an open position,
or to detect or prevent unauthorized
entry through these openings.
Use of natural ventilation in cold
weather will increase your heating
costs substantially. For example, if you
were to increase the air exchange rate
to eight times its normal level in your
basement and still maintain
comfortable temperatures there, your
annual house heating bill could be as
much as three times greater than
normal.
If you normally run an air
conditioner in hot weather, your"
cooling costs will be similarly greater. •
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Reductions
The opening of windows, doors, and
vents is a very effective, universally
applicable radon reduction technique
that can be readily implemented by the
homeowner. If done properly, natuial
ventilation is consistently capable of
high reductions, probably above 90
percent if a sufficient number of
windows and vents is opened. High
reductions result because natural
ventilation both reduces the flow of soil
gas into the house, by neutralizing the
pressure difference between indoors
and out, and dilutes any radon in the
indoor air with outdoor air.
Limitations
The primary shortcoming of natural
ventilation is that extreme weather
makes this technique impractical
year-round in most parts of the
country, due to discomfort and/or
increased heating and cooling costs.
Open windows can also compromise
the security of the house.
Procedure
You should ventilate the lowest level of
your house, where it is in direct contact
with the primary source of radon: the
soil. If you have a basement or crawl
space, that is the area to ventilate. (If
you ventilate your basement, you may
find it more economical or comfortable" ,
to close it off and limit its use.) If your
house sits on a concrete slab, then your
only choice is to ventilate the living
area. Opening windows around all
levels of your house (including the
main living area) is recommended
whenever outdoor conditions permit.
As noted earlier, radon is drawn into
your house when the air pressure in the
basement or lowest level is less than
the air pressure in the surrounding soil.
Therefore, it is imperative that any
ventilation system does not further
reduce the air pressure within your
house and increase this "pull." To
guard against this, be certain to open
vents or windows equally on all sides
of the house. Also, avoid the use of
exhaust fans.
When ventilating unheated areas, be
sure to take precautions to prevent
pipes from freezing.
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Method
Forced
Ventilation
How It Works
Replaces radon-laden indoor air with
outdoor air and neutralizes pressure if
the fan is big enough. Uses fans to
maintain a desired air exchange rate
independent of weather conditions.
(Much of the information in the
preceding section on "Natural
Ventilation" is applicable to "Forced
Ventilation" as well.)
Rather than relying on natural air
movement, forced air fans can be used
to provide a controlled amount of
forced ventilation. For example, a fan
could be installed to continuously blow
fresh air into the house through the
existing central forced-air heating,
ducting, and supply registers with
windows and doors remaining closed.
Alternatively, fans could blow air into
the house through protected intakes
through the sides of the house, or could
be mounted in windows. A fan could
also be installed to blow outdoor air
into a crawl space.
Cost
The installation costs for forced-air
systems ranging from simple window
fans to elaborate heating, ventilation,
and air conditioning (HVAC) systems
will range from $25 to as much as
$1,000.
The additional cost of electricity for
forced-air systems will vary depending
upon the size of the fans, the number of
fans used, and the amount of use. A
single window fan can have electricity
costs as low as $20 per year, wMle a
central furnace fan may cost $275 a
year to operate.
Use of forced ventilation throughout
cold weather will substantially increase
your heating costs. As with natural
ventilation, if you were to increase the
air exchange rate to eight times its
normal level in your basement while
maintaining comfortable temperatures
there, your annual house heating bill
could be as much as three times greater
than normal.
If you normally have an air
conditioner running in hot weather,
your cooling costs will be similarly
greater.
Fan forces
outdoor air
into house
Radon-laden air
exits through
windows
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Reductions
As pointed out in the preceding
section, "tight" houses with low air
exchange rates are likely to benefit
more from ventilation increases than
are houses with high exchange rates. In
a typical house, to achieve a
90-percent reduction of radon you
will probably need a 500 to 1,000 cfm
(cubic feet per minute) fan.
Limitations
Forced ventilation, like natural
ventilation, can be employed in most
houses, but, in many cases, the
trade-off in decreased comfort and/or
excessive heating or cooling costs may
prove unacceptable. This approach may
be useful as an interim measure with
very high radon levels.
Procedure
You should ventilate the lowest level of
your house. (Closing off and not using a
basement may also be advisable.)
Ventilating all levels is recommended
whenever outdoor conditions permit.
Air should be blown into the house and
allowed to exit through windows or
vents on adjacent or opposite sides. In
many homes, blowing air in through an
existing central furnace is quite
practical. The use of an exhaust fan to
pull air out of the house may decrease
the interior air pressure and draw
more radon inside. The use of whole-
house fans is not recommended
because they typically operate in the
exhaust mode.
Air distribution and ventilation rates
can be controlled by the sizing and
location of fans and the use of louvered
air deflectors. EPA's experience
suggests that you should install two or
three faris rated at twice the air moving
capacity calculated to be needed for the
desired increased ventilation.
When ventilating unheated areas, be
sure to take precautions to prevent
pipes from freezing.
Method
Heat Recovery
Ventilation
(HRV)
How It works
Replaces radon-laden indoor air with
outdoor air.
A device called a "heat recovery
ventilator" (sometimes referred to as an
"air-to-air heat exchanger") uses the
heat in the air being exhausted to warm
the incoming air. In an air-conditioned
house in warm weather, the process is
reversed: The air being exhausted is
used to cool the incoming air. This
saves between 50 and 80 percent of the
warmth (or coolness) that would be lost
in an equivalent ventilation system
without the device.
Installation
Ducted units are designed, installed,
and balanced by experienced
heating/ventilation/air conditioning
contractors. Wall-mounted units are
generally less complex, and can
sometimes be installed directly by the
homeowner.
Cost
Installation costs (materials and labor)
will range from $800 to $2,500 for
ducted units and are roughly $400 for
wall-mounted units.
The cqst for electricity to operate one
of the larger units with two 200-cfm
fans is about $30 per year.
Using a heat recovery ventilator
could save you 50 to 80 percent of the
increase in heating and cooling costs
that would result from achieving a
comparable amount of ventilation
without heat recovery.
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Reductions
A radon reduction of 50 to 75 percent
can be achieved in houses of typical
size and infiltration rate, assuming
between 200 and 400 cfm of HRV
capacity. Reductions can be greater in
tight houses. Reductions will vary
throughout the house, depending on
ducting configurations.
Limitations
The applicability of HRVs for radon
reduction will likely be limited to
situations where only moderate
reductions are needed and where
winters are cold. If an HRV is intended
to serve as a stand-alone measure to
achieve 4 pCi/L in a house of typical
size and infiltration rate, the initial
radon in the house could be no greater
than 10 to 15 pCi/L. Greater reductions
can be achieved in tight houses.
Radon-laden
air exhaust
Procedure
To simplify the necessary ducting runs
to different parts of the house, the heat
recovery ventilator unit, consisting of
the core and fans, can be located in an
inconspicuous part of the house—such
as an unfinished basement or utility
room. Care must be taken to keep fresh
air supply registers well-removed from
return air withdrawal points, locating
the radon-laden air returns in the
basement or lowest level. It is crucial
that the flow-rates in the fresh air
intake duct and the radon-laden air
exhaust duct be balanced. If more air is
exhausted than is brought in, the house
will become depressurized and even
more radon may be drawn into the
house. Be sure the balancing is done
with no pressure difference between
indoors and outdoors, since the unit
will tend to maintain any pressure
difference that exists when it is
balanced.
Heat recovery ventilators are usually
cost-effective only if operated during
cold weather or in hot weather if the
indoor versus outdoor temperature
difference is large. At other times, the
same amount of ventilation and radon
removal can be achieved by simply
opening windows.
Heat Recovery Ventilator
Outdoor air
intake
L 1U-
Radon-laden
room air
intake
Warmed or cooled
air enters house
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Method
Covering
Exposed Earth
How It Works
Reduces the flow of radon into the
house.
Exposed earth—in basement
cold-rooms, storage areas, drain areas,
sumps, arid the like, as well as in crawl
spaces—is often a major entry point for
radon.
Installation
Requires installation by competent,
experienced contractors or highly
skilled homeowners.
Cost
Covering or sealing small areas (and
ventilating covered air spaces as
necessary) often costs under $100.
Pouring a new slab would cost
considerably more in a large unpaved
area.
The annual cost for operating a fan
would be about $30.
Reductions
Since radon can seep through any small
opening, the degree of radon reduction
achieved by sealing any particular area
cannot be predicted. Effectively
blocking a major entry point, however,
should result in some reductions of the
overall radon level in your house. In
houses with marginal radon problems,
covering exposed earth, along with
sealing cracks and openings, may be a
sufficient remedy.
Covering exposed earth is also likely
to enhance the effectiveness of most
other radon reduction methods, such as
block-wall ventilation and sub-slab
suction.
Limitations
As a house settles and reacts to external
and internal stresses, covered areas can
open again. Therefore, periodic
checking and maintenance are required.
Procedure
Any basement earthen floor should be
excavated as necessary and a poured
concrete floor installed. Before the
concrete is poured, four inches of
crushed stone should be placed over
the earthen floor to permit easy radon
reduction by sub-slab suction if needed
at a later date. All joints must be
carefully sealed. When the covering
encloses an air space, such as that
around a sump pump, a small fan
should be installed to exhaust the air to
the outside, preferably at roof level.
A crawl space connected to a
basement can be covered, ventilated,
and/or sealed off from the basement.
A crawl space not connected to a
basement can be ventilated (as
discussed in the section on natural
ventilation), or the earthen floor can
either be covered with a gas-proof liner
(with passive vents to the outside) or
covered with concrete.
rap Overflow
'ump
Sump
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Method
Sealing Cracks
and Openings
How It Works
Reduces the flow of radon into the
house.
Radon is a gas that can pass through
any opening in a floor or wall which
touches the soil. It can enter your
house through: openings around utility
pipes, joints between basement floors
and walls including perimeter (French)
drains, other floor drains (especially
those that discharge to dry wells), the
holes in the top row of concrete blocks,
and tiny cracks and openings (such as
the pores in concrete blocks). Sealing
such cracks and openings is often an
important preliminary step when other
methods are used. For houses with
marginal radon problems, sealing alone
may be sufficient.
In some houses, certain areas will be
difficult, if not impossible, to seal
without significant expense. These
include: the top of block walls, the
space between block walls and exterior
brick veneer, and openings concealed
by masonry fireplaces and chimneys.
Installation
Since effective sealing generally
requires meticulous surface preparation
and carefully controlled application of
appropriate substances, the work is
often most effectively done by
experienced and competent contractors
or highly skilled homeowners.
Cost
Costs are highly variable. Do-it-yourself
closure of accessible major entry points
can be low in cost. Putting traps in
drains and covering sumps can be low
to moderate in cost. Applying
membranes and coatings can be
expensive.
Reductions
When sealing is used alone, you should
expect only low to moderate reductions
in radon levels. If sealing is done
thoroughly—and all exposed earth is
"Top row
of block
Joint between
floor.and walls
Openings around pipes
Crack in floor
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covered—reductions may be sufficient
in some houses. Sealing is required for
block-wall ventilation and some
sub-slab suction systems to work
effectively.
Limitations
It is very difficult to find all the cracks
and openings in your house. This
method may have little effect on radon
entry unless nearly all the entry points
are sealed. Furthermore, settling of the
house and other stresses may create
more cracks as time passes. Also, the
openings in the top row of concrete
blocks in a wall are often inaccessible
or otherwise difficult to seal tightly. As
a house settles and reacts to external
and internal stresses, old seals can
deteriorate and new cracks can appear.
The aging process ultimately ends the
ability of sealants to block out soil
gases. Therefore, checking and
maintenance are required at least
yearly.
Procedure
If possible, the holes in the top row of
concrete blocks in the basement walls
should be sealed with mortar or
urethane foam.
Seal wall and floor joints with
flexible polyurethane membrane
sealants.
Cracks and utility openings should be
enlarged enough to allow filling with
compatible, gas-proof, non-shrinking
sealants.
A water trap should be installed in
floor drains connecting to drainage or
weeping-tile systems. Water traps allow
water that collects on basement floors
to drain away but greatly reduce or
entirely eliminate entry of soil gas,
including radon. Water traps must be
kept filled with water to be effective.
Perimeter drains (French drains)
should be filled with a urethane foam;
however, some alternative plan for
water drainage should be provided.
Porous walls (especially block walls)
require the application of waterproof
paint, cement, or epoxy to a carefully
prepared surface.
Method
Drain-Tile
Suction
How It Works
Water is drained away from the
foundation of some houses by
perforated pipes called drain tiles.
Drain tiles are rarely completely filled
with water. If these drain tiles form a
partial or continuous loop around the
house, they may be used to pull radon
from the surrounding soil and vent it
away from the house.
Installation
Normally requires installation and
testing by competent, experienced
professionals. Some homeowners,
however, might be able to install a
drain-tile suction system themselves
(particularly where work inside the
house does not require removing
concrete).
Cost
Installation costs (labor and materials)
would be between $700 and $1,500 for
an exterior drain system and between
$800 and $2,500 for a system that
drains into a sump. The actual cost will
largely depend upon the amount and
location of piping and the fan location.
For simple exterior installations, the
cost of materials (fan, plastic piping,
and some incidentals) should not
exceed $300.
Operating costs should be roughly
$30 per year for fan electricity and
$100 per year for the heating penalty
resulting from increased house
ventilation.
Reductions
In some houses, the installation of a
drain-tile suction system has resulted
in radon reductions of over 99 percent.
Limitations
The primary disadvantage of drain-tile
suction is that many houses will not
11
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X
Water in trap N
- prevents air flow
from drain exit
have complete drain-tile loops.
Installation of drain tiles in houses that
do not have them is sometimes not
cost-effective. If some portion of the
perimeter footing does not have drain
tiles beside it or if the tiles are
damaged or blocked, that portion of the
perimeter might fail to be effectively
treated. It is very difficult to determine
how extensive the drain tiles are
around a house. If drain tiles are likely
to form a large portion of a complete
loop, the advantages of the drain-tile
suction approach may make it more
cost-effective to try this approach first
before attempting a more expensive
technique.
Procedure
Water collected by drain tiles normally
flows through a pipe to a drainage area
away from the house or into a sump.
Radon can be pulled from the soil
beneath a house by attaching an
exhaust fan to the collection pipe or to
the sealed sump (see page 9).
To prevent outside air from being
drawn from the end of the collection
pipe, a water-filled trap should be
installed in the pipe beyond the point
where the fan is attached. This trap
(similar to the trap beneath a kitchen
sink) must be placed below the freeze
line. The trap must be kept filled with
water in order to be effective.
Method
Sub-Slab
Suction
How It Works
The lowest floor of most houses, other
than those built over crawl spaces,
consists of a concrete slab poured over
the earth or on top of crushed>»rock
(aggregate). Radon can be drawn from
under the slab and vented away from
the house.
Installation
Installation of a sub-slab suction system
is not an easy "do-it-yourself" job, but
some installations might be
successfully completed by a
homeowner with the necessary skills. A
do-it-yourself installation might be
most logically attempted when it is
known that a good layer of aggregate
underlies the slab.
Cost
Installation cost for a multiple-pipe,
through-the-slab system would be about
$900 to $2,500 if completed by a
professional. Material costs for a fan,
piping, and incidentals would be about
$300. Typical operating costs would be
roughly $30 per year for electricity and
$100 per year for the heating penalty
resulting from increased house
ventilation.
Reductions
Installation of a sub-slab suction system
can reduce indoor radon levels by 80 to
99 percent. In many cases, reductions
of 95 to 99 -I- percent have been
achieved when good permeability exists
beneath the slab.
12
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Limitations
Sub-slab suction has been one of the
most widely used and successful radon
reduction techniques. It is most useful
with foundations built on good
aggregate or on highly permeable soil.
When permeability under the slab is
not so good, sub-slab suction will often
still be applicable. If permeability is
less than desirable, more suction pipes
might be needed. Positioning of the
suction pipe also may become more
important.
Sub-slab suction systems require both
a fan capable of maintaining at least 0.5
to 1.0 inch pressure and closure of
accessible openings in the slab.
Procedure
A fan is used to ventilate soil gas away
from the foundation by means of
individual pipes which are inserted
into the region under the concrete slab.
The pipes can be inserted vertically
downward through the slab from inside
the house, as illustrated, or can be
inserted horizontally through a
foundation wall at a level beneath the
slab. This latter approach is more
practical for slabs poured near the
surface of the ground. Pipes should
exhaust at roof level, away from
windows and vents that could permit
the gas to re-enter the house.
Outside fan
draws radon
away from house
Pipe could also exit through roof
Pipes penetrate
beneath slab
Open Hole
13
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Method
Block-Wall
Ventilation
How it Works
Draws radon from the spaces within
concrete block walls before it can enter
the house ("wall suction") or blows air
into block walls so that radon is
prevented from entering the walls
("wall pressurization").
The concrete blocks used to construct
many basement walls contain hollow
spaces which are connected both
horizontally and vertically. Radon from
the soil—which enters the wall through
joints or tiny pores and cracks—can
travel through these connected spaces
and enter the basement through similar
openings on the interior side or through
the openings in the top row of block.
Installation
Requires installation and testing by
competent, experienced professionals
or highly skilled homeowners.
Cost
The installation of a series of exhaust
pipes in an unfinished basement would
cost from $1,500 to $2,500. A baseboard
collection system in a similar basement
would cost about $2,000 or more to
install.
Annual operating costs would
typically be $30 to $60 for electricity
and $200 to $400 for additional heating
costs.
Reductions
Very effective (up to 99 percent radon
reduction) in houses with good closure
and sealing of all major wall openings.
In other houses, radon reduction will
be significantly less.
Limitations
Applicable only to houses with hollow
block basement walls. Block-wall
suction may not be successful if you
cannot seal the top of the walls, the
space between the walls and any
exterior brick veneer, and openings that
could be concealed by masonry
fireplaces or chimneys. Noticeable
cracks and openings should be sealed.
Block walls dividing the interior of a
basement sometimes penetrate the floor
and touch the underlying soil. Exhaust
pipes must be installed in aff such
walls.
Procedure
There are two basic approaches to
block-wall ventilation.
Although this method can be used
for any radon level, it is best suited
to levels above 0.2 WL (40 pCi/L).
The easiest approach is to insert one
or two pipes into each wall and use
fans to draw radon out of the walls
and vent it outdoors, or use fans to
pressurize the walls to prevent radon
entry. The other approach involves
the installation of a sheet metal
"baseboard" duct around the
perimeter of the basement. Holes are
drilled behind the duct into the
hollow spaces within the blocks. This
second approach produces more
uniform ventilation and may be more
pleasing in appearance.
In houses which have channel drains
cast in the concrete floor next to the
block walls, the baseboard approach
should work particularly well, since it
would ventilate the drains as well as
the walls.
For either wall-ventilation approach
to work, all major holes (especially the
tops of the blocks) must be sealed. As
we pointed out previously, this might
be difficult—if not impossible—to do in
certain places. (Both of the approaches
are shown below in the "suction"
mode.)
Pipes should exhaust at roof level
away from windows and vents that
could permit the gas to re-enter the
house.
14
-------
Pipe-in-wall approach
Outside fan
draws radon
away from house
ffl
Sealant.
'-<*
Radon is drawn
from walls
through pipes
Baseboard approach
Outside fan
draws radon
away from house
Sheet metal
baseboard
Sealant
^^-'Radon is drawn
through holes
drilled in blocks
Method
Prevention of
House
De-
pressurization
How It Works
Reduces the amount of radon drawn
into your house.
Some exhaust fans and combustion
units (such as woodstoves and
fireplaces) can lower the air pressure in
your house by consuming air and/or
exhausting it to the outside. The lower
the air pressure in your house,
compared to that in the soil, the more
radon-laden air may be drawn inside
from the underlying soil.
Installation
If exhaust fans must be used, slightly
open windows near the fans. Likewise
with windows near fireplaces,
woodstoves, and other combustion
units. Doing so will facilitate the flow
of make-up air from outdoors. Install a
permanent system to supply outdoor air
to household combustion units. For
central, forced-air heating and cooling
systems, seal off any cold-air return
registers that are located in the
basement. This reduces leakage of
basement air into ducts.
Close air-flow bypasses (openings
through the floor between stories) to
inhibit air movement up through the
house. Close openings through the
house shell on upper levels to reduce
air outflow from the house.
Note: Many combustion units are
designed to accept outside air, but for
many others a modification is not only
illegal but may be unsafe. Gas furnaces
are a prime example. In this case,
directing outdoor air to a point near the
furnace or enclosing the furnace in a
room that is vented outdoors are
appropriate measures.
15
-------
Cost
Some causes of depressurization can be
eliminated by the homeowner with
little cost.
Installation costs for providing
supplemental air will vary greatly
depending upon the type and location
of the combustion unit being modified.
For some, there may be a slight
increase in operating cost due to the
typically lower temperature of the air
being heated.
Reductions
Because each situation is different, it is
impossible to predict the reduction in
radon levels that can be expected as a
result of reducing sources of
depressurization in a house. There have
been a number of individual
applications where radon reduction has
been significant.
Limitations
The effectiveness of depressurization
reduction techniques for lowering
radon levels will be time-dependent.
For example, a technique aimed at
Air intake
for woodstove
reducing depressurization by an
exhaust fan or a fireplace could have a
significant impact when the appliance
is being operated; however, the average
annual effect will be lower if the
appliance is operated for only a
relatively small percentage of the year.
Procedure
Follow the procedures given under
"Installation." When possible, avoid the
use of exhaust fans or provide a route
for outdoor air entry to compensate for
exhausted house air.
Provide outdoor air in the vicinity of
combustion units. Ductwork or piping
can be run from any suitable exterior
wall to the combustion unit. A manual
or automatic damper should be placed
in such ductwork to prevent entry of
cold air when the stove or furnace is
not in operation. Screen the outside
end of ductwork to bar pests and
debris.
Ensure that windows on the
downwind side of the house are
opened only when windows on the
upwind side are also open.
r~
16
Air intake
•for clothes dryer
"^Air supply
ft for furnace
^ hurnAr
-------
Method
House
Pressurization
How it works
Maintains that part of the house which
is in contact with the soil at a pressure
higher than that of the air in the soil.
This prevents soil gas—including
radon—from entering the home. The
most common application of this
method is to blow upstairs air into the
basement; however, in some homes,
blowing upstairs air into a crawl space
may also be applicable.
Installation
Requires installation by competent,
experienced contractor or a careful and
skilled hdmeowner.
Cost
Varies depending upon the work
required to tighten the basement shell.
Installation cost typically would be
comparable to a simple wall ventilation
system ($1,500-$2,500). Operating costs
will include the electricity to run the
fan (about $30 to $40 per year) and the
heating penalty resulting from
increased.infiltration upstairs caused by
the fan (as much as $400 to $500 per
year).
Reductions
Initial results from a few basement
pressurization applications indicate
that radon reductions of 70 to 90
percent are possible.
Limitations
The application of this technique is
strictly limited to houses with either
basements or heated crawl spaces that
are relatively tightly sealed from the
living area. Care must be taken to
prevent back-drafting of upstairs
combustion units. Also, the
performance of the system could be
completely negated if homeowners open
basement doors or windows.
Some homeowners may object to fan
noise and vibration if the fan is
mounted in the floor of living areas. To
overcome that problem, the fan may be
mounted on the basement floor and
ducted to the living area.
This is one of the least-tested
techniques. Structural effects and
reliability are not well known.
Procedure
Tighten shell between the basement or
crawl space and the upstairs and
between the basement or crawl space
and the outdoors. Blow upstairs air
down in the basement or crawl space. If
openings must be made in the upstairs
floor, the openings should have a
reasonable cross-section to avoid
suffering a severe energy penalty.
17
-------
Comparison of Features
Method
Installation Operating
Cost Cost
Maximum Comments
Possible
Reductions*
Natural ventilation:
Basement or
lowest floor
Crawl space
Forced ventilation:
Basement or
lowest floor
Crawl space
Minimal
Minimal
Low to
moderate
Low to
High to
very high
Moderate
Very high
Moderate
Up to 90 + %
Up to 90 + %
Up to 90 + %
Up to 90 + %
Useful immediate step to
reduce high radon levels.
More controlled than natural
ventilation.
Heat recovery
ventilation
Ducted
Wall mounted
Covering exposed
earth
Sealing cracks and
openings
Drain-tile suction
Sub-slab suction
Block-wall ventilation High
Prevention of house
depressurization
Moderate
to high
Low to
moderate
Moderate
to high
Minimal
to high
Moderate
to high
High
Low to
moderate
Low to
moderate
Low
Nominal
Low
Low
50-75%
No data
available
Site specific
Site specific
Up to 99 + %
Up to 99 + %
Low to
moderate
Low
Low
House pressurization Moderate Moderate
to high
Up to 99 + %
Site specific
Up to 90%
(limited data)
Air intake and exhaust must be
equal. Also, expect lower radon
reductions for nouses with
moderate to high air exchange
rates.
Required to make most other
methods work.
Required to make most other
method work.
Works best when drain, is
continuous, unblocked loop.
Works best with good
aggregate or highly permeable
soil under slab.
Applies to block-wall
basements. Sub-slab suction
may be needed to supplement.
May be required to make other
methods work. May see
seasonal impact.
Most cost-effective when
basement is tightly sealed.
These represent generally the best reductions that a single method can accomplish. You may
get higher or lower reductions depending on the unique characteristics of your house It is likely
that reductions in your house will not be as great as those shown. Especially with high initial
radon levels, several methods may have to be combined to achieve acceptable results
Sources of Information
If you would like further information
or explanation about any of the
points mentioned in this booklet, you
should contact your state radon
program office listed at the end of
this booklet.
If you have difficulty obtaining
needed information, you may call
your EPA regional office listed below.
The radiation program staff will be
happy to provide you with
assistance.
18
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EPA Regional Offices
EPA Region 1
JFK Federal Building
Boston, MA 02203
(617) 565-3234
EPA Region 2
(2AIR:RAD)
26 Federal Plaza
New York, NY 10278
(212) 264-4418
Region 3 (3AH14)
841 Chestnut Street
Philadelphia, PA 19107
(215) 597-4084
EPA Region 4
345 Courtland Street, N.E.
Atlanta, GA 30365
(404) 347-2904
EPA Region 5 (5AR26)
230 South Dearborn Street
Chicago, IL 60604
(312) 886-6165
EPA Region 6 (6T-AS)
1445 Ross Avenue
Dallas, TX 75202-2733
(214) 655-7208
EPA Region 7
726 Minnesota Avenue
Kansas City, KS 66101
(913) 236-2893
EPA Region 8
(8HWM-RP)
999 18th Street
One Denver Place, Suite
1300
Denver, CO 80202-2413
(303) 293-1648
EPA Region 9 (A-3)
215 Fremont Street
San Francisco, CA 94105
(415) 974-8378
EPA Region 10
1200 Sixth Avenue
Seattle, WA 98101
(206) 442-7660
State-EPA Region
Alabama 4
Alaska 10
Arizona 9
Arkansas 6
California 9
Colorado 8
Connecticut 1
Delaware 3
District of
Columbia 3
Florida 4
Georgia 4
Hawaii 9
Idaho 10
Illinois 5
Indiana 5
Iowa 7
Kansas 7
Kentucky 4
Louisiana 6
Maine 1
Maryland 3
Massachusetts 1
Michigan 5
Minnesota 5
Mississippi 4
Missouri 7
Montana 8
Nebraska 7
Nevada 9
New Hampshire 1
New Jersey 2
New; Mexico 6
New York 2
North Carolina 4
North Dakota 8
Ohio 5
Oklahoma 6
Oregon 10
Pennsylvania 3
Rhode Island 1
South Carolina 4
South Dakota 8
Tennessee 4
Texas 6
Utah 8
Vermont 1
Virginia 3
Washington 10
West Virginia 3
Wisconsin 5
Wyoming 8
19
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State Radon Contacts
Alabama
Radiological Health
Branch
Alabama Department of
Public Health
State Office Building
Montgomery, AL 36130
(205) 261-5313
Alaska
Alaska Department of
Health and Social
Services
P.O. Box H-06F
Juneau. AK 99811-0613
(907) 465-3019
Arizona
Arizona Radiation
Regulatory Agency
4814 South 40th Street
Phoenix, AZ 85040
(602) 255-4845
Arkansas
Division of Radiation
Control and Emergency
Management
Arkansas Department of
Health
4815 W. Markham Street
Little Rock. AR
72205-3867
(501) 661-2301
California
Indoor Quality Program
California Department of
Health Services
2151 Berkeley Way
Berkeley. CA 94704
(415) 540-2134
Colorado
Radiation Control
Division
Colorado Department of
Health
4210 East llth Avenue
Denver, CO 80220
(303) 331-4812
Connecticut
Connecticut Department
of Health Services
Toxic Hazards Section
150 Washington Street
Hartford, CT 06106
(203) 566-8167
Delaware
Division of Public Health
Delaware Bureau of
Environmental Health
P.O. Box 637
Dover, DE 19903
(302) 736-4731
District of Columbia
DC Department of
Consumer and Regulatory
Affairs
614 H Street, NW. Room
1014
Washington, DC 20001
(202) 727-7728
Florida
Florida Office of
Radiation Control
Building 18. Sunland
Center
P.O. Box 15490
Orlando, FL 32858
(305) 297-2095
Georgia
Georgia Department of
Natural Resources
Environmental Protection
Division
205 Butler Street, SE
Floyd Towers East, Suite
1166
Atlanta, GA 30334
(404) 656-6905
Hawaii
Environmental Protection
and Health Services
Division
Hawaii Department of
Health
591 Ala Moana
Boulevard
Honolulu, HI 96813
(808) 548-4383
Idaho
Radiation Control Section
Idaho Department of
Health and Welfare
Statehouse Mall
Boise, ID 83720
(208) 334-5879
Illinois
Illinois Department of
Nuclear Safety
Office of Environmental
Safety
1035 Outer Park Drive
Springfield, IL 62704
(217) 546-8100 or
(800) 225-1245 (in State)
Indiana
Division of Industrial
Hygiene and Radiological
Health
Indiana State Board of
Health
1330 W. Michigan Street,
P.O. Box 1964
Indianapolis, IN
46206-1964
(317) 633-0153
Iowa
Bureau of Environmental
Health
Iowa Department of
Public Health
Lucas State Office
Building
Des Moines, IA
50319-0075
(515) 281-7781
Kansas
Kansas Department of
Health and Environment
Forbes Field, Building
321
Topeka, KS 66620-0110
(913) 862-9360 Ext. 288
Kentucky
Radiation Control Branch
Cabinet for Human
Resources
275 East Main Street
Frankfort, KY 40621
(502) 564-3700
Louisiana
Louisiana Nuclear Energy
Division
P.O. Box 14690
Baton Rouge, LA
70898-4690
(504) 925-4518
Maine
Division of Health
Engineering
Maine Department of
Human Services
State House Station 10
Augusta, ME 04333
(207) 289-3826
Maryland
Radiation Control
Department of the
Environment
7th Floor Mailroom
201 W. Preston Street
Baltimore, MD 21201
(301) 333-3130 or (800)
872-3666
Massachusetts
Radiation Control
Program
Massachusetts
Department of Public
Health
23 Service Center
North Hampton, MA
01060
(413) 586-7525 or
(617) 727-6214 (Boston)
Michigan
Michigan Department of
Public Health
Division of Radiological
Health
3500 North Logan, P.O.
Box 30035
Lansing, MI 48909
(517) 335-8190
Minnesota
Section of Radiation
Control
Minnesota Department oi
Health
P.O. Box 9441
717 SE Delaware Street
Minneapolis, MN 55440
(612) 623-5350 or (800)
652-9747
Mississippi
Division of Radiological
Health
Mississippi Department
of Health
P.O. B6x 1700
Jackson, MS 39215-1700
(601) 354-6657
Missouri
Bureau of Radiological
Health
Missouri Deparment of
Health
1730 E. Elm, P.O. Box
570
Jefferson City, MO 65102
(314) 751-6083
Montana
Occupational Health
Bureau
Montana Department of
Health and
Environmental Sciences
Cogswell Building All 3
Helena, MT 59620
(406) 444-3671
Nebraska
Division of Radiological
Health
Nebraska Department of
Health
301 Centennial Mall
South
P.O. Box 95007
Lincoln, NE 68509
(402) 471-2168
Nevada
Radiological Health
Section
Health Division
Nevada Department of
Human Resources
505 East King Street,
Room 202
Carson City, NV 89710
(702) 885-5394
New Hampshire
New Hampshire
Radiological Health
Program
Health and Welfare
Building
6 Hazen Drive
Concord, NH 03301-6527
(603) 271-4588
20
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New Jersey
New jersey Department
of Environmental
Protection
380 Scotch Road, CN-411
Trenton, NJ 08625
(609) 530-4000/4001 or
(800) 648-0394 (in State)
or
(201) 879-2062 (N. NJ
Radon Field Office)
New Mexico
Surveillance Monitoring
Section
New Mexico Radiation
Protection Bureau
P.O. Box 968
Santa Fe, NM 87504-0968
(505) 827-2957
New York
Bureau of Environmental
Radiation Protection
New York State Health
Department
Empire State Plaza,
Corning Tower
Albany, NY 12237
(518) 473-3613 or
(800) 458-1158 (in State)
or
(800) 342-3722 (NY
Energy Research S
Development
Authority)
N. Carolina
Radiation Protection
Section
North Carolina
.Department of Human
Resources
701 Barbour Drive
Raleigh, NC 27603-2008
(919) 733-4283
N. Dakota
Division of
Environmental
Engineering
North Dakota State
Department of Health &
Consolidated
Laboratories
Missouri Office Building
1200 Missouri Avenue,
Room 304
P.O. Box 5520
Bisniarck ND
58502-5520
(701) 224-2348
Ohio
Radiological Health
Program
Ohio Department of
Health
1224 Kinnear Road
Columbus, OH 43212
(614) 481-5800 or
(800) 523-4439 (in Ohio
only)
Oklahoma
Radiation and Special
Hazards Service
Oklahoma State Dept. of
Health
P.O. Box 53551
Oklahoma City. OK
73152
(405) 271-5221
Oregon
Oregon State Health
Department
1400 S.W. 5th Avenue
Portland, OR 97201
(503) 229-5797
Pennsylvania
Bureau of Radiation
Protection
Pennsylvania Department
of Environmental
Resources
P.O. Box 2063
Harrisburg, PA 17120
(717) 787-2480
Puerto Rico
Puerto Rico Radiological
Health Division
G.P.O. Call Box 70184
Rio Piedras, PR 00936
(809) 767-3563
Rhode Island
Division of Occupational
Health and Radiological
Control
Rhode island Department
of Health
206 Cannon Bldg.
75 Davis Street
Providence, RJ 02908
(401) 277-2438
S. Carolina
Bureau of Radiological
Health
South Carolina Dept. of
Health and
Environmental Control
2600 Bull Street
Columbia, SC 29201
(803) 734-4700/4631
S. Dakota
Office of Air Quality and
Solid Waste
South Dakota Dept. of
Water & Natural
Resources
Joe Foss Building
Room 217
523 E. Capital
Pierre. SD 57501-3181
(605) 773-3153
Tennessee
Division of Air Pollution
Control
Custom House
701 Broadwav
Nashville, TN
37219-5403
(615) 741-4634
Texas
Bureau of Radiation
Control
Texas Department of
Health
1100 West 49th Street
Austin, TX 78756-3189
(512) 835-7000
Utah
Bureau of Radiation
Control
Utah State Department of
Health
State Health Department
Building
P.O. Box 16690
Salt Lake City, UT
84116-0690
(801) 538-6734
Vermont
Division of Occupational
and Radiological Health
Vermont Department of
Health
Administration Building
10 Baldwin Street
Montpelier, VT 05602
(802) 828-2886
Virginia
Bureau of Radiological
Health
Department of Health
109 Governor Street
Richmond. VA 23219
(804) 786-5932 or (800)
468-0138 (in State)
Washington
Environmental Protection
Section
Washington Office of
Radiation Protection
Thurston AirDustrial
Center
Building 5, LE-13
Olvmpia. WA 98504
(206) 753-5962
W. Virginia
Industrial Hygiene
Division
West Virginia
Department of Health
151 llth Avenue
South Charleston. WV
25303
(304) 348-3526/3427
Wisconsin
Division of Health
Section of Radiation
Protection
Wisconsin Dept. of
Health and Social
Services
5708 Odana Road
Madison, WI 53719
(608) 273-5180
Wyoming
Radiological Health
Services
Wyoming Department of
Health and Social
Services
Hathway Building
4th Floor
Cheyenne, WY
82002-0710
(307) 777-7956
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