EPA 402/B-20/007
Indoor airPLUS Technical Bulletin
Activating a Passive Radon System -EPA
Radon is a naturally occurring radioactive gas that can cause cancer. By building radon-resistant new homes, builders
and contractors provide a public health service — helping to reduce buyers' risk of lung cancer from exposure to radon in
indoor air. Using common materials and straightforward techniques, builders can construct new homes that are resistant
to radon entry.
To comply with the Indoor airPLUS and Zero Energy Ready Home programs, approved radon-resistant features must be
installed in EPA Radon Zone 1 homes. This includes the installation of a "passive" radon system with an electrical outlet
for future fan installation if an "active" system is necessary.
Passive Radon Mitigation System Vs. Active Radon Mitigation System
Passive Radon System
Active Radon System
A passive radon ventilation system consists of a vertical
vent pipe extending up from a sub-slab collection pipe or
mat, through the conditioned space of the home, and
through the roof. The natural stack effect pulls soil gases
up and out of the house.
An active radon ventilation system includes an in-line
fan installed in the vertical vent pipe. The fan pulls soil
gases up and out of the house.
Radon Gail
[Junction Box
Radon Vent Plpej
Polyethylene
Sealant! I son -Gas Retainer


Gravel Beneath Slab)
[Caulking)
Roof flashing
Sealant at alt
penetrations in
air barrier
Wiring
Electrical
junction box
Vent stack
Polyethylene
vapor barrier
Concrete slab
(Radon Gas]
Perforated drain pipe at perimeter J
added to T in order to couple
sub-slab pressure Held to vent stack

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EPA 402/B-20/007
Building a Radon Resistant Home
Radon resistant construction techniques are required for homes in Radon Zone 1 to earn the
Indoor airPLUS label. The Indoor airPLUS program recommends radon-resistant features for
homes in Radon Zones 2 - 3, as well, and recommends that all homes are tested for radon
after construction. If the indoor radon concentration level is > 4 picocuries/liter, a radon vent
fan should be installed, regardless of the home's radon zone.
The easiest time to install a radon mitigation system is during initial construction. Local radon
levels may vary from those shown on the countv-level EPA radon mar , and the amount of radon that will accumulate in a
home can't be determined until the home is built. The Indoor airPLUS Program recommends installing a passive
ventilation stack in all new homes, with an electric outlet located in the attic near the vent stack. This allows the builder or
homeowner to easily install an in-line fan, should post-construction testing indicate high radon levels in the home.
See below for details on best practices to install a passive radon system in your new home.
EPA Map of Radon Zones
How to Install a Vertical Ventilation Pipe - Slab-on-Grade Construction
1.	Select the location for the ventilation pipe (min. 3 inches in diameter). It should be
installed in a vertical run through a warm part of the house and exhausted through
the roof. The pipe discharge should be protected from snow drifts and installed at
least 1 foot above the roof (refer to local snow fall data for height of snow drifts
against buildings) and 10 feet away from any openings in the building to keep the soil
gas from re-entering the building.
2.	Lay a minimum 3-inch-diameter perforated pipe in a gravel trench or a collection mat
on top of the gravel around the foundation perimeter. Install the pipe in a loop to
allow for the soil gas to enter the pipe from two sides and connect it to either side of a
vertical "T". Communication to all sub-slab areas is required and multiple connection
points or interconnections may be required.
3.	Place the polyethylene vapor barrier around the vertical "T"; then cover the open top
of the vertical "T" and label the pipe as part of the radon system before placing the
concrete. After curing, seal the perimeter of the "T" to the concrete to reduce the soil
gas entry.
4.	Install the vertical pipe by connecting it to the vertical "T." Avoid SO-degree angles in
the vertical portion of the pipe; use sweeps if turns are needed. Label the pipe on
each floor so it is clear the pipe is not part of the sewer system. If the ventilation pipe
extends through an unconditioned attic, insulate the stack to control condensation in the pipe.
Roof flashing
Sealant at all
penetrations in
air barrier
- Vent stack
r Polyethylene
vapor barrier
Concrete slab
Perforated drain pipe at perimeterJ
added to T in order to couple
sub-slab pressure field to vent stack
5. Run the pipe through the roof and flash it properly. Provide a screened cap at the termination to prevent entry of
debris and/or nesting animals.
Testing for Radon and Activating the System
EPA recommends testing all homes for radon prior to occupancy. Short-term or long-term radon test kits can be obtained
through the mail or at local hardware stores. Short-term tests remain in the home between 2 and 90 days; Long-term tests
remain for longer than 90 days.
If the radon level is above the EPA action level (> 4 picocuries/liter), a radon mitigation fan should be installed and
activated by a credentialed and/or licensed contractor, depending on state requirements. To confirm results, EPA
recommends re-testing your home after activation, and then every two years following or any time that major renovations
or alterations are made to the home.
Learn more at:
www.epa.gov/indoorairplus

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