Radon-resistant construction techniques can help you prevent radon-related problems in your home. You may already be employing some of these techniques in the house that you’re building. They are generally easy to install.
The following are radon-resistant construction techniques.
Gas-Permeable Layer
Usually, a 4-inch layer of clean, coarse gravel is used beneath the slab to allow the soil gas to move freely underneath the house. Other options are to install a loop of perforated pipe or a soil-gas collection mat (also known as a drainage mat or soil-gas matting).
Plastic Sheeting
Polyethylene sheeting is placed on top of the gas-permeable layer to help prevent the soil gas from entering the home. The sheeting also keeps concrete from clogging the gas-permeable layer when the slab is poured.
Vent Pipe
A 3- or 4-inch PVC or other gas-tight pipe (commonly used for plumbing) runs from the gas- permeable layer through the house and roof to safely vent radon and other soil gases above the house. Although some builders use 3-inch pipe, field results have indicated that passive systems tend to function better with 4-inch pipe.
Junction Box
An electrical junction box is wired in case an electric venting fan is needed later to activate the system.
Sealing and Caulking
All openings in the concrete foundation floor are sealed to prevent soil gas from entering the home. Also, sealing and caulking the rest of the building envelope reduces stack effect in the home.
Is there a way to test the lot before building?
Soil testing for radon is not recommended for determining whether a house should be built radon- resistant. Although soil testing can be done, it cannot rule out the possibility that radon could be a problem in the house you build on that lot. Even if soil testing reveals low levels of radon gas in the soil, the amount of radon that may enter the finished house cannot be accurately predicted because one cannot predict the impact that the site preparation will have on introducing new radon pathways, or the extent to which a vacuum will be produced by the house. Furthermore, the cost of a single soil test for radon ranges from $70 to $150, and at least four to eight tests could be required to accurately characterize the radon in the soil at a single building site. Therefore, the cost to perform soil testing is very high when compared with installing the passive radon system in high radon-potential areas.
Why not wait to install the features until after the home is completed and a radon test is performed?
It is much easier and far less costly to prepare the sub-grade to improve soil-gas flow before the slab is cast. Also, the pipe itself can be run more easily through the house before it is finished. This significantly improves aesthetics and can reduce subsequent system operating costs by planning to route the pipe through warm space to maximize passive operation of the system.
The best way to determine the radon level in a home is to test the home for radon after occupancy.
Would I incur liability by installing the features?
New homes built in the U.S. are not required to meet a specified radon level. You are not required to test a home, nor to guarantee that a home will meet a specified radon level. By installing radon-resistant features, you are pro-actively offering your home buyers features designed to reduce radon levels. Adopting radon-resistant building techniques should not increase your liability risks in any jurisdiction as long as due care is exercised in following the proper construction techniques. Especially in high radon areas, radon-resistant features may actually help you market and sell the homes you build.
In conclusion, radon can be easily drawn away from a home by incorporating radon-resistant construction techniques. Generally, soil testing should not be relied on to determine whether a house should be built radon-resistant. It can not rule out radon-related problems altogether. Although new homes are not required to meet a specified radon level, homebuilders should consult with radon professionals to be pro-active.