Mechanical Barriers

Knowing that the greatest contributor to indoor radon concentrations is the air from the soil entering the building through the foundation, it was thought that a good place to begin building a radon-resistant home is to make the foundation as radon resistant as possible. Figure 31.10 illustrates the principle of a radon barrier. Many materials (concrete, polymeric coatings, and plastic films) are outstanding air barriers and retard the transfer of radon gas by a large factor. In practice, the difficulties that arise when using barrier techniques are numerous. Failure to seal a single opening may negate the entire effort. Barriers may degrade with time or may be damaged during installation. The use of barrier techniques as a stand-alone system is not recommended, but it is recommended that some amount of effort be made to limit the entry of radon through the foundation. This can be done by using9

1. Foundation materials themselves, sealing cracks, joints, and penetrations.

2. Foundation coatings, normally used for dampproofing.

3. Membranes surrounding the foundation.

It should be pointed out that attempts to control radon by making a gastight barrier around the foundation have not been completely effective. It is likely that they have done some good, but many

FIGURE 31.10 Radon-resistant barrier theory. (Adapted from U.S. EPA, Radon-Resistant Construction Techniques for New Residential Construction—Technical Guidance, EPA/625/2-91/032, U.S. Environmental Protection Agency, Washington, DC, February 1991.)

newly constructed buildings that relied on barriers as the only radon reduction technique have elevated levels of indoor radon. It is not known, however, what the indoor radon concentrations would have been if the barriers had not been installed.

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