Mitigating Radon in Homes

Sustainability and Green Building

January is National Radon Action Month, an important reminder to ensure homes are protected from this naturally occurring radioactive gas that can seep from the soil into a home. Negative pressure in buildings can suck radon in, allowing it to become trapped and concentrated in the home.

According to the American Cancer Society and U.S. Environmental Protection Agency (EPA), indoor radon is the second-leading cause of lung cancer in the United States. The gas is colorless, odorless, tasteless, invisible and chemically inert; testing or monitoring is the only way to determine the radon level inside of an individual home.

The EPA’s action level for radon is 4 pCi/L (picocuries per liter), and elevated levels can be found in both new and existing homes, whether single-family homes or any type of multifamily building. However, radon is more likely to be in the soil in some areas of the country than others. This EPA map shows in which zone (1, 2 or 3) your county falls. Note that regardless of your zone location, you may be subject to local regulations regarding radon-resistant construction.

There are construction practices to reduce indoor radon levels in new homes, as well as mitigation techniques if it is detected in existing homes.

Radon-Resistant New Construction

The goal for radon-resistant construction is to keep radon from entering the home. This includes sealing radon entry points (such as potential re-entry points where the gas is vented), installing a barrier or layer between the soil and the home from which to collect the radon gas, and venting the gas away from the home and other structures. Passive systems rely on the natural upward flow of air to exhaust the radon; active systems include a fan to pull the air through the vent pipe. A Home Innovation Research Labs study, ‘Radon-Resistant Construction Practices in New U.S. Homes 2016,’ found the average costs for providing radon-resistant construction for a single-family home are $375 for a passive system and $700 for an active system. For multifamily buildings, the average costs are $415 for a passive system and $760 for an active system.

Mitigation for Existing Homes

The goal for radon mitigation is to reduce the indoor radon level to at least below 4 pCi/L. Cracks and openings in the foundation are sealed to limit the flow of radon into the home. Several types of passive and active soil depressurization systems are available; costs will depend on the home’s construction style and type of system installed, but in general, they range from about $1,500 to $2,500.More detail on radon mitigation techniques for both new and existing homes can be found at

For more details about NAHB’s sustainable and green building initiatives, contact Sustainability and Green Building Program Manager Michelle Diller. To stay current on high-performance residential building, follow NAHB’s Sustainability and Green Building team on Twitter.

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