Radon in New Home Construction

Find a Builder Using Radon-Resistant Construction

Diagram of a house showing radon-resistant construction techniques

Construction Techniques

Radon-resistant construction techniques may vary, depending on the foundation and site requirements. A house built to radon-resistant standards will include these basic elements:

  1. Gas-Permeable Layer - a layer placed beneath the slab or flooring system allows the soil gas to move freely beneath the house. In many cases, the material used is a 4-inch layer of clean gravel.
  2. Plastic Sheeting - plastic sheeting placed on top of the gas-permeable layer and under the slab helps prevent the soil gas from entering the home. In crawlspaces, the sheeting is placed over the crawlspace floor.
  3. Sealing & Caulking - sealed openings in the concrete foundation floor reduce soil gas entry into the home.
  4. Vent Pipe - a 3- or 4-inch gas-tight or PVC pipe (commonly used for plumbing) running from the gas-permeable layer through the house to the roof ensures that radon and other soil gases are safely ventilated above the house.
  5. Junction Box - an electrical junction box can be installed in case an electric venting fan is needed later.

Radon-resistant construction techniques can not only reduce radon levels, but can also decrease soil moisture. This reduces mold, mildew, and odor, especially when activated with a radon reduction fan.

Local Requirements

Currently in Boulder County, new homes must be built with Radon Resistant New Construction (RRNC) in

  • The City of Longmont
  • The Town of Superior
  • Unincorporated Boulder County

Testing After Occupancy

While a home may be built with Radon-Resistant New Construction, most new homes are built with passive techniques (no fan). This means that the home still needs to be tested after move-in. If testing shows a level of 4.0pCi/L or more, a fan can be installed to the existing piping to reduce the level.

A 2006 Fort Collins study showed that, on average, passive RRNC reduces radon by about half, and reduces the number of homes above 4 pCi/L by about half.

Learn More

 Related Links


Air Quality Program

Main: 303-441-1564
Submit a question



3450 Broadway
Map & Directions
Hours: 8 a.m.-4:30 p.m. M-F