Radon - 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 RRNC, most new homes are built with passive techniques (no fan). This means is that the home still needs to be tested after occupancy. 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 study from Fort Collins (from October 2006) has shown that passive RRNC reduces the radon by about half on average, and reduces the number of homes above 4 pCi/L by about half as well.

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