Radon-Resistant Construction Basics and Techniques
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By building radon-resistant new homes, builders and contractors provide a public health service — helping to reduce buyers’ risk of lung cancer from exposure to radon in indoor air. Using common materials and straightforward techniques, builders can construct new homes that are resistant to radon entry.
- Radon-resistant features can be an important selling point for health-conscious home-buyers.
- The cost to a builder of including radon-resistant features in a new home during construction can vary widely. Many builders routinely include these features in some of their homes. The cost to the builder of including these features is typically less than the cost to mitigate the home after construction.
- Builders should provide customers with a checklist of included RRNC features.
- RRNC, an integral part of the green building movement, is part of or included in three labeling programs:
- More than 1.5 million new homes have been constructed since 1990 with radon-resistant features, based on an annual survey of builders conducted by the National Association of Home Builders (NAHB) Research Center.
- Builders can often obtain radon-resistant new construction training from state programs and private service providers. Visit RRNC Training for more information.
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Homebuyers today are increasingly concerned about the indoor air quality of their homes. Issues like:
- carbon monoxide
- toxic chemicals
have received greater attention than ever as poor indoor air quality has been linked to a host of health problems. Builders can employ a variety of construction practices and technologies in their new homes to help address these concerns.
Radon-Resistant Construction Techniques
For more detailed techniques view Model Standards and Techniques for Control of Radon in New Residential Buildings.
All of the techniques and materials described below are commonly used in home construction. No special skills or materials are required when adding radon-resistant features as a new home is being built.
While the techniques may vary for different house foundations and building site requirements, the five basic features that builders should include to prevent radon from entering a home are:
- Gravel: Use a 4-inch layer of clean, coarse gravel below the “slab,” also called the foundation. This layer of gravel allows the soil gases, which includes radon, that occur naturally in the soil to move freely underneath the house. Builders call this the “air flow layer” or “gas permeable layer” because the loose gravel allows the gases to circulate. NOTE: In some regions of the country, gravel may be too expensive or unnecessary. Alternatives are allowed, such as a perforated pipe or a collection mat.
- See Building Radon Out pages 35-40 for more information.
- Plastic Sheeting or Vapor Retarder: Place heavy duty plastic sheeting (6 mil. polyethylene) or a vapor retarder on top of the gravel to prevent the soil gases from entering the house. The sheeting also keeps the concrete from clogging the gravel layer when the slab is poured.
- A Vent Pipe: Run a 3-inch or 4-inch solid PVC Schedule 40 pipe, like the ones commonly used for plumbing, vertically from the gravel layer (stubbed up when the slab is poured) through the house’s conditioned space and roof to safely vent radon and other soil gases outside above the house. (Although serving a different purpose, this vent pipe is similar to the drain waste vent, DWV, installed by the plumber.) This pipe should be labeled "Radon System." Your plumber or a certified radon professional can do this. For more information visit:
- Sealing and Caulking: Seal all openings, cracks, and crevices in the concrete foundation floor (including the slab perimeter crack) and walls with polyurethane caulk to prevent radon and other soil gases from entering the home.
- Junction Box: Install an electrical junction box (outlet) in the attic for use with a vent fan, should, after testing for radon, a more robust system be needed.
A new home buyer may ask the builder about these features, and if not provided, may ask the builder to include them in the new home. If a home is tested after the buyer moves in and an elevated level of radon is discovered, the owner's cost of fixing the problem can be much more.