Radon in New Construction: Building Healthier Homes from the Ground Up

RRNC, or radon-ready construction, includes preventive construction techniques during the building process that limit radon gas entry and provide future rough-ins for a full radon mitigation system.

Benefits of RRNC include:

• Cost effectiveness. Providing rough-ins or even a full radon mitigation system costs less during the construction phase than retrofitting a home later.
• Increased home value. As a selling point, homebuilders can market their homes as radon-resistant. RRNC can also enhance home resale value.
• Reduced lung cancer risk. Radon is an invisible, odorless radioactive gas that can seep into homes from the soil below. As it decays, it emits particles that are radioactive and damage lung tissue which causes lung cancer. Radon is the #1 cause of lung cancer among non-smokers and the #2 cause of lung cancer overall. RRNC can limit radon exposure within the home.
• Improved indoor air within the home. RRNC measures can also reduce concentrations of other soil gases and help control moisture.

Examples of RRNC features include:

• Gas permeable layer or “air flow layer”: a 4- inch layer of clean, course gravel below the slab/foundation that allows radon gas to circulate underneath the house.
• Pipe or mat loop layer: a sub-membrane perimeter loop of pipe or geotextile soil gas collector and plenum to the vertical vent pipe (ex. soil gas collector mat).
• Soil gas retarder: heavy duty plastic sheeting or a vapor retarder is placed on top of the gravel to prevent radon gas from entering the house.
• Vent pipe: solid PVC 40 pipe that runs vertically from the gravel layer through the house’s space and exits above the roof. Pipe should be labeled “Radon System” so it’s not confused with plumbing pipes.
• Sealing and caulking: seal all openings, cracks, and crevices in the concrete foundation floor (including the slab perimeter crack) and walls with polyurethane caulk.
• Junction box: install an electrical junction box (outlet) in the attic in case a radon fan for an active radon mitigation system is needed in the future.

Essentially, RRNC provides for a “passive” radon control system that can be more easily upgraded to an “active” radon mitigation system if the radon levels in the home are high or become elevated over time.

RRNC post-construction radon test

ANSI/AARST standards in the United States requires a short-term radon test to be performed by a certified/licensed radon measurement professional within 60 days of home occupancy. If the radon levels measure high, then further measures must be taken for radon reduction. A long-term radon test (90+ day test) is also required to be given to the homeowner so that a more accurate measurement of radon in the home can be completed.

Health Canada recommends a long-term radon test of at least 3 months to be performed during the first heating season (months of October through April) that the home is occupied. During the colder winter months, referred to as the “heating season”, elevated radon can accumulate indoors because windows and doors are kept shut and the stack effect is more likely to draw radon inside the home.

RRNC standards – U.S. and Canada

ANSI/AARST RRNC-2020 standards in the U.S. provide minimum requirements for radon rough-ins in new homes being constructed. In addition, some states and municipalities have adopted Appendix F of the International Residential Code (IRC) for RRNC standards.

The National Radon Proficiency Program (NRPP) in the U.S. offers an Advanced Certificate in RRNC that can be attained by certified radon mitigators. With this certificate, radon mitigators can design, install, inspect, and verify the radon-resistant features in new residential construction.

The National Building Code of Canada (NBC) has set the minimum mandatory requirements for radon resistant new construction. National Standard of Canada’s Canadian General Standards Board (CGSB) standard, CAN/CGSB-149.11, also provides RRNC standards that are supported by Health Canada.

The Canadian National Radon Proficiency Program (C-NRPP) offers a certification for radon-resistant construction methods. The certification, called Controlling Radon in New Canadian Homes (CRNCH), trains builders and inspectors to design, build, and inspect new homes to minimize radon entry and makes sure standards are met.

In any state or province, the local building codes should be consulted for the RRNC requirements that have been adopted in the area.

Radon-resistant construction should be used in all new homes

With public awareness growing, radon resistant features should be a standard, not an option, in all new home construction. Builders can distinguish themselves by offering radon-resistant homes, municipalities can lead by updating building codes, and homeowners can request these protective measures.

Reducing radon-induced lung cancer can begin before a home is even built.

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