Radon-resistant new construction
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The basic features of radon-resistant new construction, why they cost less during building, and how to activate the system if needed.
If you are building a house, the cheapest time to deal with radon is before the slab is poured. Radon-resistant new construction (RRNC) builds in the parts of a mitigation system from the start.
The basic features
EPA describes a set of techniques that work together:
- Gas-permeable layer. A 4-inch layer of clean gravel (or an equivalent) under the slab or crawl-space membrane lets soil gas move freely to a collection point.
- Plastic sheeting. Polyethylene sheeting on top of the gas-permeable layer helps keep soil gas from entering and keeps concrete from clogging the gravel.
- Sealing and caulking. Openings, cracks, and crevices in the foundation are sealed.
- Vent pipe. A 3- or 4-inch gas-tight pipe runs from the gravel layer up through the house and out the roof.
- Junction box. An electrical box in the attic makes it simple to add a vent fan later.
With only the pipe (a passive system), natural air movement pulls some soil gas up and out. If a test after move-in shows elevated radon, adding a fan turns it into an active system, usually at modest cost.
Why it matters where radon is common
EPA originally developed its Map of Radon Zones partly to help building code officials decide where radon-resistant building practices should be a priority. Many jurisdictions in high-radon areas have adopted radon-resistant construction requirements in their building codes. Check with your local building department. You can see your county’s zone with the ZIP lookup.
Test the soil first?
EPA does not recommend testing soil to predict indoor radon. It says soil tests have not proven reliable for predicting what the finished home will measure, because the house itself changes how gas moves. EPA’s advice is to build radon-resistant, then test the home after it is finished.
Test after you move in
Even with RRNC features, test the finished home. If results are 4 pCi/L or higher, a fan can be added to the vent pipe. See how radon mitigation systems work.
Questions for your builder
- Will the house include a gravel layer, sheeting, sealed openings, and a vent pipe to the roof?
- Is there an attic junction box for a future fan?
- Will the builder test the home before closing, or should you arrange it?