A: The EPA has set a recommended action level for radon at 4.0 picoCuries liter (pCi/L). If the annual average level of radon in a home is above this action level, the EPA and the MDH have recommended that action be taken to lower radon levels. A system with ventilation pipes and fans can greatly reduce the levels of radon in a home. These systems can sometimes be installed through a crawl space. Sealing foundation cracks can also reduce radon, although this is not recommended alone.
For major renovations or additions, the space should be tested for radon before the project begins. There are some radon resistant options for doing new constructions:
- Add a gas-permeable layer, which generally consists of clean gravel between the slab or floor system and the soil. This allows gas to move freely beneath the structure.
- Add a layer of plastic sheeting between the gravel and the slab, so the gas stays under the structure.
- Seal all cracks and openings in the foundation, so soil gas stays out.
- Add a vent pipe that starts at the gas-permeable layer and goes through the house, existing at the roof, which will allow gas to go from the soil under the structure, outside.
- A vent fan is added to the attic, to move the gas out.
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