What Type of Houses Are Prone to Radon?

Location

• Most radon enters homes from the soil, so homes built in areas with higher-than-normal amounts of uranium in the soil are more prone to radon problems. Areas where rocks and soils derive from quartz-rich igneous rock such as granite typically have above-normal amounts of uranium and radon. Homes in areas with dissolved radon in ground water are likely to experience radon problems. Loose soils are more likely to convey radon into homes. Regions with the greatest amounts of soil radon include the upper Great Plains states, the lower Great Lakes states and the Middle Atlantic states. Regions with the least soil radon include the Southeastern and West Coast states.

House Design

• Radon enters homes from the soil through porous basement walls, cracks in walls and floors, and through plumbing and wiring access points in foundations. Radon is typically pulled into homes from the soil because most houses have lower air pressure inside than exists in the soil. Homes with basements are most prone to radon invasion, followed by homes on crawl spaces and then by homes built on slabs. Homes sealed for energy efficiency and homes closed up for winter will see higher radon concentrations than homes opened up to natural ventilation for summer.

Testing

• Since you can't see, smell or taste radon, the only sure way to determine radon levels in your home is with a radon test kit. These are available in home centers, in catalogs and on the Internet. Short-term passive tests are intended for use for periods of two to three days. Long-term passive tests are intended to be in place for periods exceeding 90 days. Conduct your radon tests according to the directions on the product you purchased. If test results show radon levels exceeding 4 picocuries per liter of air, you have a radon problem that requires corrective action.

Radon Reduction

• You can't do anything about the geologic presence of uranium or soil porosity, so radon reduction efforts focus on leakiness and pressure differentials. Radon mitigation systems for homes with basements use a sub-slab suction system consisting of a pipe that passes through the floor slab and up through the roof, with a suction fan at the pipe's top to pull radon from the soil and vent it to the outside air. Homes on crawl spaces need crawlspace fans or natural ventilation to reduce radon infiltration into the home. In any home, the simplest solution may be to open the windows on the lower floors to let in fresh air; but once you close the windows, radon can return to former levels within 12 hours. Any radon reduction plan requires that you seal foundation or basement cracks and the pores in block walls.