Posted on Jul 1, 2018

D&M Home Inspections

On a home inspection I performed, the radon test came back high at 7.3 pCi/L (picocuries of radon per liter of air.) The average indoor radon level is estimated to be about 1.3 pCi/L. A radon level of 0.4 pCi/L is normally found in the outside air. The Environmental Protection Agency (EPA) has set a national action level of 4 pCi/L for indoor air.

The property seller had the home tested for radon when she bought the house three years earlier. The level at that time was 1.6pCi/L, well within the acceptable range for radon in the air, and far lower than the level found when she decided to sell the house. How could this happen?

After she bought the house, the home owner had an indoor foundation drain system installed. The system consisted of a series of floor drains around the perimeter of the inside of the basement. Radon that had been trapped below the floor was now released into the inside of the home. New windows, insulation, and a ridge vent had also been installed, along with bathroom exhaust fans, as recommended at her earlier home inspection.

These changes increased the energy efficiency of the home, but also created a high negative air pressure area in the living space. The exhaust fans and ventilation system were drawing air out of the basement, pulling radon out of the ground and into the living space.
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