Opinion ID: 1176318
Heading Depth: 2
Heading Rank: 5

Heading: Percentage of Air Entering the House from the Crawl Space

Text: In the model adopted by EFSC, radon-222 enters the living area of the house from the outside air and from the crawl space. Because the radon-222 concentration in the crawl space is ordinarily higher than that of the outside air, the fraction of air entering the living area from the crawl space (X[f]) is a crucial determinant of the radon-222 concentration in the living area. Relying on expert testimony that it was proper to assume that air leakage around the surface of the living area of a house was uniform, EFSC chose an X[f] value of 0.34 because the floor area of a 1,250 square-foot house with an 8-foot ceiling is 34 percent of the house's surface. Petitioners' expert contended that the equal-leakage assumption ignored the effect of heated air rising within a house. Using data from studies of three houses, the expert testified that 0.55 was a more appropriate value for X[f]. TWCA countered that petitioners' expert ignored the effect of wind speed and that an Oregon Department of Energy study of 56 houses found an X[f] value of 0.20. EFSC's consultant testified that the equal-leakage assumption was acceptable for lack of sufficient scientific evidence to the contrary. Given this evidentiary record, EFSC's finding was reasonable.