Opinion ID: 1176318
Heading Depth: 2
Heading Rank: 4

Heading: Air Changes in the Crawl Space

Text: The radon-222 concentration of the crawl space, which is an important determinant of the radon-222 concentration in the living area of the house, is inversely related to the number of air changes per hour (ACH) in the crawl space. Crawl space ACH is a function of many factors, including crawl space volume, crawl space vent area, wind speed and the temperature difference between the crawl space and the ambient air. Using ACH measurements made in the crawl space of a test house constructed on LRP, which were correlated with wind speed to provide extrapolated annual data, TWCA's expert witnesses estimated an annual average crawl space ACH of 7.0. Measurements of ACH in the crawl spaces of four real houses in the Albany vicinity yielded values of 4.8, 5.6, 12.0 and 21.4 ACH. EFSC's consultant criticized the test house measurements because the test house crawl spaces were substantially smaller than those of normal houses and therefore would be expected to have higher ACH values. When the undersized crawl space vent area of the test house was taken into consideration as well, however, TWCA's experts, using EFSC's consultant's method for scaling test house measurements to houses of normal size, calculated that the hypothetical 1,250 square-foot house would still have a crawl space ACH of 7.0. Petitioners' expert, who testified that he had measured crawl space ACH values of 1.1, 2.4 and 4.4 at three houses in Northern California and Portland, Oregon, argued that 3.0 was a more appropriate ACH value. He also stated that the ACH values of 12.0 and 21.4 measured by TWCA in Albany-area houses were theoretically impossible. EFSC found that the proper ACH value was 7.0, relying on the estimate made by TWCA's experts. EFSC rejected petitioners' expert's suggested value because ACH is greatly influenced by climatic factors, and petitioners' expert's estimate was based upon measurements made in houses outside the Albany area. EFSC did not, however, compare the actual climatic conditions during the periods in which ACH was measured at the various houses. In the absence of such a comparison by EFSC, we do not find its reason for rejecting petitioners' data particularly convincing. Moreover, given the evidence in the record, we are somewhat dubious of the validity of the 12.0 and 21.4 ACH values measured by TWCA. On the other hand, TWCA's experts questioned the accuracy of the measurements made by petitioners' expert. In sum, although we might have been persuaded to choose a lower ACH value, the evidence in the record is not such that we can say that it would have been unreasonable for EFSC to choose an ACH value of 7.0. [12]