Radon entry into buildings: Effects of atmospheric pressure fluctuations and building structural factors

This dissertation examines three issues associated with radon entry into buildings: (1) the influence of a subslab gravel layer and the size of the openings between the soil and the building interior on radon entry; (2) the effect of atmospheric pressure fluctuations on radon entry; and (3) the development and validation of mathematical models which simulate radon and soil-gas entry into houses.; Experiments were conducted using two experimental basements to examine the influence of a subslab gravel layer on advective radon entry driven by steady indoor-outdoor pressure differences. These basement structures are identical except that in one the floor slab lies directly on native soil whereas in the other the slab lies on a high-permeability gravel layer. Our measurements indicate that a high permeability subslab gravel layer increases the advective radon entry rate into the structure by as much as a factor of 30.; Experiments were conducted in the structure with the subslab gravel layer to examine the importance of radon entry driven by atmospheric pressure fluctuations. In the absence of a steady indoor-outdoor pressure difference, atmospheric pressure fluctuations drive 1.5 times more radon entry into the experimental structure than diffusion. Pressurizing or depressurizing the interior of the structure diminishes the contribution of atmospheric pressure fluctuations to the long-term radon entry rate into the experimental structure.; Based on the results of our measurements and analyses of soil-gas and radon entry driven by atmospheric pressure fluctuations, we estimate an upper bound on the contribution of these fluctuations to the long-term, time-averaged radon entry rate. Over the long-term, atmospheric pressure fluctuations drive approximately the same amount of entry as diffusion; consequently, radon entry produced by these fluctuations will probably not cause long-term elevated indoor radon concentrations. However, for houses built in low permeability soils {dollar}rm(kle10sp{lcub}-11{rcub} msp2),{dollar} atmospheric pressure fluctuations typically drive between 20% and 50% the total long-term radon entry. Therefore, in relative terms, atmospheric pressure fluctuations cause increased health risks for occupants of houses located at these sites. (Abstract shortened by UMI.)...