How does wind affect the radon entry into seven detached houses

Abstract

The wind speed and wind direction affected concentration of indoor radon in seven houses, which are located in three region of southern Finland. In the case of houses (B F) which are built on upper slope of a permeable esker, according to the analysis of covariance the highest concentration of indoor radon, 20 33% over grand mean, was observed when wind (v≥0.4 m.s) direction was perpendicular the esker, leading to increasing pressure of soil gas and consequently to increased radon entry and concentration. In the same houses the lowest concentration of indoor radon, 22 44% under grand mean, was observed when the wind was blowing parallel from the top of the esker. In the slab-ongrade house (A), these factors have unimportant effect on because the house is located on a gently sloping rocky surface. Thus, movement of the wind through the top soil generally has only a limited effect on pressure conditions in the soil. In this house, the concentration of indoor radon was highest, 19% over grand mean, in windy conditions when the wind probably induced transport of containing radon air from the non-ventilated room to the ventilated living space. In the crawl-space house (G), which was built on flat and clayey field, wind speed was not found to influence the concentration of indoor radon although the radon concentration was higher, 12% over grand mean, in the crawl space when the wind came from shielded directions. In addition, the lowest concentration of radon in the crawl space, 13% under grand mean, was observed when the wind blew from unshielded directions. Radon concentration in soil in vicinity of the house probably decreased during these wind directions. Wind speed affected only slightly the mean value of concentration of radon in these seven houses because radon concentration in the groups of the wind speed did not differ from each other. This study showed that the effect of the wind speed on the concentration of indoor radon was difficult to foresee because the effect of the wind depended strongly on wind direction.