Dependence of radon concentration on pressure difference in a crawl-space

Radon concentration in a crawl space remained at the same level during autumn ( 756 Bq m-3 ) and inwinter ( 767 Bq m-3 ) because both air exchange rate and negative pressure (measured across thefoundation wall) increased after a installation of a new ventilation system in the crawl space. Inaddition, relative humidity and water content remained constant in the crawl space air during the sameperiod of time. Radon entry rate was explained by the pressure difference across the crawl space wallwith percentages of 51 % (winter) and 76 % (autumn). The degree of explanation for the whole datawas found to be 75 %. Relative humidity and water content in the crawl space air were explained bythe pressure difference across the crawl space wall with 35 % and 28 %, respectively. Thus, bothradon and moisture from soil were carried similarly by the air flow driven by negative pressure in thecrawl space and a separate mechanical ventilation might be recommended to prevent also moldproblems.