Impact of precautionary measures on indoor radon levels in retrofit homes

There has been substantial concern about the potential for radon levels to increase in homes undergoing energy retrofits, especially those including substantial air sealing. This study evaluated if precautionary measures could curb increases in radon in over 250 homes receiving energy efficiency retrofits. The goal of these precautionary measures was not to provide full radon mitigation, but rather to avoid increases in radon following retrofit. Primary precautionary measures included installation of exhaust ventilation, covering of bare dirt in foundation spaces, and installation of sealed sump pump covers. Large cracks in the foundation were also sealed in some homes. Radon was measured in every basement and on every ground floor for a two-week period. In an attempt to account for variability of radon due to external factors, control homes were measured at the same time. Control homes were located in the same general vicinity as retrofit homes and did not receive any energy efficiency upgrades during the project period. Radon was measured before retrofit and after retrofit. In as many homes as possible, radon was also measured approximately one year after retrofit to assess the persistence of the measures. The results showed that, relative to a prior study in which these precautionary measures were not done and radon levels increased by a statistically significant 0.4 picocuries per liter (16 Becquerels per cubic meter) in the lowest occupiable level of the home, no statistically significant changes in radon were found with the precautionary measures installed.