Installation of supply/exhaust ventilation as a remedial action against radon from soil and/or building materials

Abstract

Installation of supply/exhaust ventilation systems is a possible remedial action against excessive concentration of radon. Installations in some 15 one-family houses in Sweden have been evaluated regarding effectiveness, costs and impact on energy demad. This remedial action is most suitable when exhalation from the structure itself is the major source of radon. The resulting decrease in concentration of radon can be estimated from dilution in the increased flow of air through the building. The exhalation from the building materials is constant and unaffected by ventilation rate. When the radon originates from the soil subjacent to the building the inflow of radon is a function of untightness and pressure difference between soil and indoor air. The result of retrofitting a ventilation system will then be the combined effect of dilution and a possible change in pressure difference. The defects in these buildings are normally remedied by more cost-effective action based on sealing the route of entry or depressurising/ventilating the subjacent soil. If a ventilation system is installed, it should preferentially be a balanced supply/exhaust system in order to give a minimal negative pressure indoors.