Impact of subslab ventilation technique on residential ventilation rate and energy costs

Radon is the largest source of risk to human health caused by an indoor pollutant in the industrial countries. Subslab ventilation (SSV) is one of the most effective and common methods of reducing indoor radon concentrations in houses with a basement. In this paper, the impact of SSV on the air exchange rate is quantified, through numerical modeling of a prototype house with basement for a range of permeabilities of soil and subslab aggregate and various sizes of the cracks in the basement floor. We show that a SSV system can increase the air exchange rate by as much as a factor of 4.5. Then the energy and capital costs of a subslab depressurization (SSD) system are compared with those of direct ventilation of the basement which is required to lower the indoor radon concentration to an acceptable level for a Chicago climate. We show that (1) an exhaust ventilation cannot significantly reduce the indoor radon concentration and may even increase it, and (2) a balanced ventilation with heat recovery is only effective for low premitigation radon concentrations. However, both SSV and balanced ventilation systems are probably too expensive to be recommended in houses with low premitigation radon concentrations. A SSD system is the most cost-effective technique for reduction of high radon concentrations.