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, at least in the industrial countries. Subslab Ventilation (SSV) is one of the most effective and common methods of reducing indoor Rn concentrations in houses with a basement. In this paper, we first quantify the impact of this technique on the air exchange rate, 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 We then compare the energy and capital costs of a Subslab Depressurisation (SSD) system to those of direct ventilation of the basement as required to lower the indoor radon concentration to an acceptable level, for a Chicago climate. We show that 1) an exhaust ventilation cannot reduce efficiently the indoor radon concentration and may even increase it; 2) a balanced ventilation with heat recovery is only efficient for low premitigation radon concentrations. However, both SSV and balanced ventilation systems are too expensive to be used in low premitigation level houses. A SSD system is the most cost effective technique for reduction of high radon concentrations.