The objective of this research is to quantify the effect of varying levels of induced duct leakage on differential pressures and subsequent radon levels in a typical Florida residence. The heating and air conditioning (HAC) system of a residence was modified with the addition of a fresh air ventilation system. This modification provided the ability to simulate either a return leak or a supply leak in the HAC system. The amount of leakage induced can be varied using flow control dampers and an auxiliary fan located in the ventilation system ductwork.
The house was pressurized and depressurized by adding 0.06 m3/s of ventilation air into the return side and removing 0.05 m3/s of ventilation air from the supply side of the air handling system, respectively. The subsequent changes in house pressure and ventilation rates reduced the indoor radon concentrations from 1865 Bq/m3 to 170 Bq/m3 under pressurized conditions and to 305 Bq/m3 under depressurized conditions.