Two Case Studies on Ventilation for Indoor Radon Control

Health Canada’s cross-Canada residential radon survey report from 2012 demonstrated that roughly 7% of Canadian homes contain radon levels above the Canadian guideline of 200 Bq/m3. The research outlined in this paper evaluates the effect of ventilation rates on radon levels in two homes located in Ontario, Canada. The first case study consisted of short-term (2 day) radon monitoring in a home using three ventilation strategies; one heat recovery ventilator (HRV) running, two HRVs running, and both HRVs turned off. The results displayed the potential benefits of increasing the ventilation rate in an airtight home to reduce occupants’ radon exposure. When both HRVs were off the measured air exchange rate was 0.05 h-1 and maximum radon concentration was 222 Bq/m3. When both HRVs were operating, the air exchange rate was 0.40 h-1, and within four hours the lowest radon concentration measured was 33 Bq/m3. The first case study provided justification for conducting longer-term radon monitoring (2.5 months) in a second home using three ventilation strategies. During this time period, an energy recovery ventilator (ERV) was successively operated in three different modes: continuously, running 20 minutes per hour, and turned off. When the ERV was off, the average basement radon concentration was 872 Bq/m3 and the air exchange rate was 0.16 h-1. When the ERV in the house was operating continuously, the air exchange rate rose to 0.28 h-1. However, possibly a result of the second home being leakier and the initial radon concentration being higher than in the first home, it was not possible to reduce the average radon concentration (242 Bq/m3) below the Canadian guideline of 200 Bq/m3 solely via ventilation. The results obtained in both homes suggest, 1) studies using a larger number of homes would be beneficial for evaluating ventilation as a solution for radon control and 2) when considering ventilation as a radon reduction technique, both the initial radon concentration and the natural ventilation rate of the home should be considered.