Agreement in Radon Variability Between Proximate Houses

Radon is a naturally occurring gas that is hazardous to human health, making it desirable to minimize exposure. Radon can infiltrate buildings and accumulate to concerning levels, especially in those with tight exterior envelopes and low fresh air exchange rates. Previous research has suggested that air sealing, a common tool for improving building energy efficiency, can increase indoor radon concentrations (Pigg et al. 2017). However, since radon levels naturally fluctuate over time, both short term and seasonally, it can be difficult to conclusively attribute a change in radon levels to retrofit activities. Significant efforts have been made to study this relationship, using a “difference-of-differences” approach, where proximate homes not undergoing substantial modifications are measured concurrently and used as control sites to correct against natural radon variation (Francisco 2020). An investigation into this control correction method was conducted to determine its necessity and applicability. Results suggest that although the correlation in radon readings decreases as distance between the sites increases, the relationship with distance is not strong, and there are many instances where similar nearby buildings have weak or even sometimes negative correlations to each other.