Using Indoor Radon Data to Infer the Impact of Home Energy Efficiency Measures on the Air Exchange of Dwellings

A major objective of home energy efficiency upgrades is to reduce uncontrolled ventilation in order to reduce heat loss. Such reduction also affects concentrations of indoor pollutants by reducing the ingress of pollutants from the outdoor air and the egress of pollutants generated inside the home, which may lead to increased levels of indoor pollutants. In the absence of routine monitoring of the effect of home energy efficiency measures on air exchange, we develop a simple model of the relationship between indoor radon concentrations and dwelling air exchange and, for the first time, use population radon survey data for the United Kingdom to infer the impact of home energy efficiency improvements on home air infiltration. The model suggests that concentrations of radon rise steeply for quite modest reductions in air exchange, especially at low air exchange levels. We estimate that an increase in indoor radon of 10 Bq/m 3 implies a mean reduction in air change rate of 0.22 air changes/h (ach), with 10th, 50th and 90th centiles of 0.03, 0.15 and 0.51 ach, respectively. Applying the model to observed data on current radon levels in UK homes with different levels of energy efficiency suggests a range of effects depending on the initial and final energy efficiency characteristics of the dwelling. For example, the maximum difference in indoor radon, between a typical UK home without any energy efficiency measures and one with wall insulation, glazing and loft insulation, is around 35 Bq/m 3 , which according to our model would correspond to a reduction in air change rate of 0.79 ach. The results suggest that current home energy efficiency measures may be associated with an appreciable decrease in air exchange in UK homes and that retrofit design principles may need to be re‐evaluated to avoid embedding unintended adverse consequences for indoor air quality and health.