Air change rates can be measured using tracer gas techniques which can be costly and intrusive. Moisture data is more accessible, and there is a relationship between moisture conditions and ventilation. This study aims to investigate the relationship between vapour pressure excess and air change rates in bedrooms. The CO2 decay method was used to estimate air change rates when bedrooms were unoccupied in the morning. The relationship between the average hourly change in vapour pressure excess and the air change rate was examined. Results showed a very weak to no correlation between the variables possibly due to moisture buffering and airflow from other rooms.