UCL Institute for Environmental Design and Engineering


Jala Ahmed

Air exchange rates in existing buildings

Knowledge of air exchange rates in existing buildings is increasingly important, especially in the context of retrofit. There are many established techniques for measuring air exchange rates in buildings, but there is currently very little data available regarding ventilation rates of existing dwellings in the UK. This is partly due to the complexity and cost of deploying established techniques, e.g. tracer gases, at scale.

However, through the increasing uptake of smart thermostats it is likely that temperature and humidity data will be available for large numbers of dwellings in the future. This project aims to explore how this data can be used to estimate ventilation rate. Provided both internal and external hygrothermal conditions are recorded, the resulting vapour pressure excess can be derived. Since vapour pressure excess is effectively a function of internal moisture generation and ventilation effectiveness, estimates of ventilation rate can theoretically be made using vapour pressure excess.