Impact of Air Leakage on the Thermal and Moisture Performance of the Building Envelope

The air tightness of building envelopes systems is critical to the performance of a building. Uncontrolled airflow movements can cause moisture-induced damage by transporting large amounts of moisture, and may also impact occupant health and safety, sound control, fire control and energy efficiency. Building envelopes are often designed to control airflow by providing a resistance to the bulk flow. Implementation of air barrier systems to restrict airflow is commonly used to reduce the quantity of airflow movement between the exterior and interior environments through the wall. This paper presents a preliminary assessment of the influence of airflow on the moisture performance of a residential building envelope system. The combined heat, air and moisture (hygrothermal) transport in a selected wall is numerically investigated. Vapor diffusion, liquid transport and temperature dependent sorption isotherms are included in the investigation