Computer simulation of thermal impact of air infiltration through multilayered exterior walls

Convective air circulation occurring through wall layers is frequently observed in building envelopes. Significant thermal coupling can take place between the incoming cold/warm air and the wall structure, thereby modifying the thermal performances of the envelope. This paper presents an unsteady threedimensional numerical heat and air transfer model, which was developed to
characterize the air leakage effect on the thermal performance of a complete multilayered exterior wall. The modeling for coupling between heat transfer and air infiltration is compared with the commercial software FEMLAB. The results show the substantial impact of air infiltration on the thermal performance of the wall system. Overall heat losses (by conduction and due to the infiltrated air) are evaluated depending on the airflow rates and the air leakage routes. For an airflow rate of 0.001 kg/s, the heat recovery factor varies between 7 % and 15% depending on the air flow path. The reduction of heating load at different scenarios and airflow rates reaches 8%.