Modeling the combined conduction—Air infiltration through diffusive building envelope

This paper presents a comprehensive study of the thermal performance of the diffusive building envelope. As the infiltration air moves through the building envelope, it exchanges heat with the solid matrix. The temperature profile in the building envelope deviates from that of pure conduction, because of the heat exchange between infiltrated air and solid matrix. Numerical study was carried out to determine the contribution of air infiltration to the heat gain/loss through the diffusive building envelope. The model validation process was carried out at two different levels: inter-model comparison; validation with experimental data. At the inter-model level, the infiltration heat exchange efficiency of a wall was compared with the infiltration heat exchange efficiency predicted by an existing model in the literature. The results show good agreement between two models. The second level of validation compares the model's prediction with the existing experimental data. The results confirm that there are excellent agreement between prediction made by the numerical model and the experimental data.Furthermore, a simplified analytical model was developed to the prediction of the thermal performance of the diffusive building envelope. In the model, the whole wall was divided into ventilated and non-ventilated areas, and the ventilated area was modeled by adopting a uniform velocity distribution. By comparing the results obtained by the validated numerical model and the analytical model, it was shown that the analytical model can accurately predict the performance of a diffusive building envelope.