Assessment of impact of building envelope porosity on energy

This paper presents a numerical model for the analysis of impact of building envelope porosity on energy. In the porous envelope, the infiltrating air entering a building can change in temperature, along the infiltration path due to heat exchange between the air itself and the porous insulation matrix; hence the envelope effectively behaves as a heat exchanger. The presented model is based on combined airflow and heat transfer through porous media. Microscopic energy equations are formulated for solid and gas phases separately. Overall macroscopic heat transfer modeling is derived using volume average method and is applied for varying infiltration paths and porosity. Modeling results indicate that heat exchange performance is mainly determined by airflow rate with secondary influence from the infiltration path. Comparatively, under the same inlet velocity, the influence of porosity variation is not significant