Wind-driven ventilation of Double Skin Façades with vertical openings: Effects of opening configurations

Abstract

Insufficient airflow in the cavity of Double Skin façade (DSF) systems has resulted in the overheating risk of the cavity and the resulting reduction in thermal performance in cooling dominant climates. Previous research has focused more on buoyancy-driven natural ventilation, and there is a lack of research on utilising wind-driven ventilation in the cavity as a dominant natural force for the heat dispersion from the cavity. Additionally, geometrical features of the cavity and wind direction as influential factors on wind-induced airflow have not been addressed in DSF studies. This paper presents a detailed evaluation of the impact of opening configurations on the ventilation performance of an integrated tall building with DSF with respect to four wind orientations (0°, 30°, 60°, and 90°) to the facade. The evaluation is based on three ventilation performance indicators: (i) induced airflow rate, (ii) wind speed ratio, and (iii) airflow distribution across the cavity length. High-resolution 3D steady RANS CFD simulations of cavity ventilation were performed for a range of sizes of the DSF cavity. The CFD simulations were validated against wind-tunnel measurements. The results show that the ratio between the areas of the front and lateral openings is a critical factor for improving the ventilation in the cavity at the wind incident angle 0° < ϴ < 30°. As wind direction increases to 60° and 90°, cavity size tends to be of the highest importance. Employing three front openings on the external skin of DSF (M3) can increase the efficacy of the system in a broader range of wind direction and cavity size.