Ventilation performance of a naturally ventilated double-skin façade in buildings

Using a double-skin facade for natural ventilation is not a new idea, but the behind mechanism and impacts of those environmental and designing factors on its performance are still unknown and critically needed. Therefore, through this study, the influences of the façade and room configurations, together with the environmental factor on buoyant-driven natural ventilation, are addressed. An experimentally validated numerical model has been adopted to analyse the airflow characteristics inside the NVDSF and the room caused by combined radiation and natural convection. Results reveal that the primary influence comes from the dimensions of NVDSF, followed by the size of window openings. For the analysed NVDSF, an optimal gap depth is found at 0.2 m, and an optimal vent height is around 0.2–0.3 m. More gap depths result in more counterflows at the top, while a taller vent unnecessarily weakens the heat transfer. Besides, influences from room/window configurations also cannot be overlooked. Windows on the sidewall are found to deliver better indoor airflow coverage, although it gives around 2.5% less ventilation rate. Compared to a ‘no room’ condition (i.e., all the openings of the NVDSF are directly connected with outdoor but not room), our models with room only achieved 85–93% of the airflow rate depending on window sizes. It highlights the importance of considering room and windows for an accurate and practical assessment. Although the window locations and room dimensions draw minor impacts on the ventilation rates, the changes in airflow distribution prove their own importance in terms of air quality assessment.