Evaluating the influence of window types on the natural ventilation performance of residential buildings in Hong Kong

Unlike cold climate regions, where natural ventilation is not preferred during winter, natural ventilation is always preferred in Hong Kong for cooling because of the subtropical climate. It also provides better indoor environment quality and energy conservation. Natural ventilation performance of a residential unit is affected by internal as well as external factors. External factors are often subject to constraints beyond the control of site planners and architects. Internal factors include opening configurations and window types, which site planners and architects are free to design the way they deem proper. However, little information is available about their precise impact. An earlier study by the authors on opening configurations identified the best and the worst out of twelve configurations. The best was with cross ventilation and the worst was with single-sided ventilation. In this study, the focus is on the influence of window types. CFD simulations were performed based on the best and worst opening configurations, different building orientations, and varying wind conditions, to evaluate the influence of different window types on natural ventilation performance using the mean age of air (MAA) as the criteria. Four window types were studied: side hung, top hung, full end-slider, and half end-slider windows. Evaluation results indicate that for cross-opening configurations natural ventilation performance was better with full end slider and side hung type windows. For single-sided opening configurations, side hung windows performed much better than the other three types. It can be concluded that better natural ventilation performance can be achieved by the use of side hung windows.