Evaluating the influence of transom window designs on natural ventilation in high-rise residential buildings in Hong Kong

Abstract Transom window (TW) has been proven to be useful for ensuring adequate ventilation in residential units. However, previous studies have never considered the impact of different physical characteristics of TW on ventilation, particularly in the context of characteristics of high-rise residential buildings. In this study, the effectiveness of TW of different designs in enhancing natural ventilation is evaluated on the basis of a high-rise residential development in Hong Kong. Site measurements were conducted at two carefully selected units to determine the influential design characteristics. Novel statistical methods were used to determine local wind environments. Air change per hour (ACH) was used to quantify natural ventilation. Further CFD validations and simulations were done to predict the ACH achievable by different TW designs. Based on the simulation results, a rigorous sensitivity analysis using artificial neural network was performed. The results show that ACH is most sensitive to the presence of TW and the rate is affected the most by the position of TW to the window, followed by wind speed, size of TW, orientation of TW, and wind direction. It was found that depending on the TW’s physical characteristics, the improvement in ACH because of its incorporation ranges from 2.0 % to 110.2 %, and the average is 108.1 %. The results of this study are expected to be useful for decision making by policy makers in search of improvement in natural ventilation in Hong Kong and elsewhere in the world.