Energy saving by utilizing natural ventilation in public housing in Hong Kong

Building occupants can enjoy a healthy and comfortable indoor environment and use less cooling energy if sufficient natural ventilation is available in their dwellings. Assessing the natural ventilation performance of building designs requires modelling of the external wind environment, the natural ventilation rate and the thermal environment in individual rooms, and reduction in the use of air-conditioning equipment. These are complicated processes. A practical approach for assessing the natural ventilation performance of residential building designs is presented in this paper. The method includes prediction of wind pressures upon window openings in the building fa§ade by computational fluid dynamics simulation, natural ventilation rate prediction using a flow network simulation model, and indoor free-float temperature and air-conditioning energy-use predictions using a building heat transfer and an air-conditioner performance simulation programme. Additionally, the method includes a simplified statistical approach to deal with the random variations in the speed and direction of the wind. This method has been applied to assess the natural ventilation performance of a standard public housing block design widely used in Hong Kong, taking into account when the wind wing walls were incorporated into the building fa§ade and when the separation distances among the building blocks were widened by 25% and 50%.