Urban ventilation design for megacities: Hong Kong and beyond

The 2002 Sars outbreak in China focused global attention on the issue of poor air quality in major cities. The Hong Kong government responded by developing a mandatory air ventilation assessment framework for new master plans. The aim is to ensure that massing of new developments is specifically designed to enhance air ventilation at street level and avoid stagnant pockets of contaminated air. With 60% of China’s population likely to be living in cities by 2020, the framework could have wide application beyond Hong Kong. This paper introduces the framework and looks at outdoor airflow in cities from a building aerodynamics standpoint. A number of measures are provided that can be adopted to improve and enhance air ventilation at pedestrian level.