Air ventilation assessment (AVA) for building developments

Abstract

Pedestrian level wind environment has long been the focus of many major world cities concerning the safety and comfort of pedestrian due to unacceptably strong winds. More recently, natural ventilation and air quality has captured the attention of the general public and government authorities concerning the health and well-being of city inhabitants. Air ventilation assessment (AVA) is a major initiative introduced in 2006 by the Government of the Hong Kong Special Administrative Region (HKSAR) to address the alarming deterioration in the past decades of air quality in Hong Kong. The catalyst for the introduction of AVA was the outbreak of Severe Acute Respiratory Syndrome (SARS) in 2003 from which many people died. This paper outlines the contributions of wind engineering in the implementation of AVA, particularly in the process of expert evaluation, and in developing wind tunnel test techniques and analysis methodologies for site wind availability study and detailed AVA study. A case study is used to highlight the role and importance of each of the suggested critical elements and each step of the proposed analysis procedure in the wind tunnel simulation. The case study also provides a relevant benchmarking to verify the achievability of the proposed air ventilation guideline that the mean wind speed of the development site should be at least or more than 1.5 m/s at pedestrian level in an existing urban area in Hong Kong. The impact of the interaction between the prevailing wind climate of and the urban fabric on air ventilation performance is discussed