Air infiltration rates in residential units of a public housing estate in Hong Kong

The air infiltration rate in a high-rise residential building can influence indoor air quality and building energy consumption. This study was carried out to estimate the air infiltration rates of all the residential units in Cheung Sha Wan Estate, a public housing estate in Hong Kong. Computational fluid dynamic (CFD) simulations were conducted for the neighborhood to obtain the wind pressures on the building envelopes through the use of annual weather data from the Hong Kong Observatory. Various cases with different wind speeds and directions were conducted to cover the majority of the possible scenarios. The resulting wind pressures were used as input data in the multizone airflow network model to calculate the infiltration rates of all the residential units. On-site measurements of infiltration rate were carried out in four residential units in Cheung Sha Wan Estate for estimation of the effective leakage areas for the multizone airflow calculations. Based on the calculated results and the probability of occurrence for each scenario, statistical measures of the estimated air infiltration rates were determined. The results show that the mean annual-average infiltration rate among the 596 residential units of Cheung Tai House was 0.26 h(-1) with a standard deviation of 0.11 h(-1). Furthermore, the infiltration rate was positively associated with the wind speed, negatively associated with the volume of the residential unit, and insensitive to the floor level. When the arrangement of the surrounding buildings provided a clear path for the wind, the infiltration rate was higher.