Infiltration of outdoor air in two newly constructed high rise residential buildings

The transmission of SARS in high rise residential buildings in Hong Kong has highlighted the importance of indoor environmental quality. One of the important parameters that requires investigation is natural ventilation. The air change per hour (ac/h) of living rooms was studied in two newly constructed vacant tall buildings in Hong Kong. The aim was to benchmark the air change rate of high rise residential buildings. The scope of the work covered the measurement of air change rate in living rooms under both natural ventilation and air conditioning operation. The air change rate was measured using sulphur hexafluoride (SF6) tracer gas. The results show that these concrete residential buildings are not airtight. When all windows and doors were closed, the mean background air change rate in the living room was about 0.36 ac/h. When a window type air conditioner was switched on, this was increased to about 0.74 ac/h. The background air change rate depends on building orientation. In fact there was no strong evidence showing that the background air change rate inside a tall building depends on height. The lift lobby could be a vital path of natural ventilation. It was concluded that other factors such as architectural design and local topography affects natural ventilation in high rise residential buildings.