The stack effect
Stories from Physics for 11-14 14-16
The stack effect is a phenomenon that occurs in tall buildings. In hot weather, lower density warm air rises and escapes through windows or cracks at the top of the building, creating an area of relatively low pressure at the bottom of the building in comparison to the outside. The pressure differential causes air to be drawn into the base of the building through cracks and holes. The stack effect can lead to the exertion of strong forces on conventional doors, hence, most high-rise buildings have revolving or double doors to mitigate against the effect. The stack effect can be observed on buildings that are being renovated and covered in sheeting. In hot weather, tarpaulins tend to be drawn in at the bottom of the building and pushed out at the top. The direction of the effect is reversed in cold weather.