A new, integrated method to calculate the energy contribution of night ventilation techniques to the cooling load of a building is presented in this paper. The method is based on the principle of ＇＇Balance Point Temperature＇＇ and permits the calculation of the energy required to cool a building to acceptable comfort conditions when night ventilation techniques are used. It also permits the calculation of the energy contribution of night ventilated buildings compared to conventional air conditioned buildings. The proposed method is successfully validated with data from an extended and detailed simulation procedure using the TRNSYS simulation programme to calculate dynamically the thermal performance of buildings using night ventilation techniques. It is found that the method is of sufficient accuracy and can be used during the predesign as well as the design phase of a building to access the performance of night ventilated buildings.