Night ventilation is a low energy strategy for cooling a building. It works by using natural or mechanical ventilation to cool the thermal mass of exposed internal building surfaces at night so that they can absorb heat during the day, thus requiring less energy for conditioning the air. This paper investigates the predicted effectiveness of night ventilation in four buildings, two passively cooled and two air-conditioned. A simplified thermal and ventilation model is used for the predictions; the model has been compared with measured values to increase confidence in the results. It is concluded that such a model is a valuable tool to demonstrate the benefits of night ventilation and low energy design principles to clients. It was also found that using a hybrid ventilation strategy, i.e., air conditioning during the day and natural ventilation during the night, energy savings of about 5% of the cooling energy could be obtained in typical buildings and up to 40% in buildings optimized for maximum benefit from night ventilation compared to the same building without night ventilation. The suggested energy savings would occur without any compromise on the internal thermal environmental conditions.

Units: Dual