Night purging is a highly effective method of pre-cooling a building or room during the night, before it is occupied again the next day. It involves operable windows or louvres being opened for a pre-set period of time overnight, allowing natural air flow through the building.

Designing the rightly sized louvres and opening can result in obtaining pre –cooling of the building. The strategy is highly effective for the building located where there is high temperature difference between night and day.