Natural ventilation is a whole-building design concept. The principal function of the natural ventilation system is to supply outdoor air to building interiors to release the excessive heat caused by a build-up of plant and solar heat and most important of all to reduce energy use and cost. The natural ventilation system relies on pressure differences caused by wind to deliver fresh air through buildings. Fresh air is required in buildings to alleviate odors, provide oxygen for respiration and increase thermal comfort. Depending on the climate and the need for fresh air, the system adjusts and harmonizes the indoor climate of the building by controlling the air change through the operable windows. It is very energy-efficient for the benefit of both the environment and the operating economy of buildings.