Buildings Guide

Natural Ventilation  »  Buoyancy induced ventilation


Buoyancy driven ventilation is the result of movement of air within a stack due to temperature gradient between warmer air and colder air within the stack. The warm air rises in the stack, removed from the top and is replaced by cooler air at the inlet. In tall buildings atria can be used to great effect as a thermal chimney and can be used to aid ventilation. Some of the devices and strategies to design stack ventilation in buildings are:

  • Thermal chimney
  • Wind catchers/Towers
  • Roof monitors
  • Double facades


Buoyancy induced ventilation or stack ventilations are widely used in vernacular architecture world-wide, many can be found in middle east. Current denser built environment in the city with limited cross ventilation and the need for deep-plan buildings make the application of stack ventilation more important (Ismail & Rahman, 2012).


In buoyancy induced ventilation, high air exchange rate in cooler climates can result in higher thermal due to cooling of the building interior resulting in significantly higher heating load. Similarly care must be taken in hot climate zones in open systems to remove the internal load through ventilation. The design also has to take into consideration of the possible outdoor noise and pollution that can enter a building and minimised where possible when planning for natural ventilation. Mixed mode ventilation considers some of the limitation and allow indoor comfort environment.

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