Buildings Guide

Natural Ventilation

Key Message

Natural ventilation is the preferred means of ventilation in most parts of the world. Designing effective natural ventilation strategies in conjunction with mechanical ventilation systems (such as mixed mode ventilation) creates avenues for potential energy savings. Studies show that effective use of natural ventilation as opposed to buildings with air conditioning and mechanical ventilation reduces the carbon emissions by half.


Adequate ventilation is first and foremost required to provide sufficient oxygen and to dilute indoor pollutants to an acceptable level. Ventilation also creates a sense of thermal comfort to the building’s occupants and aids in passive cooling by regulating body temperature and also interior temperature of the building. Cooling through ventilation is based on the fundamental heat-transfer mode of convection, where the air flowing next to a surface carries away heat, provided it is at a lower temperature than the surface. When it passes over the human body, it increases the evaporation rate from the skin and en-hances heat extraction. Thermal comfort can be achieved even when the incoming air is at a higher temperature than the mean radiant temperature of the indoor air. For example, an increase of air veloci-ty by 0.15 m/s compensates a temperature increase of 1 °C at a relative humidity of 75%. Perceived temperature differences up to 2 °C may occur when air movement is increased by 0.8 - 1.6 m/s.


Natural ventilation is predominant means of ventilation as well as passive cooling in most parts of the world. The effectiveness of natural ventilation however, depends on the climate and function of the space. Spaces with high internal heat gains smoke and fume generating spaces such as kitchen and laboratories, infectious wards in hospitals etc., however, require enhanced ventilation systems.


Air movement through buildings can be wind-induced or caused by differences in pressure due to a temperature gradient (stack effect). Temperature differences will cause the air to have different densities and air will flow naturally between the colder (denser) part of the building and the warmer (less denser) part. For wind induced ventilation shallow floor plans with windows or openings at either side work well, as do internal courtyards. Stack effect causes the hot air to rise up, which can then be extracted at the top, drawing fresh air into the building through an opening at the lower level.

Please note that the focus of this section is on building design with respect to natural ventilation. For information on siting, urban and microclimate effects on wind patterns and ventilation refer to Passive options “site” and “micro climate”. In addition please refer to recommendations to find in which cases natural ventilation is required. For example, cross ventilation for thermal comfort is highly recommended in hot-humid climate while it is undesirable in hot and dry climate.


For the effective natural ventilation, building design need to consider opening’s detail, climate and microclimate of the site and building’s functional use.


In some cases due to extreme climate conditions, security issue and cultural issues, openings are remained close which lower the ventilation rate. The possible outdoor noise, dust and pollution must be taken into account and minimised where possible when planning for natural ventilation. Mixed mode and hybrid ventilation is suitable to overcome such situation (WHO, 2009). For natural ventilation control and to increase its effectiveness, modeling tools help to analyse and check the indoor thermal comfort at differing operating conditions and outdoor environment.


Sriraj Gokarakonda
Christopher Moore
Shritu Shrestha


  • Kleiven, T. (2003). Natural Ventilation in Buildings: Architectural concepts, consequences and possibilities. Norwegian Univesity of Science and Technology.
  • Walker, A. (11. November 2014). Natural Ventilation. Abgerufen am 25. August 2015 von Whole Building Building Design Guide: https://www.wbdg.org/resources/naturalventilation.php
  • WHO. (2009). Natural Ventilation for Infection Control in Health-Care Settings. World Health Organisation press.

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