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Natural Ventilation – A vital essence of Green Building

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The concept of ventilation can be seen very predominantly in the ancient buildings and castles in the periods of early civilization. However, research and studies on modern ventilation techniques started from as early as 1895 by The American Society of Heating and Ventilating Engineers (ASHVE).

When people or animals are present in buildings, ventilation air is necessary to dilute odors and limit the concentration of carbon dioxide and airborne pollutants such as dust, smoke and volatile organic compounds (VOCs). It also helps in heating, cooling, humidification or dehumidification of the ventilated area.

The Definition:

Ventilation as defined by National Building Code 2005 (Part8, Sec1, Sub-Sec 5.1)

“Ventilation of buildings is required to supply fresh air for respiration of occupants, to dilute inside air to prevent vitiation of body odors and to remove any products of combustion or other contaminants in air and to provide such thermal environments as will assist in the maintenance of heat balance of the body in order to prevent discomfort and injury to health of occupants”

Ventilation as defined by ASHRAE – American Society of Heating, Refrigerating and Air-Conditioning Engineers (Standard 62.1) states:

“Ventilation is the intentional movement of air from outside a building to the inside. Ventilation air, as defined in ASHRAE Standard 62.1 and the ASHRAE Handbook, is that air used for providing acceptable indoor air quality. The vents or flues expels the products of combustion from the building in a way which does not cause harm to the occupants of the building”.

The concept of ventilation and/or natural ventilation has evolved over years with various research studies happening on this subject since ages. Ventilation combines both experimental and numerical computational techniques. In fact numerical methods have been known since the time of Newton in the 1700s.

Concept of Natural Ventilation:

Natural Ventilation (National Building Code 2005, Part8, Sec1, Sub-Sec 5.4):

“The rate of ventilation by natural means through windows or other opening depends on :

  1. Direction and velocity of wind outside and sizes and disposition of openings
  2. Convection effects arising from temperature of vapour pressure difference“.

The code also provides the basis and guidelines for natural ventilation in both Industrial and Non-Industrial buildings. Under Sub-sec 5.4.3, the NBC also states the various design guidelines for Natural ventilation considering:

  1. Wind action – depends on wind behaviour
  2. By stack effect (A stack effect occurs when air inside building is at a different temperature than air outside. When the inside temperature is higher than outside, cool outside air will tend to enter through opening at lower level and warm air will tend to leave through opening at higher level. It is therefore advantageous to provide ventilators at ceiling level or provided in roof).

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