With people now opting for eco-sensitive designs, terms like ‘passive’ cooling and ‘natural’ cooling — common terminology used in the traditional architectural and building industry — are now witnessing a revival. Passive cooling refers to ways in which a building can be cooled naturally using sensible design techniques, minus the use of extensive and energy guzzling mechanical, electrical technology.
Within the gamut of passive cooling are multiple techniques. One such technique that has fascinated me is the design of a wind-catcher — a simple device, which when planned right, will trap the cool breeze at a higher level and direct it into the interior of buildings.
This device has been used for many centuries to create natural ventilation in buildings. Wind-catchers originated in Iran and can be found extensively in traditional Persian architecture of the Middle-East, Pakistan and Afghanistan.
The device is a tall tower designed with a cover on top, but with openings at the side that would face the prevailing wind, thus ‘catching’ the wind and bringing it inside the building. This creates an air flow and cools the interior spaces. The greater the height of the tower, the more access it has to cooler breeze.
Apart from this typical one-way wind tower, there are also two-way towers where, other than the opening along the wind direction, there is another opening on the opposite side that will release warm air circulating within the building. Multi-direction wind towers have also been used with openings on four or eight sides, with the ability to control one or more openings according to the changing prevailing wind direction. Traditionally wind-catchers used in Persia tended to have either one, four or eight openings on each side.
The design of window towers or wind-catchers vary based on climate zones. In hot and dry areas, evaporative cooling can be achieved when the wind-catcher is located above a tank of water. In Egypt, wet hay or pots of water were placed along the course of the wind flow inside the tower, providing evaporative cooling. In warm and humid climate zones such as that of urban Chennai, wind towers can provide the much-needed natural ventilation and continuous air flow.
The sizes of the openings also vary depending on the temperature of the outside air. Used in combination with other passive cooling techniques such as courtyards and verandahs, wind-catchers assist in an overall ventilation and heat-management strategy for the building.
A functional and environmentally sensitive design feature, it can be aesthetically appealing as well. A wind tower is a great way to add a unique design identity to the building as they come in different shapes and sizes.
The author is the founder of Green Evolution, a sustainable architecture firm
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