Wind catchers

Wind catchers (Fig. 14.6) have been standard architectural features on the roofs of buildings in hot dry climates for centuries. However, in order to reduce

Fig. 14.6 Wind catcher. Illustration: Courtesy of Monodraught

Control dampers

Fig. 14.6 Wind catcher. Illustration: Courtesy of Monodraught energy costs associated with air-conditioning systems, this additional source of natural ventilation can now be designed into larger temperate-climate buildings to supplement other natural ventilation systems.

A wind catcher operates by capturing the air on the windward side of the shaft, and deflecting it down one quadrant by a series of vanes. The force of the wind drives it into the space below. As the entering air is cooler and more dense than that within the building, it displaces the warm vitiated air which rises by natural stack ventilation through the other quadrants of the shaft, leaving through the leeward side of the wind catcher. With a symmetrical system one quadrant will predominantly face the prevailing wind to act as the catcher and the opposite quadrant will provide the majority of the stack-ventilation effect. A glazed top to the wind catcher, which heats up further the vitiated air, can enhance the stack effect. Dampers can be used to reduce air flow during winter months. Wind catchers should be located near to the ridge on pitched roofs to maximise their efficiency.

For functioning in multistorey buildings, wind catchers require appropriate ducting and damper systems, and may incorporate heat exchangers from the central heating system to admit tempered fresh air in winter operation.

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