Passive Cooling

The fierce summer heat can turn a badly designed home into an oven and dramatically increase power bills to run mechanical air-conditioning.

Passive cooling your home will save on energy bills, reduce your impact on the environment, and make your home more comfortable.

This is achieved through good design.

The main elements of design for passive cooling are:

  • Reducing heat gain through correct orientation, glass area and insulation.
  • Effective shading.
  • Maximising air movement.
  • Capturing cooling breezes.
  • Night time cooling
  • High thermal mass construction
  • Use of light coloured roofs and walls to reflect solar radiation

Cooling breezes are often in the form of nighttime cool air currents in late evening and early morning. These breezes should be directed into the house at night to cool the interior and high thermal mass construction. High thermal mass can be concrete floors and masonry or rammed earth walls.

The thermal mass is cooled down and will remain cool throughout the following day.

A whole house fan located centrally in the building is an effective means of assisting the movement of cool air into the interior. Ceiling fans are another simple low cost way of creating air movement.

An appropriate depth of eaves overhang is the most effective way to shade windows and walls.

Trees and high bushes offer an effective form of sun protection on west and east walls.

Pergolas can provide shade to windows and outdoor living areas. Vines, closely spaced slats or angled louvres are examples of coverings for pergolas.

The angled louvres are most effective facing north where the high angle summer sun is stopped but the low angle winter sun penetrates through into the living areas.

Pergola with Angled Louvres

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The roof receives the most amount of direct sunshine. As a result heat becomes trapped in the roof space and will pass through the ceiling and into the rooms below. A light coloured roof to reflect unwanted heat, and appropriate levels of insulation will dramatically reduce heat penetration into the rooms.

If mechanical cooling is required then evaporative coolers should be considered as a first choice.

Evaporative coolers can save 50% of the initial cost and up to 80% of the operating costs of refrigerated air- conditioning.

See Passive Solar Heating and Thermal Mass pages for more information.

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