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Keep your home cool through passive cooling.

Find out about some of the most important aspects of passive cooling - shading, insulation and ventilation.

The term "passive cooling" refers to the practice of keeping a building cool using no or very little energy. The principle of passive cooling is to prevent heat from getting into a building during a warm day, and bringing in cool air from outside when the temperature drops.

Different Aspects of Passive Cooling

Shading
Shading windows externally is essential for passive cooling, as direct heat from the sun passes easily through glass. Double glazing can prevent the transfer of "ambient" heat (heat in the air) but will still be penetrated by the sun's rays, so the key is to prevent them from hitting the glass in the first place. Internal curtains do little to cool rooms in summer (although they can be a big help in winter).

There are two basic types of external shading- fixed and adjustable. Fixed shading options include eaves, pergolas and battens. Adjustable external shading options include canvas blinds, awnings, roller shutters and shade cloth structures.

  • North facing windows receive the most direct sunlight, so it is essential that they are well shaded; however, they should also be able to let in winter sun. Appropriate design of fixed shading devices enables them to block out the higher summer sun whilst allowing the lower-angled winter sun through. If this can't be achieved then adjustable shading is the best option.

  • East and west facing windows should also be well shaded - the best option is adjustable shading that can cover the whole window, to block out low-angled early morning or afternoon summer sun. South facing glass does not generally receive direct sunlight but some south-east or south-west facing windows may also need shading from low-angled sun.

  • Skylights and transparent roofing (such as fibreglass sheeting) should also be completely shaded in summer - shading should be external and adjustable so that they can let light in when desired.

    • Insulation
    To ensure a comfortable temperature, a building must have insulation in the floors, walls and ceilings. Buildings are required by law to have a certain level of insulation in the walls and ceiling, however many older buildings that predate this regulation do not have any insulation. It is easier and more economical to install floor and wall insulation during construction or major renovations, although ceilings are often fairly easy to access at any stage to install or top up insulation.

    Ventilation
    Ventilation systems can provide your summer cooling needs naturally and ensure you don't need an energy intensive air conditioner. There are several approaches to cooling by ventilation:

  • Convection Flow- Opening low to high windows across a room / space so that when the outside air is cooler, high windows can be opened to release the warmer air, which rises. The lower windows draw in cooler air from outside.

  • Cross Ventilation- When the air outside is cooler (often during the night) open windows on opposite sides of the building so that cooler air is drawn in, replacing the warmer air.

  • Fans- exhaust fans can be used to pull warm air out of the building, creating a pressure imbalance that will draw cool air from outside via open windows. Make sure exhaust fans are self sealing to stop heat escaping through them in winter. Ceiling and portable fans are cheap to run, costing about 1c per hour, and can be very effective for cooling.

    • It is important to remember that ventilation only works when the temperature outside is cooler than the temperature inside - the building should be kept closed during very hot parts of the day, and opened up when the temperature outside is cooler than inside.

    Landscaping
    Careful selection and positioning of plants around your windows can also make a difference to passive cooling. Avoid paving/concrete in front of windows as it reflects heat up into the window during the day, and will store heat and release it during the night. Other things to do include:

  • Using trees and shrubs to buffer against hot northerly winds.
  • Leaving southern aspect of your garden open to cool breezes/cool change.
  • Keeping vegetation trimmed on the northern side so that low angled winter sun can enter through your windows and warm your home.

    • For further information about passive cooling or any of the above aspects contact MEFL to speak to a staff member on (03) 9385 8585.

    EnTechneVision Inc.