Passive design in the home

Here in Perth, we are lucky to enjoy a temperate climate for much of the year. However, in summer and winter we do experience extremes that can make life at home less comfortable if we do not have any heating or cooling systems in place.

One way to make things more comfortable is to employ passive design principles within the home. Thanks to Your Home, here’s some more information about passive design and how it can benefit us in Perth…

‘Passive design’ is design that takes advantage of the climate to maintain a comfortable temperature range in the home. Passive design reduces or eliminates the need for auxiliary heating or cooling, which accounts for about 40% (or much more in some climates) of energy use in the average Australian home.

Paying attention to the principles of good passive design suitable for your climate effectively ‘locks in’ thermal comfort, low heating and cooling bills, and reduced greenhouse gas emissions for the life span of your home.

Passive design utilises natural sources of heating and cooling, such as the sun and cooling breezes. It is achieved by appropriately orientating your building on its site and carefully designing the building envelope (roof, walls, windows and floors of a home). Well-designed building envelopes minimise unwanted heat gain and loss.

Good passive design ensures that the occupants remain thermally comfortable with minimal auxiliary heating or cooling in the climate where they are built. Each of the eight main climate zones in Australia has its own climatic characteristics that determine the most appropriate design objectives and design responses. Here in Perth, we live in a warm temperate climate with four distinct seasons.

This is an atypical zone in that it includes a more diverse range of climatic conditions than other zones. This diversity is particularly evident in the hours of sunlight, and direction and reliability of cool breezes.

Minimising heating and cooling energy use should be a primary design objective.

Design considerations

• Careful, individual site analysis is needed to identify conditions that call for specific design adjustments.
• In all sub-zones, passive solar heating and cooling are important.
• Different approaches are required for passive cooling depending on the patterns and reliability of cool breezes.
• To reduce heat gain, avoid inappropriate or overuse of glazing.
• Passive solar heating is always desirable and simply achieved where access to adequate sunlight is available. Where solar access is not available, consider using lightweight building frames that respond quickly and efficiently to minimal, carbon efficient auxiliary heating.
• Lower thermal mass requirements allow for low embodied energy solutions.
• Use roof spaces as a thermal buffer zone by ventilating them in summer and sealing them in winter.

Windows and shading

• Avoid overuse of glazing.
• Carefully size and orientate windows, as this will often yield ideal results with less expensive glazing options.
• Reduce expenditure on glazing and divert the savings to efficient appliances and on-site renewable energy generation, generating effective carbon reductions.
• Use passive solar shading on northerly windows.
• Shade all east and west-facing glass in summer (see Shading).
• Consider adjustable shading to allow variable solar access in spring and autumn.

Insulation

• Use bulk and reflective insulation in ceilings, and bulk or reflective insulation in walls.
• Insulate under concrete slabs if using in-slab heating.
• Provide external insulation to all thermal mass.
• Insulate elevated floors (concrete and lightweight)
• Refer to Insulation for recommended optimal insulation levels.
• Ensure all spaces are effectively air sealed.

Construction systems

• Earth coupled slabs are highly beneficial.
• Choose low embodied energy walls, roofing and finishes.
• Composite thermal mass construction is ideal although most well-designed construction systems can achieve 10 star performance at relatively low cost.
• Choose light coloured roof materials.

For more information, visit the Your Home website or speak to your local builder.