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Sometimes revolutions begin the most unlikely places. The demonstration house at 19 Laurie Street in Kewdale, a post-war Perth suburb, for example.
This modest yet attractive house has been designed and constructed as a sustainable home using accepted and well-established building materials and processes. It achieves a remarkable seven stars for energy efficiency (on a scale of 10) under the AccuRate system – the second generation energy rating system developed by CSIRO and currently being introduced in Western Australia and some other states. |
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There’s nothing experimental about this project: no “high tech” panels made from exotic or untried materials, no special processes or techniques, and best of all, no compromises in comfort or use for the lucky eventual occupants.
The demonstration house was designed by Solar Dwellings (solardwellings.com.au) and built by
Jade Projects (jadeprojects.com.au) with assistance from Austral Bricks and Bristile Roofing.
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Heating and cooling the greatest energy challenge
Artificial heating and cooling is by far the greatest consumer of energy – 39 percent according to the Australian Greenhouse Office – in a typical Australian household. The recent rise in residential air-conditioning is expected to push the peak energy loading from winter to summer and force the construction of more power stations, generating even more greenhouse gases.
Griff Morris, Solar Dwellings principal, designed his first energy efficient house more than 30 years ago. “Today, at any one time we are working 80 to 90 homes,” he says proudly. |
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Solar Dwellings specialises in passive design, sometimes called passive solar, which harnesses natural forces to create houses with high comfort levels and low energy requirements. There are four basic principles to passive design:
| • Orientation – |
allowing the house to capture the heat of winter sun, while excluding summer heat
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| • Ventilation – |
utilising breezes to cool the house naturally
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| • Insulation – |
creating a barrier to heat transfer
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| • Thermal mass – |
using dense, heavy materials to store and slowly release heat energy |
For a design to work effectively, all four principles must be in place. “Passive design is like a Rubik’s Cube®,” Griff Morris explains. “Everything fits together, but if one piece is out the design will be compromised.” |
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Putting passive design principles to workOrientation is probably the most controversial aspect of passive design. Critics say that it isn’t always possible to have large, north-facing glass to capture the low winter sun. Griff Morris rejects this. “You can make most blocks work,” he contends. For example, the rear of the Kewdale block faces north-west, well off axis. The simple response was to orientate the rear-facing meals/family room to the north.
“The orientation can be up to 15 degrees either way off north, although 10 degrees or less is ideal,” Morris advises. Thermal mass is an essential but often overlooked part of passive design. High thermal mass materials such as bricks have opposing but complementary qualities to materials with high insulation values. “A well-insulated home may keep a consistent temperature with the aid of heating and cooling, but only for short periods of time,” Griff Morris explains. “To extend the period of heating and cooling you need the complementary effect of mass in both walls and floors (slab on ground).”
However highly insulated, a lightweight wall will not have this temperature-moderating effect in climates with a high diurnal (day/night) temperature range. “You have to use both thermal mass and insulation,” Morris says simply, a fact backed up by the Australian Greenhouse Office which advises that “appropriate use of thermal mass throughout your home can make a big difference to comfort and heating and cooling bills.” Jade Projects primarily chose the Kewdale block for its accessibility to transport and services. “We chose this site because we wanted to build a sustainable home, not just a passive design,” says director and building manager Daniel Smee. “It wasn’t picked for its orientation, which is not ideal.” |
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Conventional materials and construction practicesStructurally the demonstration house is conventional with cavity brickwork – standard practice in Perth – sitting on a concrete slab. The ceiling is insulated but insulation was not required in the walls to achieve the seven star rating.
This is supported by testing at The University of Newcastle which shows that a cavity brick wall is highly efficient at ironing out temperature highs and lows (see Further information).
Adding wall insulation and rated glass would have bumped the rating to eight-and-a-half stars “However at best we only ever insulate brickwork to the east and west,” says Griff Morris, “although we might wrap it around the corners by 500 mm or so.”
The use of brickwork’s high thermal mass as part of a passive design is only one aspect of the Kewdale house’s sustainable design. It also features a solar hot water service (water heating is the next highest household energy consumer after heating and cooling), smart lighting and wiring, rated toilets and showers, a 1300-litre tank collecting water from the Bristile Roofing tiled roof, and a grey water collection system distributing to sub-surface irrigation in the small, water-wise garden.
“The Austral Bricks Sustainable Home clearly demonstrates that it is possible to design and construct an attractive, affordable, energy-efficient house using conventional materials and techniques,” says Brad Moore, WA marketing manager for Austral Bricks and Bristile Roofing.
Griff Morris agrees with this and adds that it is feasible for energy-efficiency principles to be applied to project homes. “It’s mostly a matter of educating designers, sales people and the public,” he contends. “But in the end it’s not rocket science.” |
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Further information
Austral Bricks Background Paper, The Role of Thermal Mass in Energy-Efficient House Design. Available from Austral Bricks or download from www.australbricks.com.au (under ‘Technical Resources’).
Clay Brick and Paver Institute Research Paper 18, A Comparative Study of the Thermal Performance of Cavity and Brick Veneer Construction. Download from www.cbpi.com.au (under ‘Resources’).
Clay Brick and Paver Institute Research Paper 19, The Study of Heat Flows in Masonry Walls in a Thermal Test Building Incorporating a Window. As previous. Australian Greenhouse Office, Your Home Technical Manual, www.greenhouse.gov.au.
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