Project home with no air conditioning aims to inspire energy-efficient building in new Perth suburb
/ By Emma Wynne
Posted Sat 27 Aug 2022 at 9:40pmSaturday 27 Aug 2022 at 9:40pm
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From the outside, this display home in Brabham, a newly developed suburb in Perth’s outer east, looks a lot like the other project homes on the street with its freshly painted walls and new garden.
But this three-bedroom house has been assessed as having an energy rating of 9.2 stars according to the CSIRO’s Nationwide House Energy Rating Scheme (NatHERS).
That makes it the highest-rated two-storey house in the country, according to Mick Fabar, chief executive of Green Homes Australia, which built the house.
He hopes having a prototype that people can see for themselves will encourage them to commission buildings that use far less energy.
“That’s why we’ve built this home, so they can come in, come on the hottest day and see what it’s like,” Mr Fabar said.
No air conditioning experience
The house, which is built using a lightweight timber frame, has every element commonly associated with environmentally conscious living — a light-coloured roof, solar panels, battery storage and double-glazed windows.
Significantly, it has no air conditioning, only ceiling fans.
But Mr Fabar said it was the less-flashy elements that made the most difference to the house, like the polished-concrete floor that runs through the ground floor which provides the all-important thermal mass.
“Concrete is absolutely beneficial; you have to have thermal mass in a home to mediate the temperature whether you’re in a warm climate or a cold climate.
“You need thermal mass to be able to take the energy out of the environment, the living space, and then feed it back in at night.”
Added thermal mass is achieved with an interior brick wall — the building team chose to leave it unrendered when they were told leaving it would take the house from a 9.1-star rating to 9.2.
The second element is the positioning of the double-glazed windows for passive cooling and heating.
“All of the windows have been calculated to be in the right position to not allow the summer sun to enter the home but the right amount of winter sun to enter the home, so that’s a critical calculation,” Mr Fabar said.
“We’ve got fans to cool in summer, and in winter the design really is about that winter sun and heating up that thermal mass and using that to heat the home.”
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The design has also focused on an often overlooked element in Australia housing — airtightness — which means once the house warms up or cools down, it stays that way.
“You don’t want to be creating a living environment and then having that air leak out under the doors and under skirtings and through power points and through windows,” Mr Fabar said.
“In Australia, we’ve got a terrible history of homes that leak — 5, 6, 7 per cent — and there’s no standard.”
The display house aims to have air leakage of less than 1 per cent.
“It’s really simple building science but it’s not overly difficult, it’s just that builders aren’t applying it,” Mr Fabar said.
Everyone involved in the project is aware that spending hundreds of thousands on a new house without cooling at the flick of a switch can be a hard sell, especially in an area 20 kilometres inland where the summer sea breeze is slow to reach.
But the builders and developers are hoping the potential savings in electricity bills and a chance to see if it works will be tempting.
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Cost of building
Mr Fabar would not reveal how much the house cost to build, but said it was in the low $500,000 range and not significantly more than a comparable home.
“Building an energy-efficient home doesn’t cost you necessarily any more money if you design it properly,” he said.
“Traditionally, we’re seeing about a 2 to 3 per cent rise on cost to build an energy-efficient, sustainable home.”
But the savings in future years are expected to be significant, he added.
“Everyone lives differently. Some people sleep with the lights on or have two-hour showers, but based on the national average, the energy use will be reduced by 70 per cent.”
To find more evidence of its efficiency, the house will be studied by researchers from the University of NSW, both as a display home and when it’s occupied to get data on the true energy use.
Paul Lakey, regional general manager with Peet, the joint developer of the Brabham Estate alongside the state government, said the ongoing costs of running a home were becoming more pertinent for buyers.
“One of the biggest things that people need to work out when they’re looking at building a home is the life of the home,” Mr Lakey said.
“If you can save several thousand dollars a year on energy efficiency and costs per year, then that’s a good way to go. Over 20 years that builds up.
“The cost of energy is not going to go down anytime soon. This is a big factor in terms of the cost of living going up at the moment.
“If you can keep those ongoing recurring costs down in a simple way without affecting your living standard, then that’s got to be a good thing.”