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Home energy efficiency could be improved significantly through simple tweaks like roof colour

ABC NEWS logo ABC NEWS 23/01/2020
a close up of a brick building: Red, black or white? The colour of your roof could drastically alter your air-conditioning costs. (ABC News: Gian De Poloni) © Provided by ABC NEWS Red, black or white? The colour of your roof could drastically alter your air-conditioning costs. (ABC News: Gian De Poloni)

For most of us, our home is the most expensive purchase of our lives, but are we ignoring the true cost of home ownership?

For Perth architect Kate Fitzgerald, the lack of attention paid to home energy efficiency is baffling.

"We seem to expect that design standard for our cars and in all sorts of things and it still baffles me that we test cars for safety and emissions, but we are not really asking that of our biggest investment," Ms Fitzgerald told Damian Smith on ABC Radio Perth.

Black and white difference in roofing

International research also shows that energy-efficient homes can also fetch a higher price.

All new home buildings in Australia must be assessed under the nationwide house energy rating scheme (NatHERS), which uses software developed by the CSIRO to evaluate the design to estimate the amount of energy it will need for heating and cooling, and gives it a star rating out of 10.

Simple choices like a dark colour roof instead of a lighter one can make a huge difference, as a recent simulation showed.

"We took a project that we have recently designed, which has a 7.5 star [rating] and we changed the cladding to a dark cladding and re-ran the scenarios and it turns out that you will lose almost half a star by changing the colour to a dark colour," Ms Fitzgerald explained.

"Your cooling loads increase by about 10 megajoules per square metre in the summertime.

"Putting a dark cladding on your roof, in this day and age, I think you're highly likely to be paying much more money for your AC bill."

New builds are required to be at least six stars, but there are loopholes that mean there are some new homes that Ms Fitzgerald believes may only be two stars.

"Where it becomes difficult is that there are loopholes for situations where things aren't quite standard," she said.

Maybe you have a block of land where the only option for you is to have your long side facing west and it's actually really hard to design something that achieves a really high star rating.

"In that situation you might actually need to use an alternative method [of energy rating]," Ms Fitzgerald said.

"The alternative method is designed for one-off projects."

The other big impacts are in building material and insulation.

"You do want to insulate — you want a fluffy doona that covers your house. Double brick isn't great for that," Ms Fitzgerald said.

"Timber frame is terrific, reverse brick veneer is even better because you get the fluffy doona on the outside and then you get the still inert mass of the brick and the concrete floors on the inside.

"What that does is help maintain a constant temperature by taking out that heat from the air or releasing that heat into the air when its colder."

Above all, she recommends that prospective home builders ask questions of the people designing and building their home, and demand energy efficient design.

"You are going to keep getting the same product unless you ask for a different one," she said.

Retrofitting can make 'extraordinary' difference

For Peter Newman, professor of sustainability at Perth's Curtin University, there also needs to be a focus what can be done to retrofit buildings, as most people buy existing homes rather than building.

While replacing a roof or changing its colour may be prohibitively expensive, there are other things that can be done.

He has recently gone through the process with his own home, a 170-year-old stone house in Fremantle, which was solidly built but lacked natural light, meaning he had to have lights on continually during the day.

"That was the first thing, doing clever things with windows, and sky lights," Professor Newman said.

"The second thing was to seal it off in ways that we hadn't been doing — doors and windows didn't fit very well.

"And then we put a lot more insulation in, into the walls and roof. It's so much better now and it really works.

"It really is extraordinary how you can shut the doors and windows and walk into a cool house on hot days or a warm house on cool days."

Value-adding for consumers

Professor Newman said the energy efficiency of houses, and the ongoing costs of powering them, was becoming more important to consumers.

"The need for having a redeveloped city that has medium-density, zero-carbon housing, is very critical," he said.

"We surveyed 20-odd developments in Perth and found that location was the number one thing [buyers were concerned with].

"The second thing was the price and the third thing was sustainability, and that came even before how it looked. They really wanted to know a lot about the energy efficiency.

"This comes as a surprise to most real estate agents who are very stuck on the idea that people aren't interested in that."

In Canberra, energy ratings are a key selling point in real estate and have to be disclosed to potential buyers, and Professor Newman said it is something the rest of the country needs to catch up on.

"People respond to that because they say 'well, if I can get an eight star house for the same price as a six star house then I'll get it, because I'm going to pay less every day'," he said.

"It is a way of showing that being green is good economics.

"It's an integration that is fundamental to the transition we are going through."

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