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Choosing net zero energy homes

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We check the ‘star ratings’ and reviews before we buy dishwashers, washing machines, refrigerators and televisions. So why is it still hard to buy and run an eco-friendly, energy-efficient home?

Buildings are responsible for 32 per cent of global energy use, and generate 19 per cent of energy-related greenhouse gas emissions. Within the building sector, residential buildings use three times more energy than commercial buildings. As Australia works towards meeting its international commitment of net zero emissions by 2050, residential housing will need to play its part to achieve this goal.

Research Fellow Dr Christine Eon in the Curtin University Sustainable Policy Institute (CUSP) is working on improving residential energy efficiency, investigating the intersections between energy-efficient technologies, the construction industry and homeowner behaviour.

“As an engineer, my original focus was on the technology and how to design and build better houses,” admits Eon.

“But the technology is already here. Our current limitations all revolve around market forces, people and their behaviour.”

Niche architectural firms already offer premium performance homes, but one-off homes come at a cost. Eon asserts that the housing construction industry will remain focused on cost and amenity over energy efficiency until it is demonstrated that zero energy homes don’t have to be more expensive, and that there is a market for them.

To address this, she worked with major construction companies in Townsville, Melbourne, Canberra and Perth to improve their baseline designs for mainstream houses. The companies then built a display house in each city to demonstrate that it could be done affordably.

“You adapt the house design to the local conditions. Turning the floorplan so the living spaces face north, insulating everything properly – the ceiling, walls, and even the floor in places like Canberra.

“Double glazing in colder climates, and minimising or shading east- and west-facing glazing in warmer climates. Light-coloured roofs to reflect the heat in places like Perth, and darker coloured roofs to absorb it in colder climates.”

Major efficiency gains were made in the demonstration houses through solar-passive design, additional insulation, glazing upgrades and installing energy efficient appliances, particularly hot water heat pumps and air conditioners. A relatively small solar photovoltaic system (3-4 kW) could also be installed to cover the electricity needs of typical households.

“These demonstration projects are showing that zero net energy housing is achievable and affordable once we get economies of scale,” says Eon.

“Once high-performance products like double glazing are supplied in volume to mainstream builders, costs will come down.

“Projects like this are working to raise awareness in both the market and the construction industry, because the demand is growing.”

Policy and regulatory improvements are also needed to transition to net zero homes.

“Auditing buildings for energy efficiency is haphazard, and the rating system also causes confusion. Although there’s a system that rates houses for energy efficiency, there are other systems with different performance measures that vary between states.

“If we could create a consistent rating system for houses, so that builders can promote and market their high star-rated, energy-efficient houses like white goods manufacturers do, we may encourage a shift in the construction sector as house buyers make more considered choices.”

But Eon says that buyer behaviour is still a barrier to the zero net energy goal for residential housing.

“It’s well known that even when you live in a high-performance house, it often underperforms in practice, so a lot of my research has been focused on why this happens.”

She has recently tracked the lifestyles and behaviours of ten families living in a range of energy-efficient houses for two years, to see how the houses really performed. One common observation was a ‘rebound effect’ – if people expect that their house is going to function intrinsically well, they don’t try particularly hard to conserve resources.

“If you’ve got solar panels on your roof, you worry less about how you’re using electricity, because it’s ‘free’,” explains Eon.

“But that only works if you’re using it on sunny days, not at night or in the rain unless you’ve also got an energy storage system.

“You don’t get an instruction manual when you buy a house, so the way you run it develops around your everyday routines and habits. Energy use tends to be shaped by routines established around children, work and leisure time, and efficiency is a secondary consideration.”

Eon’s study provided insights into the connections between energy-efficient technologies and people’s everyday behaviour, and is now guiding approaches to better enable energy efficiency in the home. For example, automation can allow energy use to be flexibly disconnected from lifestyle routines; simply incorporating timers into appliances so they can be run when the sun is shining – from pool pumps and air conditioners to washing machines and dishwashers – can have a significant impact.

“Helping people understand how their houses really work doesn’t create behavioural change, as lifestyle factors drive most decision making. But by understanding people’s everyday practices, we can adapt existing technologies to their routines to improve their energy efficiency without them having to make significant changes.”

Getting residential housing to net zero emissions by 2050 is possible. Consumers want energy efficient housing, and it doesn’t have to cost much more. But it always comes down to the choices we make. Eon’s research is trying to make those choices, from the house we buy to the appliances we use, as easy as possible.

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