How does the average home rate?
The energy rating of your home will be largely influenced by when it was built. In 2011, Victoria mandated a six-star minimum NatHERS rating for new homes, apartments and major renovations.
But the average rating of houses constructed in Victoria before 1990 was just 1.6 stars, according to a study by Sustainability Victoria, and the average rating of houses constructed between 1990 and 2005 was around 3.1 stars.
Within that context the current six-star requirement seems like a comprehensive victory for energy efficiency, but according to Sustainability Victoria, it really only indicates fair, but not outstanding, thermal performance. Sustainability Victoria says the current six-star minimum falls short of desirable economic and environmental outcomes and below the minimum set by many other countries.
What’s in an eight-star home?
So, if six stars is inadequate and eight stars is desirable, what exactly is an eight-star home? Luke Middleton of award-winning Eme Design says achieving an eight-star rating is easier than people might think. “The good news is if you start with clever design it doesn’t have to necessarily cost a heap more,” he says. “If you design an efficient, well-orientated home the eight stars are readily achievable with very little extra investment.”
When designing a new home or renovating, the basics of good orientation, shading, insulation and double glazing make all the difference. Orientation to the north with plenty of north-facing windows maximises warmth and light into the home over winter, but allows for shading out sun in the heat of the day during summer.
In addition, an energy-efficient home will have a relatively air-tight building envelope to minimise leakage of heat from the home in winter and into the home in summer.
Crucially, explains Luke, smaller homes tend to be more energy efficient. “We need to get our heads around the idea that well-designed spaces don’t need the same dimensions as badly designed spaces.”
But he says householders should think beyond the NatHERS assessment criteria when optimising their energy efficiency. The ratings system doesn’t take into account trees and foliage, for example. “Planting a deciduous tree can be a great way to reduce sun in summer and increase it in winter, but the star rating doesn’t mention gardens,” says Luke. “Use the stars as a guide rather than your sole focus.”
Does energy efficiency cost extra?
The costs of achieving an eight-star home will vary across Australia and depend on the design. National not-for-profit sustainability advocate Renew estimates that it costs around $6000 more to build a new home to eight stars rather than the minimum six-star standard. But it says power-bill savings will compensate for the extra upfront cost in just six years.
Sustainability Victoria estimates that going up just one star from six to seven will reduce household heating and cooling energy needs by 30 per cent. An eight-star house will likely require half as much energy for heating and cooling as that of a six-star, and if you go up to nine stars you’ll be using 80 per cent less energy.
It all adds up to significant savings, but it’s important to remember there are factors beyond cost, says Luke Middleton. “Your house is more than a payback machine,” he says. “Energy efficiency and good design is about your and your family’s comfort. It just makes a much nicer place to live in.”