In Australia, it’s safe to say that we’re a fair way behind many other parts of the world when it comes to the thermal performance of our buildings. This is largely a result of our predominantly temperate climate and the reduced need for better insulated, higher performance walls and windows. But this means that we still use significantly more energy in heating and cooling our spaces than is necessary, given the advances in thermally efficient construction that are now available to us.
Sustainability is now front of mind for the Australian construction industry, and rightly so. In line with this, the National Construction Code (NCC) 2019 introduced increased thermal performance requirements in Section J. The updated code recognises the effects that standard aluminium window and door frames can have on a building’s overall performance through thermal bridging (whereby the frame creates a heat ‘bridge’ between the interior and exterior, allowing unwanted heat transfer).
Thermally broken windows and doors are those which minimise that heat transfer, reducing temperature fluctuations inside and thus lessening the energy requirements for heating and cooling.
Aluminium systems designer and manufacturer Alspec has long been at the forefront of thermally broken frames in this country. “If you look at the numbers, you might have 50 square metres of glass on a standard house, which means with a 10 degree temperature difference, you could lose 2500 watts of energy per hour through those windows,” says Ross Baynham, National Specification Manager at Alspec. “There’s significant heat transfer, and if you use a low performance glazing system, that’s going to happen no matter where you build in Australia.”
With a keen eye to the sustainability benefits that thermally broken frames bring to any dwelling, Ross is passionate about educating the wider industry to bring Australia up to pace with other markets. “ In the UK, 15-20 years ago, you couldn't buy single glazing, it just wasn't really an option,” says Ross. “But here, even simple double glazing isn’t being used everywhere, and as a result there’s a bit of a knowledge gap about how to use this type of technology properly. I can speak from my own experience of putting an extension on my house and watching the builders put windows in with 10mm gaps along the side of the windows that they were just going to cover with an architrave rather than actually filling the hole. You can have all the most thermally efficient windows in the world, but if you don’t install them right, they won’t do the job - I think that's a bigger industry issue, and there’s definitely some work to be done there.”
But thermally broken systems are not just about performance. They also enable architects and designers to use more glass, embrace biophilic design and natural light while still maintaining excellent energy efficiency. “There's a range of benefits to using thermally broken systems from a design point of view,” says Ross. “It might mean that you can use more windows and still meet construction code compliance, increase your window to wall ratio, it can make a building healthier, from a developer point of view can make your building more attractive. You’re also future proofing your asset, which is beneficial, because the cost of retrofitting these items later could be much more considerable.”
While there can be more upfront costs associated with thermally broken systems, the cost burden is easily outweighed by energy savings throughout the lifecycle of the building. This longer-term view is something that both buyers and the construction industry are looking towards and is central to the sustainability mindset. While the technology has been available in Australia for a while, adoption is still in its comparative infancy. But it seems certain that thermally broken systems will become an integral part of our sustainable construction future.
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