There’s only a handful of Australian houses that can boast a 10-star NatHERS rating, and now Adelaide has its first.
In fact, the designers of the ultra-energy efficient home, SUHO, expect it to perform even better than the 10-star standard.
SUHO studio manager Ruth Nordstrom told The Fifth Estate that as well as the usual features you’d expect to see in a super energy efficient house, such as airtightness and loads of insulation, it’s also decked out with smart electronics that monitor performance and allow the building to respond to climatic conditions, such as automatically turning on fans and opening windows on a hot day.
Achieving the top rating in the Adelaide climate zone had its challenges, with the area known for warm overnight temperatures. This makes it difficult to purge the building of heat at night like you can in cooler states.
Nordstrom says managing Adelaide’s climate comes down to things like the correct shading, having eaves of the right depth and automatic blinds.
The airtightness level meets the Passive House standard (a maximum of 0.6 air changes an hour) thanks to “very clever detailing” by lead construction design specialist
Geraldine Petit, who brought her European building science training to the table.
The airtightness and the extra attention to thermal bridging will hopefully see the building outperform the 10-star energy efficiency rating system, Nordstrom explains.
And while hitting-slash-exceeding the top NatHERS rating was central to the project, the house is more than an energy efficient box. The team wanted to take a holistic approach to sustainability, which includes air quality and occupant comfort.
Nordstrom hopes prototype projects like this will prevent Australia copying a major mistake made by countries that increased insulation levels without also improving ventilation, resulting in houses with mould and poor indoor air quality.
“We are of the view that we can learn from others and jump ahead.”
The team also wanted to be mindful of embodied carbon, and stick with locally sourced, non-toxic products where possible. The builders, Woolcock Constructions (a sister company of SUHO), also engaged with the KESAB Clean Site program that saw 90 per cent of materials taken from site recycled.
In a move that’s reminiscent of the “beauty petal” criteria in the Living Building Challenge, Nordstrom says the team “really wanted to push for a striking image”.
She says she actively challenges the enduring notion that there’s a choice between sustainability and aesthetics in architecture.
The all-electric house has a 5kW solar system that will meet the 0.88kWh daily (3MJ/M2 annual) energy use (based on standard usage by a four-person household).
This will amount to more than 90 per cent of the energy going back into the grid, Nordstrom says. And while it would have been possible to take the home off grid, it’s more useful to leverage solar powered energy efficient buildings as “little power stations” that export surplus energy to the grid.
Although the building is finished, there’s no one living in it yet. It will spend the next 12 months or so uninhabited so that the team can collect data on how it performs, including how it adapts to climate change. This data will be fed back to the CSIRO for research.
Ten stars isn’t cheap, yet, but 9 is achievable
As the house is a prototype – proof that it’s possible to build a 10 star house in Adelaide’s tough climate – it’s full of state-of-the-art gadgets that have made it unrealistically expensive to replicate.
However, Nordstrom says projects like this help build capability and know-how to produce higher performing homes within a standard budget. She says that it’s now possible to achieve an 8.5 or even 9 star home with simple construction methods. In the past, a 7 or a 7.5 rating was about as high as you could get before the capital costs became prohibitive.
SUHO offers a home for 7.5-8 stars as an off-the-plan offering that’s appropriate for the Adelaide climate or can be adapted for others.
The next step will be rolling out other examples of the house at different scales to put pressure on the market.