How we can build smarter
Last summer’s catastrophic bushfires, which exploded previous notions of where fire risk lies in this country, have again thrown the spotlight on how smart housing design and materials can help protect life and property.
Major fires always prompt enquiries from heartbroken home owners to the Bushfire Building Council’s call lines, seeking advice on regulations and the latest in design and materials as they set out to rebuild. But in the last year large numbers of people who watched Australia burn – but weren’t affected themselves – have called too, asking what they can do to maximise their chance of survival when the next horror rages.
Make existing homes more resilient
While built-from-scratch exemplars like the Nelsons’ Sarsfield home represent an ideal, BBCA chief executive Kate Cotter says much can be done to retrofit existing housing of any age and style to help reduce the risk of large-scale life and property loss.
“Everyone focuses on new builds, but it’s such a small fraction of the problem,” Kate says. “Legacy homes that don’t meet today’s bushfire standards are 90 per cent of our building stock, that’s 90 per cent of people in bushfire-prone areas who are highly exposed.”
A particular danger, she says, is house-to-house ignition – essentially the domino effect that spreads fire between houses set less than 10 metres apart. “It’s very difficult to protect your house from the house next door [when it’s] on fire because it burns much hotter and longer than the bushfire itself.”
She says retro-fitting existing homes to protect them from embers – which according to the CSIRO cause more than 90 per cent of building loss in bushfires – is the smartest, cheapest, most sensible thing people can do. As our bushfires get more frequent and intense, and burn for longer, our loss rate is rising, making the economics of retro-fitting “almost a no-brainer”.
Kate believes that with the right government incentives, like those offered to boost energy efficiency and uptake of rooftop solar, it could be broadly adopted. The BBCA’s Property Bushfire Resilience Star Rating – based on an expert site assessment and specific recommendations to upgrade the property – is ready to meet this need.
Guard against ember attack
Ember protection measures can be as simple as fitting fire-resistant shutters on windows that face the house next door, sealing pipe and ventilation outlets with ember mesh screening, and ensuring the perimeter of the house is free of anything that can burn.
Kate says house-to-house ignition was a significant factor at Wye River in 2015, Marysville (2009) and Canberra (2003), as well as wildfires in the United States and Canada. Conjola Park in New South Wales, where 89 homes were destroyed last summer, suffered a similar fate.
“There was a great degree of house-to-house ignition there and embers reaching into places that weren’t considered bushfire-prone,” says Kate.
She says such new at-risk areas are “a bit of a black hole” in terms of mapping and regulations, and highlight the vulnerability of tightly packed coastal and urban-fringe residential developments.
“You picture fire going into larger settlements with thousands of houses rather than hundreds and it becomes clear why we’ve got a problem.”
More than 3000 homes were destroyed nationwide last summer, 400 of them in Victoria. The bushfire royal commission noted: “The 2019-2020 bushfires and the conditions leading up to them were unprecedented. They are no longer unprecedented.”
The time to build smarter – and protect what we have – is now.
When Baldwin-O’Bryan Architects started devoting more time and energy to designing underground (or ‘earth-sheltered’) houses, it was largely driven by how they looked and their thermal advantages.
Of late the commissions have been coming fast (around 20, with more than 100 in the pipeline), with 60 per cent of their clients drawn to living surrounded by earth for the protection from bushfires it brings.
“You can’t burn through soil,” partner Sean O’Bryan says. “If the top of the house catches, it’ll be just a grass fire that won’t heat the house at all.”
Their earth-sheltered designs hinge around arches of compressed-earth blocks that frame entrances to dwellings that are covered in at least 500 millimetres of soil and grass. At around $1680 per square metre for a home with medium finishes, compared with $2600 for a conventional house with the same level of finish in Victoria, they are cost effective. Closing in the glazing with panels of magnesium oxide ups the price, but completes the cocoon effect.
“We’re excited by how you can put a building into a site and make it become part of the site,” Sean says. “We’re excited about the challenge of fire as well. We came to underground houses because of the thermals, but we’ve found the main market is coming from bushfires, which we didn’t predict.”
The practice expects to start construction of earth-sheltered homes in the next few months in Nathalia, Steels Creek and Kinglake in Victoria, and several New South Wales locations.