Penny Roberts lives in a bushfire-prone area of Victoria, but she doesn’t fear a blaze will destroy her home.
That’s because her house, nestled into the side of a hill in the town of Newham in the Macedon Ranges north of Melbourne, is predominantly underground.
The roof is covered in earth and native grasses, and three sides are built into the cool earth of the hill. Only the front is exposed for ventilation and light.
Light courts or light wells opening up through the roof allow light to enter the back of the house.
Underground, or earth-sheltered, houses are growing in popularity due to their ability to withstand bushfires and to naturally insulate the dwellings from temperature extremes.
Ms Roberts’ home, which was completed two years ago, took about two years to build after a long research and construction process.
“I started thinking about doing earth-sheltered [houses] 20 years ago,” she said.
Ms Roberts believes underground homes will become more common as the frequency of bushfires and heatwaves escalates.
“You reach a tipping point with any new idea,” she said.
“As people become more concerned about extreme weather events and fire as a risk factor, it will shift towards more [people building underground homes].”
Architects specialising in bushfire-protected homes say demand for underground dwellings has “quadrupled” since the Black Summer fires of 2019-20 devastated communities in south-eastern Australia and destroyed almost 3,000 homes.
The Australasian Fire Authorities Council has warned there is an increased risk of bushfires again this spring in eastern and central Australia, with conditions forecast to be warm and dry for most of the country.
Bushfires can’t ‘get in’
Paul Mitchell has been designing underground homes with ShelterSpace for clients across Australia, including Ms Roberts, for the past 40 years.
Mr Mitchell, who lives in his own earth-sheltered home in the Adelaide Hills, said underground homes were not a new concept.
“Humans have been living in earth-sheltered houses ever since, I’m going to say, they crawled out of the cave,” he said.
In Australia, in places like Coober Pedy in the South Australian outback, where temperatures can soar to 50 degrees during the day in summer, people have been living underground for decades.
About 60 per cent of the opal mining town’s 3,500 residents have adapted to living beneath the dry, dusty landscape to escape the heat.
And with projections for a hot and dry end to 2023 under the El Niño climate pattern, and increased fuel loads across some parts of the country, the risk of bushfires in other regional areas has escalated.
Mr Mitchell says the demand for alternative housing that can better meet the growing bushfire threat is already increasing, but he is planning to take a step back after four decades on the front line.
He’s handing the company’s reins to Dale Lloyd, who he met on the building site of an underground house seven years ago.
Mr Lloyd said ShelterSpace’s number of clients per year had quadrupled since the Black Summer bushfires, with the company now building about 12 underground homes a year.
“There’s been probably more interest than I’ve ever seen, as in we’re answering a lot of inquiries,” he said.
“But not many are going anywhere, because the majority of people can’t afford to build in the current construction climate.”
Mr Lloyd said the company’s houses were based on simple principles.
“It’s a house that’s tucked into the hill to protect itself from the elements and from bushfire risk,” Mr Lloyd said.
“You look at most Australian mammals and the reason they survive bushfires is usually because they’ve got burrows.”
Mr Mitchell said bushfires mostly destroyed houses when embers got into the roof space, but ShelterSpace’s roofs were not at risk of ember strike because they were made of concrete and earth.
“There’s nowhere where it can get in,” he said.
The windows are the only vulnerable spot, but Mr Lloyd said in high-risk bushfire areas they were protected by metal frames and roller shutters.
Despite the heightened protections afforded by earth-sheltered homes, Mr Mitchell and Mr Lloyd both said people living in underground houses should still have a comprehensive bushfire plan.
Right design essential
The price of building an underground home depends on the number of “bells and whistles” included, but Mr Lloyd and Mr Mitchell said it probably would not be at the lower end of what it cost to build an above-ground house.
However, because underground homes used the earth to heat and cool the space, they said residents’ energy costs could be reduced.
“None of our houses need air-conditioning, usually a ceiling fan is enough to get that airflow,” Mr Lloyd said.
“In winter, then all you have to do is bring it up four to five degrees to get it to that human comfort level.”
For Ms Roberts, it was important to have a house that could stay warm in winter without a heater.
“People around here in central Victoria, in all housing stock, will be heating nine months of the year,” Ms Roberts said.
“We rarely use the 1,000-watt radiator.”
Bridget Puszka, who designs energy-efficient homes with BP Architects, said interest in her underground houses had also increased over the past few years.
“Mostly because of bushfire safety, but also because of passive solar design to keep the house warm and keep your electricity bills down,” she said.
Most of the underground homes Ms Puszka designs are in Victoria’s Gippsland region, which is particularly vulnerable to bushfires.
She said it was important to work with a reputable designer to avoid problems with condensation and mould.
“If you don’t get the house design right, you can end up with a dark, damp home with musty air that is not healthy,” she said.
‘Radically alternative’ homes on the rise
Justin Leonard, CSIRO’s research leader for bushfire adaptation, said people were starting to “move towards quite radically alternative designs” to create both energy-efficient and bushfire-protected homes.
He said building into the earth was an effective way to protect homes from bushfires.
“There’s certainly no question that an earth-covered house doesn’t have any risk or issue from the earth side, [bushfires] just simply can’t get through or have any effect,” he said.
With the addition of shutters and metal frames to protect the windows, he said underground homes were very safe.
But for those opting to stay at home during a bushfire, Dr Leonard said it was important to ensure the shutters could be opened if the residents needed to evacuate the house.
“Do they require power to open? Do they have a manual override? Are they going to get jammed if they get heated? Or distorted by the heat?” he said.
“Otherwise, it’s a really, really good way to have robust protection in those areas.”
