It is summer in Australia and the temperature is soaring towards the 40s, so you reach for the air-conditioning remote but cringe at the thought of the energy bill come March.
- Residents of Coober Pedy live underground to escape the searing heat
- The University of South Australia’s Stephen Berry says indoor conditions in underground homes are stable
- One businessman has created a semi-underground house called the Earthship
The struggle for energy efficiency in a changing climate and the mental maths of keeping your home comfortable are a dominant point in day-to-day life.
But deep in the South Australian outback is a town that has been dealing with this problem for years.
So, what’s the secret?
Coober Pedy is a difficult place to live.
Set on the edge the Stuart Range, the town of 2,000 people sits atop a bed of sandstone glittered with opal, with no topsoil and practically no vegetation.
The average daytime temperature in summer is 37 degrees, but living in a house in such conditions is uncomfortable and expensive.
So, the locals turned to dugouts: underground homes.
Stephen Berry, manager of the University of SA’s Research Node for Low-Carbon Living, said it was obvious why.
“When you have a building that’s covered in earth or is underground, you effectively get infinite thermal mass,” he said.
“That means the indoor conditions remain remarkably stable — they hardly vary at all.
Despite the temperature edging into the 40s during summer, dugouts in Coober Pedy usually stay between 19 and 25 degrees, which saves residents huge amounts of money on cooling expenses.
So, why aren’t we living underground?
If underground housing has such obvious benefits, why isn’t it more widespread?
Dr Berry said not everywhere was as well suited to building underground as Coober Pedy.
“Coober Pedy is fantastic because it’s soil type allows for relatively easy construction of underground buildings,” he said.
Martin Freney, a lecturer in Sustainable Design at the University of South Australia, said while building underground homes in suburban areas was not impossible, it was extremely difficult.
“You’re essentially digging a big hole and if that’s near neighbouring buildings or fences, there’s the potential for undermining and the collapse of those structures,” Dr Freney said.
“If you want to build a fully underground house, you might get some pushback from the planning officer at council, because it probably won’t comply with the streetscape rules.”
The art of compromise
While building underground homes might be difficult, there are alternatives.
Alongside his work as a lecturer, Dr Freney also runs a business that builds a style of house known as an ‘Earthship’.
The Earthship concept was developed by an American architect named Michael Reynolds in the 1970s and was designed as a self-sustaining, off-the-grid house.
Earthship-style buildings are dug slightly into the ground and the rear of the building is covered with an earthen mound and reinforced with a retaining wall made of recycled tyres.
The mound gives the building a high thermal mass: absorbing heat during the day and radiating it at night to keep the temperature consistent.
“If you have the mound itself, ideally to the east, south and west, combined with glazed glass facing north and well insulated walls, you can get the benefits of an underground house in suburbia,” Dr Freney said.
But according to Dr Berry, much like entirely underground houses, the Earthship is not without its downsides.
“The earth sheltered concept is a fabulous one, and it’s very useful for particular situations,” Dr Berry said.
“We’re unlikely to see a high number of earth-covered buildings in suburbia … because each type of house isn’t valid in every location.”