With a low eco-footprint and high fire resistance, earth building is an old medium with modern appeal.
Homes made from unfired earth – methods such as adobe, cob, pressed brick and rammed earth – now house up to half the world’s people, according to the Earth Building Association of Australia. And Victoria isn’t out in the cold: we have a long-standing tradition of earth building, especially in Melbourne’s north-eastern suburbs.
The association’s annual conference is being held in Eltham from Friday 14 to Sunday 16 August. It will focus on themes of sustainability, energy efficiency and bushfire resistance, and include tours of existing homes.
“Very few building techniques can match earth for low embodied energy,” says vice president Ray Trappel, an architect from NSW. It’s even possible for mudbrick walls to have negative embodied energy – to save energy overall – he says, if they’re made from intercepted excavation waste (which avoids trucking the material to landfill).
The potential for extra fire resistance is another benefit. A 250-millimetre thick mudbrick wall can achieve a high, four-hour fire rating. “A lot of people are considering using earth in their rebuilding (after the January bushfires),” Mr Trappel says.
If you build yourself, earth walls can also save you money. “It’s quite realistic to save up to $50,000 by not buying your bricks and not getting a bricklayer to lay them,” he says. He acknowledges that it will take hard work, but says there are many courses and resources available to guide your toil. “The association helps people share knowledge on all sorts of issues, like the most efficient ways to make bricks and the connecting and finishing details.”
But this kind of building is not just for the DIY set. There’s also an established professional industry. “A mudbrick house can be built cheaply using prefabricated technologies, or it can be a hand-crafted, top-end product,” says Greg Slingsby, a Melbourne builder and president of the Nillumbik Mudbrick Association. “Contemporary building styles have changed the image of mudbrick housing.
“We attract people who want to spend money on a craftsman-built, quality home. We’ve got a huge portfolio of modern houses that are architecturally exciting, with every state-of-the-art convenience,” Mr Slingsby says.
Earthen dwellings have a lot of thermal mass – the heavy walls absorb and store heat, which helps to curb the extremes of summer and winter – but they don’t record high insulation ratings. When the five-star regulations were introduced in Victoria, the earth building industry questioned the rules for failing to fully consider the benefits of thermal mass in external walls.
Mr Slingsby says that while the rating program has improved, it still doesn’t reflect the high comfort levels and low energy needs of residents living in mudbrick homes.
“Earth building, to my mind, is the most eco-friendly building medium there is,” he says. “The internal environment is healthy, low in humidity and comfortable all year round. These homes embody the very notion of green building.”