Straw bale houses: More than fairy tales.

Straw bale houses: More than fairy tales.

07 May 2013

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Australia — A farmer in north-west New South Wales says the thermal qualities of straw is what attracted him to the idea of building a straw bale house.

Hugh Gentle from Piallamore is also a builder so he knows his way around a building site.

“The sub-floor structure is steel, the walls are straw bale, the roof consists of timber trusses with loose timber and the roof will be covered with iron cladding.

“The bales are laid on there flat, so the walls are approximately 450mm thick. We put them in seven tiers high before we compress the bales to give them their structural capacity to hold the roof load.”

The straw bales will soon be lime rendered.

Mr Gentle says, in its present state, the house is quite flammable.

“We’ve got fire-fighting measures here at the moment. Once the walls are rendered it’s a different story. Straw tends to smoulder so therefore you’ve a lot better chance of getting out of the house if there’s a fire.”

Recent research shows that Australia’s first bushfire resistant straw bale house will withstand temperatures equal to that of a worst case bushfire scenario.

Built in Victoria last year, in conjunction with CSIRO, the house was made with straw bale insulation and set into a recycled steel frame with magnesium oxide cladding.

Bushfire simulation tests showed that the design could resist bushfire attacks and withstand temperatures of more than 1000°C.

Justin Leonard from CSIRO’s Bushfire Urban Design says the key to straw house safety is encasing the bales so that air can’t access the straw.

“Therefore the straw can’t break down and the fire can’t reach the straw,” said Mr Leonard.

“Because straw bales offer excellent insulation it’s well worth considering using them. There are certainly a range of relatively easy ways to completely enclose those straw bales like using a rendering approach or, like the house we tested last summer, fully enclosing it using magnesium oxide board.”

Hugh Gentle’s house is attracting a lot of attention.

“We have about four cars pull in each day. They see the house from the road and do a quick U-turn. They’re usually very interested and full of questions!”

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