January 3, 2012

Durra Panels - the new light earth

Despite our best intentions with building in light earth, the experience has been fraught with problems. Given the time it was taking to complete them, we decided to pay someone to help us build them, only to have the finished walls fall down after he left, when we discovered his technique had been flawed. So we started considering a different approach.

We had already experimented with a pseudo-earth wall in the dining room. One of the dining walls is half internal (backing onto the entry) and half external (backing onto the verandah). Instead of making a half-and-half wall of earth and timber, which would have looked silly, we filled the internal section with gyprock and rendered it to look the same as the earth wall. It’s impossible to see which half is timber framed and which is earth (it requires another fine coat to cover the centre stud).

Left side - render over light earth. Right side - render over gyprock
Russell suggested we do the same for the remaining walls under the verandah. I was initially horrified. Gyprock instead of earth?? Was he giving up the dream, selling out to The Man??!! 
But then I remembered a compressed straw panel called Durra, made by Ortech in Victoria. It is 50mm of straw held between two layers of thick paper – no chemical binders, nothing but waste straw in recycled paper. Its credentials were good.
We ordered panels cut to an exact height, and cut them vertically to fit between the studs on the external walls, and inside the studs on the internal walls. Between the two layers we added an air gap and some R3 insulation. 
External panels set between studs.
Internal panels placed over studs, with insulation in between.
The Durra walls were cut to size and in place in two days – compared with what would have been months of work doing light earth. On top of this the walls now have a total R value of about R6+ - way better than the earth walls would have rated.
We’ll probably need to ‘rough up’ the Durra a bit to accept the same clay render we are using on the earth walls, but the finished product should be indistinguishable.

1 comment:

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