On Sat, 2010-07-10 at 22:35 +0000, Neale Brickwood wrote:
I'm thinking of a dry build using a timber frame to provide the
structure and dry enclosure with the straw being inserted from the
inside (in the dry) timber cladding outside, plasterboard inside. I
know it dosnt stack up with the purist principles but will provide
substantial Co2 savings by omitting brick, block and insulation and
obviously sand and cement.
I presume i'd need a breathable vapour barrier between the timber
structure and the cladding which would allow the straw to breathe. Do
you know if any one has done any U value calcs for this type of build
or do you forsee any problems?
Neale,
The term "breathable vapour barrier" is an oxymoron. Breathable means
"vapour permeable". You probably mean a watertight, airtight barrier.
Straw bales are traditionally coated with lime or clay plaster for two
main reasons:
-1- it provides fire resistance
-2- it provides an airtight barrier that helps the straw function
effectively as insulation
Gaps between between bales and separate fireproof layers are known to
act as chimneys in fires and these can increase the spread of flame.
Having said all that, you might want to look at the S-House design.
Cheers, Dave
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