[Strawbale] The Straw Stuff (GSBN Digest, Vol 35, Issue 6)
ArchiLogic at yahoo...
Wed Mar 9 00:46:53 CET 2011
On Sun, 06 Mar 2011 00:16:17 -0500
From: Chris Magwood
Subject: [GSBN] The Straw Stuff
> double stud framing system and using thin wood lath on the studs
> stuff the cavity with dry straw instead slip-straw.
> The wall was 12-inches deep (as was the straw/clay wall).
> placed about 18-inches of lath at a time and then packed in the dry
> So can anybody think of a reason why this might not be a good idea?
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Since this method really doesn't utilise any of the unique properties of
the straw, I had to wonder why one wouldn't simply fill the framing cavity
with blown-in dense-pack cellulose and skip the futzing about with the
labour-intensive lath strips(which don't contribute anything to in-plane
shear resistance as the more typical panel sheathing would) ) /manual
straw packing ?
12 inches of straw would yield a wall of unacceptably low (for Canada)
thermal resistance, hardly justifying
consumption of lumber for a double-stud framing system to contain it.
If one is going to be manually packing loose straw anyway, it would seem
to make more sense to pack the straw into rectangular mesh sacks and then
clip the sacks-o-straw (aka "bales") together into a panel which could
either be plastered horizontally (ie a pre-cast sandwich panel) and then
tilted up ...or plastered in the typical vertical position (not unlike the
system developed by Internatural Canada back in 1996 and described in a
report to CMHC* "Proof-of-Concept Development and Testing of the Biocrete
House Construction System (March 1996)"
The sacks-o-straw could be packed super dense so that when they are
removed from the compression rig (a box with a lever-operated compression
plate at one end) they would puff up some, essentially pre-stressing the
mesh sack before plastering.
I think that small bale-sized sacks would make more sense than simply
making each sack mattress-sized because the sides of the smaller sacks
would provide through-the-wall ties eliminating the need for stitching or
The bottom line is that the lumber for the double-stud framing system
would become redundant (and hence could be eliminated) rather than the
straw being the redundant element and a candidate for replacement by the
more suitable dense-pack cellulose.
*CMHC = Canada Mortgage and Housing Corp (for the benefit of non
=== * ===
Kanata, Ontario, Canada
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