[Strawbale] The Straw Stuff (GSBN Digest, Vol 35, Issue 6)

[RT]

On Sun, 06 Mar 2011 00:16:17 -0500
From: Chris Magwood
Subject: [GSBN] The Straw Stuff

<snipped>


> 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  
> straw.
>
> So can anybody think of a reason why this might not be a good idea?

> Thoughts?...

(full text of this message can be seen at
     http://greenbuilder.com/pipermail/gsbn/2011q1/001327.html )


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  
Robert Pins.

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  
Moose-huggers)

         http://www.cmhc-schl.gc.ca/


-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at  Y a h o o  dot  c a >
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