[GSBN] The Straw Stuff

[Derek Roff]

Like Bruce and Chug, I have some concern about increased fire risk. 
However, it seems likely that if you have stuffed the straw to the same 
density as a bale, then your fire resistance should be similar.  With 
the caveat that Bruce mentioned, of conditions changing dramatically 
if/when the lath burns and allows the straw to decompress.  I'm not 
sure that it would suddenly decompress, but it might.

It would be interesting to build a test wall section, leave it for a 
couple of months, and then cut through the lathes.  That would give 
some idea of whether the straw would acquire a compression set and be 
fairly stable in its packed form, or whether it would still be eager to 
unpack itself.

I'd like to hear more about how you determined the density of the 
stuffed straw.  I'm guessing that you found you could pack a bale of 
straw into less than a bale's volume in the wall.  Is that right? 
Chris, do you have any sense of how consistent the density was/is from 
edge to edge and top to bottom?  I would have imagined that the lathe 
would bow outward significantly, under the pressure necessary to reach 
bale densities.  If I understand your posting correctly, that didn't 
happen.

How would you compare cost and time for stuffing straw in this way to 
filling a similar wall cavity with dense-pack cellulose?  "The Straw 
Stuff" is a very interesting experiment, and I'm glad that you shared 
your information with us.

Derelict

Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: derek at unm.edu

On Mar 5, 2011, at 9:16 PM, Chris Magwood wrote:

> Hey all,
>
> This past summer, we did a little experiment with our students that
> seemed to work well, and I'm curious if anybody has tried it (or has
> good reason to not try it!) before I go ahead and try it on a
> slightly larger scale.
>
> We were building two walls with straw/clay, using a double stud
> framing system and using thin wood lath on the studs as the form/
> cage for the straw/clay. We then used clay plaster over the lath on
> the inside and outside. As usual in our climate, we were under the
> gun to get the straw/clay placed in time for it to dry thoroughly
> before plastering.
>
> As we were doing so, I wondered if we might just use the same
> framing and lath system and stuff the cavity with dry straw instead
> slip-straw. So we built a sample frame and did just that. The wall
> was 12-inches deep (as was the straw/clay wall). We placed about 18-
> inches of lath at a time and then packed in the dry straw. We
> measured the density of the original bale and we were able to get
> the straw into the wall cavity at a slightly higher density than the
> bale itself. We had pieces of lath cut to go across the wall to keep
> the straw packed down at the intended density, but found we really
> didn't need them. The whole thing went together really, really
> quickly and plastered up nicely.
>
> So can anybody think of a reason why this might not be a good idea?
> Yes, I know it's not as fun and natural as stacking bales... I'm
> still a huge fan of doing things that way. But so many people are
> building stick frames of one kind or another and then going to all
> kinds lengths to notch, trim and otherwise jam bales into those
> frames. This system fits a double frame wall really well, accepts
> plasters really well and in general seems like a decent way to go
> about using straw as an insulation. The thickness can be varied to
> reach intended insulation values.
>
> Thoughts?...
>
> Chris