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Re: GSBN:Question regaarding toe-ups

Sawdust is mighty eager to compost.  I don't think that this would be a
terrible problem, but I suspect that between settling and a little
bioactivity, the insulation value that they are looking for from the
sawdust layer would drop substantially in the first few years.

Rice hulls might not be locally available in many places, but they've got a
lot of pluses, and should be affordable for this application, even when
shipped moderate distances.


--On July 16, 2006 8:41:14 PM -0400 MattsMyhrman@...:

I recently spent some time on the phone with one of our friends at Red
Feather Development Group.   They have been using a toe-up design that
involves double 2 x 4's on the outside and double 2 x 6's on the inside,
giving a total height for the toe-up of 3 inches (7.6 cm.) and a gap
between the outer and inner elements of about 14 inches (about 35.5 cm.),
when using 3-string bales. They have been using custom-cut strips of
rigid foam insulation board to fill this gap, but would prefer to be
using a method that would require less labor and a material that would be
less expensive, not petroleum based, derived more locally and lower in
embodied energy.   Because they are working in areas characterized by
very cold winters, they are also concerned about the insulation value of
the flller material.   For this reason, they are questioning the use of
pea gravel as the gap-filler.   We talked about volcanic pumice, but found
ourselves unthusiastic based on the damage done to the landscape during
mining process, and the lack of any regional source.

They build their box-beam roof-bearing-assembly (RBA) in a way that blocks
any water from getting down through to the top of the wall, should the
roof leak.   In view of this, it occurred to me that if they were willing
to provide a moisture barrier, like roofing felt, under the toe-up, it
would be safe enough to use something like sawdust to fill the gap.   To
provide some support, along the centerline of the gap, for the first
course of bales, one might lay in place some separate support elements.
These could be assembled from short pieces of 2 x 4 scraps or from pieces
cut from warped, unsellable 2 x 4's donated by a friendly lumber yard.
With these in place, one would fill in around these separate support
elements with sawdust, and then put the first course of bales into place.

They and I would appreciate any thoughts any of you might have about the
sawdust system described above and any suggestions for alternative
solutions to the problem.   Let your creative juices flow.   Just don't
let any of those juices drip on your bales.   Let cellulosic aridity


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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@...