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GSBN:SBH with moisture-related problems



I built two strawbale structures in Texas, and after some time I noticed
tiny cracks appearing in the stucco. After a rain, in the area around the
cracks, there was a slight change in color that seemed to indicate
differences in rates of drying. The area near the cracks took longer to dry
than elsewhere on the wall.

When I moved my company to the far more humid south Louisiana, I was afraid
that there would be serious moisture problems. The central problem, as I
understood it at the time, was not the straw, but the sealing off of the
straw within the wall. If water could not penetrate the stucco, then the
straw would remain reasonably dry.

When the French first settled Louisiana, they figured out how to protect a
wall from moisture. Often they combined cured moss with mud, and they packed
this within a wall. If the wall was directly exposed to rain, they protected
it with lap siding. If the wall was partially protected by a porch, they did
not use lap siding.

So then I figured that lap siding was the way to proceed in Louisiana, and
fiber cement lap siding was ideal since it did not involve the direct use of
wood. But how does one attach lap siding to a wall of strawbales? Lap siding
demands studs, but once we use studs, then it is best to fill the cavity
created by the studs with chopped or loose straw. In Louisiana, rice straw
is abundant, but at the same time, the rice plant gives another by-product
that is far more resistant to moisture penetration and fungal decomposition.
This is the rice hull. This then led to the concept of the rice hull house
as you see in: <a  target="_blank" href="http://www.esrla.com/shotgun/frame.htm";>http://www.esrla.com/shotgun/frame.htm</a>

We ran a series of ASTM tests on the rice hull. The Moisture Vapor Sorption
Test gave some amazing results, and the Test Report for Resistance to the
Growth of Fungi was also quite interesting. See:
<a  target="_blank" href="http://www.esrla.com/pdf/astm1.pdf";>http://www.esrla.com/pdf/astm1.pdf</a> as well as
<a  target="_blank" href="http://www.esrla.com/pdf/astm2.pdf";>http://www.esrla.com/pdf/astm2.pdf</a>
It would be interesting to run the same tests on wheat or rice straw to make
a comparison.

So with lap siding that does not crack and with an agricultural waste
material that is highly resistant to water sorption and fungal
decomposition, the reflection was advancing. But the use of the rice hull is
limited in that it serves only as an insulation material. The next challenge
that I see would be to make structural members out of rice hulls, and Liam
Devlin out of Australia has patented (for Australia only) an accelerator
that bind cement to rice hulls. In this way one could fashion 2x4's or 2x6's
out of rice hulls and cement.

So in conclusion, the rice hull house concept is a reflection thoroughly
within the strawbale movement. When in Louisiana I saw the problem of
moisture coming, and I was hesitant and side-stepped it altogether. This put
me in a strange position with only one house to demonstrate the concept and
with a concept that is far from complete. It will take the mature reflection
of the GSBN to figure out what happens next.

Thanks.

Paul Olivier
ESR International LLC
519 West Dejean Street
PO Box 250
Washington, Louisiana 70589
USA

Tel 1-337-447-4124
Cell 1-337-826-5540
<a  target="_blank" href="http://www.esrint.com/";>http://www.esrint.com/</a>