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Re: GSBN:plaster and straw question



At 8:19 PM -0500 7/2/06, Paul Olivier wrote:
The solution I chose to prevent moisture penetration is fiber-cement siding
or paneling. But to attached either of these products to bales of straw is
somewhat precarious. In the end, a wall truss is needed. A wall truss
consists of two 2x4's fastened together by three plywood gusset plates at
top, middle and bottom. The outer edges of the two 2x4's can be pulled as
much as 12 inches apart.

On the outside of the wall truss, the fiber cement paneling (4x10ft) is
ideal. Fiber cement panels come in a stucco finish, and joints are easily
smoothed over with a special plaster to give a seamless stucco finish. A
sheet of Tyvec is inserted between the panel and the truss. Once the outside
panel is up, lose straw can be inserted in the 12-inch cavity of the wall
truss. On the inside of the wall truss, sheet rock is laided down
horizontally in increments of 4 feet, and this make it easy to insert the
straw.

An alternative to straw is rice hulls. They come from rice mills at an 11%
moisture content, and generally they are available free of charge. Rice
hulls easily flow into every small space of the wall cavity. Once in the
wall, they show no evidence of subsidence or collapse. Rice hulls are also
far more resistance to moisture absorption and fugal decomposition than
straw. They contain about 20% amorphous silica that is intimately bound to
cellulose and hemi-cellulose. They can also be transported by means of a
blower for quick and easy insertion into floor, wall and roof cavities. They
require no chemical treatment or other preparation to pass all ASTM tests
relating to cellulose insulation.

Hi Paul,

I'm very interested in using rice hulls - probably in the roof and
possibly at the gable ends as you're describing.  I've read your Rice
Hull House paper and poked around on the topic a bit.  But I'd like
to minimize the use of fiber cement and drywall, and don't
particularly want tyvek.  And I've kinda grown to like straw bale.

We'll have good sized porches all around if all goes as planned, so
we're not overly concerned about rain.


--
Bill Christensen
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