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GSBN:Re: Exterior cladding question



--On Sunday, February 6, 2005 10:38 PM -0500 Chris Magwood
cmagwood@... wrote:

The issue is permeability. Obviously, the compressed earth bricks are
going to be less permeable than the plaster, based on the thickness (10
inches) and the density.

I think the issue is a bit bigger than permeability.  You will have a
materials change interface outside your insulation, between the bales and
the block.  This means that almost every day, during part of the day, the
compressed block will be substantially cooler than the interior of the
building.  This will be worst in the winter.  While the bales will have a
temperature gradient from inside to outside, the bale to block interface
will be a condensation site, much of the time.

I think this creates a potential site for serious moisture problems.
Substantial liquid water from condensation will be more destructive than
the same amount of moisture would be, if it stayed in vapor phase.  And the
moisture in vapor phase might still be a problem, given the relatively low
permeability of ten inches of compressed earth block.

Are there other options?  One that comes to mind, is to build your brick or
compressed block appearance walls at the outside of an unheated wrap-around
porch space.  The bale walls could be set inside by eight or so feet.  This
space could be a comfortable display space during part of the year, and an
airlock-like wind/weather buffer during the winter.

I don't know if this will work with the site and the plans, but my point is
to look for new options for meeting the appearance desires, without having
the bales close to the bricks or blocks.

Derek

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@...