[GSBN] Vapor Barrier

[martin hammer]

Jeff -

Derek has given you good supporting language from Bruce King, John Straube
and even Yogi Berra.  I wouldn't yield to this building official without
challenging him.  Can you quote the code section the official is pointing to
for this vapor barrier requirement?  I think you should be able to avoid
this "requirement" by going through the alternative materials and methods
section of the code, and use the expert language Derek has suggested as
supporting documentation.

Persevere and you will prevail.

Martin Hammer


On 7/17/08 12:06 PM, "Derek Roff" <derek at unm.edu> wrote:

> I'm sure Jeff has already explored trying to educate the code official,
> but that seems like the only safe approach to me.  I would hope that
> the book "Design of Straw Bale Buildings" by Bruce King and friends
> would be convincing.  But of course, that would require that the
> building code official read it and evaluate it on its merits, which
> some will refuse to do.
> 
> Here are a few quotes from the book that I consider relevant to this
> important question:
> 
> "I just don't want to make the wrong mistake" (Bruce quoting Yogi Berra)
> 
> "The best moisture control strategies always involve designing problems
> OUT - not solving them after they have been needlessly designed into
> the enclosure."  p. 144, John Straube (emphasis in the original
> included bold type for the entire quote, and the capitalization of the
> word "OUT").
> 
> "Some building codes have required vapor barriers for framed walls.
> These requirements, based on a limited amount of research conducted
> over 50 years ago, have recently come under question.  The
> International Residential Code is being changed to remove this
> requirement for all but the coldest climate zones of North America.
> Straw bale walls are quite different than framed walls... [Their]
> behavior is similar to that of traditional solid masonry or adobe
> walls, which have never required a separate low permeance plastic vapor
> barrier."  p. 156, John Straube
> 
> "For a typical residence the vapor permeance of the interior plaster
> skin should be kept as high as possible to encourage inward drying, but
> low enough to avoid a significant amount of cold weather diffusion
> wetting."  p. 156, John Straube
> 
> 
> Since the winter interior humidity level for most houses in Colorado is
> likely to be too low, rather than too high, I think the first half of
> John's last quote is the operative one.  The building official is
> endangering the structure and the health of the occupants (through
> decreased indoor air quality) by requiring this vapor barrier.
> 
> That puts Jeff in a very difficult position.  I'm thinking that if Jeff
> follows this requirement, primary responsibility for any problems will
> still fall on him.  I'm guessing that in the case of future moisture or
> respiratory problems, it would be very difficult to transfer the
> responsibility for this poor approach back to building department, even
> though that is where it belongs.  I hope Jeff can find a way to avoid
> being pushed into building the wrong way.
> 
> Derek
> 
> --On Thursday, July 17, 2008 12:06 PM -0600 Jeff Ruppert
> <jeff.ruppert at gmail.com> wrote:
> 
>> Hello Everyone,
>> 
>> We are dealing with a picky building official and are interested in
>> options to seal interior earthen plaster with a sealer that offers a
>> low  permeability and that is also non-toxic.  The building official
>> is  requiring the use of a vapor barrier on the interior and we are a
>> little  stumped as to what to use.  Code requires something with a
>> perm rating  of 1 or less.  Anyone tackle this particular one yet?
>> 
>> Jeff
> 
> 
> 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
> 
> _______________________________________________
> GSBN mailing list
> GSBN at greenbuilder.com
> http://greenbuilder.com/mailman/listinfo/GSBN