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GBlist: If my climate were drier, I wouldn't be a crier



SEMI-RANT:

I'd like to add to Fred's excellent comments on moisture.

The understanding of how moisture affects buildings is actually quite a
new science. It's only been  in the last decade or so that this
knowledge has been disseminating into the general building community.
Yet, I continue to see misstatements in print, hear misstatements in
discussions, and hear them from insulation manufacturers. As a rule,
people in the weatherization community (like Fred) and those building
superinsulated houses seem to have a good understanding of what is a
relative complicated subject because tight houses often are less
forgiving. 

The best book I can recommend is Joe Lstiburek's Moisture Control
Handbook, but if the subject of moisture is new to you, it can seem
daunting. There's more to moisture than meets the eye. You can't
possible get a good understanding of the subject of moisture without
really delving into it.

The vast majority of our knowledge about moisture migration has been
derived from stick-frame construction. The same basic laws of physics
apply to all framing methods (wood, steel, straw, adobe, etc.) but there
are undoubtedly nuances related to less conventional framing methods
that aren't yet fully understood.

Some chronic moisture problems manifest themselves quickly, sometimes
within a year or two of a house being built. The problems with EIFS is
an example. 

When I hear people talk about the straw-bale houses that have been
standing for over a century, my first thought is "Those are the ones
that were built correctly, and have lasted. What about the ones that
didn't last? Failures advance our knowledge the most." I saw some
discussion on a straw-bale discussion list about straw turning to
goo—something that scares people, but doesn't seem to be common (or,
perhaps, it isn't visible yet). To me, gooey straw would be a
catastrophic failure. I worry more about less serious problems, whose
effects are more subtle or take longer to manifest.

I certainly don't have anything against straw bale as a building
material, but I suspect that there are going to be some failures because
of our imperfect knowlenge, or because some houses are going to be built
without using the knowledge we've already gained—knowledge that still
isn't fully diffused throughout the buiulding community. Personaly, I
can't afford to risk building a house based on imperfect knowledge.

Moisture control is serious business. If someone doesn't understand very
well how it applies to conventional construction, they'd better do some
reading before tackling unconventional construction.
-- 
John Bower, The Healthy House Institute
http://www.hhinst.com/    email: healthy@bloomington.in.us
430 N. Sewell Road, Bloomington, IN 47408
Phone/fax 812-332-5073
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