[greenbuild] Re: cotton insulation, wood treatments, durablock

From: "joel gagnon" <joelpgagnon@xxxxxxxxxxx>
To: greenbuild@xxxxxxxxxxxxx
Date: Wed, 11 Sep 2002 10:44:34 -0400




Michael Burns <burns@xxxxxxxxx> wrote:

I also have alot of wood that I would like to treat and wonder about what
non-toxic treatments are avaliable.

Also, I am considering using "durablock" which is essentially like drywall
but made out of concrete in smaller panels for the inside, south facing
walls of my new house. I'm thinking these would absorb more heat from my
southside windows and woodstove than drywall. Is this stuff difficult to
work with? Is it hard to finish nicely? Too expensive? Am I crazy?


My reply:

What application are you treating the wood for? Is it just at risk of 
occasional dampness or is in ground contact? For ground contact, I wouldn't 
bank on any treatment lasting forever. Even CCA leaches with time unless the 
environment is pretty dry. ACQ will probably replace CCA in most of the 
current places CCA is currently used. Locust (only the heartwood is rot 
resistent) is good for 20 years or so. White oak and catalpa are in the same 
league. They would be ok for bottom plates (although I believe the code 
requires pressure treated) or porch floors and the like. Since the point of 
preservatives is to kill fungi, they cannot be "non-toxic". The best we can 
do is minimally toxic to humans. Copper napthenate (in Cuprinol, among other 
brands)is a paint-on product with relatively low human toxicity 
(attributable to the vehicle in which it is suspended, a volatile 
organic)and suffices to beef up the rot resistance of things like porch 
floor joists where the wetness is not continuous. Boric acid treatments also 
work, but only if the protection is for a rare event, since the borate 
leaches readily. I also know of no source for a paint-on borate-based 
preservative. Above ground protection for wood surfaces can be enhanced with 
water repellents, of which there are many excellent products. I can supply 
you with a simple formula for making your own from linseed oil and paraffin 
which is very pleasant to work with, but you do need a solvent (turpentine, 
mineral spirits, or naptha) to dissolve the paraffin in.

From your description of "durablock", it sounds like you are describing 
Durock, a cememtitious backerboard generally used for tile. It may have a 
slight advantage over gypsum in mass, but the cost of gypsum and comparative 
ease of use are overwhelming. It would be far easier and cheaper to add 
extra layers of drywall if the objective is to add mass. Boring, but easier. 
For greater interest, consider doing a veneer of plaster, which could be 
tooled for a "touched by human hands" feel. Veneer plaster is generally 
applied over "blueboard", a gypsum walboard with surface properties 
specially designed to accept the veneer plaster. Regular gypsum can be used, 
but you will need to apply a bonding agent.

Joel Gagnon

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[greenbuild] Re: cotton insulation, wood treatments, durablock

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