[Cob] Other components: How bad is Tyvek?

[David Atmoweg]

Greetings, everybody.

A while ago the combination of light clay straw and wool came up.  I was happy to report that there's finally a place in North America that offers wool as 
insulation.  After two particularly tough winters, we're a little disillusioned.
We're working on a two-hundred year old cabin in the Catskills, and used light clay straw for the walls, with which we're quite happy.  We haven't even plastered 
over it because it's so lovely by itself.  We tried to make panels of light straw clay to fill our rafter spaces, but the stuff proved awfully heavy to try to hang, and all 
the spaces are different widths and we ended up using wool.
Now, the light straw clay doesn't let a lick of air through, so far as we can tell, but it takes a long time to warm it up.  Its thermal mass seems to be working 
more as a heat-sink than a storage mass when it's below zero outside, and I'm wondering if we should seal it better from without.  The wool, meanwhile, isn't 
living up to its R-value because this is a leaky, gappy old structure and wool batting doesn't halt a breeze.  The upshot is we have at times a fifty Fahrenheit 
degree temperature differential between the floor downstairs and the air in the rafters.
We wanted to cover the wool upstairs with burlap, which is cheap and low-impact and would look like a good compliment to the light clay downstairs, but we 
begin to think we need a real barrier up there.  Our woodstove is churning out the BTUs and they're getting away from us.  So the question is, do we buy three 
rolls of Tyvek, trap the wool upstairs and back the light-clay downstairs?  We need to maintain some moisture flow for the light clay, of course, but we appear to 
be living in a seive now.  Is Tyvek made in a toxic, wasteful process?  What benign substance can we seal this place up with?  I tried to infuse a sheet of burlap  
with beeswax, but it's just too coarse.  Canvas might work that way, but it's expensive and heavy.
Somebody out there has the answer, I'm sure...

-d.

http://www.flamingbunny.org
-- 
___________________________________________________________
Sign-up for Ads Free at Mail.com
http://promo.mail.com/adsfreejump.htm