[Greenbuilding] Cob as an alternative to spray foam sealant?

[Steve]

> I see a ".ca" in the "greengeek" edress so I going to ass-u-me that we're
> talking a MooseLand locale ?

Yep, I'm in Canada. Victoria, BC to be specific.. not too many moose
around here that I've seen. :)

> And if that assumption is accurate-  just wondering: Where in Canada are
> there naturally-occurring perlite deposits ?
> (And "no" I don't think that the "insulation" or "plastering supplies"
> aisles at the nearest Home Despot qualify)

It was Ann & Gord Baird of Eco-Sense (a well-known local cob house
project) who renewed my interest in using natural volcanic stone as
insulation. I checked again, and it was actually pumice, not perlite,
that they used. My mistake. They sourced the pumice from a location
right here on Vancouver Island.

> ie Does it make Green sense to import a "natural" (if being
> mined/pulverised/packaged/transported by massive machinery qualify it as
> "natural")  thousands of kilometers and across international borders just so
> that one can say that an insulation is "bio-degradable" ?

If it wasn't available locally, then no it wouldn't be worth it, no
matter how biodegradable it was.

> Not only that, the resultant mixture likely wouldn't even provide the
> minimum R-values for a wall as required by the Codes (assuming that the
> cavity is standard 2x4 or 2x6  wood-frame construction) and would not seal
> very well once it has dried and shrunk away from the framing.

I was thinking it could be used as a later to provide an air seal, in
addition to something like blown-in cellulose, or perhaps as a
spray-on finish for strawbale, rather than filling wall cavities
completely as the only insulation. I'm not a builder, and have only
limited hands-on experience with either cob or clay plaster, so this
is just a thought.

> So I have to wonder: "Why bother ?"  ... knowing that here in Canada, a more
> readily-available, lower environmental  impact, plentiful, "natural",
> bio-degradable, blow-able "waste" material with about the same or better
> insulation value as perlite (depending upon density of the form of perlite
> used) exists.  (Sawdust, chopped straw or even chopped up recycled newsprint
> etc  )

It was just a thought; there are many different levels of "green
building", ranging from light green barely-LEED-Silver designs to deep
green natural building techniques such as cob, strawbale, etc. I was
just thinking if the materials are available locally and would provide
some benefit in place of oil-based spray foam, then it might be a way
to make natural products more appealing to a conventional builder or
client. Chopped straw might still be a bit of a leap for some people,
something that went up like lightweight concrete probably wouldn't.

-Steve
-- 
http://www.greengeek.ca