Re: GBlist: Request info on Dow Corning's insulation (any
Tue, 11 Feb 1997 08:14:36 -0500 (EST)

Lawrence wrote
"I need to insulate the interior surface of a concrete block wall in
my house with Dow Cornings's FORMULAR rigid high density insulation
(FORMULAR 600, which has the highest density/PSI rating). This is in
my living space in a room heated with a woodstove. I plan to construct a
cavity wall to cover this insulation and to provide thermal mass, i.e. the
insulation will be sandwiched between two block walls and sealed
against contact with room air with cement and caulking as necessary.

Does anyone know whether FORMULAR will outgas toxic fumes over the short
or long term? Will my containment system be adequate to prevent
infiltration of any possible toxics into my living space? As it will be
exposed to moderate heat due to proximity to the outer block wall warmed
by the woodstove I am wondering if this factor would result in the
stimulation or acceleration of outgassing.

If FORMULAR turns out to not be acceptable for this application does
anyone know of a rigid insulation that would be?

Many thanks for any advice or pointers to resources on this subject.

Some of you may find my renewable energy page interesting.

Lawrence London
Chapel Hill, N.C."

Hi Lawrence. Under ordinary conditions extruded styrene mainly outgases the
blowing agent. Most of this is gone within a few months of manufacture (the
exponential decay of R-value is probably a good indicator of time constant of
decay). They used to blow it with a CFC but I believe they changed that some
years back. I've used it in buildings with people who are very sensitive to
chemical exposures with no difficulty. John Bower has had the same
experience. If the material is heated up, it is likely that at some point
the long molecules will pyrolize, producing compounds that are the products
of thermal degradation and are not found in the list of materials used to
manufacture it. Almost certainly some of these will be irritants. The
thermoplastics generally begin changing in the greater than 140xF range.
It's unlikely that you would encounter these temperatures inside a CMU wall.
I've used the foam in exactly that application, no problems for 15 years.