Re: GBlist: Request info on Dow Corning's FORMULAR rigid pol

JBunzick (
Tue, 11 Feb 1997 09:14:18 -0500

I don't know whether foamed polystyrene outgasses, though I have not
heard of this problem. I disagree with the reply comment about it
loosing its blowing agent in 6 months. This foam is closed-cell, and
it looses its blowing agent much more slowly than the
polyisocyanurates, which have permeable cell-wall membranes. They do
loose their blowing agent in 6 - 12 months. This process occurs
progressively more slowly as air replaces the blowing agent, thereby
lowering its insulation value. Polystyrenes are not known to loose as
much R-value, though they don't claim as high an R-value to start
with. The end result is that both types, polystyrene and
polyisocyanurate, end up with similar R-values over time. The
polystyrene is also less water absorbent.

To clarify brand names, Dow Chemical Company (not Dow Corning) makes
Styrofoam; UC Industries makes Foamular (with an 'a', not Formular
with an 'r') though I believe they have been sold but can't remember
to whom; and Amoco makes a foamed styrene called Amofoam.

I am wondering though, why you plan to use the higher density
material. The higher density material will cost you more, but it
has the same R-value per inch. The higher density is intended for
use in deck insulation situations where there are compressive
loads on it.

John Bunzick, CCS, CCCA
Dean Architectural Alliance (new name)

______________________________ Reply Separator _________________________________
Subject: GBlist: Request info on Dow Corning's FORMULAR rigid polysty
Author: "Lawrence F. London; Jr." <> at Internet
Date: 2/10/97 10:52 PM

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.