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GBlist: Re: EEBA-L: ureathane foam

In a message dated 9/7/97 1:12:02 AM, you wrote:

<<I am currently building a home in mid-Michigan.  One of the local
contractors offers spray ureathane foam.  This product is ported to be non-
toxic and having a R-8.14/in.  This seems wonderful, and I am considering its
use.  The only drawback I can figur' is that it will be impossible to run any
addition wiring in these wall at a later time.  I  would be using the foam
only on exterior(2x4) walls( bottom to top plate)  Does anybody have any
experience with this product?   It seems like a wonderful product.
G. Michael Molnar>>


Terry here.  I've used foamed in place polyurethane in many applications over
the years.  The things that most struck me about it are:

1)  it's foamed with a refrigerant (which is how gets a high R-value - like
R-10 per inch or so the day it's foamed.  The refrigerant begins outgassing
immediately according to Ficke's law of diffusion, eventually stablizing at
around R-5 per inch)

2)  refrigerants contribute to global atmospheric changes that are bad news
for humans and a large number of other species (probably good news for a
whole different set of species)

3)  they contain isocyanurates, which are a) potent chemical sensitizers and
b) highly toxic.  The burden of these two things is born by workers who
manufacture the resins or use the resins to manufacture other products and
people who live near the manufacturing sites (according to the polyurethane
assoication the reason most workers leave industries where urethane resins
are used is because they have developed disabling sensitivites to the

4)  although widely reported as a fire hazard because of the toxicity and
smoke developed numbers, they have the same smoke developed and toxicity
values as white pine - very, very bad if you breathe it.  I beleive that
means that it should not be exposed in interior spaces or return plenums to
meet any of the national codes.  I beleive this qualm is a fifth order effect
with regard to fire safety.  It is far more important to air seal a building
to prevent the quick spread of fire and smoke.

5)  don't spray it around electrical wires.  Electrical wires are rated for
current flow with air surrounding them so they can cool convectively.
 Sealing them in a high R value foam is probably ok for the loads most
circuits see, but it is a step towards the edge of a cliff - overheated
wiring causing fire.  In combination with a couple of other steps towards the
edge, like a nearby source of heat and a couple of overloaded circuits - why
risk it?  The insulators I used always sprayed around the wiring so it was
left exposed.

6)  it sticks to everything except polyethylene (damp dirty rocks, wood, wet
concrete, metal).  There is nothing that works so effectively at insulating
and air sealing nooks, crannies and odd shapes (rim joists, cantilevered
overhangs, bay and bow windows, skylight vaults, crawlspace walls).  Oh,
yeah, it especially sticks to skin, clothes, boots and is like a colossal
darg to breathe 'cause it sticks to lung tissue too.  Installers need full,
fitted respiratory protection for particles and gases.  There are some
solvents available that will clean it up while it is still tacky (seconds),
after that it wears off.

7)  sprayed into stud cavities, the entire wall becomes a structural panel.
 Good when using exterior foam board to cut down the stud losses with let in
T bracing.  It also generally expanded out past the stud surface and needed
to be ground or knocked off.  Figure a day of clean-up.

8)  it's relatively expensive, and many of the benefits can be achieved with
high density blown or glue sprayed cellulose.  The foam is far more
impermeable to moisture migration than the cellulose.

I think that's all my experience with the stuff.  - Terry
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