From: clewis@ferret.ocunix.on.ca (Chris Lewis)
Newsgroups: misc.consumers.house
Subject: Re: urethane spray foam insulation
Date: 12 Apr 92 07:31:27 GMT
Organization: Elegant Communications Inc., Ottawa, Canada

In article <1992Apr8.234948.4123@phx.mcd.mot.com> fredch@phx.mcd.mot.com (Fred Christiansen) writes:
>Anybody chosen to have sprayed-in urethane foam insulation installed
>in their exterior walls instead of fiberglass batts?

You mean UFFI (urea-formaldehyde)?  The stuff has a history of outgassing
formaldehyde, which can cause allergic reactions in moderately sensitive
people.  Definately bad news for house values 'round here.  In fact,
house sales contracts now have covenants that UFFI has not been used, and
later discoveries are very expensive on the seller's part.

[When properly mixed/installed UFFI seems to be reasonably inert.
However, there's enough horror stories about extreme reactions that
noone wants the stuff.  It's the kiss of death on house value.  Ie:
20% discounts or more.  People who have it either tear it out, or
install air-2-air heat exchangers for ventilation.  There is apparently
a neutralization method that works well at stopping any outgassing,
but it's expensive and nasty on its own - pumping in anhydrous ammonia!]

>It seems to me that one never really achieves the nominal R-rating
>(approx R3/inch) with batts because of gaps, compression, dust infiltration,
>etc.  However, with sprayed-in foam, well done, you could get uniform
>R7/inch (true?).

One wonders whether you could get a truly uniform spray-in with no
gaps.  It is tricky even when using the new kinds of foam for gaps in
window/door frames.  If you use rock-wool instead of fiberglas, you'll have
no gaps or sag.  The stuff is much more rigid than fiberglass, and is R4/inch.
And a good vapor barrier does a heck of a lot to alleviate the effect of any
voids.

Too bad you can't see the rock wool job we just did in our local church.

>How do they compare cost-wise?  What's the payback?  Any negatives, such as
>curing or persistent odor, irritants, allergies?

Potential irritants/allergies - see above..

Very flammable.  May require special treatment - ie: thicker drywall.
Noxious fumes when heated.  Fiberglass is moderately inert (the binders
burn and outgas).  Rock wool almost perfectly inert - it doesn't even
deform in a oxy-acetylene torch.  Sheds water amazingly well too.

Cost?  Well, the spray cans of the non-UFFI foam are hideously expensive.
You'd go broke trying to use that as a general insulation.

Rock wool can often be found at comparable prices to fiberglass.

>I've been thinking 2x6 walls with R-19 batts plus 1" white styrofoam (R3.6?)
>with stucco over ext sheathing.  Might be able to cut out some of the up-front
>costs by going to 2x4 walls with 3" sprayed foam and stucco directly over
>the sheathing (+ felt paper).

I suspect R21.5 rock wool batts in 2x6 walls will be cheaper than a
3 inch layer of urethane.

>Interestingly, around here, folk are putting 2" foam on roofs (over sheathing),
>but, due to esthetics, just on flat roofs (and not pitched roofs).

Note that's on *top* of the sheathing....  The foam's water resistance
is the main reason for this - on a flat roof you need all you can get.
-- 
Chris Lewis; clewis@ferret.ocunix.on.ca; Phone: Canada 613 832-0541
Psroff 3.0 info: psroff-request@ferret.ocunix.on.ca
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