Hi, I was wondering if that spray foam insulation that comes in cans is
considered safe. When that kind of insulation first came out I think about
20 years ago, a friend of mine had his whole house done, only to learn that
the product outgassed formaldehyde, and had to take the house down to the
studs. Do the new products now still have that problem? I just want to fill
some holes and cracks to keep out cold air.
There are two kinds of foam - expanding and non-expanding. The first
is polyurethane with an R value of 6.5 per inch, the second is urea
formaldehyde with an R value of 5.5 per inch. Normally, the foam
which expands is polyurethane, and that is the most common kind you
find in spray cans. Polyurethane is dangerous only if it subjected to
the heat of a fire. The gas produced under those circumstances is
dangerous, even lethal. Urea-Formaldehyde is relatively inert, but
the danger has always been that it outgasses formaldehyde which is
irritating to some (NOT ALL) people. Plywood also outgasses
formaldehyde, although less so. (formaldehyde is used in the glue
which glues plies together)
For your use, I wouldn't worry about either. I used polyurethane foam
around my electrical outlets, being careful not to apply too much. I'm
still here five years later with no ill effects. Main insulation here
is fiberglass with 12" of cellulose over 12" of fiberglass in the
I am not sure that it still contains formaldehyde. I injected some foam
into my walls, and the MSDSs and the company's web site specifically
said that they don't contain it.
The formaldehyde was not the real issue with that type of foam as an
insulation product. All sorts of things give off tons of formaldehyde,
carpet, your new car, some paints, and furniture. The problem with the foam
as insulation is that it shrank over time and thus allowed thermal bypasses
to form and total loss of R value. The Urethane form you get (great stuff)
is non shrinking and a different catalyst. For small air sealing it is
fine, but do not inject into cavities that can be damaged by the expanding
foam pressure. Use a low expansion (window and door) foam for filling
window cavities and other sensitive spaces.
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