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Offgassing of spray foams

offgridbuilder's picture

I used Great Stuff insulating foam sealant around all the windows of our latest project, a super-insulated off-grid home. Messy business but a good tight sealant.  I used the same product in the old cottage we are presently in, to seal various gaps and keep the cold winter winds out. The fumes, even though they are no longer noticeable, give me headaches and burning sinuses at night (the bedroom was one of the areas I worked on). We sleep with the window open a bit at all times, but the problem persists, two weeks later.

Question: does this spray foam, and others like it, stop offgassing eventually? We won't be moving in for months, so time is on our side. The main culprit is diisocyanate. Since the new house has a special emphasis on excellent indoor air quality (no MDF, particleboard, carpets, alkyd paints) I will tear out all that foam if it turns out to be a potential problem. Of course, there is not much else on the market I can use instead. Does anyone have any knowledge on this? Are there foams available in small quantities which use more innocuous propellants and solvents? Thanks, guys.   Paul

First off, even "Great Stuff" (post #205517, reply #1 of 5)

First off, even "Great Stuff" comes in several different varieties, with varying chemical compositions.

Dap used to sell (not sure if they still do) a low-expansion foam that was latex-based, containing far fewer volatile compounds.  Quite expensive, though, because a can only goes maybe 1/5 as far as a can of regular foam.

It may be that there are some commercially installed foams that have less outgassing, or with less obnoxious compounds.

In general, offgassing will follow an exponential curve, starting high and "decaying" over time, though never reaching zero.  Basically it will have a "half life" (could be minutes, hours, days, or weeks) and every "half life" the outgassing will be reduced by half.  So if it's a week then the outgassing will be reduced by a factor of 16 in 4 weeks.

Of course, the problem is that human sensitivity to odors and the like is roughly exponential in the opposite direction.  Reducing the chemical concentration by a factor of ten, say, may only reduce the perceived concentration by a factor of two.  Or, in some cases, reducing the concentration can actually cause an odor to smell stronger.

People differ a lot in terms of their sensitivity to volatile chemical compounds.  Mostly this has to do with the makeup of the DNA in the mitochondria in the body, and whether there are any "oddities" in the way the mitochondria consume (or not) the compounds.

(Also keep in mind that headaches and the like that come on when a house is sealed may be due to an increased CO concentration or some similar problem.  Check the furnace in your "cottage", and check other combustion appliances.)


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Dap foams (post #205517, reply #2 of 5)

Thanks, DanH. I looked up the Dap product and it is called "DapTex latex expanding foam sealant'. I haven't seen it around but I'll go find some and try it out. It is apparently VERY low expansion and doesn't go very far as you suggest, but I'll try it anyways. Paul

EPDM foam gasket? (post #205517, reply #3 of 5)

I haven't used it but Conservation Technologies has a gasket for this that folds in half and you tuck in the gap. I suspect it doesn't work with window mounting shims in the way though.

John

Certainly with any spray foam (post #205517, reply #4 of 5)

Certainly with any spray foam you should use some sort of backer for gaps over about 1/4" wide.  The spray foam layer only needs to be maybe 1/4-3/8" thick to do its job of sealing.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

I'm confused. You say you (post #205517, reply #5 of 5)

I'm confused.

You say you sleep with the window open a bit at all times.  Why even put the foam in?