Canned foam R-value
wood0619
| Posted in General Questions on
Does anyone know the R-value of canned foam, specifically Dow Great Stuff window and door? I can’t find it published by Dow. I know 2-part closed cell foams are generally R6-7. I’m wondering if the canned 1-part stuff is potentially a much lower R-value?
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I haven't seen published R value info for Great Stuff, either, and my guess is the reason for that is due to the widely varying conditions that the material tends to be used for. That's a fancy way to say that you don't get very predictable expansion or density of the foam.
Loctite's Tite Foam *does* have a published R value of R4 per inch. Since that foam tends to be denser and more consistent (in my experience anyway) compared to Great Stuff, I'd peg Great stuff at something less than R4 per inch, maybe R3-R3.5 per inch. That would put great stuff at similar R value per inch to a typical low-density fiberglass batt. This is NOT bad performance, but I wouldn't try to use Great Stuff as your primary insulating material in a wall or other building assembly.
Great stuff works, well, pretty great for it's intended purpose though, which is sealing up holes and larger gaps between framing members. I would have no problem using it for those applications (and I do). I like to use Loctite's product for applications that require a more secure foam, such as where the foam is holding something in place (i.e. cut'n'cobble insulating jobs).
Bill
I agree canned foam is closer to an R-3. If it's not published it can't be good, which leads me to my next question.
I am trying to spray foam the exterior top of the wall sill plate. I have used some window and door foam to seal under air chutes gently. Next, I must fill the void above the 2” foam under the chute. In some areas. I must fill up to 4” tall by 3” outward. I may need to go the froth-pak route (benefit of better R value) or maybe bring in a foaming pro, but that will be pricy. Any advice to deal with this? I think it will be too difficult to cut in foam strips which I would then need to spray foam anyways. I have attached a photo for clarity.
You probably won't be able to get a good layer that thick. I've usually found that when trying to fill excessively large voids (more than maybe 1.5" or so), there is a tendency for the Great Stuff to leave a single, huge bubble inside that doesn't cure right and stays gooey for a long time, and eventually sets up as a sort of hard-edged bubble. Loctite's product *might* be better for this (I've never tried it for this), since it's more consistent when applied, but it could well be a problem too. Misting some water in before spraying can also help, but only a little.
I have used the Kraken Bond canned foam that is intended for larger areas, and it will work better for your application than Great Stuff. Note that you need to get one of the foam guns they recommend, since the tips they provide won't snap onto the regular Great Stuff gun. This product isn't as good as two-part kit like the Frothpak, but it's a LOT better than "regular" canned foam for larger areas.
If you have a lot of this to do, I'd get a quote from a contractor. I find that contractors are often similar price or less than the Frothpak kits when doing mid-size jobs like this. Those Frothpak kits (and the other brands of the same basic thing) are very expensive for the amount of foam you get.
Bill