I’m getting 3" of closed cell foam spray in my cellar, but will still have roughly 2.5" of space in the cavity. (2x6 framing) Since the closed cell foam will form the vapor barrier, can I stuff the rest of the cavity with fiberglass batts before putting up the sheetrock?
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Sure, you could, but why not just spray more foam?
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I think it’s a lot more expensive?
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the one main rule of insulation is just never do 2 vapor closed insulation types on each side of sheathing.
other than that, go wild.
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I think that means I’m ok to do what I’ve proposed?
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This is essentially what I did (blow in, instead of batting). The foam sets up rigid, and to our surprise - made the plumbing in the wall really loud, so we filled in with standard insulation solely for the noise factor. You don’t need more than 3" of closed cell, and it would get quite expensive.
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I did 2” of closed cell, let that cure and off gas then came back and filled with 4” of open cell.
*Texas, heat was my main concern
How long did that take?
2 weeks, saved money by using open cell and it gave me max R factor
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Did you folks who had closed cell foam sprayed in your cellar vacate your house for any length of time? I just read that in some cases you should leave for 24-48 hours? If that’s true, my wife is going to be irritated with me since I had no idea and told the guy to do it tomorrow.
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we did not, but our cellar is on the ground floor in a converted garage (daylight basement, I believe is what they call it). Ours is a 3 story house, and that room is easily closed off (obviously), and most of the living space is on level 2, main bedroom on level 3. It was a little stinky, particularly as you got nearer, but it wasn’t bad for us. Disclaimer: we also nearly always have windows open, unless it’s over 70 outside 
What R value do you have now? I’ve forgotten the ratio of inches to R value for close cell.
Supposedly, 3" will be close to 20. But I read somewhere that you actually lose some of that by having open space remaining in the stud cavity? Not sure if that’s true, but it seems cheap enough to close up the gap with fiberglass batting and perhaps add another 10 in the process.
It’s cheap and I guess it can’t hurt.
I did it when I built my cellar. 3” closed cell topped with r-30 batts.
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Wow.
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We did our entire house in foam while we were building it so didnt have to make that call…but it is some NASTY stuff. If it was me, i would for sure try to stay out of the home for a day or so.
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Wow, they did a great job. I didn’t smell a thing. They sectioned the area off and ventilated it all to the outside and then left the ventilation running for another hour. Was just down there and it doesn’t really smell at all anymore. And it looks like I got closer to 5" in most spots than 3".
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i really, really hate spray foam. it’s often a necessarily evil however. it doesn’t air seal relatively well. there’s usually better ways to insulate. wine cellars/natatoriums/steam rooms aside, vapor barriers have little use above grade.
with all that’s required re ppe with installing spray foam, i don’t think it makes sense to live in a house when a product is off-gasing. meaning you want to breath in what the person installing wouldn’t be caught dead breathing in? however we all have sealants, adhesives, and often carpets/flooring with this shit.
erv’s are great and im having one installed in the house im building, but a wise man once said dilution is not the solution to indoor air pollution.
3" of closed cell should be enough. I’d stop there and keep things simple.