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Old 05-18-2017, 06:13 PM   #1
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Insulation, *again*

So I have an idea I'm playing around with. Say I get a small amount of spray foam DIY, and spray one layer, just enough to cover the surface, and immediately jam a precut board of rigid foam insulation in it, squish and seal. Would this work? Would it not cure properly that way?

Assuming it WOULD work, I'd do a layer of reflectix on top of that and call it done.

Trying to combine layers of insulation and get the best benefits of each in the mix. Spray foam granting some structural stability and soundproofing qualities, rigid foam taking up the bulk of space and cost, but also being foam, which is pretty good, and reflectix giving a good radiant barrier for a heat envelope.

Whatcha think? Bad planning? or good idea: try it?
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Old 05-18-2017, 06:28 PM   #2
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It's interesting to see that idea come up now and then. I had the same plan at one time. Apparently the spray foam won't cure properly if it's not exposed to air. I thought that would be a good way to glue in panels of rigid insulation, using spray foam. Apparently it's been tried. Some very interesting methods have been tried at times.

So, this is showing a good thought process. I never experimented with trying this type of application, rather choosing to take the word of experience in this case. It's kind of a big deal for one of us to mess up the insulation bad enough that we have to tear it out again.
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Old 05-18-2017, 07:00 PM   #3
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I have a little different speculation on the idea.. I think a 2-part foam will cure fine, but that it'll cure so fast that the stuff at the beginning of the panel will be somewhere between firm and hard before you've finished spraying and it wouldn't be possible to press the foam board into it.
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Old 05-18-2017, 07:06 PM   #4
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I have seen this done with recycled refrigerator foam and it did sorta "glue" it onto the spray foam, however it was a terrible botch job, there were several gaps because the foam didn't expand well that needed to be filled. So I would say success is about 50/50.
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Old 05-18-2017, 07:45 PM   #5
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Well I know people are using spray foam to seal the EDGES of rigid foam against it's sides, but I thought spray foaming the wall thinly in the first place would provide a better seal and prevent condensation better, otherwise won't you just get condensation right there in the middle of the foam panel where there was no foam? Or do you think it really works the same? Concerned about details here... lol

Also, how fast does foam really start to harden? I watched a video where within several minutes of spraying the stuff on a test board, he touched it and it tore, so he reapplied. It didn't seem to cure very fast, it wouldn't take me several minutes to add a board of rigid foam, I'd go bit by bit and be careful.

I'm really loving this discussion, moar plz!
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Old 05-18-2017, 08:13 PM   #6
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Originally Posted by DreamWeaverBus View Post
So I have an idea I'm playing around with. Say I get a small amount of spray foam DIY, and spray one layer, just enough to cover the surface, and immediately jam a precut board of rigid foam insulation in it, squish and seal. Would this work? Would it not cure properly that way?

Assuming it WOULD work, I'd do a layer of reflectix on top of that and call it done.

Trying to combine layers of insulation and get the best benefits of each in the mix. Spray foam granting some structural stability and soundproofing qualities, rigid foam taking up the bulk of space and cost, but also being foam, which is pretty good, and reflectix giving a good radiant barrier for a heat envelope.

Whatcha think? Bad planning? or good idea: try it?
You're thinking similar to me about it.
I'm buying one, MAYBE two of the spray foam diy kits and will be using foam board for the "bulk", and the spray for the odd areas and stuff. you dig?
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Old 05-18-2017, 08:17 PM   #7
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I was told the foam around the edges sets up fine after you press the rigid insulation panel into it, but that the area in the middle of the panel tends to turn to goo. I never tried it, but I'd imagine if it were possible it would work a lot better with two sets of hands. It still sounds interesting, but I'm not willing to spend the money to try it when it's already reported as not working.
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Old 05-18-2017, 08:19 PM   #8
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I was told the foam around the edges sets up fine after you press the rigid insulation panel into it, but that the area in the middle of the panel tends to turn to goo. I never tried it, but I'd imagine if it were possible it would work a lot better with two sets of hands. It still sounds interesting, but I'm not willing to spend the money to try it when it's already reported as not working.
I'll be putting in the foam board, then the spray foam. I don't see how there'd be any problem doing that at all. WHo's reported that as not working??
We aren't talking about using "Great Stuff"... That stuff is corrosive in a bus-type environment.
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Old 05-18-2017, 08:45 PM   #9
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You're thinking similar to me about it.
I'm buying one, MAYBE two of the spray foam diy kits and will be using foam board for the "bulk", and the spray for the odd areas and stuff. you dig?
I dig, but I'm thinking backwards to you, I was thinking spray foam first, then squish rigid foam on top. Everything I've been reading has people doing like you though, spray foam in between and on top of the rigid foam.

I guess I could do it either way, I just thought as long as it cures right under the middle of the board, it would work better underneath rather than around and on top.

But Robin says apparently it gets gooey in the middle, so mb spray foam on top is better if I wanna do it that way.

I was thinking one, MB two kits tops as well, but I'll need to run the numbers again on a hypothetical bus I haven't bought yet, for an insulation budget. I'd hate to spend more than 2K on insulation, my budget is small, and I'm basically using 2k for the bus, 2k for plumbing, 3k for electrical system, and the other 3-4k is for everything else, like insulation and extra odds and ends, out of a 10-12k budget. (I already factored in extra cash on the plumbing and electrical budgets.)

I plan on moving north so insulation will need to be good, if not great, but cost is a factor and you get what you pay for, so I'm not sure how to do the best insulation for the cheapest price. Here in Southern Illinois I doubt I'm gonna get an $800 spray foam estimate. 1K minimum for DIY job.

Again, I need to rerun the numbers but if I gave 1k for DIY spray foam kits, which would give me roughly two kits, then add in reflectix, and add in some rigid foam, my lowball GUESS is 2-2.5K, based on my budgeting recently, for 750 square feet of floor, wall, and ceiling.

I'd ideally like to get a ten window bus.
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Old 05-18-2017, 08:49 PM   #10
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I'd forget the reflectix. A bunch of foam would be immensely superior to bubble wrap with mylar.
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