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To start off I know it's not the same to polyurethane, but it's waaay cheaper than paying someone to polyurethane a van. Has anybody used DOW GREAT STUFF spray foam insulation in a mobile dwelling, and how has it held up over the long term?
If you've ever removed spray foam from a van, the rust and mold behind it is not a pretty sight.
The folks over at Skoolie.net vehemently recommend against it. Great Stuff is open cell foam, so moisture and humidity can penetrate it. That humidity can then condense against the cold metal body, thus promoting rust.
There is a relatively new product call Gaco Flash Foam that might prove very useful. Gaco is a well known roof coating company, odds are there's a distributer near you...here its sold through Ace Hardware.

https://www.youtube.com/watch?v=2qgs9gJe83Q

It is a closed cell 3# foam that comes in kits. Its 2 part, so you get 2 propane size containers, and the gun + hose to hook them up. I believe we paid under $300.

I contacted their area rep via email to ask about R-value and appropriateness for RV/marine use as insulation. He responded, saying: " I do not see why this wouldn’t work. The foam kits have an R-value of 7 for every inch. I used it on my A/C duct work inside my garage and attic."

copied from another post, pic of Great Stuff removed...shows how it trapped moisture:

http://i557.photobucket.com/albums/ss15/...f419e1.jpg
(11-21-2015, 01:24 AM)debit.servus Wrote: [ -> ]To start off I know it's not the same to polyurethane, but it's waaay cheaper than paying someone to polyurethane a van. Has anybody used DOW GREAT STUFF spray foam insulation in a mobile dwelling, and how has it held up over the long term?

Do yourself a favor and don't use it!

Aside from the fact that it's open cell foam so that it attracts and holds moisture, it's been known to deform the outer skin on vehicles. If you spray it in the upright posts in a van, the post metal is stronger than the wall metal so the expansion pressure is on the outer panel. Also, if it's contained in the uprights, it might not even all cure, the center will stay in the original state of wet foam.

Oh and then, given time and vibration from driving, the foam will crumble because it's not actually adhered to the painted metal, so then you get squeaking as you drive.

We tried using it in vans back in the 70s and 80s.

Insulating a moving vehicle is a whole lot more than just blocking out heat...we have movement, structural forces, rust, off-gassing and moisture to all take in to consideration.
do not use Great Stuff, it's open cell foam and acts like a sponge. I have seen a couple of people use this and it seriously rotted their sheet metal. highdesertranger
Wow! I was almost going to pick up a can and decided to practice spending procrastination on buying GREAT STUFF. Then not seeing a thread here I though to ask about it.

I have read the skoolie forum (desire my next rig to be a school bus conversion) and was aware of the corrosiveness of spray foam.

Insulating is just like painting. I haven't seen a decent and cheap method. It's either cheap and short-lasting or super-expensive and long lasting. Somebody should make comformable foam block insulation. Some kind of insulating sheet that one can heat it up, form & stretch it and it will keep it's shape forever when it's cooled back down. Or closed cell spray foam in a can.
That Gaco 3lb. foam looks like a pretty good product, though not cheap.  Once applied, consider it permanent.  I wouldn't put it over any electrical wiring or plumbing.
(11-22-2015, 02:32 AM)debit.servus Wrote: [ -> ]Somebody should make comformable foam block insulation. Some kind of insulating sheet that one can heat it up, form & stretch it and it will keep it's shape forever when it's cooled back down.

Now there's an idea. One could experiment by putting various existing rigid sheet foam products in a low-temp oven and see what happens. Perhaps even devise a temporary solar or wood-fired oven to heat large sheets.

There are also several soft, flexible closed-cell foam products. It is expensive, when purchases brand new, but could be cheap if you buy used matts from various sources.
"Now there's an idea. One could experiment by putting various existing rigid sheet foam products in a low-temp oven and see what happens. Perhaps even devise a temporary solar or wood-fired oven to heat large sheets."

If I had money for experimenting I would be the tester. So I have a valid excuse, can somebody else conduct rigid sheet foam soften-and-conform testing, documenting AND sharing the process and results???
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