Open Cell or Closed Cell Foam in a Can

[Kevin H]

I see a lot of videos where folks are filling gaps and supports with Great Foam. They also GF around the poly-iso foam to seal as well as anchor it.

My understanding is that Great Foam is open cell foam. That means it can absorb water. Closed cell foam does not. Has anyone used a polyurethane closed cell foam for the same purpose? If so, what did you experience odor/vapor wise? How did it work out overall? What brand did you use?

Getting ready for insulation and suffering from analysis paralysis. Still have not made up my mind between poly-iso or Thinsulate - but let's not go there right now

 

[John61CT]

No it's 80% closed cell, I don't think urethane can be open.

And the outside skin is tight.

Not to be used as a primary, too expensive anyway.

Any poured or sprayed foam can be offgassing if you don't do it right, especially too cold or too thick.

Some people are very sensitive.

Do your wiring channels and any vent/window/utility openings, structural mount points, battens for panels, L-track etc first, once it's done consider it permanent. Have a clear idea how your innermost liner material e.g. luan will get mounted, ideally removable if damaged.

Best IMO is to use the two-part kits to do a very thin but complete layer (in hot ambient temp onto warm steel) as if painting. Careful not to leave any "bubbles" with bare metal to rust from water vapour getting trapped underneath. Especially do pillars and beams, no metal "bridging from the outside body steel to the inside.

Then put in thick as possible polyiso, most on the ceiling, then sides least on the floor. Gorilla glue if necessary, but spray foam (great stuff if used all the 2-part) in the gaps should hold it, again try to be thorough, no big gaps or very thin parts - but don't go nuts, PITA to have to trim the excess.

IF you're doing 3" or thicker rigid board, put 1" XPS of that to the cold side, polyiso for the balance on the warm side.

This approach, getting a full continuous seal without air flowing from the living space to the steel will be **much** more effective than any batting, never mind R-value BS.

But thinsulate has no chance of gassing, breathes (IMO a negative) and is easily removed (huge positive)

If not camping in the snow maybe OK.

Don't skimp on major active high CFM ventilation!

 

[MrAlvinDude]

This guy also have something to say about closed cell insulation.
http://www.monolithic.org/blogs/presidents-sphere/r-value-fairy-tale-the-myth-of-insulation-values

One of the things I take away from it, is that there is a huge difference in insulation value between half-pound foam density and  two-pound foam density.


I have myself been wondering about where and how to get closed cell foam.
Where I live it seems that the closest thing that is easily available is what they call  "well foam", meaning it is foam meant to be used when sealing cement tubes. Tubes that are typically used when digging old fashioned wells.

I would not use open cell foam in a car. But it does then become challenging to find something else to fill those crooks and crannies. I have not yet found the optimal solution.

So far I have been thinking if a layer of this kind of spray would lower the amount of surface condensation on the inside of the "skin" of the car.
https://www.valvolineeurope.com/english/products/tectyl/aftermarket/cid(7167)/tectyl_ml_spray


All I know is, that it takes a surprisingly thin layer of anything, to significantly lower the condensation tendency on a cold glas or metal surface. 


Sorry if I am only adding to your analysis paralysis :-(

 

[johnny b]

this place has 2 part kits from 1200 board feet down to 12. (board foot = sq. ft. at 1" thickness)

https://sprayfoamkit.com/spray-foam-kits/

 

[John61CT]

I bet if you get friendly with the local contractors, they wouldn't charge much to use up some leftovers if you brought your rig over toward the end of a job.

Just make sure it's over 80°, and you've got your masking all set ready to go.

 

[timoat]

Great stuff used to fill cracks around xps or polysorbate will be fine if you cover it with aluminum tape. That will seal it off. Technically you could use great stuff all over , as long as you have a proper vapor barrier.

Post no 2 is overkill unless your planning on spending prolonged periods in antarctic conditions.

Thai is what m doing ; 2 inches of xps glued in with 70% closed cell foam, then a vapour barrier of polythene or reflextic stuck with aluminium tape. , then my siding, probably 4 mm plywood.

 

[highdesertranger]

Great Stuff is not closed cell it will rot your sheet metal. highdesertranger

 

[John61CT]

Great Stuff is not closed cell it will rot your sheet metal. highdesertranger

Are you really sure? Check Dow's spec sheet, I found 80% closed cell, and the skin that forms on the outside definitely seems impermeable.

I thought urethane can't even be open.

If not, I would not rely on a vapor barrier to make the difference in a van.

wrt "overkill", being thorough not only means camping anywhere, but also much higher levels of comfort at lower cost over the life of the vehicle.

At really not much greater cost or effort.
You certainly don't want to have to rip everything out to get in there and improve it later.

Sure you can reduce thickness (R-value) if you don't want to sacrifice the space.

But don't skimp on getting rid of all gaps and thermal bridges.