Spray foam insulation

[RVucan2]

This may have been asked before, if so I am sorry. I have a 1996 class B but so much of it is weight I do not use even though it all works, like hot water heater and furnace. I am thinking of upgrading to a much newer van and have my son and son-in-law help me do a van build. I have probably watched a hundred van build videos but my adult son has not. He says we should do spray foam or some kind of spray insulation which would better seal all air leaks, but I never see van builds going this route. Can someone tell me why spraying insulation is not a better method? Is it just expense. Thanks in advance for your time.

 

[safarivan]

IMO it is the best method. the only motorhomes ever built and sold by any auto manufacturer GMC used this method and so do aircraft.

I have done it by using foam board insullation for the big sections and using spray foam around the edges of it to attach them in place but you have to use masking tape until it dries. then just spray the smaller areas.

 

[safarivan]

here is a pic of a GMC under restoration


and the rear section where they did not cover at the factory that is done with foam board insulation like I mentioned



this really is the best way to insulate one. and you can also then add the reflectix chrome bubble wrap insulation over it too. many do this but Im not sure how effective that stuff is.

 

[ratfink56]

Spray foam is difficult to control the expansion rate. Too much foam in tight spaces will deform sheet metal. Too much foam in open spaces requires trimming the excess which is a difficult, tedious, messy job.
Polyiso, sold in 4x8 sheets, is used a lot because of it's superior r value and it's ease of installation. It's also fairly inexpensive. My Home Depot sells it for around $11 a 4x8 sheet for 1/2" thick. Most use that thickness because of the flexibility and then add another layer if they want. Then using crack filler spray foam in the tight spots. The crack filler does not expand as much and is easier to control. One of the major factors in insulating is what kind of climate(s) you will visit.
Not sure how much reading you have done here but there are many devoted to this topic. Probably more than you want.

 

[B and C]

There are two types of spray foam, open cell and closed cell. You do not want open cell as it holds moisture and leads to mold. The type in a can at the home improvement stores is usually open cell. Closed cell is usually a pro job. There are kits that are closed cell. And has been stated, controlling the expansion is the hard part.

 

[highdesertranger]

^ what Brain said. highdesertranger

 

[B and C]

^^^I like that; "Brain". Wish I still had a good functioning one

 

[highdesertranger]

oops, sorry. highdesertranger

 

[John61CT]

Yes glue rigid board (I prefer polyiso) then use closed cell foam to fill the gaps

and if major temp differences, energy conservation is important, make sure all the metal's well covered to prevent thermal bridging and put a vapor barrier in place before sheathing.

Read up on the kit's instructions, especially ambient temps, don't go too thick per cure and always leave an escape path

 

[Canine]

I strongly considered spray foam, but wussed out because I didn't want to learn how to do it well. It takes practice. I knew I could cut polyiso and do a very good job. Polyiso was less expensive, too, so I cheaped out compared to spray foam. My trailer with polyiso turned out superbly in regards to insulation, but the trailer inherently didn't have a bunch of air leakage. My trailer was also square unlike all the bends, nooks, and ribs of a van.

Polyiso is a high performer and would still give you first rate results if you decided to go that route.

 

[RVucan2]

IMO it is the best method. the only motorhomes ever built and sold by any auto manufacturer GMC used this method and so do aircraft.

I have done it by using foam board insullation for the big sections and using spray foam around the edges of it to attach them in place but you have to use masking tape until it dries. then just spray the smaller areas.

So glad to hear this...thanks!

 

[johnny b]

I'm also in favor of the polyiso sheets for the majority of space in a van...1/2" thick is easiest to work with for the curve of van walls. 2 sheets gives 1 inch thick, R7 rating.
For closed cell foam to fill in, there are small quantity 2-part kits available here:
https://sprayfoamkit.com/spray-foam-kits/
(bottom of page) 45 bucks for 12 board feet. [square feet, 1" thick]

Also lots of info on this site, but 'beware' all the claims of how easy it is to DIY. Remember, they're trying to sell the kits!
IF choosing to spray a van, I would pay a pro.

If anyone is considering the DIY route and has never sprayed this stuff before, I would recommend investing in a 100 foot kit (280 bucks), plus the protective gear, and get some big ass cardboard boxes to practice on. Be sure to be in an open space away from anything that might be hit from over spray.

Of course this adds a bunch to the DIY cost...just one more reason to pay a pro.

 

[John61CT]

Big difference between spraying a whole vehicle (get a pro) and just filling in gaps.

But yes, absolutely have to wear disposable coveralls, gloves, mask, full PPE

and thoroughly mask any areas you don't want covered

just like spray painting a car.

Acetone apparently will clean it up before it sets (very fast)

but only physical methods work after that, scrape, sand, steel wool, plastic buffing wheel on a drill if you're trying not to destroy the paint underneath.

For small quantities Great Stuff will do, got through to Dow's tech support and it is closed cell, rated at 80%.