Monday, December 12, 2016

Is Great Stuff good? DIY Polyurethane Sprayfoam Pros/Cons

We went through most of the typical options for insulation found on the web. We read from both homebuilding sites like and conversion van forums and travel blogs, and watched dozens of DIY camper renovation videos. (I particularly liked The Ultimate RV Camper Build series from Billy D @ UsaRcJets on Youtube.)

We decided on polyurethane spray foam (SPF) although I'll say why I would consider other options next time. (This is, after all, our first vehicle. so we're going to take some chances. "We got a van") We also did not use spray foam exclusively, and opted to include some fiberglass insulation (Hey, we never said we were doing it green!) and some Reflectix, which I'll talk about more in another post. The foam was the first layer of insulation, directly on the interior metal of the van.

The Basics

A can of normal Great Stuff gap and crack filling spray foam is about $4, but we got ours for half price. If you are doing something with heat like a kitchen or heater, they have Fire Block spray foam in a black can, and if you need less/no expansion, they have Door & Window spray foam in a blue can for $6. I got a can of that but didn't end up using it- I felt it was easy to not put too much foam into tight areas. You can also get the Pro stuff for twice the price of a normal can, but we didn't see any need.

You shake the can for at least a minute (I recommend longer, but your arms start getting really tired after the first few cans,) then you screw the applicator straw on and unlock the anti-leak front nozzle. Even on full blast where you get the widest application, it's usually only about an inch-round bead, but when you get the hang of applying it in rows or square spirals, you should be able to cover up a large flat-ish area like a wall or door rather quickly, as well as tighter areas...

Not that I give the product marks for being easy to apply. It's made for sealing cracks and gaps, so applying an even layer all over a wall takes a bit of finesse. Still, I don't know why people go with the big applicator kits from companies like Foam It Green... using the individual cans was fine for us, rather cheap, and we didn't have to worry about ordering, mixing the A & B chemicals in right proportions (which is super important for performance and safety,) we just shook the cans.

Once you start using a can, you can only stop for 20-30 seconds before it closes up for good and the can is junk. (I think you can open it back up with solvents but I guarantee you're not gonna want to do take the time to do that, like, ever.) It takes about eight hours to cure and starts expanding quickly, but it doesn't seem to be particularly easy to work with at any point during the cure, (if you wanted to shape while it's still soft that is.)

The packaging is right when it says that cold decreases performance. Specifically, it will not come out as well or spread out as much, (much like cold caulk/glue in a caulking gun,) it will not adhere to surfaces well, and it will take longer to cure. We were doing ours in New England between autumn and winter and got it done, though, so it doesn't need to be that warm to apply. Just turn the heat on... but don't shut the doors and concentrate those explosive gases!

It feels, looks and sounds a lot like packing peanuts after it is cured, but luckily not so squeaky, soft or fragile. It definitely does a really good job insulating for the amount of material, and we think in combination with the Reflectix, it'll do a really good job.


-Affordable (Only took around 20-25 cans, normally $4 each, but we paid half price, so what would have cost us only $100 cost half that!)

-Available (Great Stuff and other polyurethane spray foams are available everywhere as far as I know, considering how useful the stuff is and how many builders swear by it.)

-Vapor blocking (Which means we didn't feel we needed to prime the walls, which would have added extra hours of work)


-Toxic, you need a respirator and PPE (personal protective equipment). There is good info available about safety with polyurethane spray foam, but I'll say from personal experience that you minimally want: gloves, eye protection (unless you want the chance of an eyesplash sending you to the hospital), great ventilation in the work area, and a quality and well-fitted respirator with a filter made for aerosols, We will also make sure the walls are sealed up well so that dust from the foam and fiberglass insulation won't harm us.

-Fragile longterm (Haven't seen this personally, but definitely could see this stuff wearing down longterm, so we're making sure not to put any weight on it or put it under anything. I'm mostly concerned about the all the banging around and rocking motion it will experience and whether pieces of foam insulation will start dropping out the bottom openings that are made to drain water. And on that note...

-Vapor blocking (Huh? Yup. There are a lot of different opinions on vapor barriers, especially when you're trying to be able to live in both temperature extremes like we are. Although vapor barriers keep moisture from coming in, they make it harder for it to get out, too, so you have to think about how moisture is coming and going, and know that you're editing/removing those routes as you sprayfoam, which could concentrate moisture problems in one spot, just for one thing. Short of engineering training, I don't know how to get around the possibility of doing something weird to your moisture profile (or whatever it is called), so I recommend to do as much research you can into the moisture issue (including both physics and experiences from other DIY/van conversion/tiny home people online.)

-Difficult to apply - Many forum users opt for the big applicator kits (for hundreds of dollars) or having spray foam applied professionally (for potentially thousands.) After applying my own spray foam successfully for the first time and so far being happy with it, I still understand why they may go that route. Why? Ease of application clearly varies a lot between people, and because the cans aren't necessarily made for insulating large areas, some people may find it difficult or awkward to apply properly. I could imagine just as many people slamming down their last can in frustration cursing the technique, as I could applying it with little or no problems and swearing by it afterwards.  If you're ambitious and dexterous, I say go for it. If you're unsure if you or a helper can make a good application without gunking the whole job site up, you may want to try a different insulation method, like pink fiberglass, which we also used.


So, we applied a single layer of spray foam over all the walls and doors (besides up front, which we will insulate without spray foam, or spray later). Read the next blog post about insulation...

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