Recommendations/experiences with spray foam for existing shop

[gsganzer]

In the video, they said the foam heats up as it cures reaching 200 degrees F, so they just apply a thin coat first to minimize the heat and also to insulate the metal from the thicker final coat. I'm guessing that's what happened. Thermal expansion and then the foam hardens and results in the distortion. However, in another photo, it looked like it was the inside ceiling, also made from r-panels. So, possibly foam sprayed into an enclosed void.

Certainly, a question I'll be asking the foam contractors that bid the job.

Some others had mentioned a vapor/plastic barrier so panels can be removed or replaced later. I don't know how you do this and still have the foam properly adhering to the panels. The only reason I can see having to remove any panels is due to hail damage on a roof. I recently had hail damage at my house with a 70MPH hail storm, causing $72K in damage. An interesting thing to note is that the metal roof on my shop, that had roll insulation underneath and is more rigid suffered almost no damage. The adjoining shed roof that covers some horse stalls and is uninsulated underneath has dings all over it. I think if you sprayed foam to the back side of a roof, you'd also make it considerably more resistant to hail damage due to the added rigidity.

 

[EscapedSuburbia]

Some others had mentioned a vapor/plastic barrier so panels can be removed or replaced later. I don't know how you do this and still have the foam properly adhering to the panels. The only reason I can see having to remove any panels is due to hail damage on a roof.

I've seen plenty of damage to panels from falling trees and being bumped into by vehicles. Not a problem for a barn, but it's not uncommon at airports to see a row of parallel cuts from a propeller.

 

[ultrarunner]

Back when over the top car sound systems were a big thing the local ACE sold a lot of canned foam and it distorted a lot of old Impalas

The manager brought in low expanding and no issue.

 

[WinterDeere]

I did 2" closed cell. I wish I did more thickness. Buy once, cry once. The money I saved going only 2" disappeared into propane bills shortly after.

It's been 10 years since I ran all of the numbers, but here's what I remember:

1. Cost of heating and cooling the shop is very tiny, if you let your thermostat auto-regulate at 50F heating / 80F cooling. I don't need it to be 70.0F out there 24/7, I'm just looking to keep machines dry, and not have it be too terrible when I run out there for a quick job.

2. Doors and windows are everything. The losses thru the walls (I did 4" - 6" sprayed foam) are so tiny, but two big overhead doors are not! Esp. my doors, as I went with old-school joinery stile/rail/batten doors, just built from PVC instead of wood. No insulation in those, and they have two big rows of single pane glass.

You can surely dig up the loss numbers for your construction and door/window types, heck they probably have handy online calculators for this today. But I'd bet the difference between 2" and 4" is not that big compared to your doors, and that the overall heating cost difference is probably not that terrible in a shop that's not kept super warm.

If doing it all over again, I'd still do 4" to 6". But I also wouldn't worry much about it if I were in your shoes with 2", it probably doesn't make that big a difference in your heating and cooling bills.

BTW, I've always heard that one should spend the most on their roof insulation, versus walls. So if budget is a big factor, consider reducing insulation in the walls, before the roof.

 

[CH4Ohio]

I had several spray foam guys recommend that I spray the bottom of my roof. A couple others recommended NOT doing that IF I was going to install a ceiling in the shop. They said just blow in cellulose and go for a much higher R-value for less money. That's what I did.

One big concern for me was maintenance down the road. I was very concerned about trying to repair or track down a water leak after the bottom of the roof was sprayed. No telling where the water would eventually come out. Also concerned that water would sit in pockets and pool causing corrosion of the roof from underneath. With a roof that's installed with screws and rubber-grommet seals on every panel, I want to be sure I can find a definite drip at the source if that should happen.

This really proved true shortly after getting the building walls foamed. I found water on the floor coming out from under the foam where it meets the floor. It was about 2' from a window but I went all over it with a light inside and out trying to find the leak and the path the water was taking. No luck. We used silicone to go all around the window flange and the edges of the metal siding where it was cut around the window. Fortunately, it worked and stopped the infiltration -- but we never could determine exactly where it was getting in. Tracking a water leak behind this foam can be a real problem.

As far as replacing a damaged metal panel -- Hope I don't need to do that. But we've discussed it. If it was due to a hole or a dent, I'd be inclined to tap it down smooth (from the outside) and just put another panel or patch over it. It would take a lot of patience and work to remove an intact wall panel after foaming -- IF possible at all.

 

[EddieWalker]

I'm struggling with 200 degrees being so hot that it distorts the metal. I know my metal roof doesn't get that hot, but I do believe it gets in the mid hundreds during the worse part of summer. I would think the metal would be fine well above 200 degrees Fahrenheit.

 

[CH4Ohio]

I'm struggling with 200 degrees being so hot that it distorts the metal. I know my metal roof doesn't get that hot, but I do believe it gets in the mid hundreds during the worse part of summer. I would think the metal would be fine well above 200 degrees Fahrenheit.

When a building expands and contracts normally, it happens gradually and all at the same time. If they spray cold metal panels with hot foam it adheres and immediately causes just that section of metal to expand. I think you'd almost have to do it intentionally, but if the panels are cold and they hit it with a thick initial layer, I'm told it can buckle.

 

[MH8675309]

Be sure the metal around your windows and doors is SCREWED down. Not unusual for the metal to just be laying in the "track" around windows especially. You need to push on the metal and anywhere that it's loose, put a screw in it. Othewise, when that foam hits it will expand out of the gap and bulge out the other side. You can trim it back, of course, but the metal is permanently pushed out a bit. You can also manually (by hand) just push on the metal outside as he sprays foam around the windows. It only takes a few seconds to let it grab. But if he squirts it into a gap, it will push out the other side and cause a bulge. (I learned this the hard way.) They can spray it over plastic or paper or tape, etc. so use anything to close up gaps and openings to the outside so it doesn't squirt through. You'll have a heavy solid surface on the inside wall and along all the framing, so you don't need it to fill crevices and gaps within the metal skin.

Chose not to spray the bottom of the roof panels and glad I didn't. Instead, we installed metal on the bottom of the trusses for a nice flat ceiling and I had cellulose blown in on top of that. "Attic" space above that is ventilated and my roof panels had the "condenstation stop" foam backing on them anyway.

Also, don't let them skimp on prep work like taping off and plastic drop coverings. That stuff is a real pain to clean off doors and glass, etc.

It sure does keep the heat out in the summer and heat in during the winter. The whole building is like a big igloo cooler.

Agree - spraying the under side of the roof eats up a lot of material and is the most costly part of the job. We do spray foam and I generally try to talk customers out of doing this and using either blown cellulose or fiberglass on top of the ceiling. On a decent sized building it really adds up

 

[MH8675309]

Does foam degrade indoor air quality by off-gassing?

What about fire resistance?

The product will off -gas for at least 24 hours during which the windows and doors should be left open. The exception is if the installer piles up too much material - a 2" pass needs a half hour minimum to off gas before adding more material. A man out east built a house and wanted 2 x 10 walls (can you say overkill?) of which he wanted the stud cavities filled with closed cell. Installer must've been new because they went ahead did it all at once. They couldn't get the smell out of this brand new home and the material had to be removed - a miserable job at best. I'm told that fella got out of the spray foam business after that. There is fire resistant foam available that is more expensive