Does anyone know anything about closed cell spray on foam insulation? I want to insulate my garage and originally wanted faced roll on fiberglass insulation. A contractor came over and recommended closed cell spray on insulation as it has a higher R value. I however do not know anything about this and am concerned about moisture collecting on the inside of the roof and damaging the wood sheathing. The roof is vented at both the ridge and the soffits. I have always thought that if I keep those areas open with good airflow that I wouldn't have a moisture problem but this spray on foam obviously attaches itself right to the wood.

Had it done on two homes and I am sold on it.

It certainly increases R value but only if you apply it at a certain thickness level. The costs is rated according to the thickness applied and after a certain level, there is no additional gain in R value.
So knowing that you must inquire as to what thickness is being quoted.

It definitely offers a sound barrier feature as does loose or batted insulation but I think foam is probably more effective in that regard.

The most interesting benefit I found was that it appears to act like some type of adhesive in that binds together all the structural members (ie..studs,joists, rafters and roof sheathing) for a more solid build. This became very obvious in one home that was constantly subjected to severe winds where creaking noises etc no longer exist.

I would not hesitate to use it again, the faced roll stuff has it's place in interior walls or floors but foam is definitely the way to go in my opinion.

Only advice is knowing the exact type or composition of the foam type in your situation as I understand there are a few different types. Professional application is probably the way to go also, if memory serves me, there is a relatively short cure time with that stuff.

I had it done in my shop and house attic. Really great stuff with all of the pluses mentioned above. Only problem I found was direct sunlight on the foam will tend to make it "funky." I had to put up wall board in the area where the sun would shine on the exposed foam.

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Bill

I had it done on a addition to my Tennessee house. I would recommend it highly.

my bil had it done to his commercial shop. it really stiffens up the walls besides doing a great job off insulation

How does the cost compare with faced fiberglass? My planned garage is 2x4 and 24'x24'.

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The only downside (other than cost) to spraying it between the rafters is that asphalt shingles will age a little faster without cooler air circulating below them

An engineer friend of ours figured out Urea foam back in the late fifties while laid off from Kaiser Aluminum. He made good money demonstrating and selling it spud farmers. They sprayed the inside of their large corrugated metal spud bins. I remember him showing how to mix the two chemicals then watch while the foam formed and grew out the top of the container, he then told me to pick up the container and I was amazed at how hot it was. He said "That is a chemical reaction."

I don't know if they use polyiso in spray foam as it is more expensive, but it has been found to actually decrease in R-value at lower temps (below 40º or so) , although it works as advertised in resisting heat. Caused a bit of gaffuffle in the industry when that was revealed.

Temperature Dependence of R-values in Polyisocyanurate Roof Insulation

I'm trying to understand your garage construction. Are the trusses open to the attic so no ceiling in the garage? That would mean the garage is vented outside through the ridge vent. I would think you would want to install a finished ceiling in the garage, or floor in the attic, to close the garage off from the unconditioned, vented attic.
If there is a ceiling in your garage the best way to spray foam insulate would be to spray down on top of the ceiling from above in the attic filling the truss cavity and encapsulating the truss bottom chords.

This is the way to go or have them attach plastic to top of top of the bottom chords and spray up into plastic from below. Make sure applicator is comfortable with this.

There is no attic. There are 2X8 rafters that go from the soffit or side wall of the garage all the way up to the ridge which they are attached to. The ceiling of the garage is perhaps 15-20 feet high in the center. It is all completely open all the way up to the rafters.

Thanks for all the replies. I think I will contact the contractor and go ahead with the project.

Just realized where you are. Active Foam Specialist 847 497 9480 Mike. This is not me. Contractor we use

Close cell didnt do anything for sound for me. It is rigid. Open cell is the way to go for sound proofing.

I have no experience with open-cell foam, but, if sound proofing is important, Roxul Safe 'n Sound batts are the way to go. Some genius decided to put sheets of rigid white insulation (EPS) in the joists above the shooting positions at our range and it was a total waste of time and money.

@torzius, re "acting like some type of adhesive in that binds together all the structural members..." This doesn't surprise me. It's pretty stiff when cured and sticks like you-know-what. My prefab house uses what the mfr. calls their Smart Wall system, which uses CNC-cut EPS very tightly press-fitted between the studs, and those walls are RIGID!

Its more expensive but the benefits are worth it imo. If you plan on spending a lot of time in the garage I would certainly recommend the foam in between exterior wall studs. It definitely cuts down the sound and wind penetration. However, I would use air chutes in the soffits and not foam the rafter cavities.... instead try to get wet blown insulation in attic space (on top of a drywall ceiling) I would continue to try to vent that roof using vented soffits and an open ridge peak. A breathing roof is a happy roof. Best of luck on your building project!

I build houses and small office buildings and have researched it quite a bit. Foam insulation costs about 80% more than blown in netted insulation and is probably 30% better at insulating. If you ever have to make a plumbing or electrical repair or run an IT wire or something down the wall its going to be bear! You will have to rip all the sheetrock out and start chipping out the foam with a screw driver or razor knife. The extra money it costs could be spent on better windows or thicker blown-in insulation so you have to weigh out those trade-offs before making a decision.

Have an old house-insulation in the attic but the walls are non insulated with tongue and groove under sheetrock-does a pretty good job either way

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I live in a metal skinned wood framed pole barn. I sprayed closed cell directly on the metal. Closed cell is more waterproof and really ridged. You are right, if I wanted to change anything it would be a mess, even trying to pull one of the corners off would break the seal on the foam. Closed cell was 4X as much as open cell in my my case. The building is 2100 Sq. The Elec bill is around $100 year round, but I also have two outbuildings with Elec that run 24/7. All that being said, I would not do it again because of difficulty in repair remodel