open cell or closed cell
I have a pole barn that is covered in metal . It has a cement floor,insulated garage door,it will be a/c only ,an its in central fla. One contractor wants to use closed cell at 11/2”. Number 2 guy wants to do closed cell on roof an open cell on walls [2×6]. Number three guy wants to do the entire building in open cell. I,ve read alot of info on these products, I,ve talk to guys about it an I,m still unsure. I,m leaning towards the closed cell but iI,m not sure about the thickness of it. also the closed cell is the lowest price [still pricey] I,d your thoughts on this .. tks so much bill [ I posted this in a diff forum which I think was the wrong one]
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1.5" of closed cell foam is only R9-R10-ish. That's a code-min residential wall in FL, but nowhere near a residential code-min roof.
For about the same money you can buy roughly twice the thermal performance with 5.5" of open cell, using the same amount of polymer, and (in most cases) a dramatically more benign blowing agent. At 3.5" you'd meet code min for walls, but you'd want at least 8-9" in the roof (installed in 2 passes, with a multi-hour cooling period between passes), especially if your roof is a low pitch, or not a "cool roof" finish.
So far only Lapolla has converted to using a low-impact HFO1234 blowing agent for closed cell foam. Most others are still using HFC245fa, which packs a gia-normous lifecycle greenhouse gas hit (1000x CO2.) Open cell foam is blown with water.
In your climate the AC will keep the open cell foam dry. With a roof leak there may be some drip-drip, but you'd be able to identify where the leak is, and you can just let the foam dry out.
With closed cell foam at 3" or more you get some additional structural capacity, but that capacity can be had more cheaply by other means.
ps. on the open/closed cell building . the inside space will be drywaled an the ac will not be all the time the garage will be open once in awhile. the attic space can ac to balance the space. i don,t know if this info adds anything......tks again you guys provide a great service to guys like keep it up !!! bill
The primary moisture drive in central FL is outdoor air. As long as it's air tight and the AC runs at least SOME of the time there isn't much of a mold risk, and that risk doesn't change appreciably whether it's open cell vs closed cell.