Another Spray Foam Thread

[loosegoosegarage]

Question for those that spray foamed their steel building (mine is 30'x50'x14'). I am in Connecticut, so decently hot summers and cold winters.
I've been reading around about both options and now it has me worried as I get closer to this step that the metal panels will warp if foam is applied directly to them.
Did you use a barrier between foam and siding/ roof panels? (Some say Tyvek is good, some say foam won't stick to it, others say 1/8" plywood, but either way it makes me worry about air gaps behind it.)
If you did, what did you use and how is it holding up?
If you did not, did you have issues with panels warping?

 

[cannuck]

I did my 26 x 39 roof a few years ago with 5.5" of closed cell foam and absolutely no distortion when sprayed directly on panels. I suppose that might not be the case for an exceptionally large, unsupported area but I am 24" between supporting members with fairly low profile ribbing in IIRC 22 ga. skin. I would reccomend using MIPs instead of spray in place, but as in my case already up (for nearly 40 years) so not much choice.