Post-frame Roof Assembly

[rossv]

I am looking at the pros/cons of the 2 roof assemblies.

1. Metal roof
Synthetic underlayment
OSB/plywood
Closed sprayfoam
Perlins/trusses


2. Metal roof
Closed spray foam
Perlins/trusses


I think option #1 is superior. Despite the additional cost is it worth it?

 

[geneg]

I am looking at the pros/cons of the 2 roof assemblies.

1. Metal roof
Synthetic underlayment
OSB/plywood
Closed sprayfoam
Perlins/trusses


2. Metal roof
Closed spray foam
Perlins/trusses


I think option #1 is superior. Despite the additional cost is it worth it?

Option #1. You won't hear rain or hail. You have a secondary watertite system under the metal, condensation will be limited. I'm assuming standing seam. In any event, you won't have to walk only on the purlins if the roof has sheeting.

Option 2 is cheaper.

 

[jack stand]

I never try to talk someone out of a great insulation "pkg", but dollar for dollar you could have a nice ceiling for lighting, wiring and less c/f of air to condition. Probably with money leftover.
Now if you've already planned on a ceiling anyway, option 1 is first class but to a degree, unnecessary. I'd think about using the synthetic tp on the purlins with option 2.
Welcome to GJ

 

[billconner]

I believe building codes would require covering or coating on the closed cell foam if no ceiling under it.