Just bought a house with a tube frame 31 x 30' steel building
I want to insulate it, and put in an airconditioner.
It has horizontal frame members, that go accross the building about 7 1/2' off the floor. At the ends of these are diagonal braces, that brace them to the legs.
I was thinking of putting a plywood ceiling under the horizontal frame members, and under the diagonal braces, and over the wall legs.

If I laid fiberglass insulation on the ceiling, what should I do for a vapor barrier? How about the walls, where there is only 2 1/2" between outside metal and inside plywood.
I suppose I could take the metal on the sides off if needed to do it if needed to put something between the siding metal and frame legs. I'm not taking the roof panels off!

Also thought of rigid board insulation with a foil face, as a radiant barrier, for the sides.

Any suggestions welcome.
Spray insulation is not within budget.

I'm in humid SW FL.