Here is a picture from just after the floor was poured. The builder put in a 1 sheet wide 'wainscot' all around the bottom. Its just attached to the lower girts. The iso-board is just attached to the girts the same way and ends up flush with the inside of the posts. So the wainscot and iso are...
Found some more pictures of the framing that happened a year later. From these pictures the 'outside' was skinned in 1/2" ply (except against the barn wall), the Kraft backed fiber with the paper facing 'in' then covered 'inside' with drywall.
This was back in 2010, so I had to do a little hunting. Here is a picture of the inside as I was putting the floor paint down. You can see the foiled iso-board attached to the girts. I used drywall screws with roofing disks to attach directly to the girts. All the way to the top and along the...
My spares/cutoffs turned into a matching outside compressor shed. A couple years later leftovers/cutoffs from a metal roof install on the house turned into a chicken coop. Though I still have some small bits from both jobs leaning against the wall outside with some other odds and ends awaiting...
Fellow Floridian here. It sounds like you will have someone else doing the work. Ask if they may have done something similar before so see what they think?
I did something similar myself in a 30x40 that looks very much like your barn where I made a 10x30 conditioned space. Right way/wrong way...
Our place came with crank open windows in the clearstory. The PO also left a long 1x board with a hole in the end that slipped over the crank handle so the crank could be operated from the ground. They do get a but sticky if not operated or maintained for a while.
Summer + Florida = Hot + Humid :-)
Without closing things in, insulating, and running a big AC the shed is basically a shady spot out of the rain. That said though, at least at my place, when it is closed up during the work week it gets a bit warmer than ambient inside but also a little dryer...
No one has mentioned your electrical hookup. From the description I read you are running 240V from the basement to a switch in the garage and back again? An AC contactor with a remote switch would make for a much shorter run of heavy cable $$.
I have a couple of gates at our place that were farm made. Not quite as heavy as yours but perhaps a similar setup would work. The gates have 2 short bits of pipe welded to the side sort of like seven hills described above. On the post side there are two big bits of threaded rod that go through...