Insulating a metal shop?

ESP47 said
I saw those kits but the amount of kits you'd need to purchase for a 30x50x12 building is a lot.

I've been reading so much conflicting information about insulation that it's making my head spin.

If I wind up doing the foam board insulation with a 1" air gap, do you think it's best to use some spray foam to seal up the air the best I can in the shop corners where I can see some light coming through or should I just seal up part of it but leave some spots open so air can travel in and out?

The 1" air gap and the reflective side of the foam board should reflect a good amount of heat into that space. I'm not sure if allowing that air to flow out is better or keeping it trapped in there is better. What do you think?

Honestly I would leave that air space open, during the summer it would allow the air in the space to escape if it heats up to the point that it’s hotter than the outside air. And in the winter it would allow moisture to escape because you could still get condensation on the back of the outer metal panel.

Realistically you won’t make that space airtight anyway so it probably isn't a big deal, but especially for keeping it cool in the summer I'd want somewhere for that hotter air to go. If you were more worried about keeping it warm in the winter it might be a different story, but knowing where you're at I'd be leaving those gaps open.