Insulating a metal shop?
There are a number of DIY spray kits available....as close as Home Depot, probably Lowes. I got a catalog with my "spacer adhesive" from a place called J&R Products Inc. WOW is all I can say.....packed full of scrapers and shavers and blowers and everything that you'd want! Probably at full scale prices too.....
I don't know what the "material data sheets" say about installing this DIY spray directly on tin....but if science is real....and rust can't happen in the absence of air and water......well then spraying this directly on the tin would be OK! I just wonder about the temp of the tin in direct contact with the sun.....how well would the stuff handle this temp!? Pretty danged hot! But do some research and ask questions.
One thing about the fiber glass insulation is that it is bascially some fibers in a bag displacing air.....but not much....air is still in there.....and as we know air transfers temperatures..... or slows it down a little bit.
I'm suggesting that this type of "batting" insulation is a sort of stop gap measure. The plastic film on the rolls likely does the big job of stopping moisture movement..... The air amongst the fibers slows down the heat transfer but doesn't block it like closed cell (spray) foam or the ISO board mentioned above.
BUTT, putting this stuff up is still a wise choice before you move in!!!!
Shop looks nice!!!! I vaguely remember the day my shop was empty.......! :)
Steve