[milner351]

EXCELLENT!
All I needed was a little convincing on the pvc sch 80 air line to help me make the decision, sounds like my brain was failing me on the 300psi rating, I bet that's for the white sch40 pipe, gray sch80 has a thicker side wall and the 600psi rating you speak of.
COMPRESSOR:
YES! build a closet around it and insulate it with some room for it to breath, I hope to do so under my stairway leading to my loft storage area.
I'm VERY impressed with your numbers for heat / ac cost, again you build my confidence THANK YOU.
I will likely go with the spray in insulation because of the way my building was built. It's a wickes steel structure with the purlins on the outside of the posts and the steel directly on the outside of the purlins. So, any air gaps at the seams of the steel panels, holes in the siding from mis aimed neighbors pellet guns, etc, and i've got air and water leakage against whatever insulation I use. The spray in stuff will keep all this sealed up, and remains somewhat flexible to allow the steel to expand and contract with temperature changes. I will put 4x8x2" foam board on the inside of the purlins, and interior liner steel panels on the inside of that. The walls will end up with about 3" of insulation, and will be about 3" thick, with steel inside and outside. No taping, mudding, caulking, painting. Put it up and be done with it. Not the cheapest way to go, but I'm 32 and hope to be working in this building till I'm at least 62, so I am hoping I'll get my use out of doing it right the first time.

STEEL ROOF:
anybody got any ideas how to remove the fiberglass "skylights" I have now and replace them with steel panels to stop the leaks?
I've heard horror stories about walking on steel roofs and popping nails and causing all kinds of leaks, that is NOT what I want to do right before spraying $2000 worth of insulation on the underside of the roof !!

See
I told you you'd be sorry you got me going, I tend to ramble at the keyboard.

Thanks again and best of luck with everything.
When I get my shop set up as I'd like it, I hope to offer some repair / tuning / engine building / engine design (desktop dyno) and sandblasting / paint services to the cobra club community around Detroit.