I just got my permits for a new garage in Denver and the building dept is requiring:
R15 against the foundation walls to the footings
R10 below the slab
R21 in the walls
R38 in the ceiling
This garage will be far better insulated than my house!!!
What about an off the grid solar setup? I don't know much about them, but might be worth investigating. Would need a generator as backup for the welder though.