radiant heat

the most expensive operating part of the radiant in-floor heat is the first few hours after you raise the temp. If you don't mind keeping it at a constant temp, and your shop is pretty airtight, then it will be pretty efficient as far as heat goes. Also, any shop tools (press, drill press, lathe, etc... won't rust!
I have 2x6 construction, stick framed barn roof, with regular R-19 in the walls and R-30 in the ceilings. I use a vermont castings wood stove that is meant to heat about 2400 sq ft. Floor space in my shop is 1,000 and I can close off about 250 of that so it gets warm pretty quick (unless it is during the middle of winter and I have not been out there for a few weeks).