Within the last year I framed in a portion of my garage for a shop area to work on my airplanes (15'X23'). I insulated the walls and ceiling and installed a Mini-Split system (heat pump). I can't say enough about this unit. It's quiet and energy efficient. I live in GA so it gets pretty hot in the summer and can get pretty cold in the winter. The unit I purchased is rated at 12000 BTUs and works beautifully. I only had to cut a three inch diameter hole in the wall for the lines. It will set you back about $900 though. The inside air exchanger is only about 15"X36" and the rest of the system is mounted outside the shop. One of the better investments I have made.