A few years ago I bought a new metal garage door, which was insulated with a foam core and double-pane windows. Naturally, I paid extra for the insulated 16-foot wide garage door. After having it installed, I realized that the purchase was pretty silly, as I have two wire screen openings in my garage walls that are required by code to provide combustion-air for my furnace and water heater that are located in the garage. So much for that idea.
Fortunately it rarely gets below 40 degrees F around here during the winter.