The reason I thought that we needed a garage heater is because we keep a second refrigerator in the garage. I wasn't sure what would happen if the outside of that refrigerator dropped below freezing. I suspect that the cold would have seeped in and frozen everything inside.
For that reason we put in the garage heater. It keeps the garage above 40 degrees, and now we are able to store canned goods out there in cabinets as well. However...
One part of the garage wasn't insulated, and that was the garage doors. I am not sure what the r-value of 1/16" sheet metal is, but it probably isn't very good :). We went through last winter without insulation on the garage doors, and the heater ran quite a bit. Electricity is cheap here, but it's still wasteful to let all that heat escape.
This season I decided to insulate the garage doors, and found some cool styrofoam panels to do the job. The panels are made by a company called Matador. The front side is covered with a vinyl cloth, and the back side is scored so that you can break it off at the desired height. Below is a picture of the back side of a panel.
I got to work, and it was pretty easy.
Here is how it turned out. It took about an hour and a half to insulate the doors of a 3 car garage. In this case, each panel had to be cut down somewhat to fit. I am pretty pleased with the fit and finish. Also, as a bonus, the doors open and close *much* more quietly!
The biggest pain in the butt was clean-up. It was impossible to get all the little styrofoam boogers cleaned up. They have a lot of static cling, and were still hanging from the inside of the garage doors when I rolled them up.
I ended up sweeping up as much as possible, then I used a leaf blower to knock them off the doors. Afterwards I used the leaf blower to blow them out of the garage, because by then they had gone everywhere :)
The garage holds heat into the night-time quite a bit longer than it did before, and so I expect that the heater will be running a lot less often.