Garage door manufactures want hundreds of dollars for an insulation kit. A new insulated garage door can cost thousands. For about $100 you can insulate your garage door in about two hours. On the right, you can see the uninsulated section, on the left, the insulated panels.
Our garage is also our laundry room, so it gets warm in the summer and cold in the winter, and it is not fun to do laundry there. When we bought the house, the previous owner had installed the cheapest aluminum garage door - which was uninsulated. In addition to being ugly, it was a huge thermal load in the garage.
We explored a "kit" to insulate it, but that was hundreds and hundreds of dollars. A new door was thousands. With about $120 of plastic-coated polystyrene (Styrofoam) we were able to insulate the door in about two hours.
The material was bought at Lowe's. We bought 8 sheets for about $13 apiece. We used seven. The foam is coated with foil on one side, and a clear plastic on the other. We used the clear plastic on the inside, as it provided an attractive, wipe-clean surface.
This Perma "R" material is very lightweight, which means that even seven sheets of it won't add a lot of weight to the garage door. The material is 3/4" thick and the door is 1.5" inches thick, so two sheets fill up the space between the channels.
The material cuts easily with an X-acto knife. Score one one side, bend and break, and cut the other - like sheet rock, only easier.
Insert thin strips (2-2.5" wide) behind the main channels. We tried cutting a piece to go behind all the channels, but installing it was impossible.
Bow the panel outward to get it to pop into the channels. We originally cut these panels 20.75" tall but found that 20.5" worked better and did not "bow" as much when finished.
Work the panel into the channel gently, and then work it into place. You may have to get rough with it. If you cut the panels properly and worked them into place, they should lay flat. If the panel is oversized slightly, it may bow a bit. We got better as we went along. I went back and removed some earlier panels and cut them down 1/4" to make them fit better. Be sure to use a finished (uncut) edge against the outside of the beams for a neat appearance. Repeat for each section - two 3/4" panels fit into the 1.5" door perfectly.
The finished product looks much neater, is quieter and cooler and was inexpensive and took little time to install.
Overall cost: About $120 (we had one panel left over). Time: About 2 hours.
The garage is already quieter and cooler. We have an old window unit in there to keep it cool. Great for working on your car!