In effort to save money on energy bills, people think insulating anything and everything will help retain heat and thus run the furnace a little less. While that is true in areas of the house that are conditioned with heat or AC, this isn’t the case for the garage. Trust me, I found out the hard way. I insulated my entire garage which is not heated … the walls, ceiling, and garage door and notice only a small difference.

Here in Colorado where temperatures get into the single digits, my garage is at most only 15°F warmer than outside and I spent about $500 insulating it. When going from 5°F to 20°F, you still aren’t going to spend a whole lot of time in the garage, so why bother? Now if I spent a lot of time in the garage and added a heater, that’s a different story and I would probably see a big difference. In that case, insulating the garage is definitely worth it.

Unless your garage is heated though, insulation will have little affect on the temperature of your garage in cold climates. Just because you add insulation won’t make the garage that much warmer or cooler. The main purpose of insulation is to slow the conduction of heat from the walls and ceiling to the outside and vice-verse. Insulation does not generate heat. If your garage is already cold, the area will virtually remain the same temperature whether you have insulation or not. And remember this, when you open your garage door in an unheated yet insulated garage, you recycle the air in a matter of seconds then trap the new cold air until you open the door again. And no, things like a refrigerator, freezer, or lights will not heat the garage to make the insulation worthwhile.


Some have argued that the wall(s) which separate the main house from the garage will allow some heat to pass and thus warm the garage, but that shouldn’t be the case! The walls which separate the garage from your main house should be insulated to prevent as much heat as possible from conducting into the garage from the house. If those walls are not insulated or not insulated enough such that your garage is warm without a heater, then that is something I would fix immediately so as to retain as much heat as you can in the living space of your house where your heater is working hard to keep it warm. In that case, adding more insulation may be necessary.

Now, if you do want a warm garage, then I would add a heater and insulate the ceiling, walls, and garage door. Depending on the size of your garage, insulating the walls with batts of R-13 will typically run you about $100. If the ceiling has 24″ center joists, that will cost about $200. The garage door will cost about $100 if you use the pink Styrofoam stuff from Home Depot, but that will only insulate your door to about R-6. If you spend a lot of time in the garage, buying an insulated garage door might be better, but it will cost you about $1500.

But before you do anything, the best way to make your garage a little more comfortable is to stop any cold air infiltrating into your garage from the outside. Put new weather-stripping down where the garage door makes contact with the ground. If you have a door entrance from outside into the garage, make sure the seal is intact and no air is coming in around the frame. These are good first steps that will only cost you about $40 and can make quite a difference. Even a slight draft can make your garage feel much colder than it really is when it’s 10°F outside.