Insulating Garage Walls and Ceilings

Due to the fact that fiberglass insulation is extremely irritating to the eyes, throat and skin I wore full length pants and a long sleeve shirt, even though it was about 75o degrees in the garage. I also wore goggles and a mask to protect my eyes and throat.

To insulate the garage walls I first measured the wall height and counted the number of bays between walls studs. With this information I was able to calculate the number of linear feet of insulation required and purchase the necessary rolls of insulation. I did the same for the garage ceilings.

To install the garage wall insulation, I simply cut lengths of insulation on the floor of the garage, equal to the wall height. I used a utility knife and a length of 2×4 to cut the insulation. Cutting faced insulation works best if you cut it from the faced side while pressing it down with the 2×4. Next I installed the lengths of insulation into the wall stud bays, making sure that I didn’t leave any gaps. I also made sure to have the paper side face inwards, toward the inside of the garage. I then stapled the paper faced tabs to the wall studs.

After insulating the wall stud bays I then filled in the small crevasses with either strips of fiberglass insulation or with foam insulation that comes in a can. The foam insulation works great for very narrow spaces around doors and windows. For a quality insulation job it is important to insulate all gaps in the walls, so don’t skip insulating these crevasses.

Once I completed insulating the garage walls I then moved on to the ceiling. First, however, I nailed up 1”x3” strapping to the roof joists. I ran them perpendicular to the roof joists and placed them on 32” centers, and used two nails per roof joist to secure the strapping.

I then installed, or weaved the insulation up into the roof joists bays, such that the insulation rested on the strapping. I positioned the insulation so that the faced side faced inwards to the garage. I also stapled the insulation to the adjacent roof joists. Once I insulated the garage ceiling, I then went back and installed additional pieces of strapping lumber in-between the existing strapping pieces. In the end, the strapping was effectively on 16 inch centers. The entire effort only took a day, and this was for a 24’x24’ garage. So if you are contemplating finishing your garage with drywall, spend the time and money and first insulate the garage walls and ceilings. Your garage will be warmer during the winter months, regardless if you heat it.

Living in New Hampshire I typically observe the garage to be about 30o warmer than the outside air temperature during frigid cold nights.  I observe this by noting the outside air temperature from my car thermometer when I first get into the car, and then watching the temperature drop as I leave the garage and drive to work. Living in New Hampshire I typically observe the garage to be about 30o warmer than the outside air temperature during frigid cold nights. I observe this by noting the outside air temperature from my car thermometer when I first get into the car, and then watching the temperature drop as I leave the garage and drive to work.