How To Insulate A Garage: Walls, Door and Ceiling

Hot during the summer. Cold as heck during the winter. Your garage doesn’t have to be a place where you compromise with comfort for half the year.

Insulating your garage will maintain the temperature during summer and winter. You’ll save on electricity if you decide to heat or cool down your garage. You can turn your garage into a livable space which will increase the cost of your home.

Learn how to insulate a garage from the garage door to the walls with a little bit of know-how and the proper tools.

Find out everything you need to know about insulating your garage below.

Benefits of Insulating Your Garage

The #1 benefit of insulating your garage is comfort. Insulation can provide a 5 to 20-degree temperature difference which expands your livable square footage. An insulated garage can become a workshop, a hangout area, or just a place to hide from uninvited guests. 

Insulation adds protection to your vehicles and belongings. Insulation keeps vehicles warmer in the winter, while also reducing wear and tear on lawn equipment and any electronics you keep in the garage.

When you insulate your garage it will contribute to better energy efficiency. Air has a tendency to think the grass is always greener – for example, warm air will want to go to cold spaces and vice versa. Every time you park your car in the garage and walk into the home, heated or cooled air is going to try to rush to escape. Quality insulation can save anywhere from 15 to 25% in heating and cooling costs over the long run.

Understanding R-Value for Garage Insulation

R-value is the measurement of how resistant an insulation is to heat coming into and going out of an area. The higher the R-value, the more energy-efficient your property will be. 

Typical construction with 2X4 lumber will require an R-Value 13 or R-15 wall insulation. Modern building with 2X6 walls needs a bit more resistance, with an R-Value in the R19 or R21 range. Since heat rises, you want to contain it and thus a higher thermal resistance is required in an attic, anywhere from R-30 to R-60 depending on your climate. 

Pros/Cons of Each Type of Insulation

Aside from determining how much insulation is needed in your garage, you’ll also have to select the material that will help you reach those thermal resistance goals. Here are the most commonly used products and their pros and cons: 

  • Fiberglass batts – the most commonly used material is fiberglass insulation consisting of tiny glass shards spun together and bonded with heat. Fiberglass insulation are easy to install, as they are manufactured to the exact length and width of standard wall and joist pockets. Fiberglass insulation is very itchy and inconvenient to install though and can compress over time. 
  • Loose-Fill Insulation – fiberglass or cellulose (recycled paper or denim) is most often used for insulating the garage attic. It is a great product for retrofitting as it can be blown through holes. Cellulose is very heavy though, and will also settle over time. 
  • Rigid Foam Panels – rigid foam panels made of products such as polyisocyanurate offer great R-value of up to 6 per inch and are also often manufactured with foil backing that serves as a vapor barrier as well as a resistant to radiant heat. Foam panels cannot be cut around outlets and pipes as well as loose-fill or fiberglass, however. 
  • Spray Foam –  Spray foam can be used on attic ceilings and on walls to create a virtually impenetrable barrier, especially with closed-cell foam. This is a very expensive process however that requires professional application. 

Best Type of Insulation for a Garage

fiberglass batts

In most cases, fiberglass batts are the default choice for the best insulation in a garage. Energy efficiency is important in every room, but the garage is typically heated and cooled to a lesser extent than a living or a bedroom. 

Fiberglass batts are preferred because they are cost-effective and easy to install even as a DIY project. Fiberglass batts can be sold in precut dimensions so there is no cutting involved, making installation as easy as peel and place. 

Fiberglass batts could conceivably also be used in garage roof insulation since not as much heat needs to be retained compared to in the house. Loose-fill will always be the best bet for attic insulation, however, even in a garage. 

Cheapest Insulation for a Garage

Not only is fiberglass the most convenient option for insulating your garage, but it’s also the least expensive. No special equipment needs to be rented for installing fiberglass like there is with the blown-in materials. 

The average cost per square foot to install fiberglass insulation ranges from $0.64 to $1.19. Even on the high end, that’s about a $200 project for an average-sized garage. Having blown-in insulation installed starts out at $500 but can range up to $2000. Spray foam gets more costly the thicker you apply it, also starting off at about the $500 range for the bare minimum and in the open cell. 

Should I Insulate My Garage?

You should consider insulating a garage if you’re spending time during the winter and summer months working in your garage. The exterior wall of the home that is shared with the garage is probably already insulated, but doubling up never hurts. Your home is going to lose a lot of heat or AC air every time the door is opened without insulation. 

There are some other things to consider when insulating a garage, however. In an unfinished space, it’s always best to cover up the walls with sheetrock after the insulation is installed. Exposed insulation can be a haven for rodents to nest in, and the material also attracts moisture which leads to mold and mildew growth. Getting drywall hung does add to the project budget rather significantly. 

Insulating your garage is also a great way to seal your garage and reduce the amount of sound coming inside. Sure to keep out the noisy neighbors!

The easiest way to start insulating your garage is by insulating your garage door. Below you’ll find everything you need to how to insulate your garage.

Tools you need to Insulate a Garage

The only real special tool you’ll need when installing insulating is the blower if using blown-in cellulose or fiberglass. A stick is also needed to break up the insulation so that it can get chopped up in the mixer and transferred through the hose. 

Otherwise, the only other thing needed when insulating your garage door is a sharp utility knife. You’ll have to make cuts around pipes and outlets whether you’re using fiberglass or foam. Fiberglass is also very itchy, so gloves and protective masks are a must as well. A stapler comes in handy when installing faced batts that are secured to the wall studs. 

How to Insulate a Garage 

Garage Door Insulation:

The best route to take is to purchase a garage door that already has insulation in it. The combination of steel and polyurethane does a great job of creating a thermal barrier when the garage door is closed. 

You can also use a garage door insulation kit. Radiant barriers are the easiest to install on your garage door, as they involve placing a reflective aluminum sticker on the door to block heat from entering. Insulating an existing garage door with fiberglass or foam involves adding panels, which add weight and can affect clearance when opening and closing your garage door. 

Ceiling Insulation:

Loose-fill is the best for ceilings because it fills in every area before it can start to pile up. The loose fill has a way to get into tight cracks and crevices that fiberglass doesn’t cover. 

Installing loose-fill insulation is a two-person job, however. One person needs to load the insulation into the hopper and break it up, while the other sprays the product between the floor joists. 

Wall Insulation:

Insulating the walls is a relatively straightforward process, especially with pre-cut fiberglass batts that are the exact dimensions of the wall pocket. Unfaced batts are tight enough that they squeeze into the garage wall pocket and stay in place, but in order to avoid settling over the years, faced batts are stapled to the studs. 

About Roy Cohen

I'm Roy, founder of Hack My Garage. I started out like most not knowing how to hammer a nail, but now I know more than most people about home improvement and DIY. I want to spread my wealth of knowledge with the world and hope to make it a better place.