Here’s How To Insulate a Garage

Unfinished walls, thin metal doors, and concrete floors make the garage a chilly place to hang out, but with some ambition and a weekend DIY insulation plan, you can turn that around. Not only will your garage feel more like a part of the house, but installing insulation will save you money on energy costs and make for better storage space.

Dig in deeper below as The Drive partners up with our friends from BobVilla.com to provide all the information you need in The Drive’s guide, How To Insulate a Garage.

The goal of insulation is to insulate or protect something with a heat- and sound-resistant material, the inside of the garage from the harshness of the world outside. Basically, it keeps it hot inside when it’s cold outside and cold inside when it’s hot outside. The key benefits include: 

There isn’t just one type of insulation, despite what big box stores and their name-brand insulation would have you believe. Let’s dig in. 

The most common type of insulation is seen in the form of batts or rolls, which are generally called blanket insulation. The main difference is a batt is a pre-shaped and cut rectangle, while a roll of insulation comes wrapped up like a Fruit By The Foot.

Unlike blanket insulation, loose-fill has no shape, as it resembles the stuffing from inside a teddy bear. It is typically blown into spaces on top of a barrier and is great for filling odd shapes or spaces.

One of the easiest methods, spray or foam insulation is literally spread over and throughout areas by shooting the insulation at the wall like a hose.

Added to the frame of the building, rigid foam insulation boards are typically used when remodeling or building a house.

As the name suggests, reflective insulation reflects heat. It helps cut down on downward heat flow. 

A radiant barrier is made to keep spaces cooler, with special designs that protect against consistent intense sunlight. 

The Department of Energy states R-Value is the measurement of the ability of insulation material to reduce heat flow. The higher the R-Value, the better the insulation.

“Insulation is rated by its thermal value (R-value), and the higher the number, the greater the insulating effect.”

Due to its solid R-Value, wide availability, relatively low cost, ease of installation, and relatively unmessy nature, we recommend fiberglass batts or rolls for your DIY project. 

Estimated Time Needed: Approximately 1-2 days, depending on how big the garage is

Skill Level: Beginner

Working in your garage can be dangerous and messy, so here’s exactly what you’ll need to ensure you don’t die, get maimed, or lose a finger—hopefully.

We’re not psychic, nor are we snooping through your toolbox or garage, so here’s exactly what you’ll need to get the job done.

Organizing your tools and gear so everything is easily reachable will save precious minutes waiting for your handy-dandy child or four-legged helper to bring you the sandpaper or blowtorch. (You won't need a blowtorch for this job. Please don’t have your kid hand you a blowtorch—Ed.)

You’ll also need a flat workspace, such as a garage floor, driveway, or street parking that’s also well-ventilated. Check your local laws to make sure you’re not violating any codes when using the street because we aren’t getting your ride out of the clink.

In this example, we will use fiberglass matts as the primary method of insulation. We assume the exterior walls of your garage have typical wooden stud framing and are without drywall. Let’s do this! 

Note 1: As mentioned, some insulation needs to be stapled or nailed in place. Others, however, use friction and force to hold in place. Check the insulation for instructions.

Note 2: Some garage walls might have electrical lines running through them. Do not place the insulation over the wiring or electrical lines. Instead, cut small slits into the insulation and tuck the electrical wiring inside of the insulation.

Note: Keep insulation at least three to five inches away from any light sources. Insulation installed too close to a light fixture could result in a fire.

“The simplest way to install insulation in a typical garage attic will be to blow it in. The ceilings in most garages will already have drywall installed or plywood panels and there's also probably an access door, in order to get to the wiring, etc. The homeowner will need to be able to get into the attic to blow in the insulation. Where he has to be careful is to step only on the joists, he can't step between them on the underside of the drywall, or his foot will go through. He can cut some 2-foot-by-4-foot pieces of plywood to lay across the joists to step on if he likes. That's a bit more secure.

“The other thing he has to be careful about (and this is all on the bag of insulation) is not to block intake vents in the eaves with insulation. When you blow-in insulation, it actually comes out pretty slow and drippy, so it's not difficult to avoid the vents. Some builders like to cut a strip of batt insulation and use it to block the eave vents and then pull it out after blowing in the insulation.

“Oh, and it's a two-person task. One person remains in the garage and loads insulation into the hopper while the other holds the end of the long flexible hose and directs the flow of insulation.” - Taylor

A vapor barrier, also known as a vapor diffusion retarder, prevents moisture buildup. Its ability to help stop the rate at which vapor can transfer through a material is measured in “perms” (permeability). 

For example, glass, sheet metal, a polyethylene sheet, or a rubber membrane are Class I vapor retarders with a rating of 0.1 perms or less. Class III vapor retarders, greater than 1.0 perms but less than 10 perms, include unfaced fiberglass insulation, cellulose insulation, brick, or concrete blocks.

In general, vapor barriers are needed in areas with cold or mixed climates. Some insulation has facing already built-in, so check which type you have. Check with local building codes and consult a professional while buying your insulation to determine if it’s needed in your home and in your area. When installing, be sure to seal any openings where air could potentially leak.

BobVila.com says: 

“Vapor barriers are highly controversial because anything that can keep moisture from seeping into a structure can also keep it from seeping out, which can lead to mold and mildew growth. There may already be a vapor barrier (like Tyvek) between the sheathing and the siding. Some communities require a vapor barrier on the inside of the insulation in living spaces, and some don't. They may want to check with the local building authority but it's probably just a matter of choice since it's a garage. Now, if they were converting it to a living space, stricter rules would apply.

“The facing on faced insulation will form a vapor barrier. Whenever you're insulating with faced insulation, the faced side goes toward the climate-controlled part of the structure--toward the inside of the garage.”

Painting a garage floor will not help with temperature regulation, but it makes it look a whole lot nicer. For more information, read The Drive’s guide, How To Paint a Garage Floor.

Our pals at BobVila.com have performed dozens of garage projects and have knowledge and experience with insulation. Here’s what they had to say: 

We're not all reading learners. So here's a helpful video to get you on your way.

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