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How to Insulate a Garage: A Step-by-Step Guide

A man installs fiberglass insulation between studs of a garage frame.

Most garages aren’t fully insulated, and even attached garages only have insulation on the wall shared with the house. However, there are several benefits to insulating a garage.

If you have a heating or cooling system in your garage, insulation is necessary to save on energy costs. Insulated garages without temperature controls can also reduce the impact of extreme temperatures in the summer and winter months. 

Installing insulation is a pretty achievable DIY project, depending on your space and insulation choice. Read on to compare insulation types to decide which is best for your home garage. 

Why It’s Important to Insulate Your Garage

Insulation helps prevent heat and moisture transfer so that you can spend more time in your garage, regardless of the weather. Consider insulating your garage for these benefits:

Illustrations represent 4 key garage insulation benefits, including temperature, moisture, and noise control.

Garage Insulation Types

Different insulation types have different efficiencies and specialized benefits, so consider how your garage is built and your goals before choosing insulation. 

For example, some types of insulation are best for interior living, like spray foam for a converted garage office. Others, like double bubble insulation, are ideal for controlling moisture in a metal garage. 

diagram of different garage insulation types

All insulations feature an “R-value” that gauges how well a material insulates. R-values go as high as R-60, but exterior wall insulations are best between R-13 and R-20. 

Here’s an introduction to popular garage insulation options:

  • Fiberglass batts: Common insulation that fits between joists and studs.
  • Woven: A mix of foil, bubble, and woven materials for controlling temperatures in a metal building
  • Cellulose: A loose-fill insulation to fill cavities behind drywall and ceilings
  • Rigid foam: Foam boards or sheets with a high R-value.
  • Spray foam: An energy-efficient chemical insulation for interior living spaces and converted garage spaces.
  • Double bubble: Sheets of insulation with a foil backing for metal garage walls that help prevent condensation.

Insulation isn’t one-size-fits-all, so you’ll need to compare the pros and cons of each type to choose what’s best for your garage. Consider how your garage is built, how you’ll install the insulation, and what benefits you need for your space. 

Insulation TypeBest For:ProsCons
Fiberglass BattsStick-built garagesAffordable, easy to install, accessibleCauses, irritation, prone to moisture damage, mold, and mildew
WovenMetal garagesEasy to install when a metal building is being erectedDifficult to install after building is erected
CelluloseStick-built garagesEco-friendly, fire-resistant, accessibleExpensive only for finished walls
Rigid FoamUnfinished walls and garage doorsAffordable, noise reduction, cut to fit difficult spacesSusceptible to moisture, must be tightly installed, may fail air-venting codes
Spray FoamInterior living spacesFlexible for tight spaces, available in open cell (affordable) and closed cell forms (water resistant)Closed cell foam is expensive, not ideal for metal garages
Double BubbleMetal garage wallsMoisture control, inexpensiveNot suited for temperature control

How to Insulate a Garage

Insulation installation varies depending on the type of insulation you purchase, so always follow the manufacturer’s guidelines for a proper install. 

Since fiberglass batts are the most popular type of insulation for garages and homes, we’ve outlined the installation process for this type of insulation below. Note that spray foam insulation is a much more challenging installation process, so consider contacting a professional for help if you choose to use spray foam insulation. 

Tools

  • Protective eyewear
  • Gloves
  • Dust mask or respirator
  • Utility knife
  • Staple gun
  • Ladder
  • Hammer
  • Caulking gun
  • Screwdriver

Materials

  • Insulation (fiberglass batts)
  • Drywall screws
  • Caulk

Step 1: Clear the Walls

Bare framing of a garage with exposed studs and joists.

Fiberglass batts are installed between joists and studs, so you’ll need to clear everything off of the walls before you begin. Ideally, you’re still in the construction phase or working with an exposed frame. If not, you’ll need to remove your drywall, too. 

Step 2: Inspect and Seal the Wall

A contractor applies caulk between the garage frame and a window.

Take a look at your wall and check for any access to the outside through the exterior wall. Repair any damage or cracks with an exterior sealant to prevent moisture and insects from entering your walls. 

While there, inspect your wall framing for damage or loose fasteners and repair them as necessary. 

Step 3: Take safety precautions

Protective eyewear, gloves, and masks are essential for safe fiberglass insulation installation. Fiberglass is made of tiny glass particles that are harmful to skin, eyes, and lungs. Safety equipment prevents irritation and long-term respiratory concerns. 

Step 4: Install insulation batts

A man wearing safety equipment pushes fiberglass batts between garage studs.

You can begin installing your insulation batts once you’ve prepared the wall sealants and they have cured. Set batts between wall studs so that they fit snugly against the lumber. 

As you place your fiberglass, you’ll have to work around some other features in your walls:

  • Cables: Split the insulation batt so that it goes around the cable and insulates both sides. 
  • Electrical boxes: Trim the insulation with a utility knife to fit tight around the box. 
  • Pipes: Install insulation behind existing pipes so they’re exposed to the interior heat.

Step 5: Trim insulation to size

Close up photo of a gloved hand cutting fiberglass insulation with a utility knife.

You have two options to trim your batting—measure your stud spaces and cut the insulation to fit or trim the excess off once the batt is in place. Cutting placed insulation is more efficient, but you can always pre-measure batts if it doesn’t work out for you.

In either case, leave a little extra insulation to prevent any gaps. Don’t leave too much excess, which can cause the insulation to bulge and bunch. Consider giving an extra half inch to the length and width.

Step 6: Fill in other exterior edges

Spray foam insulation is installed in framing gaps where fiberglass insulation can't fit.

Your walls aren’t the only part of your garage that benefits from insulation. It’s critical to install insulation between ceiling joists to prevent heat loss through the roof. 

You should also take a look at your windows and doors. You can split and install fiberglass insulation around window and door frames where air leaks are especially common. 

Your garage door also benefits from extra insulation, but you’ll need insulation designed for garage doors. Fiberglass batts aren’t a good fit for rolling doors. 

Step 7: Finish your walls

A woman uses a power driver to secure drywall over the insulated garage frame.

After all of the insulation is secure in the wall studs, it’s time to cover the fiberglass. Consider a vapor barrier to prevent moisture damage, rot, mold, and mildew.

After the vapor barrier, installing drywall over everything is the nicest way to finish your garage. It also supports the insulation’s temperature control and soundproofing. Measure your garage interior to determine how much drywall you need, and secure the sheets with drywall screws. 

If you’re not interested in drywall, you can install a poly membrane sheet over the insulation instead. Some building codes may even permit exposed insulation, but know that fiberglass can irritate your eyes, lungs, and skin if you interact with it. 

Frequently Asked Questions

With so many insulation options, there’s more to consider than an R-value. Learn more about garage insulation best practices and costs below.

What’s the Best Way to Insulate a Garage?

Batt and blanket insulation is the best and most popular way to insulate a garage. It’s cost-effective, simple to install, and a strong insulator. 

Fiberglass batt is the most popular, but you can also purchase mineral wool insulation. It’s more expensive but has a higher R-value. 

What Does Garage Insulation Cost?

Garage insulation costs range between $0.65-$3 per square foot of wall and ceiling area. The total project cost can range between several hundred dollars for DIY installation to several thousand for professional installation. 

Costs vary by material type and garage size. Material type impacts both the material cost and labor cost. Some insulation, like foam spray, is harder to install and requires more time and experience. 

Here’s an overview of costs per square foot by material choice:

  • Fiberglass Batt: $0.65-$2/sq.ft.
  • Double-bubble: $1.50/sq.ft.
  • Foam Board: $2.40-$3.75/sq.ft. 
  • Woven 17: $3/sq.ft. 
  • Spray Foam: $3.15-$7.50/sq.ft. 

Should You Insulate an Unheated Garage?

Yes, there are several garage insulation benefits whether the structure’s heated or not. Insulated walls and ceiling will help prevent heat transfer, keeping your garage more comfortable throughout the year.

Insulation also reduces noise pollution from the outside and softens garage noises, like heavy impact drills and table saws. 

Heated garages see the greatest benefits since good insulation reduces energy costs. But you don’t need a temperature-controlled building to enjoy an insulated garage.

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Alan Bernau Jr

Alan Bernau Jr. is the founder and owner of Alan’s Factory Outlet. He has helped more than 75,000 homeowners design and install custom carports and garages over the last 20 years.

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