How to Insulate a Garage for a Cost-Effective Space

Allie Ogletree
Written by Allie Ogletree
Updated September 12, 2022
The interior of a home garage with a white SUV and an ATV parked inside
Photo: Kiril Gorlovl / Adobe Stock

Your garage just got a whole lot cooler

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If you have an attached garage, then you know all too well what it feels like to open the door, and either have a hot gust of air turn your house into a sauna or a seeping cold breeze turn what should be a warm and cozy home into a chilly one. This might not be a problem for some homeowners, but poor insulation could be a major issue if you want to make good use of your garage. Here's everything you need to know about insulating a garage. 

Why Should I Insulate My Garage?

There are several reasons why it's beneficial to insulate your garage. The main reason is that insulation helps regulate the temperature inside your space. A well-insulated home is also energy-efficient, meaning you won't have to spend as much on heating and cooling. While you don't have to insulate your garage, consider insulating it if you can relate to any of the following scenarios:

  • You spend a lot of time in your garage throughout the year.

  • You store valuable items in your garage that could break or deteriorate in extreme temperatures.

  • You plan to transform your garage into a game room or general hang-out spot.

  • You’re concerned about keeping your car in tip-top shape.

  • You have an attached garage with a shared wall to your home.

How Much Does It Cost to Insulate a Garage?

You’ll pay anywhere between $800 and $3,250 to DIY your garage insulation. The insulation cost, however, depends on the surface area of your garage, the type of insulation you choose, and the thickness of the insulation.

How to Prep for Insulating a Garage

Before you can get started insulating your garage, there are a few things you’ll need to do to prepare for your project. 

Choosing the Right Material

Workers installing cellulose insulation on the side of a building
Photo: helivideo / Adobe Stock

The insulation material you choose greatly affects what steps you’ll take to install insulation in your garage. Here are the types of insulation to choose from:

  • Fiberglass batts: Popular and affordable material that comes in sheet form

  • Cellulose: Loose-fill insulation made of paper and wood that is blown or sprayed

  • Rigid foam: Petroleum-based foam that comes in solid sheets

  • Spray foam: Plastic-based foam that is sprayed into the walls

You’ll need to remove the drywall in your garage if you want to install fiberglass or rigid foam insulation, but fiberglass insulation is one of the best insulations for garages because it is readily available, affordable, and easy to install.

If you opt for spray-based insulation, you might be able to get away with cutting a hole in the drywall and simply spraying inside. However, this option might leave gaps and spaces, making the insulation less effective. Your best bet is to hire a spray foam insulation contractor near you to do the job correctly.

Calculating How Much Insulation You’ll Need

Measure and then multiply the length and width of your garage's walls, door, ceiling, and floors to calculate the amount of insulation you'll need for insulation that comes in sheets, like fiberglass or rigid foam.

For blown-in insulation like cellulose or spray foam, a good rule of thumb is to multiply the square footage of your garage by how thick you want the spray foam. One set of spray foam will cover around 4,000 square feet if you opt for a one-inch thickness.

Safety Tips

You should follow safety precautions before you install any insulation, but you’ll want to be extra cautious when DIYing with spray foam, loose-fill, and fiberglass insulation. The U.S. Environmental Protection Agency states that some insulation types can harm your lungs, eyes, and nose, and cause respiratory issues if inhaled, so be sure to do the following:

  • Wear gloves, long sleeves, and pants to prevent your skin from coming in contact with the insulation.

  • For optimal protection against dust and particles, wear a face mask and eye coverage to protect your face.

  • Make sure your installation space is well-ventilated during the installation.

  • Wear full-body protective gear if you're using spray foam or loose-fill insulation.

How to Insulate a Garage by Area

Insulate Your Garage Walls

All garages that need temperature control can benefit from having insulated walls, but this is especially true for houses with separate garages and garages with exterior-facing walls. There are a few methods you can use to insulate your garage walls.

Use Fiberglass Batts or Rigid Foam 

  1. Remove the drywall (if there’s drywall in your garage).

  2. Clear out the stud cavities and clean the installation space thoroughly.

  3. Ensure there’s no mold, debris, nails, or screws on the walls.

  4. Seal any cracks in the garage wall with foam.

  5. Fit the fiberglass or rigid foam into the wall.

  6. Use a nail or staple gun to secure the insulation (optional).

  7. Add pieces of insulation to gaps in the material.

  8. Install a vapor or reflective barrier (optional).

  9. Cover the insulated walls with drywall.

Use Blown-in Cellulose or Spray Foam Insulation

  1. Cover immovable items in your garage.

  2. Inspect the walls for gaps and seal them with foam as needed.

  3. Create holes that are one inch in diameter into the wall cavity or remove the panels entirely.

  4. Shake the insulation well.

  5. Test the spray-based insulation on a small surface to see how much it expands.

  6. Use a spray foam kit to spray the foam or cellulose insulation into the cavity.

  7. Let the insulation set for eight hours, keeping it free from UV rays.

  8. Reinstall any drywall you removed to fill the walls.

Insulate Your Garage Ceiling

Insulating the ceiling of your garage is an absolute must for preventing heat loss and heat gain in the home. Any cracks or spaces in the ceiling will allow hot air from your furnace to slip through, wasting energy. You’ll find the process is similar to installing insulation in the walls, with a few differences. Here’s how you can insulate your garage ceiling:

Use Fiberglass Batts or Rigid Foam 

  1. Cover items that you can’t clear out of the room.

  2. Remove the drywall (if present).

  3. Clean and clear any debris that could pierce the material.

  4. Seal any cracks in the ceiling with foam.

  5. Measure the space between the framing.

  6. Cut the material to size. 

  7. Install rafter vents with a staple gun (optional).

  8. Using a ladder, install the insulation by placing it between the joists.

  9. Staple the insulation to the sides of the joists.

  10. Install a vapor or reflective barrier (optional).

  11. Reinstall the drywall. 

Use Blown-in Cellulose or Spray Foam Insulation

  1. Clear the area and cover what you can’t remove. 

  2. Either remove the drywall or drill one-inch in diameter holes.

  3. Wipe down and clean the space you’ll install the insulation.

  4. Fill in gaps and cracks with foam.

  5. Inject the insulation into the rafters, filling all surface areas.

  6. Let it set in a dark room for at least eight hours.

  7. Reinstall the drywall.

Insulate Your Garage Door

While you’re insulating your garage walls and ceilings, don’t skip insulating your garage door. Garage door insulation can really help to regulate temperatures and filter noise from outside. Installing insulation around your garage door is slightly different than the other areas of your garage, and you’ll want to avoid spray-based insulations and instead opt for fiberglass batts. Here’s how to do it: 

  1. Install two retainer pins per panel.

  2. Fit the material into each panel, giving a gentle but firm push.

  3. Tuck the insulation into the door panels.

  4. Use a retaining cap to pin the material in place. 

Insulate Your Garage Floor

If the concrete in your garage feels cold, it might be a good idea to also insulate the flooring in your garage. You’ll want to use rigid foam boards to do this job, as they’re strong, durable, and level. The best way to insulate garage flooring is as follows:

  1. Clean your garage floor and clear out the space.

  2. Repair any damage to the flooring.

  3. Install a vapor barrier to prevent moisture buildup. 

  4. Install rigid foam boards on top of the vapor barrier, leaving a 1/4 inch of space around the outer areas.

  5. Tape the panels down with strong tape.

  6. Lay 1/2-inch plywood panels on top, perpendicular to the foam, leaving 1/4 of an inch space between the panels and 1/2 inch spaces around the perimeter.

  7. Apply another layer of plywood and secure it with screws.

  8. Add a threshold strip for garages that need a smooth surface for parking.

  9. Install flooring or seal the plywood with epoxy.

Tips for Installing Garage Insulation

Workers installing spray foam insulation
Photo: Banks Photos / E+ / Getty Images

To ensure your project doesn’t turn into a confusing mess, having a few tips up your sleeve can help make your project run more smoothly. Check out these hacks for installing insulation in your garage:

  • Organize your materials and tools so that you have them ready when installing.

  • Pre-cut pieces of batt, roll, or rigid foam materials ahead of time.

  • Follow the instructions on your insulation for securing the material.

  • Check to see if you should also install a vapor barrier or radiant barrier.

  • Avoid installing within three inches of light sources.

  • Do not install insulation over electrical wiring; tuck the wiring into a cut in the insulation.

  • Make sure your garage door can handle the added weight of your insulation.

  • Consider using a garage door insulation kit for a quicker installation.

  • Seal any gaps around the door to block drafts.

  • Ask a friend to help while using a ladder to install ceiling insulation.

DIY vs. Hire a Pro

There's no question that DIYing your garage insulation will save you considerable time. While most roll, batting, and rigid foam installation projects are DIY-friendly, you'll want to avoid installing blown-in materials because they're more complex and may require special equipment. You must also have the correct measurements for your desired R-value, so if you're unsure of how much material you need, you might want to skip doing it yourself.

If you do end up hiring a local insulation company, the price to insulate your garage will likely double. Labor costs to install insulation range from anywhere between $0.25 to $1.50 per square foot, depending on the material and complexity.

Frequently Asked Questions

Fiberglass insulation is one of the most affordable insulation materials for garages, coming in at only around $0.30 per square foot

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