Garage Insulation: Everything You Need to Know

Man installing garage door

Many homeowners make the mistake of not insulating their garages. They think of their garage not as an extension of their house but as an extension of the outside, so they choose to skip the insulation.

However, attached garages are notorious energy guzzlers. The heat from the adjacent room can seep through the shared wall and into the garage. The heat transfer can also happen inversely, meaning the garage can bring in heat from the outside and into the house. These two scenarios force your HVAC system to work twice as hard, resulting in higher energy costs.

It is very important that you insulate your garage. The results may not be immediately visible, but your utility bills will thank you for it in the long run.

When it comes to garage insulation, the first thing you should do is to look at the different types of insulating material that are available.

Types of Garage Insulation

There are four primary insulating materials to choose from: fiberglass, cellulose, rigid foam, and spray foam. Each has its own advantages and applications.

Fiberglass Insulation

Fiberglass is the most popular insulation material for garages. It comes in pre-cut batts, rolls, or blankets. Fiberglass is also available as loose-fill insulation, although this is mostly used in unfinished attics.

Fiberglass insulation is relatively cheap, which is why it’s popular. You can make a DIY project out of the installation if you’re choosing fiberglass batts since it’s easy to install. This insulation type is ideal for unfinished walls, floors, and ceilings.

Rigid Foam Insulation

Rigid foam or foam board insulation comes in stiff panels made from polystyrene, polyurethane, or polyisocyanurate. It offers a high R-value despite its thinness and can be cut to fit almost any space.

The best thing about foam board is that it’s the only type of insulation that blocks heat transfer through structural elements.

Rigid foam insulation is a good option if you’re planning to convert your garage into a living space. The foam would be installed under plywood or another wall or subfloor material.

Be sure to check the foam’s fire rating. Some types of rigid foam aren’t fire-resistant, which means they’re not suitable for exposed applications.

Cellulose Insulation

Cellulose insulation often comes as loose-fill. It’s made from recycled newspaper treated with a fire retardant, making it an eco-friendly option.

The contractor will use a special blowing machine to fluff up the insulating material and blow it into the space. You have the choice to rent a blower at a rental store if you want to do the insulation yourself. Some home centers will also loan the machine to you for free if you buy cellulose from them.

However, cellulose insulation is only applicable for unfinished garage walls and ceilings, since it’s loose-fill. If your garage is already finished, the contractor will cut strategic holes in the walls then spray the material between the framing members. They’ll patch the gaps afterward.

Spray Foam Insulation

Spray foam insulation is the best option for homeowners because of its high insulating value and air-sealing capacity. The contractor sprays the insulating material, which creates a solid barrier that blocks air and moisture gaps.

Spray foam insulation can be expensive though, so it may not be the most cost-efficient choice to insulate your garage. However, it’s an excellent option if you’re turning your garage into a full-time living space.

When choosing your garage insulation, it’s best to consult a contractor to make sure you’re picking the most suitable one for your needs. Describe your garage and how you plan to use the space to help your contactor make an accurate recommendation.

Alongside the walls, ceiling, and floor, you also have to insulate your garage door. Attached garages with uninsulated doors can decrease the efficiency of your HVAC system, especially since garage doors are often made from metal.

Garage Door Insulation

Large garage 2 doorsWhether or not you should insulate your garage door depends on how you use your garage. If you open and close the door several times a day, then there’s no point in insulating it. The frequent movement will just let out the heat you’re trying to keep inside the room. Additionally, the repeated motion can cause the insulating material to flake and pull apart.

However, if you’re using your garage as a workspace, then an insulated door is a worthwhile investment.

Insulated garage doors hold less heat than uninsulated ones, so they’re better at maintaining the temperature of the room. Plus, the insulation helps reduce noise pollution. It’s an effective soundproofing material, which is perfect if you want to turn your garage into a studio or office.

How to Insulate Your Garage Door

The best way to insulate your garage door is to buy one that’s already insulated. This saves you the trouble of having to install the installation. However, if you want to add insulation to your current garage door, you can purchase an insulation kit at home centers.

Garage door insulation kits come in two options: fiberglass batts or polystyrene rigid foam panels. The first option offers an insulating value of R-8. You only need to tape the material to the inside surface of the door.

The rigid foam kit, on the other hand, has an R-4 insulating value. The panels are cut to length, so you only need to snap them into place, between the horizontal rails on the door panels.

Just like in other parts of your house, garage insulation needs to be supplemented with air-sealing to achieve maximum energy efficiency. Air gaps might be letting out heat or letting in drafts, reducing the performance of your insulation.

How to Air-Seal Your Garage

Garages aren’t built to be airtight, so yours likely has air leaks if you haven’t insulated it yet. These gaps can let in cold air, which can seep into the attached rooms. The EPA says that air-sealing your garage can cut an estimated 15 percent off your heating and cooling costs.

Follow these steps to properly air-seal your garage.

1. Weatherstrip the Door Connecting the Garage to the House

Air-seal around the entire door frame on both sides. To check for air leaks, turn on the lights in the garage then exit. Turn the lights off on the other side of the door, then inspect the doorframe to see if any light comes through. If it does, that means you have air leaks.

You can seal wide air gaps using felt tape or self-adhesive foam. For tiny leaks, you can use a caulk gun to cover them up.

2. Caulk the Joints Connecting the Walls to the Floor

The soil under the garage is prone to shrinkage because of how it was built. When this happens, the floor moves, shrinks, or swells, which shifts the joints connecting the walls and the floor. This movement causes gaps in the joints, letting outside air into the garage.

Cover the cracks using a latex- or silicone-based caulk or a foam sealant. The ground never stops moving so be sure to check the joints between the walls and the floor at least once a year.

3. Insulate the Outlets and Light Switches

The holes in your garage wall holding the light switches and outlets aren’t always cut perfectly. There’s a big possibility that there are tiny cracks around these lighting components. You may think that the gaps won’t do much harm because they’re so tiny, but even the smallest leaks can be bad for your home.

Aside from cold or hot garage air leaking into your home, there’s also the risk of carbon monoxide poisoning. The fumes from your vehicle can travel through the small cracks on your walls and enter your home without your knowledge.

You can insulate outlets, wall switches, and electrical boxes using spray foam or rigid foam. Seal around the box or switch using the same caulk you used for the floor-to-wall joints.

4. Weather-Seal the Garage Door

You need to weather-seal your garage door to maximize the insulation’s energy efficiency. The door’s bottom edge, top, sides and the threshold might have gaps that let in outside air. You can use a strip of vinyl or rubber to seal around the door.

5. Seal the Cracks on the Floor

Garage floors are prone to cracks. The damage can be due to improper installation, poor drainage, or shrinkage. Regardless of the reason, these cement cracks can leak cold air from the ground. Worse, if water constantly enters these gaps, the water can freeze and expand, causing foundation upheaval.

For small cracks, you can simply use an epoxy concrete crack filler. But if the damage is too big for a filler, you need to remove the broken concrete and undercut the crack’s edges. Use sand mixed with an adhesive additive to patch the gap. Then, use a trowel to level the surface. Once it dries, grind down the area until it’s level with the rest of the floor.

The key to properly insulating your garage is to get an energy audit beforehand. This assessment will identify the spots in your house that guzzle energy. It will also recommend solutions for each problem area, helping you reduce your utility bills.

Insulate Your Garage with A+ Insulation

A+ Insulation offers a wide range of insulation solutions for different parts of your home, including your garage. Our experienced contractors ensure that your garage is well insulated and air-sealed to achieve maximum energy efficiency.

Schedule an appointment for a FREE home energy assessment!