Thinking About Insulating Your Garage Door? Here’s What You Need to Know

Insulating the garage door will help keep your workshop comfortable year round. Here’s what to know about the best types of insulation for the job, and how to get the project started.

By Glenda Taylor and Bob Vila Staff | Updated Nov 8, 2023 4:37 PM

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Man fitting rigid foam insulation into a garage door panel.

Photo: Amazon.com

As the weather cools, it’s the perfect time to gird your garage against the colder temperatures on the way, especially if you’ve got your home workshop in there. Metal garage doors block strong winds but do little to maintain a comfortable temperature.

If you’re not ready to spend more than $1,000 on a new, pre-insulated door, consider gearing up the garage door you’ve got. We’ve assembled all the info you need to understand how to insulate a garage door successfully, plus tips to help you get maximum benefit out of the project.

The Benefits of Insulating a Garage Door

There are a couple of really good reasons that make the task of insulating a garage door worthwhile:

  • Adding insulation to the door’s interior channels can help keep your garage an average of 10 to 12 degrees warmer in winter and as much as 20 degrees cooler in summer.
  • An insulated garage door reduces noise transfer, too. Not only will you hear less street traffic (if any) when you’re in your workshop, but you’ll also spare your neighbors the sounds of your son’s garage band practice.

RELATED: 7 Places That Could Use More Insulation (and Why)

What to Know About R-Values and Garage Door Insulation

Most garage doors are made of metal and offer very little protection from outdoor temperatures. Insulating the doors can help, but not all types of insulation can be considered the best insulation for garage doors.

Insulation is categorized by its ability to reduce heat and cold transfer. The higher the insulation’s thermal-resistance value, or “R-value,” the better it will stop heat and cold transmission. The key points you need to remember about R-values when researching garage door insulation are:

  • The thicker the insulation, the higher the R-value.
  • When batt-type insulation is compressed or gets wet, its R-value is reduced.
  • For the best overall thermal resistance, consider insulating bare stud walls as well as the door.
  • Insulation with a high R-value will not significantly reduce thermal transfer if the garage is drafty and cold air flows in.

Garage Door Insulation Kits

how to insulate a garage door

Photo: Amazon.com

The simplest way to insulate a garage door is to buy a kit that contains either vinyl- or foil-faced batts, or foil-faced rigid foam boards. Garage door insulation kits, such as the Reach Barrier garage door insulation kit, start around $50. Some sets cost a bit more, but include all of the supplies you need: adhesive, tape, a utility knife, gloves, and perhaps even a dust mask. That’s all in addition, of course, to garage door insulation panels that are pre-cut to standard size.

The main benefit of using an insulation kit is that it comes with specially designed retainer pins. Made of lightweight plastic or metal, the pins have plates attached that adhere to the back of the garage door channels to help anchor rigid foam or batts in place. This stabilizes the insulation, so it won’t fall on your car when the door is open. If you choose not to use a garage insulation kit, there are other ways to hold the insulation in place.

RELATED: Buyer’s Guide: The Best Garage Door Insulation Kits We Tested This Year

Types of Garage Door Insulation

The main types of insulation used on garage doors are batt and rigid foam. Most folks go with rigid foam because any rolled batt that doesn’t come in a garage door insulation kit is likely to be too thick for the door.

Rigid Foam Insulation

how to insulate a garage door

Photo: Amazon.com

Most DIYers who don’t use a garage door insulation kit opt for foil-faced rigid foam board insulation panels that can be measured and cut with a sharp utility knife or table saw to fit the channels inside the garage door.

There are three main types of foam board, and they are all acceptable to use as garage door insulation as long as they are foil-faced and fire-rated. Do not use non-faced foam board, which is flammable and will produce dangerous fumes if it burns. In fact, using it might violate your local building codes.

  • Expanded polystyrene (EPS): Available in various size panels, expanded polystyrene foam can be either rigid or slightly flexible and used to line the inside of a garage door. It resists damage from both moisture and heat, and it has an R-value of about 4.6 per inch of thickness. It’s available in sheets in various sizes, and comes faced or unfaced.
  • Extruded polystyrene (XPS): It’s not difficult to identify extruded polystyrene: These colored foam boards are usually blue, pink, or green. XPS offers an insulating value of R-5 per inch of thickness. It’s available in both faced garage door insulation panels and unfaced.
  • Polyisocyanurate (ISO): All polyisocyanurate foam panels are faced (often with foil) because the boards are manufactured by spraying a liquid against a substrate. Polyiso is often used in roofing, but is a suitable option for insulating a garage door. It offers a high R-5.8 insulating value per inch of thickness.

Whichever type you select, you’ll want to use foam board that’s slightly thinner than the thickness of the door’s interior channel enclosures. For example, a standard garage door channel is about 1¾ inches deep, so you would want to cut pieces from a 1½-inch-thick foam board.

Although it may not be true of every kind of door, most garage door channels have “lips” that hold the boards in the channels, but rigid foam boards can still rattle around a bit if they don’t fit snugly. A bit of foam-safe adhesive, applied to the back of the garage door channel before inserting a board, will help hold it in place.

If need be, you can use expanding foam to seal gaps around the sides of the boards, but keep in mind that a little expanding foam goes a long way. Check the label of any adhesive and expanding foam spray to ensure that it’s compatible with the foam board you’re using—some adhesive will melt foam board.

RELATED: How to Heat a Garage: 11 Tips for Keeping Your Workshop Warm in Winter

Batt Insulation

how to insulate a garage door

Photo: Amazon.com

Batt insulation doesn’t refer to a specific type of insulation but rather indicates the material’s form—either strips or rolls. Batt insulation is made from various components and is available faced or unfaced. You can purchase batt insulation on it on its own, or in garage-door-insulating kits. Unlike rigid foam, batts are flexible and soft.

While standard batt insulation is readily available—you might even have an extra roll laying around—and it’s often slightly cheaper than foam board, it’s probably not the best choice for garage door insulation if you’re not using a garage door insulation kit. The thinnest standard batt, at 3½ inches thick, is too thick for most garage door channels, and compressing the batts greatly reduces their ability to insulate a door.

If you’re set on using batt insulation, look for thinner, 1½-inch-thick foil-faced batting—the kind used for wrapping HVAC ducts—at a plumbing supply store, or order it online. Do-it-yourself centers don’t often carry it. The 1½-inch-thick Johns Manville batt insulation is well-suited to the task. To hold the batts in place, you’ll also need to use the correct adhesive and tape recommended by the batting manufacturer.

  • Fiberglass batt insulation: The most common type of batt insulation and the most affordable, fiberglass batts are made from thinly spun threads of glass. They come in strips and rolls. A 1.5-inch-thick fiberglass batt offers a thermal resistance value of R-4.7 to R-6.45, depending on density.
  • Rockwool batt insulation: Also known as mineral or slag insulation, rockwool insulation is the byproduct of recycled steel that’s blown into fibers at intensely high temperatures. Depending on its density, a 1.5-inch thick rockwool batt has an R-value between R-4.3 and R-5.16.
  • Ceramic batt insulation: A relatively new kid on the block, ceramic batt insulation is made from spun ceramic fibers and is mainly used for insulating around high-heat appliances, such as furnaces, but is also suitable for insulating garage doors. It’s a bit more expensive than fiberglass or rockwool, but it provides an R-6.45 thermal value per 1.5-inch batt.

RELATED: How Much Does Insulation Cost to Install?

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After You Insulate the Garage Door

Man replaces the rubber sealing on the bottom of a garage door.

Photo: istockphoto.com

Once the door’s insulation is in place, there are a few finishing touches to take care of that will keep the space warmer and less drafty:

  • Replace the rubber sweep on the bottom of the garage door, or install a rubber garage door threshold where the door mets the ground. Both will keep out drafts, water, debris, and pests.
  • Be sure to install weatherstripping around the sides of the garage door to prevent icy drafts from blowing in.
  • While insulating the garage doors is a significant first step, you’ll enjoy more heat retention if the rest of your garage is insulated too. Heat can still escape through a non-insulated roof or sidewalls.

Any steps you can take before Old Man Winter comes calling will keep you toastier inside your workshop. But we warn you: Now you’ll have no excuses not to get things done in the garage this winter!

RELATED: 9 Garage Floor Options Worth Considering for Your Next Reno

Final Thoughts

For those who use their garages year-round as workshops, insulated garage doors can make the difference between working on projects in relative comfort or not using the workshop at all during the coldest or hottest seasons.

Insulating a garage door should be undertaken in conjunction with installing weather-stripping around a walk-through door, a threshold seal at the bottom of the door, and (optimally) adding batt insulation in open stud walls. Some garage doors also have gaps around their perimeter, and sealing these is a vital step in getting the garage ready for winter.

FAQs

Batt insulation between the studs of garage walls.

Photo: istockphoto.com

Q: How can I insulate my garage door cheaply?

The least expensive method is to insulate the door with fiberglass batts approximately 1.5 inches thick.

Q: Does insulating a garage door make it too heavy?

Most types of insulation are lightweight, and an insulated garage door should not be appreciably heavier than an uninsulated one. In addition, insulation should not affect the ability of a garage door opener to open and close the door.

Q: What is the R-value of an insulated garage door?

That will depend on the thickness of the insulation. A 1-inch-thick foam EPS foam board offers a thermal resistance value of about R-4.5, while a 1.5-inch-thick rockwool batt can provide up to R-5.16.

Q: Does it make sense to insulate the door of an unheated garage?

It does make sense if other air gaps are sealed in the garage and the stud spaces are also insulated. If the garage is drafty, however, an insulated door won’t make much difference.

Q: Does insulating a garage door keep it cooler in the summer?

If the garage door receives direct sun rays from the south or west, insulating it can help keep the temps inside the garage from soaring during the hot summer months.

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