Somewhere in the world, the cold winter months are approaching, and people might be asking themselves how much does it cost to insulate a garage. And on the other side of the world, the hot summer months are approaching and people should be asking that same question.

Whether from the heat or the cold, an insulated garage is a good idea. Because getting in a freezing cold car in the morning is just as horrible as getting in a boiling hot car. Especially when there is a fairly simple fix.

If you’ve read any number of our articles here, you might have realized we love to make your lives easier by providing handy calculators. So it shouldn’t surprise you to learn we have a calculator to help you estimate the cost of insulating your garage.

The cost to insulate a garage can vary widely. Variables such as geography, the type of insulation used, and the number of square feet all factor into the price. Fiberglass batts for an average-sized 2-car garage could cost between $150 – $200 for materials alone.

Read on and I’ll provide details on the calculator.

How to Use the Calculator

As mentioned above, there are several variables that dictate the final cost of insulating a garage. Or anything, for that matter.

First of all, you need to determine what type of insulation you want to use. Are you simply interested in the cheapest type, or do you have some other criteria in mind? If so, I’ll discuss each type in depth below, but for now, we’re simply interested in the cost, right?

Whether or not you choose to use the calculator, you need those costs. To help with that, here is a snapshot of per square foot pricing on three different categories of insulation and their costs at the time of this writing. These are:

  • Fiberglass Insulation
  • Reflective / Radiant Barrier
  • Spray Foam Insulation
Snapshot of insulation prices
Snapshot of approximate insulation prices in 2021. Details below

Now assuming you do plan to use the calculator, I’ll detail where we’re pulling the information from and how to use it.

Where We Get Our Prices

The pricing on both spray foam and reflective/radiant barriers is from HomeAdvisor. HomeAdvisor is a US company, but they have subsidiaries around the world. They are:

  • In Canada: HomeStars
  • In France: 123Devis & Travaux
  • In Germany: MyHammer 
  • In Italy: Instapro
  • In the Netherlands: Werkspot
  • In the UK: MyBuilder

HomeAdvisor works with contractors, helping to connect them with homeowners.

The price for fiberglass batts comes from the U.S. Department of Energy. I don’t think I need to give an explanation on who they are and whether their pricing is trustworthy. Although . . .  No. Let’s not go there. Of course, we trust the government. Right?

Whatever type you are using, you can refer to the chart above for pricing.

Once you’ve selected what type of insulation you’re planning on using in the pulldown menu, you need to fill in how many doors your garage has. Is it a single-car garage? Two car? Are you fortunate enough to have three? Filling in this field will provide an estimate of the cost to insulate each door, which is approximately $100 per door.

Your next step will be adding the length and height of your walls, but you need to do something else first.

To keep the calculator simple, we didn’t add all the necessary input fields for calculating a garage roof, since there are mor variables. For example, a pitched roof will equal more square feet than a flat roof. So calculate the amount of insulation you’ll need and add that to your estimates for wall coverage.

Now, I mentioned above that I would get into more detail with regards to types of insulation, so here goes.

Types of Insulation

Insulation comes in several different forms. And if this is a DIY project you are embarking on, some will be much easier for you to install than others. I’ll list the main types and then provide more info on types included in the calculator.

The main types are:

  • Fiberglass batts or rolls
  • Spray foam
  • Blown-in
  • Foam or rigid boards
  • Reflective or Radiant Barrier

Fiberglass Batts or Rolls

Best for: DIY projects on unfinished ceilings, floors, and walls.

Fiberglass insulation is easy to work with and relatively inexpensive

This is the stuff that will make you itch for days if you get in on your clothes or embedded in your skin. And you can inhale the fibers as well, so masks should be worn at all times.

Although pink may come to mind when thinking about fiberglass insulation, that’s just some great marketing. Owens Corning wants you to think all fiberglass is pink, so you’ll buy theirs.

In reality, fiberglass is transparent, but the resin that’s used to bind the fibers together can be dyed any color.

Despite the above-mentioned prickly problem, fiberglass batts or rolls are easy to work with, and better yet, they are relatively inexpensive. They are a great choice for DIY projects since they are designed to fit between all standard width studs, rafters, and joists.

If you choose standard batts and rolls, they have R-values between R-2.9 and R-3.8 per inch of thickness. However, you can also get medium or high-density batts and rolls, and they have R-values between R-3.7 and R-4.3 per inch of thickness.

Spray Foam Insulation

Best for:  Hard to get at spaces

Spray foam insulation
Spray foam insulation is great for filling in small gaps and good at preventing air leakage

Spray foam is made from polyurethane and is a great choice if you are dealing with air leakage. It’s better than any other type of insulation when it comes to filling in small gaps.

Spray foam is available in both open and closed cell.

  • Open-cell has a density of 1⁄2 pounds per cubic foot
  • Closed-cell has a density of about 2 pounds per cubic foot

The higher the density, the higher the R-value. Open-cell has a lower density and has an R-value of about 3.7 per inch of thickness. Closed-cell has an R-value of around 6.2 per inch of thickness. Not surprisingly, closed-cell is more expensive.

Unless you are buying a kit for a small job, spray foam is done by a contractor. Two chemicals are combined on site, and this is what creates the foam. The foam is sprayed via equipment on a truck parked in your driveway. If you’ve ever had your ducts cleaned, it’s sort of the same setup.

Once the chemicals mix the chemical reaction ensues, and foam is created. It then expands and hardens.

It should be noted that on top of being available in open and closed cell, there is other significant difference in types.

  • Injection spray foam. This type of spray foam expands very slowly and can be used behind finished walls.
  • Spray in place foam. This foam expands in seconds and isn’t recommended for use behind finished walls.

Reflective or Radiant Barriers

Best for: Attics, ceilings, floors, and unfinished walls.

This type of insulation is very different from the types listed above. First, it doesn’t measure effectiveness by R-value. Second, the process of standard insulation is to reduce heat flow inside the home. In contrast, reflective or radiant barriers work to block heat from entering the home in the first place. It is reflected away. If you’ve ever seen people put tinfoil on their windows, this is what they are doing, preventing heat gain and radiant heat transfer to the inside their home.

Since the attic typically attracts the most heat gain in a home, reflective or radiant barriers are often used there. Between beams, joists, and rafters.

This insulation is constructed by attaching a reflective surface—like the tinfoil mentioned above—to another material, such as Kraft paper or polyethylene bubbles.

Installation of reflective or radiant barriers doesn’t require a professional.

Why Insulate Your Garage?

The basic advantages to insulation your garage are:

  • Keep the heat in
  • Protect your pipes
  • Reduce noise
  • Protect your electrical

Obviously, it’s not as imperative as insulating your living space, but it is a wise step.

However you heat your garage, it’s going to cost money. And since most of us don’t have money to burn—literally or figuratively—it just makes sense to conserve whatever heat you can.

There are other reasons too. Many laundry rooms are now in a mudroom just off the garage. Are there any pipes that run through the garage as well? Perhaps to a hose outlet? Whatever the reason, those pipes need to be insulated.

Do you live in a row of townhouses? I bet your neighbors—or the family still upstairs watching TV—likes to hear you using your garage workshop at all hours. Or not!

Finally, unfinished garages have a lot of exposed electrical work. Adding insulation and drywall adds a few layers of protection.

In two of the cases above, the need to hire a plumber or an electrician would end up costing you more than it would to insulate the garage in the first place.


There are a lot of smart, valid reasons to insulate a garage. And the good news is it’s not too expensive. And now you have a calculator that can help you easily determine the approximate cost.

Take some time to look over the information about the types of insulation. Do you want to do the job yourself? Is it a small job, or do you have a large garage? Remember, in certain instances, you may need to hire a contractor, which will add to your final cost.

Thanks for reading this far! Why not take a look at the related articles listed below and see if there is anything else we could help you with.