Garage Insulation: A Complete Guide

Garage Insulation: A Complete Guide

Your garage is one of the most important rooms in your home.

It’s usually where you store valuable possessions and spend time on DIY projects, which is why you need to ensure that you insulate it. 

What are the benefits of garage insulation?

By taking the time to insulate your garage properly, you can help to increase its energy efficiency and make it more comfortable.  

With that in mind, let’s look at how to insulate your garage in its entirety, from floors to ceilings and even its doors! We’ll start by checking out the most common types of garage insulation. 

Types Of Garage Insulation 

If you’ve never had to insulate a room in the house before, you’ll probably feel a bit unsure of what insulating materials to use.

Here’s a rundown of some of the most common types of insulation, looking at their pros and cons. 



Rockwool is a type of insulation that’s easy to install and comes in batts.

It’s made of rocks, which might sound strange, but how it’s made is that natural rock gets heated to extreme temperatures so that it can melt and become a liquid. It’s then put under a high-pressure stream of air before being spun into long fibers.

These strands get collected and they’re compressed into dense mats. Finally, these are cut into smaller batts so that they can be used as insulation.

Since it’s fire-resistant, rockwool is ideal for use in the garage. It’s resistant to water and this means it prevents mold and mildew from forming.

Rockwool can also insulate a room against sound. It doesn’t degrade over time, so it’s highly durable. Rockwool is very easy to install: the batts are simply cut with a handsaw and then snugly fitted into place. 

One of the drawbacks associated with rockwool is that it is quite expensive. Another one is that it’s not as widely available as other types of insulation, such as fiberglass.

Rockwool insulation will cost between $0.91 – $1.65 per square foot. 

Cotton Batts


Instead of rockwool, you might consider insulating your garage with cotton batts. This is an interesting type of insulation because it’s made from recycled clothing, such as denim, which is why you’ll find that cotton batts are blue in color.

Since most of the content in cotton batts is made from recycled material, it’s good for the environment and perfect for insulating gaps, such as stud walls. Cotton batts are flame-retardant because of how they’re treated with boric acid solution.

However, one of the drawbacks of cotton batt insulation is that cotton absorbs water. Even if this just refers to moisture that’s in the air, it can cause dampness. 

Cotton batt insulation will cost between $0.76 and $1.41 per square foot.  

Loose-Fill Fiberglass


As you probably already know, fiberglass is a common and popular choice for insulation purposes and it’s widely available. It can come in what’s known as loose-fill form, which is basically used in ceilings or it can be blown into wall cavities.

Loose-fill fiberglass is made up of particles that can conform to any size and space, so it’s perfect for situations in which it’s difficult or impossible to use other types of insulation.

It’s also very useful if you need to add insulation to a finished area or move around obstructions, such as in the ceiling. Loose-fill fiberglass insulation can be blown using special equipment or it can be poured during application (via Energy. Gov). 

You need to wear protective gear when installing fiberglass. You need to protect your eyes with goggles, wear gloves to protect your skin, and wear a dust mask so you protect your lungs.

And, unless you’ve chosen plastic-sealed fiberglass batts, you’ll need to install a vapor barrier when insulating your garage to prevent moisture from striking. 

Loose-fill insulation can cost between $1 to $1.50 per square foot. 

Foam Boards


These are cheap and easy, and they’re made of polystyrene. They’re usually recommended for insulating your garage door.

The benefit of using foam boards is that they’re light to work with but durable so they can handle extreme weather conditions. Another advantage of them is that they offer high insulating value with little thickness.

Foam boards get sold in large panels that you can cut to find the right size for your garage insulation needs. Foam board insulation can cost approximately $3.95 per square foot. 

Spray Foam


This is a useful type of insulation to help you seal finished areas with drywall, and for insulating hard-to-reach areas. It basically makes use of liquid polyurethane that’s sprayed inside a wall where it can expand, become rigid, and effectively seal up any leaks.

However, spray foam isn’t really recommended for use if you’re not a professional because it’s very messy and can be expensive as a result of how you have to purchase the correct equipment to use it. 

Open-cell spray foam (which is softer) will cost between $0.35 to $0.55 per board foot, while closed-cell spray foam costs between $1.00 and $2.00 for one board foot (via Havelock Wool). 

Note: a board foot is basically one square foot with material that’s applied at one-inch thickness. 

Loose-Fill Cellulose


This is a fantastic option for you if you want an effective type of insulation that’s also eco-friendly. Loose-fill cellulose is often used to insulate attics.

Since cellulose insulation is basically made out of small pieces of paper it can fit neatly around framing joints and other objects. Cellulose insulation can be derived from any cellular plant source, like sisal or corn cobs.

Loose-fitting cellulose is dry so it’s usually applied in the form of dense cellulose bales that are put into an insulation blower.

The cellulose insulation is basically blown into the walls or attic via long tubes and then the cellulose settles over time. Afterwards, the walls will be patched up and then painted. 

Cellulose is useful because it’s inexpensive and can be injected into walls that are already finished, which makes it practical (via The Spruce).

However, one of the drawbacks of loose-fitting cellulose insulation is that it has to settle in over time. This can lead to pockets appearing above the areas that have settled, which could transmit cold or hot air into the home. 

Loose-fill cellulose costs approximately $1.20 per square foot.  

How To Insulate A Garage Door

How To Insulate A Garage Door

If you want to insulate your garage door, it’s good to know that there are three common ways to do this. Here’s a rundown of them. 

  • Batt insulation. This is made of fiberglass and is often backed by foil or paper which work as barriers to vapor and air. 
  • Foam board insulation. These are hard panels that are made out of polystyrene and are usually around an inch thick. 
  • Reflective insulation. These are hard boards that have reflective aluminum foil on either one or both sides of the insulation, which takes the form of polyethylene bubbles. This is useful insulation if you want to keep your garage cool because it reflects the heat

When you want to insulate your garage door, it’s important to take the garage door material into account. If your door is steel, you can get away with using any kind of insulation.

If your door is made out of wood, you’ll need to fit hard insulation into the recesses between the frames. If your garage door is flat, reflective insulation or foam board are suitable and easy to apply. 

Since insulation can add weight to a garage door, you need to be careful that it doesn’t interfere with how the garage door opens and closes.

If there are problems, you’ll need to adjust your door’s spring tension. Bear in mind that if you have an automatic garage door, it will probably have a weight limit, so your insulation material should be strong yet thin and lightweight. 

How To Insulate The Roof Of Your Garage

How To Insulate The Roof Of Your Garage

Insulating your garage roof can help to make it cooler during the hot months while also maintaining the quality of your roof’s structure. This is because extreme changes in temperature can shrink and expand the wood in your home. 

The best insulation for your garage roof is fiberglass insulation, which is sold in batts or rolls. This is an easy DIY choice because it’s easy to work with and use between framing. 

Once you have your fiberglass roof insulation, you will be able to start your DIY insulation project. Here are important tips to follow.  

  • Always make sure you avoid insulating objects in the roof such as electrical outlets or lighting structures, as you want these to have enough air circulation around them to prevent hazards of an electrical or fire nature.
  • So, cut out parts of the fiberglass batts to accommodate space for these items. You need approximately three inches of ventilation around light fixtures and about an inch of ventilation around sources of heat.
  • Make sure you purchase bats of fiberglass that will match your roof’s design. So, if there are frames or wooden trusses in your roof, you’ll need fiberglass batts that fit snugly around them.
  • This is known in the industry as friction-fitting batts. For a cathedral roof, you’ll need to purchase attic baffles (otherwise known as channel vents) that will encourage airflow through the attic. These allow space between the fiberglass insulation and the wood. 
  • If your roof is in a flat style, you will apply the batts from the bottom, while installing them into a cathedral roof will require you to do so from the top and into the roof. 
  • Depending on where you live, you might have to install a vapor retarder over the fiberglass. This is important if you live in a cold region as it prevents water from causing mold and mildew in the insulation. 

How To Insulate Your Garage Ceiling 

It’s really easy to insulate your ceiling. Here are some important tips to bear in mind so it’s a safe and smooth process. 

  • If you’re using batt insulation, you can move it left to right as long as it doesn’t overlap. The most important thing to remember when installing ceiling insulation is that you don’t leave any gaps between the insulation.
  • When insulating your garage ceiling, it’s important to add a vapor retarder to prevent moisture and condensation. You really don’t want any moisture to accumulate on the wood trusses and sheathing!
  • Always make sure you measure the distance between the joists in the ceiling because this will affect the amount of insulation you need to buy.
  • You also need to measure how deeply these joists drop (it’s usually between eight to 10 inches). The more they drop, the larger your insulation panels or pads will need to be. 
  • Just like with insulating your roof, fiberglass insulation is recommended for your ceiling. It’s cheap, easily adjustable, and very durable. 
  • You will need to put the fiberglass pads into place and secure them with the use of a staple gun. Adjust the pads as you go and check for gaps – you can fill these in with leftover scraps. 
  • By the time you’re done with the insulation job, you should have a rough but flat surface that is in line with the bottom of all your ceiling joist beams. 
  • If you want to trap warmth in the garage, such as if you live in a cold region, you could go one step further and place a sheet of copper over the insulation pads. You can cut these to the same size as your pads and staple them into place around the perimeter of the new ceiling (via Do It Yourself). 

How To Insulate Your Garage Walls

How To Insulate Your Garage Walls

One of the benefits of insulating your walls is that you can prevent the potentially dangerous situation of having freezing pipes in winter.

When insulating your garage walls, the best type of insulation includes fiberglass, fire-resistant rigid foam, or spray foam insulation. However, if you’ve chosen to go the DIY route, then you’ll likely choose fiberglass or foam.

Here are some important tips when insulating your garage walls. 

  • You’ll need to ensure that you prepare the walls for insulation by cleaning away any debris and checking the walls for any mold. This should be dealt with before you go ahead and insulate the walls. You’ll also need to remove drywall if you have it (which you probably do). 
  • If you’re using fiberglass or foam insulation, you’ll need to staple it to the side of the wall stud. Avoid stapling it onto the face of the stud as you need to keep the stud face exposed to install the drywall over the insulation later!
  • Place a piece of wood on top of the insulation material – this can be used as a guide to help you cut the insulation to the correct size. Tuck the insulation so that it will be easier to staple.
  • Use a staple gun to secure the insulation all the way down the side of the stud.
  • Finally, screw and glue your drywall to the stud. 

Extra tips for applying wall insulation:

  • When you put insulation batts in place, make sure you cut notches so that they’ll fit nicely around electrical boxes.
  • Always measure the areas where you want to put your insulation so that you don’t overstuff it – this can cause it to have a lower R-value, so it won’t be able to resist heat conduction as well as it was designed to.

Related Questions 

What is the R-value of insulation? 

The R-value of insulation tells you how well the material will resist heat conduction, so a higher value means that the insulation will be able to insulate better.

A higher R-value is therefore ideal for you if you live in a cold region.

Can you insulate your garage yourself or should you call the pros? 

You can insulate your garage without needing the help of professionals.

You just need to ensure you have the right tools, as well as the correct insulation for your needs. That said, if you need special equipment or the process is messy, such as with spray foam, it’s best to call a professional. 


If you want to insulate your garage, you’ll have to do more than just insulate its ceiling or garage door. For the best results, you need to insulate every part of your garage.

In this article, we’ve provided you with information on how to insulate your garage doors, ceiling, roof, and walls to keep out moisture and gain better temperature control.  

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