What Are My Options For Insulating A Detached Garage?

Stacy Randall
by Stacy Randall

If you have an uninsulated detached garage, it’s probably sweltering in the summer and freezing in the winter. Merely stepping inside of the room to grab some supplies can be unbearable! Insulating your detached garage will make the temperature inside much more comfortable and turn your detached garage into a habitable space for you and your family.

There are tons of options available for insulating a detached garage, including spray foam, blown-in, and fiberglass batt insulation. Though, for best results, you want to choose a material with a high R-value, as the higher the R-value, the better the material is at insulating. With an R-value of 3.8 per inch, spray foam insulation works incredibly well at insulating detached garages.

In this article, we will go further in-depth about the ways and materials you can use to insulate your detached garage. That way, you will be able to keep warm, or keep cool, regardless of the weather, your belongings will stay safe, and you can work comfortably in your garage space.

Do You Need Insulation Installers?

Get free, zero-commitment quotes from pro contractors near you.

Should I Insulation My Detached Garage?

There are numerous advantages to choosing to have your detached garage insulated. These include:

  • Comfort. Of course, it’s much more comfortable to work in a garage that isn’t blazing in the summer or freezing in the winter. By insulating your detached garage, you will help reduce drastic temperature changes in the structure, even without introducing any additional heating or cooling.
  • Protection for your belongings. Some items that you store in your garage may not do well in exceptionally cold temperatures. For example, an unheated garage can be hard on paints, caulks, batteries (particularly lithium ion) and a number of chemical-based products. Erratic temperatures changes in fall and spring can result in condensation in the garage, presenting potential mildew and rust problems.
  • Energy savings. In most cases, adding insulation to a detached garage also adds heating and/or cooling. In other words, the better that the garage is insulated, the more you’ll save on energy costs.

Types of Insulation for Detached Garages

There is such a wide variety of insulation styles and materials to choose from when it comes to insulating a detached garage. Let’s take a look at some of the most popular choices.

1. Spray Foam Insulation

Spray foam insulation is a spray-applied plastic used to insulate your detached garage. It expands as it dries so that it will fill any gaps in your walls and ceiling. This ability to fill the gaps helps provide a genuinely air-tight seal and stop air and heat leakage. It can also prevent outside contaminants from entering your garage, like pollen and pollution.

If you’re planning on cooling and heating your detached garage, the seal created by spray foam insulation stops energy waste. Spray foam insulation can save you about 20% on your utility bills, and using it with other forms of insulation can ensure you’ve sealed all gaps.

Why Choose Spray Foam?

Spray foam insulation is less permeable to air than its counterparts, and it is impervious to water. The fact that water can’t get through is excellent news for you if you live in a wet area that floods often. You’ll incur less damage to the structure of your detached garage.

Spray foam insulation is made of an inert polymer that keeps it from becoming a breeding ground for mold and mildew. Even if you live in a humid climate, this method will keep out pesky bacteria!

How Long Does Spray Foam Last?

If properly maintained, spray foam insulation can last a lifetime. If properly installed, this method can increase the strength of your structure and reduce noise pollution. Think of your newly insulated garage as the perfect place for your rock band rehearsals!

However, it is imperative to install spray foam insulation correctly to avoid cavities. If you miss spaces during installation, it won’t seal your walls like it should, resulting in leaking air and heat. You want to hire a professional to handle your spray-foam insulation, as improper installation can make the benefits of spray foam virtually disappear!

Cost To Use Spray Foam

Spray foam insulation is usually a costlier method than fiberglass insulation but tends to be cheaper than blow-in. It would help if you always weighed the benefits of any insulation method with the costs of installation.

2. Blown-In Installation

Blown-in insulation is a method of insulation that involves “blowing” materials through a hose to fill joints and cavities. The substance, known as blown-in cellulose, is made from wood-based materials like recycled newspapers and cardboard. The cellulose is treated to make it both flame and mold-resistant.

Like spray foam insulation, blown-in insulation is an energy saver for the homeowner. It seals cracks and joints to prevent leaks. Installation of blown-in insulation is a quick and easy process for a professional. Qualified professionals can finish installation in a few hours and carefully cover all cavities, joints, and seams.

Provides A Soundproof Barrier

Blown-in insulation helps to soundproof your space and reduce condensation in the area. Reduced condensation will prevent mold, mildew, and rot, but blow-in is not entirely impervious to moisture. If this form of insulation gets very wet, it is likely never to dry completely.

Cost To Use Blown-in Insulation

Blown-in insulation can be costly because it requires both professional installation and purchasing of materials. It tends to be more expensive than both spray foam and fiberglass insulation. You can use calculators like this one from Lowe’s to estimate how much insulation you will need for your project.

3. Fiberglass Batt Insulation

Fiberglass batt insulation is made of very fine glass fibers interspersed throughout a wool-like plastic. It is the most common kind of insulation found in homes and is very budget-friendly compared to other counterparts.

It is relatively easy to install and could even be a DIY project if you feel up to it! Fiberglass batts are blanket-like, and you can cut them to fit your spaces easily. However, if you lack experience, it may be a good idea to call a professional. Mishandling of fiberglass batt can lead to inhalation of the material, which is terrible for your health.

Fiberglass For Fire Safety

Fiberglass insulation is not flammable, so it protects your walls from quickly becoming a fire hazard. When fiberglass batt insulation is exposed to high temperatures, it will simply melt.

Sound Proof Qualities

Like its counterparts, fiberglass insulation has soundproofing and energy-saving capabilities. However, there are quite a few issues with fiberglass to consider before using it to insulate your garage.

Safety With Fiberglass

There are small particles in the insulation that can be harmful to you when inhaled or if they come in contact with your skin. Insulation also does not guarantee as tight a fit as its counterparts, so there is a higher likelihood of air leakage. Fiberglass insulation can also trap dust, moisture, and allergens, which can easily lead to mold.

R-Value And The Importance Of A High Score In Your Garage

An insulation’s R-value measures its resistance value. It gauges how useful the material is insulating. Thus, the higher the R-value, the better the insulation at doing its job.

Of the three insulation methods listed, spray foam insulation offers the best R-value at R-6.5-7 per inch. In comparison, blown-in insulation offers anywhere between R-3.2 and R-3.8 per inch, and fiberglass batts offer around R-3.7 per inch. If you’re looking to install the insulation with the highest R-value, spray foam insulation is the way to go.

Insulating The Garage Door

When looking to insulate your garage, don’t forget your garage door! If you insulate all the walls and ceilings but ignore your door, this will negate all of your hard work in the rest of the space. Insulating your garage door can prevent additional heat and air leakage when it is closed.

The most popular methods of insulating garage doors are fiberglass batt, foam board, and reflective insulation. Batt insulation costs about $0.30 per square foot and offers an R-value between R-3 and R-4. Foam board costs about $20 for a full sheet and offers anywhere between an R-value of R-3.3 and R-6.5 depending on thickness. Reflective insulation costs $42 for a roll and provides an R-value between R-3.5 and R.6.

Budget Considerations

It would be best if you weighed the costs of material and installation with the material’s efficiency. This can be an easy DIY project, but if you are hiring someone to insulate the rest of the garage, it may make the most sense to have them do the door as well.

Some experts suggest not insulating the garage door and only buying a pre-insulated door instead. You can also choose to forego insulating your door and weatherstrip it as an alternative. This will seal the edges and prevent air from flowing in and out but still let the door function properly.

How Much Does It Cost to Insulate a Detached Garage?

There really is no one-size-fits-all answer to this question, as the cost of detached garage insulation varies considerably based on the shape and size of the garage, as well as the insulation material you choose. Though, the average cost to have a two-car detached garage insulated by a professional is between $1,500 and $3,500. Where your project falls in the range will depend on which areas of the garage are being insulated and the specific R-value.

That said, the cost of insulating a detached garage could be as little as $500 or more than $5,500. The lower end of this range would involve a DIY project with loose-fill or fiberglass insulation, while the higher end describes a professional insulation job with closed-cell spray foam.

Related Questions

Should I get a vapor barrier for my newly insulated garage?

A vapor barrier will help prevent moisture from seeping into your insulation. If you’re redoing your detached garage, it is a good idea to install a vapor barrier as a measure to prevent mold. It should be placed on the warm side of the insulation to work properly. 

Should my garage be ventilated?

Yes! If you plan on making your garage into a liveable space, ventilation will keep it from feeling uncomfortable and stuffy. If you use your garage to store your car, this will help keep out fumes and gases. 

Do You Need Insulation Installers?

Get free, zero-commitment quotes from pro contractors near you.

Wrapping Up

If you’re looking to insulate your detached garage, you can use spray foam, blown-in, or fiberglass insulation. Each has different advantages and disadvantages that you should weigh when choosing to insulate.

The higher the R-value of the insulation material you choose, the better it is at insulating your space, so be sure to check those values before deciding on your material.

Make sure to insulate your garage door when insulating your detached garage. Forgetting your garage door can lead to air leakage, making your new space stuffy and uncomfortable.

No matter how you decide to do it, properly insulating, your detached garage will upgrade your home and give you more comfortable square-footage.

Stacy Randall
Stacy Randall

Stacy Randall is a wife, mother, and freelance writer from NOLA that has always had a love for DIY projects, home organization, and making spaces beautiful. Together with her husband, she has been spending the last several years lovingly renovating her grandparent's former home, making it their own and learning a lot about life along the way.

More by Stacy Randall