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What is the Best Insulation for a Garage?
Amanda Ringler

By: Amanda Ringler on August 24th, 2020

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What is the Best Insulation for a Garage?

injection foam insulation  |  spray foam insulation  |  cellulose insulation  |  fiberglass insulation  |  garage insulation

The time has finally come – it’s time to insulate the garage, but you're wondering "what insulation should I use in my garage?"

Whether you’re looking to make the garage itself more comfortable, or you’re just looking to stop outside temperatures from getting into your house through the garage, insulation can definitely help.

The best insulation options for your garage will depend on whether the space has existing drywall or if the walls and ceiling are exposed. The most common insulations used in garages include fiberglass, cellulose, spray foam, and injection foam. 

RetroFoam of Michigan has been in the foam insulation game since 2002. While we specialize in foam insulation, we know a lot about other insulation materials and how they work.

Now let’s get down to the nitty-gritty of garage insulation.

The Best Insulation for Garage Walls and Ceiling

There are a lot of reasons to insulate your garage.

  • Your garage is attached and allowing the outside air to get inside your home through the common wall.
  • The bonus room above the garage can’t maintain a constant temperature and is uncomfortable.
  • The smells from the garage are getting in your home.
  • You want your garage to be a more comfortable space that can maintain a regular temperature.
  • You want to utilize the area as a man cave or a she-shed.
  • The builder didn't finish the garage with drywall and insulation, so it's always been on your to-do list.

There are a couple of material choices for garage wall insulation and garage ceiling insulation. Here are your options and how they are applied.

Fiberglass Garage Insulation

Fiberglass insulation can be installed in the garage as batts or rolls in the exposed wall cavities and exposed ceiling. There is also fiberglass made specifically for insulating the garage door.

Fiberglass is a common insulation found in homes and garages. The rolls and batts need to be cut to fit into the wall or ceiling cavity perfectly and stapled into place. If you don’t intend to tear down your drywall, fiberglass isn’t a good fit, as it can only be installed in the open cavities.

Fiberglass is an inexpensive option that you can install on your own, but you have to take safety precautions if you are handling the material. Small fiberglass fibers can embed in your skin and can even be inhaled.

If you are looking to stop all air movement into your garage, fiberglass isn’t the best fit as it still allows for air to move through it.

Cellulose Garage Insulation

Cellulose insulation can be blown-in to the walls and ceiling cavity of the garage.

This will only work if the walls and ceiling cavity are covered with drywall. The cellulose is blown into the cavity through holes that are drilled into the drywall and then covered, or it can be done from the outside by removing a row of siding or drilling into the mortar to blow the cellulose into the cavities.

If the walls are exposed, wet-applied cellulose is recommended, as blown-in won’t work in this application. Wet-applied cellulose is mixed with a bonding agent and sprayed into the wall cavity. If mixed properly, the wet cellulose will stick to the cavity without a netting requirement.

Cellulose is another cheap option for garage insulation. For both applications, it would be best to hire an insulation contractor as the installation process is more complicated.

Much like fiberglass, cellulose will still allow for air movement through the material.

Spray Foam and Injection Foam Garage Insulation

Spray foam and injection foam are similar, as they are foam-based products, they are just applied differently.

Spray foam insulation would be applied to the open cavities of the walls and ceiling to create an air seal. Open cell spray foam and closed cell spray foam are the two materials you can choose from.

Open cell spray foam is more pliable and is better suited if you plan to add drywall after the foam is installed. Closed cell spray foam is better if you plan to keep the walls exposed because it is very durable and can take being knocked into. The closed cell spray foam can also be used to insulate the garage door.

Injection foam is installed in the enclosed cavities by drilling holes in the drywall and injecting the foam. A good contractor will apply a rough patch over the plugged holes in the drywall. This can also be done from the outside similarly to the blown-in cellulose.

One thing to keep in mind is if the garage ceiling is finished and you want to use closed cell spray foam, then the drywall will need to be taken down. If you choose open cell in the same scenario, only strips will need to be cut to apply the foam. In either case, the drywall is replaced with a rough patch of mud to cover the seams.

Foam insulation is the more expensive option and can only be installed by an insulation contractor. While foam is more expensive, it will save you money in the long run in energy savings each month.

Best Way to Insulate Garages

When it comes down to it, it’s up to you to decide what insulation material will work best for your garage.

Your expectations and what your overall goals are will help you determine the insulation that works best. If you want a conditioned space that keeps the cold air out of your home or bonus room, a material that creates an air barrier is your best bet.

Fiberglass and cellulose don’t create the kind of air barrier you’re looking for in this scenario, so foam insulation is a better option.

If you want to learn more about the benefits of an air seal and foam insulation, check out the Learning Center on our website.

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Foam Insulation Learning Center

About Amanda Ringler

Amanda previously has worked as a breaking news and crime reporter, TV news producer, and editor in Flint and Detroit. Throughout her career as a journalist, she has won several awards from the The Society of Professional Journalists - Detroit Chapter and the Michigan Press Association. As part of the RetroFoam of Michigan family, Amanda uses her experience as a journalist to write content that will help educate homeowners on the benefits of foam insulation. When Amanda isn’t writing, she’s spending time with her husband and rescued huskies. She also loves knitting, making art, cooking, and hosting dinner and a movie night for friends and family.