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What is the Best Way to Insulate a Bonus Room Above a Garage?
Amanda Ringler

By: Amanda Ringler on July 4th, 2018

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What is the Best Way to Insulate a Bonus Room Above a Garage?

injection foam insulation  |  spray foam insulation  |  cellulose insulation  |  fiberglass insulation  |  bonus room insulation

That room above your garage has now become one of the most important rooms in the house.

Whether it’s becoming a room for your first child or the master bedroom, procrastinating about fixing this uncomfortable room above the garage has come back to haunt you.

With more than 15 years of experience under our belts, RetroFoam of Michigan has come out to homes where that bonus room above the garage was in desperate need of an air seal – which foam insulation is able to provide.

Stop dealing with extreme temperatures that are 10 degrees hotter or colder depending on the time of year, smells, noises, and high monthly electric bills and let’s take a look at the best way to insulate a bonus room above a garage.

Best Way to Insulate a Bonus Room Above a Garage

The best way to insulate the bonus room above your garage is going to be just like any other room in your house – insulate the exterior walls, the ceiling or attic, and the floor.

The options you have for the room in general are fiberglass batts, blown-in cellulose, injection cellulose, injection foam, and spray foam.

Now let’s talk about each section of the room and the best way to insulate it.

Cathedral Ceiling or Attic Insulation

Do you notice ice dams on the roof above your bonus room in the winter and it’s impossible to keep it cool in the summer?

You probably have little to no insulation in the ceiling or attic of your bonus room.

The way to insulate the ceiling will differ depending on whether it is a cathedral ceiling or actually has an attic.

For a cathedral ceiling, your options depend on the amount of remodeling you want to do. You could update the fiberglass batts that are already up there. Another option could be adding spray or injection foam insulation.

If you went with the fiberglass batt option, then the drywall ceiling would need to be removed and the batts would be stapled into place. Keep in mind, fiberglass doesn’t create an air barrier, so you will lose air through the roof.

If you want injection foam insulation, your insulation contractor would drill holes into the ceiling and inject the foam into the cavity. The holes are then filled and a rough patch is placed over them.

If you choose spray foam, which is our preferred method, then panels would be cut out of the ceiling and the foam would be sprayed into each cavity. The drywall would be replaced and a rough patch of mud spread across the seams.

Both injection foam and spray foam create an air seal that will keep you from losing treated air through the ceiling.

Now if your bonus room has an attic, your options are a little different. You could opt for spray foam, fiberglass, or cellulose.

Cellulose can be either a loose-fill or blown-in insulation in this application. The material is installed on the floor of the attic. Cellulose must be maintained as it is known to drift to one side or the other as air movement happens.

The other option for the attic above your bonus room is fiberglass. The fiberglass batts need to be cut to perfectly fit into the cavities of the attic flat. If not, then even more air will leak out through the attic.

Spray foam insulation can be sprayed either on the roof deck or the flat of the attic. The roof deck creates a sealed envelope of the space and makes the attic part of the conditioned space of the home. If you decided to insulate the attic flat instead, then that would seal the attic off from the rest of the house.

While foam insulation is the more expensive option in either application, it is the only material offered that creates an air seal. That air seal stops air movement and will help lower those monthly energy bills.

Exterior Walls Insulation

Many times, when we come to a home to insulate the bonus room, we find that there is nothing in the walls at all, which is contributing to your uncomfortable room.

All of those drafts coming in through the outlets and windows will make your AC unit and furnace work overtime because this room is is 10 or more degrees hotter or colder than the rest of your home. That’s a pretty big temperature difference.

Your options are injection foam and blown-in cellulose. Both are installed similarly with holes drilled into the stud cavity of the wall from the outside, with no need to tear out drywall.

One thing to keep in mind is the cellulose will settle over time, which will leave areas in the wall with no insulation coverage. While the injection foam is a more expensive option, the material will completely fill the cavity creating an air seal. You will also save money on monthly energy bills, which will pay you back in the long run.

Bonus Room Floor Insulation

The floor of your bonus room is probably the forgotten about area, and the spot that will give you the most trouble when it comes to extreme temperatures.

Your garage probably isn’t heated or air conditioned, which means whatever temperature it is, your bonus room will be too. Not to mention the smells and noise that come from a garage.

You have two options for the ceiling of your garage, which is the floor of your bonus room – spray foam and fiberglass.

The fiberglass batts can be cut to fit the cavities of the garage ceiling. They have to be cut so they fit perfectly into the cavities. Keep in mind, fiberglass is known to retain allergens and pollutants, so whatever comes into the garage will permeate the fiberglass which will affect your bonus room.

Spray foam can be installed on the underside of the bonus room floor in the garage. The benefit of spray foam for this area is its sound dampening qualities. Spray foam will also help to keep the temperature regulated as it will cut off the air from the garage making its way into the bonus room.

Bonus Room Above Garage Insulation

The only insulation material that creates the air seal you will need to keep your bonus room comfortable is foam insulation.

Traditional insulation will still allow not only for air movement into the space, but also the odors from your garage and moisture.

If you’d like to learn more about the benefits of foam insulation for your home, check out the Learning Center on our website.

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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.