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Should I Insulate the Wall Between the Garage and House When Updating Exterior Wall Insulation with Foam?

injection foam insulation | Existing walls insulation

Should I Insulate the Wall Between the Garage and House When Updating Exterior Wall Insulation with Foam? Blog Feature

By: Ryan Litwiller on October 26th, 2020

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Those annoying drafts, uncomfortable rooms, and higher-than-you-care-for monthly energy bills have caused you to look into upgrading your exterior wall insulation.

However, you’re not quite sure if you should insulate the wall between the garage and the house. When considering all the exterior walls, how important is re-insulating this one wall with injection foam insulation?

As a foam insulation contractor for more than 17 years, we frequently encounter this situation at RetroFoam of Michigan. If you find yourself in this same scenario, here are a few things to consider to help you make this decision.

Why Wouldn’t a Homeowner Want to Re-Insulate the Wall Between the Garage and House?

Injection foam is great to seal up all the gaps in existing walls without the need for a long and messy remodel.

This provides an air seal that improves the comfort and energy efficiency of homes with outdated insulation.

There are typically a few common reasons why a homeowner would only want to insulate three of the four exterior walls, leaving the common wall off of their scope of work.

Obviously, the cost is a factor. Insulating three walls is less than four, so some homeowners who want to cut costs will opt out of the insulating this one wall.

With drywall up on this wall, as required by code, the crew would need to drill holes between each stud cavity to inject the foam. Even though the install crew will clean up any mess and do a rough patch, the homeowner will need to provide the final finish and repaint the wall, if desired. Even though not a huge deal, this extra work and expense will sometimes turn homeowners away.

Finally, many homeowners don’t see the wall between the garage and house as important to re-insulate. They don’t consider this common wall an exterior wall like the other walls of the home since it is somewhat protected by the other garage walls.

At the end of the day, a homeowner wouldn’t include this wall in the scope of work because he or she doesn’t see the value in insulating it.

The Importance of Insulating the House and Garage Common Wall

What most homeowners don’t realize is that this wall is just as important as any other exterior wall, and can have a negative impact on the project’s effectiveness if it is not re-insulated with the other exterior walls.

Now for some explanation.

When you were a kid, why did your parents tell you to shut the front door? I’d imagine it was probably something like:

“You’re letting all the heat out,” or “You’re letting the cold air come in,” or even “You’re letting the bugs in.”

In the same way, if the wall between the house and garage isn’t insulated properly, the entire envelope of the home won’t be sealed up. This means the rooms adjacent to the garage will experience air loss and drafts -- one of the main reasons you wanted to re-insulate the walls in the first place.

Think about your home like the expensive cooler you might take camping with you. That cooler has thick walls, a thick bottom, and a thick lid. These coolers are also filled with closed cell foam. Everything in the cooler stays nice and cold because of the air seal the foam created.

When you insulate all the exterior walls, even the garage common wall, you are now sealing the entire building envelope and creating an air barrier between the inside and outside of the home. This helps keep temperatures consistent and comfortable in the house as they should be.

Another thing to consider is if you leave the garage door open all the time. 

If you leave that large door open, all of the outside air is now in that space. If the common wall isn't insulated, that outdoor air now has direct access to your home.

Additional Benefits of Insulating the Internal Garage Wall

In addition to seeing the maximum comfort and energy savings from updating the exterior wall insulation, there are a few additional benefits that come with insulating the wall between the house and garage.

Reduce Noise in From the Garage

Sometimes you just want to work on something in the garage and it can sometimes get a little noisy when running the air compressor or using the saw.

An additional benefit of injection foam insulation is the ability to dampen sound. It won’t completely soundproof all the noise in the garage, but will definitely help to reduce it, something your family will be happy about.

Keep Emissions Out

Even though you aren’t running the car in the garage with the door down, there is probably still times when there are some sort of emissions in your garage.

After insulating this wall with foam you will have peace of mind that any sort of emissions or allergens that could previously pass through the fiberglass of the unfinished wall will now be blocked from entering your home.

No More Moisture Concerns

Since your garage is probably way hotter or colder than the inside of your home depending on the time of year, there is the possibility for moisture to form in the walls with fiberglass due to the meeting of the hot and cold.

With foam insulation in the walls, moisture is no longer a concern as it would be with only fiberglass insulation.

The Common Garage Wall is Critical to Your Home’s Comfort and Energy Efficiency

If you want to see all the benefits of comfort and energy savings that you are looking for, it is critical to make sure the building envelope is completely sealed.

Remember, your parents said it first.

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