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Foam Insulation Options When a House Has No Exterior Wall Sheathing

injection foam insulation | spray foam insulation | Existing walls insulation

Foam Insulation Options When a House Has No Exterior Wall Sheathing Blog Feature
Clayton Humphrey

By: Clayton Humphrey on February 17th, 2020

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You’re looking to add insulation to your exterior walls but were surprised to find that you don’t have any sheathing under your siding.

This can be a real issue, as that sheathing is key to insulating your walls. This is especially true when it comes to injection foam insulation because when it’s installed, the holes drilled into each stud cavity is through the sheathing.

As a project manager here at RetroFoam of Michigan, I understand how we can make sure a home can be insulated with foam, even if there isn’t any sheathing under the siding.

I’ll explain that process more in just a bit. First, I’d like to explain to you what house sheathing on a house is and how to insulate a home without sheathing with foam insulation.

What is Sheathing on a House?

House sheathing is a board or panel in either the floor, wall, or roof assemblies.

The sheathing works as a surface that other materials can be applied, like spray foam or injection foam. The sheathing is important to your home for another reason and that’s because it acts as another barrier to protect your home from the outside elements.

For this article, we are talking specifically about sheathing under the siding.

How Can I Insulate My Walls with Foam Insulation Without Sheathing

Insulating walls in an old house with no sheathing can be a challenge, but it can be done.

Whether the sheathing was skipped to cut building costs, to save time, or out of inexperience, the lack of it isn’t doing you any favors.

Here’s the thing, if your home doesn’t have house sheathing then injection foam is out of the question. Basically, what would need to be done is to remove all of the siding and add the sheathing. Only then could injection foam be used.

I know what you’re thinking, “why can’t it be done from the inside?”

Injection foam can’t be installed from the inside in this instance because the sheathing is what would be needed for the foam to adhere to. You would also run the risk of the foam pushing out the siding or leaking through the seams.

While the injection foam insulation won’t work without taking the siding off and then adding sheathing, you still have options.

Spray foam is definitely a viable option, but it still requires the homeowner to remove all of the siding from the home and have it replaced once the installation is finished.

In this case, a good contractor will spray the stud cavities while the siding is off. 

Honestly, this is a great project to tackle when you’re replacing your siding because it will all be pulled off anyways.

This is an unfortunate situation because there’s not much you can do as a homeowner without the insulation installation becoming a huge project.

Adding Foam Insulation to Your Home

This is a big project, and the choice is yours if you want to tackle it.

Keep in mind though, while it’s a big project the benefits you’ll experience from the foam insulation make it worth it. 

You were obviously experiencing challenges in your home like uncomfortable rooms, cold walls, and drafts. The good news is that foam insulation can help with all of those, it’s just going to take a lot of work before we get there.

If you’re still on the fence, another thing to keep in mind is that with other materials, like cellulose or fiberglass, you’ll need to do a lot more demolition. For these traditional materials, some contractors recommend tearing down the drywall and doing the installation from the inside.

That is a lot of disruption in the home.

If you’d like to learn more about foam insulation and what it has to offer, check out the Learning Center on our website.

Related Articles 

Installing RetroFoam into Exterior Walls with Different Siding Types

What is the Highest R-Value Insulation? (Ratings/Types/Charts)

How Air Sealing Insulation in Your Home Works Like Your Airtight Cooler

Foam Insulation Learning Center

About Clayton Humphrey

Clayton’s experience working with people gives him the ability to help homeowners solve their insulation problems. Seeing new places and meeting new people are just some of Clayton’s favorite parts of his job. The great work environment and inviting and friendly staff are his other favorites. When he’s not at work, Clayton likes to go to the gym and spend time with his family.