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4 Situations When Injection Foam Can’t Be Installed as Exterior Wall Insulation

injection foam insulation | Existing walls insulation

4 Situations When Injection Foam Can’t Be Installed as Exterior Wall Insulation Blog Feature
Amanda Ringler

By: Amanda Ringler on May 11th, 2020

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You’re all set to have injection foam insulation installed in your exterior walls, but something has been discovered that has pushed the brakes on the project.

There’s not much we can’t work around here at RetroFoam of Michigan, but there are a few things that can stop us dead in our tracks. Sometimes, these issues can’t be detected until the day your injection foam is scheduled to be installed.

Some of the reasons the injection foam insulation can’t be installed include if there is glued-in cellulose in the walls, there is no house sheathing, there isn’t a wall cavity, and if the home only has stapled-in paneling on the walls.

Now, let’s go more into detail how each of these situations gums up the works of your foam insulation installation.

Reasons Why Injection Foam Exterior Wall Insulation Can’t Be Installed

While these situations aren’t very common, we can’t in good conscious inject the foam insulation and just hope for the best and sometimes it’s just not possible, but in some cases, there are workarounds.

Below, I will go more in-depth into each instance and what, if anything, can be done to add foam insulation to your exterior walls.

The Old Exterior Wall Insulation is Glued-In Cellulose

This is the most common reason why our installation crews halt the injection process – glued-in cellulose.

Back when the home was built, a contractor placed wiring inside the wall and sprayed the cellulose into place with an adhesive mixture. The problem is this insulation method still allows for air movement, as you’ve likely noticed, even though it is glued into place. The bigger problem with this method is there is no good way to remove the glued cellulose.

Unlike fiberglass, this cellulose isn’t going to compress in the wall so there is room for the injection foam. What will more likely happen is the pressure build-up will cause the drywall to bow or crack, this is why an experienced contractor will halt all of the work so there is no damage to the home.

There is No House Sheathing

Another reason why injection foam can’t be used as external wall insulation is if there is no sheathing on a house.

Usually, when a home is built, sheathing, which is a board or a panel, is placed on the outside of the wall cavity, then the siding is placed over the sheathing. This sheathing works as a surface that other materials can adhere to or be applied to, like spray foam or injection foam.

When an insulation contractor runs into a home without sheathing, then injection foam is out of the question but there are other options – spray foam or remove all the siding and add sheathing.

If the homeowner chooses spray foam, then they would have to have all of the siding removed and the foam would be sprayed into the cavity. The homeowner would then have to have the siding put back on.

Under normal circumstances, if the injection foam can’t be done from the outside, then it can be done from the inside. In this instance, there is a sheathing that stops the foam from pushing out the siding.

This isn’t the case in homes without sheathing.

The only option to add injection foam is to add injection foam when there isn’t sheathing, which is to remove all of the siding and add sheathing.

If you plan to replace your siding, then this would be a great project to tackle before the new siding is put in place.

There is No Wall Cavity

You would think that every home needs a wall cavity, but there are houses out there without them.

It happens a lot with brick homes and what we’ve seen out in the field is either brick on brick where the cavity should be or brick on blocks. Sometimes it’s drywall furred onto a brick wall.

Unfortunately, there aren’t a lot of options for insulation when this is discovered.

If the Home Has All Stapled-In Paneling on the Walls

It’s uncommon, but occasionally there will be a house where all of the interior walls are paneling that is just stapled to the studs.

This poses a problem as the injection foam will pop those panels away from the studs. This paneling can’t take the pressure of the foam as it’s injected.

All is not lost though, a homeowner with this thin paneling does have options.

An experienced contractor would make sure the injection foam pressure doesn’t build-up in the wall cavity. There is a good possibility though that drywall screws will need to be used to secure the paneling back to the wall.

A safer option would be to remove the paneling and spray foam the wall cavities.

Adding Exterior Wall Insulation to Your Home

Don’t be discouraged if you find yourself in one of these situations.

A good contractor won’t leave you in a lurch and will help you figure out what the best course of action will be to insulate those exterior walls. Another thing a good contractor knows is that sometimes the materials they offer aren’t the best fit, so they will recommend another approach and even recommend another contractor for the project.

Related Articles

Will Injection Foam Insulation Bow or Crack Drywall?

Foam Insulation Options When a House Has No Exterior Wall Sheathing

Will Plaster or Paneling Impact Injection Foam Installation?


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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 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.