Spray foam insulation has some great applications, heck we even sprayed the inside of a man-made cave to make it look more like rock.

While spray and injection foam can be used for a new or existing home, you might be thinking of other projects where home insulation isn’t the best fit.

So, why isn’t foam insulation used in homes a good fit for certain applications or situations? Because we’ve been in the foam business since 2002 and we said so. Jokes aside, there are just instances where it won’t work how you think it will and others where it just isn’t possible.

Part of our mission is to educate homeowners like you, so let’s take a look at the instances when foam insulation can’t be installed.

What Can’t Be Insulated with Spray or Injection Foam

Whether there’s no way for a human to fit in the space or it’s not the best idea, here are five things that can’t be foamed.

You’re Looking for Flotation Foam for Boats

You want expanding foam for boats, and while the open cell spray foam we use expands, it’s not a great fit.

The thought is that you’re trying to add structural integrity to the boat hull for example, if it gets hit by another boat or you hit a rock. Sure, closed cell spray foam can work to protect a metal hull but think about the added weight and space the foam takes up.

While regular spray foam insulation found in homes and pole barns isn’t the answer, there are products available to you avid boaters.

Mix and pour foam for boats is one such option. This foam is a closed cell system which boasts 2-pound density with 60-pounds of float per cubic foot.

If you’re looking to add that flotation to your boat, there are definitely options out there for you.

You Want to Add Buoyancy to Flotation Devices

Just like our spray foams aren’t a good fit for boats, it's not a good fit for wooden kegs, homemade rafts, coolers, or tanks.

Much like the mix and pour foam for boats, there are smaller cans of spray foam that can be used for these projects. It’s important to know before you buy, some of these foams could retain water so you’ll want to avoid this or the thing you want to float might end up at the bottom of the river.

Most spray foams used in home insulation are too dense to be used for any kind of buoyancy. 

Exterior Walls with Glue Spray Cellulose

In most cases, when we inject foam into exterior existing walls the existing insulation can stay put.

In other cases, we vacuum out the existing cellulose insulation from the exterior walls to properly insulate the cavity. But every now and again we come up against one of our arch nemesis – glued in cellulose. 

Glued in cellulose is going exactly nowhere, so while we would love to give you the foam insulation of your dreams, the majority of contractors know there’s no good way to get it out without tearing out walls.

You Want the Exterior Walls Insulated, But There’s No Wall Sheathing

Just when you thought you were going to add foam insulation to your walls, a startling discovery puts the brakes on the project.

There is no exterior wall sheathing.

The most basic functions of sheathing, according to Buildipedia, is to form a surface where other materials can be applied.

If an injection foam installer removes a row of siding and finds no sheathing, the installation can’t continue. This is because the foam can actually cause the siding to bow out, as there is no sheathing to keep it from pushing out.

Your Tiny Space Needs Insulation

A good foam insulation contractor can tackle most obstacles, but if there’s no access or a person can’t fit then the job can’t be done.

On average in a crawl space, a spray foam insulation installer needs about 18-inches of workspace from the ground to the floor. In some cases, this 18-inches is really pushing it and it’s not for the claustrophobic. 

There are also attics with a hip roof that can prove to be challenging and at times impossible to insulate. This is because a hip roof is a type of roof where all sides slope downwards to the walls. The pitch of the slopes really determines if the roof deck can be sprayed or if the attic flat is the better option.

Getting Foam Insulation for Your Project

We get it, everyone wants to get foam insulation for their project.

The best bet to make sure foam insulation meets your expectations and needs, it’s best to have a professional take a look and explain everything to you. 

Remember, there are no stupid questions. Ask your contractor what they recommend if their product won’t work for your project. You’ll likely find them to be a fountain of knowledge and eager to help you solve your problems.