Can I replace the insulation in my walls with spray foam?

If you've spent any time on TikTok or Instagram, you’ve probably seen short videos showing just how "simple" and "easy" it is to replace your home’s wall insulation with spray foam. These videos make it look like a quick project anyone can tackle in an afternoon. Unfortunately, while the videos may be catchy and look convincing, the reality is a bit different. The truth is, replacing your wall’s insulation with spray foam isn’t as simple as these social media posts make it seem.

In this week’s post, we’re going to dive into what you need to know about replacing your home’s wall insulation with spray foam. We'll break down why it’s not as straightforward as it might seem and explore the complexities behind the process. Let’s separate fact from fiction, and help you understand what to expect if you're considering this type of project.

Understanding How Wall Insulation Works

Before we get into the details of replacing wall insulation, it’s important to understand how insulation works in the first place. Insulation is what keeps your home warm in the winter and cool in the summer by reducing the flow of heat. There are different types of insulation, but the most common in older homes are fiberglass batts, cellulose, or sometimes foam board.

Attics are one area where you’ll typically find insulation because heat rises, and in the winter, you want to keep that warmth inside your home. Attic insulation is often laid on the floor of the attic or blown into the space. In most cases, replacing or adding attic insulation is relatively easy since you can access the attic and lay down new insulation on top of the old.

Walls, however, are a completely different story. Unlike an attic where insulation is laid out in the open, wall insulation is tucked away between the studs. On one side, the insulation is held in place by the drywall, and on the other side, it’s covered by the exterior of your home, which could be brick, stone, or siding. This makes the insulation much harder to access and replace.

Why Replacing Wall Insulation is Not a Simple DIY Project

Unlike attic insulation, which is often accessible, wall insulation is sealed up tight inside the walls. This means that in order to replace it, you either need to remove the drywall from inside the home or remove the siding, brick, or stone from the outside of the house. That’s no easy task.

Let’s think about what that would involve. If you’re planning to replace your wall insulation with spray foam, the first step is getting to the old insulation. Unfortunately, this means either tearing down the drywall or removing part of your home’s exterior. Neither option is particularly pleasant.

Removing drywall requires a lot of time and effort. After taking down the drywall, you need to clean up the mess and safely dispose of it. Then, you’ll be able to remove the old insulation and finally install the new spray foam. After that, you’ll need to put up new drywall, finish it, and paint it to match the rest of your home. As you can imagine, this can get expensive quickly, especially if you’re hiring professionals to handle the job.

On the other hand, removing part of your home’s exterior can be just as challenging, if not more so. Whether your home has siding, brick, or stone, tearing it off just to access the wall insulation is a major project that comes with its own risks. Not only is this process labor-intensive, but it can also leave your home vulnerable to weather damage if the project isn’t done quickly or properly.

Spray Foam in Walls: Why the Challenge?

Spray foam insulation is one of the most effective types of insulation available today. It provides an excellent air seal, improves energy efficiency, and lasts much longer than other types of insulation. However, it’s not always easy to install in wall cavities, especially in an existing home.

For spray foam to work its magic, it needs to be applied directly inside the wall cavity, and it expands to fill every nook and cranny. This works great when you’re building a new home or adding an addition because the wall cavities are still open. But in an existing home, where the walls are already finished, there’s no easy way to spray the foam in without tearing out the drywall or exterior.

Even if you could somehow inject spray foam into the wall cavity without removing anything, there’s another problem: the old insulation. Most homes have some form of insulation already in place, whether it’s fiberglass batts, blown-in cellulose, or something else. For spray foam to work properly, the old insulation needs to be removed. Otherwise, the spray foam can’t fill the entire cavity, and you won’t get the full benefit of the material.

Are There Any Alternatives to Removing the Walls?

At this point, you might be wondering if there are any ways to replace wall insulation without having to remove the drywall or exterior. Unfortunately, the answer is not so simple. In some cases, professionals may be able to use a method called “drill and fill.” This involves drilling small holes in the drywall or exterior of the home and injecting spray foam or another type of insulation into the wall cavity.

While this method sounds more convenient, it’s not without its drawbacks. For one, the old insulation still needs to be removed or compressed, which can be difficult to do through small holes. Additionally, the “drill and fill” method may not work as effectively as a full spray foam installation because the foam may not fully expand into all parts of the wall cavity.

Why You Might Want to Keep Your Current Insulation

Given the challenges of replacing wall insulation with spray foam, you might be wondering if it’s even worth the trouble. In many cases, the answer is no. If your home’s current insulation is still in good shape, you may be better off leaving it in place.

Most insulation materials, including fiberglass batts and blown-in cellulose, have a long lifespan. If your insulation isn’t damaged, wet, or moldy, it’s probably doing its job just fine. Rather than going through the hassle and expense of removing your walls to replace the insulation, you may be able to improve your home’s energy efficiency in other ways.

For example, you could add more insulation to your attic or seal up air leaks around windows and doors. These simple steps can make a big difference in your home’s comfort without the need for a major renovation.

When is Replacing Wall Insulation Worth It?

There are some situations where replacing your wall insulation might be necessary. If your current insulation is old, damaged, or not performing well, replacing it could improve your home’s energy efficiency and comfort.

For example, if you’ve noticed that your home feels drafty in the winter or your heating and cooling bills have been steadily increasing, your insulation may be to blame. In some cases, insulation can become wet due to leaks, and once it’s wet, it no longer works properly. Mold can also be a problem with certain types of insulation, especially if your home has experienced water damage.

Another ideal time to consider retrofitting wall insulation is when your drywall is already being removed for other reasons, such as major electrical repairs, flood damage, or large-scale renovations. Since the wall cavities will already be exposed, it’s the perfect opportunity to install spray foam insulation without the added expense and hassle of tearing down drywall just for insulation replacement.

The Bottom Line: Don’t Believe Everything You See on Social Media

While TikTok and Instagram videos might make it look like replacing wall insulation with spray foam is a quick and easy project, the reality is much more complex. In most cases, replacing wall insulation requires removing either the drywall or exterior of your home, which can be a time-consuming and costly process. Spray foam is an excellent choice for insulation, but it’s not always the best option for existing walls due to the challenges of installation.

If you’re considering replacing your insulation, it’s important to weigh the costs and benefits carefully. For many homeowners, the hassle and expense of tearing down walls to replace insulation may not be worth it, especially if the existing insulation is still in good condition.

As a spray foam installer, I can tell you that the only reliable way to retrofit wall insulation in an existing home is by removing one side of the wall—most often the drywall. This gives us access to the wall cavity so we can properly remove the old insulation and apply the spray foam the way it's meant to be installed. Without taking down the drywall or the exterior of the home, it’s almost impossible to ensure the spray foam will completely fill the cavity and create the proper air seal, which is essential for it to work effectively.

That said, if you do happen to find an installer who claims they can replace your wall insulation with spray foam without removing one side of the wall—and actually does it well—give us a call. We’d love to meet the first company that has figured out how to get it right! So far, no one has cracked that code, but we’re always excited to learn about innovative solutions that can make the process easier and more efficient for homeowners.