Can You Put Spray Foam In Existing Walls?

You want your home to be more energy-efficient. Your energy bills are too high. You know your walls have little to no existing insulation. Will adding insulation to your walls lower your energy bills? If so, is spray foam insulation the solution to insulate your existing walls?

South Central Services has insulated hundreds of homes with spray foam insulation. We work with customers every day to find energy-efficient solutions that will work for their homes. Wall insulation may not save energy like you're hoping it will.

By the end of this article, you’ll understand:

• Which walls should be insulated with spray foam
• If existing walls can be insulated with spray foam
• What other products are available to insulate existing walls
• Other places in your home to insulate for energy-efficiency

Should You Install Spray Foam In Your Walls?

The decision to use spray foam in your walls depends primarily on whether you're insulating exterior or interior walls.

Spray foam insulation is recommended for exterior walls. The walls on the outside of your home need high-performing insulation. Your exterior walls are the main barrier between your home environment and the outside world. With a high R-value and airtight seal, spray foam insulation helps to keep your home comfortable year-round while reducing energy costs.

In contrast, interior walls typically do not require the same level of thermal insulation as exterior walls. We insulate interior walls to prevent sound transfer. Spray foam can provide some sound attenuation but may not be the most cost-effective solution for this purpose. Other materials, such as acoustic insulation, might be more suitable for interior walls where sound dampening is the main goal.

Can You Install Spray Foam In Your Existing Walls?

Installing spray foam insulation in existing walls is a more complex process than in new construction. Effectively installing spray foam in existing exterior walls often requires removing the interior drywall or exterior siding to access the wall cavities. Either option can be a significant and invasive renovation, as it involves tearing down parts of your walls. For many homeowners, this level of disruption may not be feasible or desirable.

However, if you are planning a major renovation or a gut job, this could be an opportune time to install spray foam insulation. It offers a chance to significantly enhance your home's energy efficiency while the walls are exposed.

What Other Insulations Can Go Into Existing Walls?

For homes where tearing down walls is not an option, injection foam insulation presents a viable alternative. Injection foam can be installed in existing wall cavities without extensive demolition. It's particularly suitable for walls with no insulation. The injection foam insulation is injected through small holes drilled into the walls.

We only recommend injection foam for walls that lack any insulation. An empty wall cavity can be reliably filled with injection foam. However, a wall cavity with ineffective batt insulation inside is difficult to insulate around. Existing insulation poses roadblocks for injection foam. The foam may miss entire sections of the wall.

Where Else In My Home Can I Insulate For Energy Efficiency?

Insulating your existing walls may not be feasible right now. Luckily, there are other areas in your home where adding insulation can significantly improve energy efficiency. The key areas of your home that should be insulated are part of your thermal envelope. Exterior walls make up a significant portion of the building envelope, but there are other places in your home as well.

The following areas are easily accessed without remodeling or demolition:

• Attics
• Basements
• Crawl spaces

Let’s examine each of these options in more detail.

Attic Insulation

Insulating your attic is one of the most cost-effective ways to enhance your home's energy efficiency. The attic is a primary area where heat escapes during the winter and penetrates during the summer. By adding insulation to your attic, you can significantly reduce heat transfer. Attic insulation helps maintain a comfortable temperature and reduces the strain on your HVAC system. With less heat load on ductwork, energy bills are lowered.

There are various insulation options for attics, including fiberglass batts, loose-fill cellulose, and spray foam. No matter which type of attic insulation you choose, we recommend creating an airtight seal. Air-sealing will ensure that convection heat is stopped, along with conduction heat.

Learn more about the benefits of insulating your attic with spray foam.

Basement Insulation

Basements are often under-insulated, leading to significant energy loss. Insulating your basement walls can prevent cold air from seeping into your living space. With warmer floors, your home will be more comfortable. With less cold air infiltrating your home, your energy bills will be lower. Additionally, insulating your basement can increase your home's value and provide a more usable living space.

When insulating basements, it's important to consider moisture control. Below-grade spaces require a vapor barrier to prevent condensing vapor and potential water damage. We recommend closed cell spray foam, which creates a vapor barrier at approximately 2 inches of depth.

Another option for basement insulation in the ceiling. Learn whether basement ceiling insulation is right for you.

Crawl Space Encapsulation

Crawl spaces are another area where insulation can make a big difference in your home's energy efficiency. Like basements, crawl spaces can be a significant source of cold air infiltration. Crawl spaces are also dirty and musty-smelling. For this area of the home, we recommend encapsulation.

Encapsulating the crawl space reduces energy bills. This method also solves problems like mildew smells, pest infestations, and poor accessibility. By joining the crawl space to the home's conditioned space, the building envelope is given an airtight seal. As a bonus, any air that exchanges between the crawl space and living space is clean.

Discover the benefits of crawl space encapsulation for your home.

The Bottom Line About Spray Foam In Existing Walls

Spray foam insulation is an option for existing walls, but only in specific circumstances. Homeowners who are renovating or planning to tear down their walls can use spray foam insulation. However, spray foam insulation cannot be installed in existing walls without disturbing them.

If you are determined to insulate your exterior walls without demolition, consider a product like injection foam.

For homeowners who are interested in insulating other areas of the thermal envelope, these are your next steps.

• Calculate the cost to encapsulate your crawl space
• Estimate the price of spray foam in your basement walls or ceiling
• Calculate an estimate of spray foam insulation for your attic