Can You Put Spray Foam in Existing Walls Yourself?

Have you wondered, “Can you put spray foam in existing walls?” Upgrading insulation is one of the best ways to improve your home’s energy efficiency.

Adding spray foam insulation into existing walls can better seal air leaks compared to traditional fiberglass batts. Spray foam expands to fill cracks and gaps, creating a superior thermal barrier.

With professional installation, it can be applied directly into wall cavities to improve insulation levels without major disruption.

This article covers everything you need to consider when determining if spray foam is right for your home’s existing walls. After reviewing the key factors, connect with local insulation contractors to get quotes for spray foam installation.

How Can I Insulate My Existing Walls?

One effective way to insulate existing walls is by using blown-in cellulose insulation. Cellulose is a great insulator made from recycled materials that can be easily added to existing walls through small holes. Start by drilling or cutting access holes between wall studs, ideally at 14-16 inches apart.

Then use a special blowing machine to pump in the loose cellulose material until the cavity is completely filled. The cellulose packs tightly to form a thermal and sound barrier.

plug and patch the holes with filler, letting it dry before painting or wallpapering over. Blown-in cellulose has an R-value of R-3.7 per inch, so increasing cavity depth boosts efficiency.

What is the difference between vinyl, aluminium, brick and wood siding when insulation?

The type of siding used on a home can impact its insulation performance. Vinyl siding provides no insulation value itself, though it performs fairly well at reducing air infiltration if installed properly.

Aluminium siding similarly does not add insulation, and its higher conductivity actually decreases insulating ability. Brick veneer offers some insulating properties given its mass and density, with an R-value around R-0.2 per inch.

Wood siding like cedar can provide a bit of insulation, though its main benefit is its tight lap design that seals gaps when installed correctly. Fiber cement and compressed wood sidings also help moderately. For any siding type, adding continuous insulation beneath improves thermal resistance.

Vinyl, aluminium and steel sidings require an insulating underlayment layer when used in colder climates. Ultimately, proper installation for air sealing is crucial, and supplemental insulation should be used as needed.

Grasping the Basics of Foam Insulation

What is Foam Insulation?

Foam insulation refers to a spray-applied material that expands upon installation, filling gaps and forming a moisture-resistant and thermal barrier.

This insulation comes in two types: open-cell and closed-cell spray foam. Both types offer numerous benefits, such as durability, water and flame resistance, and long lifespan, making them an ideal choice for most homeowners.

Why Should You Consider Adding Foam Insulation to Existing Walls?

Adding foam insulation to your existing walls can significantly enhance your home’s energy efficiency by preventing heat loss.

This can help to reduce your energy bills, thereby saving you money in the long run. Moreover, foam insulation can also help in noise reduction, providing a quieter and more comfortable living environment.

can you put spray foam in existing walls?

can you put spray foam in existing walls?

Installing spray foam insulation in the walls of your existing home can be a great way to improve energy efficiency and comfort. But is it possible to add spray foam to walls that are already constructed without completely gutting them?

The answer is yes, spray foam insulation can be installed in existing walls through a process called retrofit foam insulation.

What is Spray Foam Insulation?

Spray foam insulation is a two-part liquid that expands and hardens when mixed, forming a rigid foam plastic material. There are two main types of spray foam to consider:

Open-cell spray foam has a spongy texture and expands to 100 times its liquid volume. It provides good air sealing and insulation value of around R-3.7 per inch. Open-cell foam is more flexible and better for retrofit applications.

Closed-cell spray foam has a denser feel and expands to only 30-60 times its liquid volume. It offers an insulation value of R-6 to R-6.5 per inch and also provides structural enhancement. Closed-cell foam works well for new construction.

Both types of spray foam resist heat flow and air infiltration far better than traditional fibreglass batt or blown-in insulation. When installed correctly, spray foam insulation forms an air-tight seal that keeps conditioned air inside your home.

How to Add Spray Foam to Existing Walls

Retrofitting spray foam insulation into existing walls can be done in a few different ways:

  • Via interior wall holes – Small holes can be cut into the drywall at strategic locations to access the wall cavity. Hoses are fed through the holes to fill the cavity space with foam. The holes are then patched.
  • Removing exterior siding – For closed cell foam, taking off the exterior siding provides full access to spray insulation directly into the wall cavities from the outside. The siding is replaced after the foam cures.
  • With dense pack insulation – Blown-in fibreglass or cellulose insulation can be “densely packed” into wall cavities before installing foam. This allows the foam to fully adhere and fills any gaps.
  • Between studs – In unfinished walls like in basements, foam can be sprayed directly between stud bays but extra care must be taken to properly seal and prepare the space first.

No matter the method, proper masking and prep are needed inside the home. An experienced spray foam insulation contractor will know the best way to retrofit foam into your particular home’s walls.

Benefits of Adding Spray Foam to Existing Walls

  • Significant improvement in energy efficiency and cost savings
  • Better temperature regulation and soundproofing
  • Air sealing to prevent drafts, moisture, and pests
  • Long-lasting insulation that won’t settle over time
  • Increased structural stability (with closed cell)
  • Improved fire resistance

Things to Consider

  • Retrofit foam insulation costs more than fiberglass batts
  • Wall cavities must be properly assessed and prepared first
  • Special equipment and contractor expertise required
  • Existing electrical could require inspection after installation

Adding spray foam insulation to the walls of your existing home is possible with the right contractor. Consider both open-cell and closed-cell foam to see which type fits your retrofit needs and budget. With proper installation, you can enjoy a more comfortable, energy-efficient home.

FAQs: Can you put spray foam on existing walls?

Does spray foam damage existing wiring or plumbing?

No, spray foam insulation should not damage wiring or plumbing when installed correctly. The spray foam completely adheres to the wall surfaces and does not apply pressure on pipes or wires. Professional installers know to avoid clogging or restricting wiring and plumbing. Covering them temporarily prevents spray intrusion.

How long does spray foam off-gas after installation?

Spray foam insulation typically off-gases for 24-48 hours after installation. Proper ventilation helps dissipate any mild odours quickly. Most off-gassing occurs with closed-cell foam. Keep windows open after application. The fumes are non-toxic but can cause a smell.

Can spray foam be removed if necessary?

Yes, spray foam insulation can be removed if desired, but it takes significant effort and costs. First, the foam would need to be mechanically scraped off the walls. Secondly, any adhesive residue would require a solvent-based cleaner. Consider it semi-permanent when installing.

Does spray foam need to be covered or have a fire rating?

Spray foam insulation often remains exposed and does not require fire-rated covering, unless required by local building codes. Check your local regulations. Most spray foam is naturally fire-resistant. Adding drywall or wood panelling over it is optional.

What is the R-value of spray foam insulation?

Spray foam insulation has a high R-value, typically around R-6.0 per inch. So a 3-inch layer would provide an R-value of R-18. The closed-cell type provides a higher R-value than the open-cell. The higher the R-value, the better the insulation properties.

How long does spray foam insulation last?

When properly installed, spray foam can last for over 50 years. It does not degrade or compress over time. Closed-cell foams have a longer lifespan than open-cell. Make sure your installer follows all manufacturer specifications for maximal longevity.

Does spray foam stop air leakage?

Yes, spray foam is excellent at sealing air leaks, gaps, and cracks. It can reduce air infiltration by up to 50 percent compared to other types of insulation. The foam expands and seals, insulating and air-sealing in one step.

Is spray foam environmentally friendly?

Spray foam insulation is considered environmentally friendly and sustainable. The base materials are derived from renewable and recycled sources like soy. It also makes homes more energy efficient. Look for eco-friendly formulations.

Does spray foam insulation need maintenance?

Properly installed spray foam insulation is very low maintenance and requires no ongoing upkeep. Since it bonds tightly to surfaces, it does not settle or degrade easily. You may occasionally inspect for pests or water intrusion.

How much does it cost to spray foam existing walls?

The average cost to spray foam existing walls is $1.50-$2.00 per square foot installed. Exact costs vary based on materials, foam thickness, and labour. Get quotes from 3-4 local contractors. Also, factor in insulation incentives/rebates for offsetting costs.


Upgrading your home with spray foam insulation in existing walls can be a smart investment. With its superior sealing against air leaks, increased energy efficiency, and ability to fill gaps and crevices, spray foam outperforms traditional fiberglass insulation.

Carefully consider any electrical, ventilation or plumbing needs when determining if retrofitting spray foam makes sense. It requires hiring professional installers to be done safely and correctly.

If your home could benefit from improved thermal protection and reduced energy costs, contact local spray foam contractors today to explore your insulation upgrade options.

With the right prep work and expert installation, adding spray foam could take your walls to new levels of comfort and efficiency.

About Mohammad Sameer

My name is Mohammad Sameer, the founder of SoundproofGears. My hypersensitive hearing turned me into a lifelong seeker of silence. After years of research, I've become an expert on soundproofing techniques and materials. In November 2022 I launched this site to share my knowledge and help others find acoustic sanctuary. About More

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