Injection Foam Insulation vs. Spray Foam Insulation: Which Is the Best Fit for Your Home?

When it comes to insulating your home, there are many different types of insulation to choose from. Choosing the right insulation type can make a significant difference in your energy efficiency and comfort levels. Two popular options are injection foam insulation and spray foam insulation – but which one is best for your home?  In this post, we will compare and contrast the two insulation types to help you make an informed decision.

Installation of Insulation

Spray Foam Insulation:

Spray foam insulation is typically installed in new homes, new additions, or metal buildings, where the walls are open. During installation, the foam is sprayed onto open wall cavities using specialized spray equipment, where it expands and hardens into a solid foam. Spray foam insulation can also be applied on roofs, attics, and floor joists, offering superior R-value and air sealing benefits compared to traditional insulation types.

Injection Foam Insulation:

Injection foam insulation is an ideal choice for older homes, where the walls are not open. The insulation is injected into the wall cavities through small holes drilled on the exterior of the home. Injection foam insulation has been installed in millions of square feet of commercial structures for over 35 years and has been used to retrofit insulation in existing homes with great success. Injection foam insulation is also compatible with many types of exterior coverings, making it an excellent choice for historic homes where it is important to maintain the character and integrity of the original structure.

Formulation and Structure

Spray Foam Insulation:

Spray foam insulation comes in different formulations, with closed-cell spray foam offering a very high R-value of 5.5+ but can be expensive to install. Open-cell spray foam, on the other hand, has an R-value of around 3.5 and is the most commonly applied type of spray foam insulation. Spray foam insulation is typically made from polyurethane and polyisocyanurate. Open-cell spray foam has an open-cell structure that allows it to provide thermal insulation, seal cracks and joints, and provide a sound barrier. It expands to over 120x its original size when installing, converting from liquid to foam.

Open cell spray foam insulation generally has a 1-hour fire rating. This means that it will resist fire spread for up to one hour. Most spray foam compounds have a flame-spread of less than 25 and a smoke-developed index of <450. This complies with all current building codes. Closed cell spray foam has a 4-hour fire rating and is often used in fireproofing – however it costs more than double to install vs. open cell spray foam.

Injection Foam Insulation:

Injection foam insulation is made of an amino acid foaming agent and a polymethylene carbamide resin. When mixed at the proper ratio, the compounds create a foam that resembles shaving cream. This foam can be pumped inside of wall cavities using compressed air. The R-value of injection foam is 4.7 per inch, compared to open-cell spray foam at 3.5 per inch. Injection foam insulation does not expand like spray foam, and has a 0.01% expansion rate. This is important because when insulating existing homes, injection foam can fill wall cavities without expanding and ruining interior drywall or plaster.

Injection foam insulation has a 4-hour fire-rating, meaning it resists fire spread for up to four hours. The flame-spread is less than 5 and the smoke-developed index is 50-100. The fire-rating for injection foam insulation is well within industry standard and allows the product to perform as a commercial fire-proofing substance.  


the difference between spray foam insulation and injection foam insulation
what is the difference between spray foam insulation and injection foam insulation

Safety Considerations

Spray Foam Insulation:

Installation of spray foam requires installers to wear special masks and suits to protect them from the compounds in the foam . Typically, spray foam insulation does contain VOC’s and off-gasses while it is installed. As long as it is installed and mixed properly, the product should become inert once it is fully-cured. The home must be unoccupied for a period of time while the foam cures. The amount of time the area needs to be unoccupied will depend on the formulation of the spray foam used, it could be 4 hours or up to 3 days. During that time contractors will have to trim off excess insulation to make the foam flush with the wall cavities. This process can create dust that will need to be carefully cleaned from the jobsite to avoid inhalation or ingestion by occupants. 

Injection Foam Insulation:

In contrast, injection foam insulation is a non-toxic formulation with no off-gassing. Installers do not have to wear any personal protective equipment while the foam is injected. Additionally, homeowners are free to live in the home as usual while the walls are insulated. The process generally takes one to two days to complete.

Cost to Install Foam Insulation

The cost of injection foam insulation versus spray foam insulation can vary depending on several factors such as the size of the project, the type of foam insulation, and the location.

The cost for injection foam insulation can range from $1.50 to $4.00+ per square foot, including installation, depending on the type of foam used. Various factors, including size of wall cavity, type of exterior covering on the home, and ability to access walls with ladders will affect overall material and labor costs.

Spray foam insulation, on the other hand, can cost anywhere from $1.50 to $6.50 per square foot, including installation, depending on the type of foam used, the thickness of the insulation, and the complexity of the installation.

Overall, injection foam insulation can be a cost-effective option for smaller projects or areas that are difficult to access, while spray foam insulation may be a better choice for larger projects or areas that require a more complex installation. It’s important to consult with a professional insulation contractor to determine the best insulation option for your specific project and budget.

Additional Information

Have questions about which type of foam insulation is best for your home? That’s why we’re here!
Give us a call or send us an email. A team member would be happy to discuss your project with you and see if your home is a candidate for injection foam insulation. 

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