What is the R-Value of Spray Foam Insulation?

When insulating your home in Southern Maine, understanding the R-value of spray foam insulation is crucial. The R-value measures the thermal resistance of a material and indicates how effective it is at preventing heat transfer. 

In this post, we’ll explore the intricacies of spray foam insulation and explore its R-value, explicitly focusing on closed-cell and open-cell spray foam insulation.


Spray foam insulation is popular for homeowners due to its exceptional thermal performance and energy efficiency. It comprises two main types – closed-cell and open-cell foam – each with unique properties.

Closed-Cell Spray Foam Insulation

Closed-cell spray foam insulation is a dense and rigid material with a high R-value per inch. 

The R-value of closed-cell spray foam insulation typically ranges from R-6 to R-7 per inch. This means that even a thin layer of closed-cell spray foam can provide superior insulation to other traditional insulation materials. 

Additionally, closed-cell spray foam acts as an excellent air and moisture barrier, which helps to enhance the overall energy efficiency of your home.

Open-Cell Spray Foam Insulation

Open-cell spray foam insulation, on the other hand, is a softer and more flexible material. It has a lower R-value than closed-cell spray foam, typically ranging from R-3.5 to R-4 per inch. 

Open-cell spray foam excels in sound insulation and can reduce noise transmission between rooms. However, it may be less effective in extreme climates requiring a higher R-value.


While the R-value of spray foam insulation indicates its thermal resistance, it’s essential to consider other factors that can impact its effectiveness. Some of these factors include:

Thickness of Insulation

The thickness of spray foam insulation directly affects its R-value. The thicker the insulation, the higher the R-value. For example, 2 inches of closed-cell spray foam can have an R-value of approximately R-14. 

It’s vital to consult with a professional insulation contractor who can assess your specific needs and recommend the appropriate thickness for optimal energy efficiency.

Quality of Installation

The proper installation of spray foam insulation is crucial for maximizing its performance. Improper installation can result in gaps and voids, reducing the overall effectiveness of the insulation. 

It’s advisable to hire a certified insulation contractor with experience in spray foam installation to ensure a proper air seal and achieve the desired R-value.

Spray foam insulation offers exceptional thermal performance and energy efficiency, making it an ideal choice for homeowners in Southern Maine. The R-value of spray foam insulation varies depending on the type – closed-cell or open-cell – as well as the thickness of the insulation applied. Consulting with a professional insulation contractor will help determine the most suitable R-value for your home.

Remember, understanding the R-value of spray foam insulation is essential for making informed decisions about your home’s insulation needs. By investing in high-quality spray foam insulation with the appropriate R-value, you can enjoy increased energy efficiency, improved comfort, and lower utility bills.
If you’re ready to learn whether your home is ready for insulation, get a free quote from Seal It Insulation Systems today!

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