Which type of spray foam is ideal for different applications?

High-density foam is used for high R-value and strength needs, medium-density for continuous insulation, and low-density for areas requiring flexibility and sound absorption.

WHAT YOU NEED TO
KNOW ABOUT SPRAY
FOAM R VALUES

Spray foam R values and the difference between open-cell and closed-cell spray foam

SPRAY FOAM INSULATION

Spray foam insulation offers a safe, affordable, and highly effective solution for building insulation. Many older homes were built with either no insulation at all, or with old technology that’s now in desperate need of replacement. At the same time, new construction projects are racing to meet the current demands of an unprecedented housing market and rapidly aging infrastructure, which require robust and cost-effective tools and techniques to build the next generation of homes, commercial centers, and industrial facilities. Both homeowners and contractors can find the right spray foam technology for their specific project by understanding spray foam R-values. The spray foam R-value provides a simple and comprehensive measure of an insulation’s resistance to conducting heat, and serves as a critical metric for evaluating new insulation projects.

WHAT ARE SPRAY FOAM R VALUES?

Thermal resistance R-values provide a simple and standardized measure of an insulation material’s resistance to conducting heat. The higher the R-value, the better the insulating properties of the material, and, vice versa; the lower the R-value, the worse the insulation. The R-value is calculated using the thickness of the application and the material’s thermal conductivity, which depend on the type of material and its density, as well as thickness, age, temperature, moisture and other factors. The R-values across different types of insulation materials generally range from approximately R-3 to R-7 per inch, and spray foam R-values simply refer to the R-values of common spray foam materials that lie on the far end of the spectrum. Spray foam insulation is known for having the highest R-value per inch of any of the common types of building insulation, which has made them a popular choice for residential and commercial applications alike.

OPEN VS CLOSED
CELL SPRAY FOAM

Open-cell spray foam derives its name from the available space present within its structure, which makes it a low density and vapor permeable type of material. These characteristics allow the absorption and retention of moisture, which is perfect for interior applications like walls, ceilings, and roofs where some vapor transfer may be beneficial. Their structure can also be advantageous for soundproofing individual rooms or even entire buildings, and provides the flexibility needed to account for shifting structures or changing environments. However, this same permeability that affords open-cell spray foams with their unique benefits is also a cause for concern. Open-cell insulation can require the use of additional vapor retardants in high-moisture environments, and exhibit relatively low R-values of roughly R-3.5 to R-3.8 per inch. This is lower than the R-value of closed-cell insulation, but sufficient for many residential applications that may not require the insulation available in the industry, or seek to leverage their moisture-focused properties.

Closed-cell spray foam has superior insulating properties compared to open-cell alternatives thanks to its higher density and closed-cell structure that make it an excellent barrier against air and moisture. Closed-cell spray foams therefore also have higher R-values than their open-cell counterparts, typically ranging between R-6.5 and R-7 per inch. This makes closed-cell insulation one of the most effective insulation materials available on the market, which has seen their widespread use for applications where effective insulation is challenging, but non-negotiable. This includes under slabs, roofs, and exterior walls, where their higher density also provides significant structural reinforcement to improve the durability of insulated building elements. Perhaps most distinctly from open-cell insulation, closed-cell materials are vapor impermeable, which prevents moisture infiltration to reduce the risk of mold and water damage. While these enhanced properties see closed-cell spray foams at a higher cost, their improved durability and performance make it a preferred choice for demanding projects.

SPRAY FOAM
R-VALUE & DENSITY

There’s an important relationship between the spray foam R-value and a material’s density. Just as insulation can be categorized by its structure, it can similarly be divided into groups based on their densities, which each offer distinct advantages for different applications. Spray foam insulation can generally be categorized into low-density, medium-density, and high-density types:

LOW-DENSITY

Low-density spray foam insulation is typically synonymous with open-cell spray foam, as low density insulation is generally a consequence of unoccupied space within the structure of the foam. Low-density insulation materials are particularly effective barriers against air, while also allowing for the transfer of moisture; a unique combination that makes it ideal for some applications. Its flexibility helps low-density foams adjust to structural shifts that make it perfect for walls, ceilings, or roofs, and their low R-values also make them an excellent soundproofing solution. Low-density spray foams are also often more sustainable than other types due to their natural blowing agents and flexibility in formulation to incorporate renewable materials.

MEDIUM DENSITY

As you might expect, medium-density spray foam insulation strikes a healthy balance between the properties of low- and high-density alternatives. Their more confined internal structures lean more closed-cell than open-cell and have intermediate R-values of around R-5.7 per inch. Their near leading insulating properties see medium-density spray foam be used in a diverse range of applications, commonly including continuous insulation, unvented attics, and interior wall cavities. Like low- and high-density foams, medium-density foams serve as strong barriers against air, but differ in their only moderate moisture resistance. Paired with their robust adhesive properties, medium-density foams offer a balanced solution that has seen their extensive use across the industry.  

HIGH DENSITY SPRAY FOAM

High-density spray foam insulation is typical of closed-cell, high R-value materials. Starting around R-5.5 per inch and often reaching R-7 per inch or higher, high-density foams translate to exceptional thermal resistance and structural reinforcement that make it ideal for exterior applications and large industrial projects. High-density foams are especially effective barriers against both air and moisture that can significantly reduce energy costs and provide maximum protection against weathering and water infiltration. High-density foams are considered the more robust and durable insulation on the market, and are the go-to choice for projects requiring maximal insulation efficiency and heightening structural support.

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FREQUENTLY ASKED QUESTIONS

What is a good R-value for spray foam insulation?

The appropriate R-value for spray foam insulation depends on the conditions of the home or building. Open-cell spray foams typically have lower R-values less than approximately ~R-3.5 per inch, whereas closed-cell foams have higher R-values of ~R-6.5 or greater. This means that high density, closed-cell foams provide the best insulation, but may be excessive for some projects.

What’s the difference between open-cell and closed-cell spray foam?

Open-cell and closed-cell spray foams differ in their internal structures. Open-cell foams have more available space that makes them vapor permeable, and offers potentially advantageous moisture transfer at the cost of a heightened risk of mold or water damage. Closed-cell foams have limited space within their structures that make them vapor impermeable, and with higher densities and correspondingly high R-values for better overall insulation.

ARMORFOAM SPRAY
POLYURETHANE FOAM INSULATION

ArmorFoam is our specialty spray foam insulation composed of polyurethane spray elastomer technology. ArmorFoam has been engineered to possess superior insulating properties compared to traditional alternatives and even other polyurethane-based insulation technologies. It offers one of the highest R-values of all commercially available spray foams, and can be used to reinforce structures to reduce the risk of structural damage caused by natural disasters or harsh weather conditions. Climate change and evolving construction standards have created more of a reason than ever before to secure your home’s insulation. Spray foam solutions can help improve your home’s energy efficiency, and high R-value foam insulation offers superior performance compared to anything on the market. If you’re interested in learning more about spray foam insulation and ArmorThane’s suite of products and services, contact us using our online form.

ABOUT THE AUTHOR

TYLER GLECKLER

I am a chemist with a specialization in nanotechnology and applied materials chemistry. My work has focused on the characterization of optoelectronic materials, namely including semiconductor nanocrystals.

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