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Why Spray Foam Outperforms

Why Spray Foam Outperforms: A Look at the Science Whether you're a homeowner looking to upgrade, or a contractor interested in offering top-notch insulation solutions, you might be curious why spray foam is often touted as a superior choice. The technical jargon can get overwhelming. Don't worry—this article simplifies the science behind spray foam insulation and explains how it can bring significant advantages to your home or business.

Spray foam insulation is created by combining isocyanate and polyol resin, which react and expand into a protective barrier. The cellular structure of spray foam traps air and provides an effective barrier against heat transfer. With closed-cell spray foam frequently achieving an R-value of 6 per inch, spray foam insulation can achieve the same thermal resistance as over 10 inches of fiberglass. The airtight seal also prevents air infiltration, which can account for up to 40% of energy loss in buildings. Not only does spray foam provide excellent thermal resistance, but closed cell foam also acts as a vapor barrier, making it an excellent solution to manage moisture when combined with proper mechanical ventilation.

For spray foam contractors and insulation businesses, understanding the science behind spray foam is vital to effectively educating customers. This article details how spray foam's unique properties allow it to outperform other insulation materials, creating more energy-efficient and comfortable buildings. Your customers will appreciate the technical expertise and be more inclined to choose spray foam for their insulation needs.

What Is Spray Foam Insulation?

Spray foam insulation is a spray-applied cellular plastic that expands and hardens into a rigid product. It provides superior insulation and air sealing in one step.


The two components of spray foam, isocyanate and polyol resin, react when mixed. Once combined, these two components expand into a protective plastic foam that hardens into a durable, seamless barrier. As the chemical reaction occurs, the liquid foam expands 30+ times its volume, filling in cracks, crevices, and voids to stop air leaks and drafts.

Thermal Performance

The dense, closed-cell structure of the most commonly installed spray foam insulation product contains millions of tiny air pockets trapped within the plastic, giving it an extremely high R-value, typically around R-6 to R-7 per inch. This means it takes a long time for heat to transfer through the thick, dense material. The exceptional thermal resistance spray foam provides helps lower both heating and cooling costs.

Air Sealing

In addition to its insulation properties, spray foam is an excellent air sealer, as it expands to seal all cracks, holes, and crevices where air can leak in or out. By eliminating air leaks and drafts, spray foam insulation can improve a home's air quality and energy efficiency. The airtight seal it provides helps prevent moisture, pests, odors, and pollutants from entering the building envelope.


Once cured, spray foam insulation forms a durable barrier that remains securely adhered to surfaces for the lifetime of the building. It will not sag, settle, or shrink over time, maintaining its insulation and air-sealing properties for decades. Properly installed, spray foam insulation helps create an energy-efficient, comfortable building environment.

The unparalleled combination of high R-value, air sealing ability, vapor barrier properties, and ability to contour to any shape makes spray foam insulation an optimal solution for many applications in residential and commercial construction. The long-term energy cost savings and improved building performance provide environmental and economic benefits for building owners. When installed by trained professionals using quality products, spray foam outperforms all other insulation options.

Evaluating the R-Value of Different Types of Spray Foam

R-value refers to an insulation's ability to resist heat flow and is the standard measure of effectiveness. As a general rule, the higher the R-value, the better the insulation.

Closed-Cell Spray Foam

Closed-cell spray foam (commonly referred to as 2-lb foam) typically has an R-value of 6-8 per inch of thickness. Its rigid, plastic structure contains millions of tiny, closed cells that provide an effective barrier against both heat and moisture transfer. Closed-cell spray foam is ideal for exposed applications like attics, basements, crawl spaces, or rim joists where its durability and moisture resistance are useful.

Open-Cell Spray Foam

Open-cell spray foam (commonly referred to as ½-lb foam) typically has an R-value of 3.5-4.5 per inch. Its structure contains open cells filled with air that still reduce heat flow. Although less dense than closed-cell foam, open-cell spray foam still excels at sealing air leaks and drafts. It is often used in wall cavities and for various soundproofing applications.

Increasing R-values

The R-value of spray foam can be improved by adding inches of thickness. For example, 3 inches of closed-cell spray foam achieves an R-value of 18-24, while 5 inches achieves R-30-40. Multiple layers of spray foam can also be installed to improve thermal performance.

The Applicator

The spray foam gun mixes liquid components in its tip to create the foam. A proportioner heats and pressurizes the liquids, then sends them through specialized hoses into a gun that sprays them onto the desired surface. The applicator must maintain the proper pressure, heat, and material ratio for even, controlled application. Too much pressure or heat can damage the foam's structure, reducing insulation value and durability.

Application Technique

Each specific spray foam material designates its own “maximum pass thickness” for proper application. Spray foam must be applied in thin, even passes, building up layers over time to achieve the desired R-value. If too much is applied simultaneously, the exothermic reaction can overheat the area and potentially damage the foam. The applicator should use a side-to-side sweeping motion, always keeping the tip moving. They should start at the top of the cavity, working down in passes. Each pass should overlap slightly.

Proper spray foam equipment, components, and application technique, combined with a skilled applicator, are required to produce spray foam insulation that meets or exceeds its advertised R-value and achieves maximum air sealing capability. When done correctly, spray polyurethane foam outperforms all other insulation types. Spray foam's performance depends entirely on execution - when you get the science right, you get superior results.


Spray foam insulation is an innovative product that continues to transform the building industry due to its unparalleled performance. Spray foam's ability to seal and insulate simultaneously helps lower energy costs, reduces pollutants entering the home, and creates a more comfortable living environment. While the upfront cost may be higher than other insulation types, the long-term benefits to homeowners and the environment make spray foam insulation a smart choice for new construction and retrofit projects. By understanding the science of how spray foam insulation works, you can either make the best choice for your home or convey these benefits to your customers with confidence.

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