Spray polyurethane foam insulation—SPF insulation, or simply “spray foam”—is one of the most stable, versatile, valuable, and energy efficient materials in the world of building.
While it’s making headlines around the globe as the next generation high-performance insulation solution, spray foam has actually been around since the 1930s. Architects choose spray foam insulation in new schools, commercial buildings, and homes because it gives them freedom to design, and adds to the health and comfort quotient of the building system. Builders and general contractors choose spray foam because it provides much higher R-value, thermal resistance to heat flow, than traditional insulations (In building terms: the higher the R-value of an insulation product the more effective the insulation properties). And applying spray foam insulation (insulation+air barrier+water vapor barrier) requires only one trade contractor versus three or more with other insulations.
Homeowners and building owners choose spray foam because it gives them a sustainable energy efficiency resource, helps them maintain excellent indoor air quality (IAQ), and provides a more consistently comfortable indoor environment.
The current energy environment is driving a new wave of innovation and increasing the demand for high-quality SPF insulation products and experienced manufacturers.
Spray foam insulation provides:
- Greater energy savings because it has a higher R-value per inch than other insulation options, acts as a thermal break, and—in its unique original state as a liquid—helps fill every crack or hole in the substrate, thus forming a monolithic blanket as part of the building envelope.
- Better indoor air quality (IAQ) because foam (closed cell) acts as a barrier to water and air, inhibits mold growth, and stops air infiltration.
- Noise reduction for both airborne noise and structure-borne noise, also called impact noise.
- Structural strength for homes and buildings (closed cell).
SPF Insulation is “an important tool to help achieve energy efficiency” and has “three-to-six times the R-value of other insulation.”
What is Spray Foam Insulation
SPF insulation is a spray-applied insulation material that also acts as an air and moisture barrier. It’s applied as a liquid and expands up to 120 times its size to fill every crack, nook, or hole in a cavity or surface. It then cures in place and hardens to a firm consistency to become a permanent part of the structure.
Spray foam is made of two components: A-side: isocyanate, and B-side: polyol resin.
These two components are stored in separate drums and mixed on-site, using special equipment mounted in a rig, trailer, or truck. Heated hoses carry the approximately equal amounts of each component to the mixing gun, and when the A-side and B-side combine in the gun an immediate exothermic (heat-releasing) chemical reaction takes place. The A+B liquid mix is then immediately sprayed onto the substrate, where it fills even the most irregular space, foams, expands, and cures.
Spray foam can be formulated to light, medium, or high-density for a range of uses including—but not limited to—residential, commercial, agricultural, and geotechnical:
- Light-density spray foam is typically open-cell (see below) and about 0.4 to 0.5 lb. per cubic foot.
- Medium-density spray foam is typically closed-cell and about 1.7 to 2 lbs. per cubic foot.
- High-density spray foam is always closed-cell and is around 2.8 to 3 lbs. or more per cubic foot. It’s generally used in commercial roof insulation.
Open-cell and Closed-cell Spray Foam
- Open-cell (OC) spray foam, sometimes called “half-pound” or “semi-rigid” foam, is the most common form of SPF insulation. It ranges from low to medium-density, expands quickly, dries to a soft solid, and has a lower R-value. In open-cell foam, the tiny cells that make up the mass are open, allowing air to fill and move across them. This gives OC foam a soft, spongy feel and keeps its R-value to around 3.5 per inch. Open-cell foam is lighter than closed-cell foam, at 0.4 to 0.5 lb. per cubic foot. OC spray foam is great at absorbing sound and is often used in above-ground walls, in the undersides of roofs in unvented attics, and to fill cavities in the interior.
- Closed-cell (CC) spray foam, also called “rigid foam,” is medium to high-density, expands more slowly, and has a higher R-value of around 6.5-7 per inch. It’s commonly used in situations where there is significant moisture present and, because it’s firm and has a high density and compression strength, can add to the structural integrity of a building. Closed cell foam weighs in at around 1.7 lb. per cubic foot to 2.0 lb. per cubic foot (medium density). Roofing foam and foam for some commercial applications is around 2.8 lb. per cubic foot to 3.0+ lb. per cubic foot (high-density) to support greater weight and provide greater R-value.
Residential codes can be found here:
Commercial codes here:
Manufacturers Matter More Than Ever
Traditionally, finding the right spray foam for the job merely involved searching for local contractors who could apply SPF insulation. When residential and commercial building took a hit, builders and GCs became more circumspect of the building materials they where using. Sustainable building is now driving many smart design decisions. Builders and GCs need great products and great partners to help their bottom lines. While homeowners and builders still search for local trade contractors, many architects, builders, and general contractors are doing more intense due diligence on the company behind spray foam brands when choosing a product. In other words, they are proactively seeking SPF manufacturers they can rely on.
The American Chemistry Council (ACC) hosts a Center for the Polyurethanes Industry (CPI) which has a Spray Polyurethane Foam Chemical Health & Safety Training to promote product stewardship and offer free SPF courses to weatherization professionals: http://spraypolyurethane.org/SPF-Chemical-Health-and-Safety-Training
Many builders and architects are now choosing the SPF manufacturer first—researching the company and its products, considering the years of experience, doing proper due diligence—and then finding a local applicator that uses that manufacturer’s product.
While it takes more time and work up front to research, interview, and check the references and reviews of the many manufacturers in the SPF industry, architects, builders, and GCs say it pays off for them in the long run because it helps identify and form relationships with partners key to their future success.
Who Should Apply Spray Foam Insulation
Spray foam insulation is not a D.I.Y. product. To be effective and safe, it is essential for spray foam to be applied correctly by a professional trade contractor who is well-trained and certified in health and safety, building science, and applying SPF insulation. Home and building owners and general contractors should only hire applicators that have recognized certifications and credentials. *Research applicators here.
Health and Safety of Spray Foam Insulation
Spray foam has been regularly used in building since the 1970s, so more than 40 years of performance data and scientific testing exist to prove that spray foam insulation is safe and non-toxic if the following conditions are met:
- Properly applied
- Fully cured
As a great testament to spray foam’s safety potential, the American Lung Association’s model healthy home uses spray foam.
There are, however; some recent concerns about whether spray foam is really safe. Specifically, there is a question about the safety of isocyanates—which have a low acute toxicity—in polyurethane released during the exothermic reaction process of applying spray foam.
Spray foam has a long history of use, thanks to fair and accurate third party testing and documentation. The current science says that if properly applied to exacting standards, and once proper curing has taken place (usually 24-72 hours after application—see each manufacturer’s technical application instructions), SPF insulation is an inert material and non-toxic.
In other words, once spray foam is cured, it is as safe for the occupants of a home or building as other common building products.
Caution: Reputable Manufacturers and Trained Application Professionals Only This cannot be stressed enough: Spray foaming is not a D.I.Y. product or job, and not to be left to unqualified or untrained applicators. Spray-on foam is an engineered building product to be applied ONLY by trained applicators. If application is done improperly or by an inexperienced applicator, too much SPF foam could result in uncured particles that linger beyond the normal curing time and the continuation of the exothermic reaction. In this situation, the uncured particles would continue to release gas and cause the space to be uninhabitable until remediated.
Trained applicators never vary the manufacturer’s suggested curing time. No human contact or habitation of the space is allowed before curing is complete. We strongly recommend choosing only trained and certified contractors to apply spray foam insulation.
The Champion Choice for Insulation
Spray foam is an excellent insulating material because of its ability to be adapted to any project, environment, and space. SPF insulation has many advantages over traditional legacy insulation materials:
- Saves money. Higher R-value means higher energy efficiency and lower energy costs.
- Becomes a permanent part of the building envelope. Instead of a precut piece of insulation being placed, rolled, or even blown into an irregular cavity, SPF insulation is a gooey liquid that fills every crack, nook, crevice, and hole, expands to a formulated density, and cures in place to become a permanent part of the structure.
- Never needs replacing. Because it becomes part of the structure, spray foam lasts for the life of the building.
- Improves IAQ (Indoor Air Quality). As an air barrier, spray foam blocks the flow of air, thus blocking molds, pollens, and other dangerous airborne particulates. As a water barrier, it helps block moisture from entering the structure, thus denying mold the thing it needs most to grow and decay—the time when it releases dangerous spores and mycotoxins into the air, which can cause lung damage in humans and pets.
- Allows for greater design and architectural options. Because it’s a viscous liquid with highly versatile application, architects and designers often choose spray foam for unique, oddly shaped, and curved or rounded structural designs. No other insulation has such versatile application ability.
Greener buildings, or sustainable buildings, are in high demand. While the definition of “green” varies, the basic tenets do not. “Green” means the building is designed and built with the following in mind:
- To use energy, water, and other resources efficiently.
- To protect occupant health and improve employee productivity.
- To reduce waste and the overall impact on the environment.
A green building may cost more up front, but saves in the long run by lowering operating costs over the life of the home or building.
As designers and builders move away from the old prescriptive approach to scientific evaluation of actual performance in choosing building materials, SPF insulation is becoming more and more popular.
The Integrated Systems Approach
For commercial buildings, the green building approach applies a project lifecycle cost analysis for determining the appropriate up-front expenditure. This analytical method calculates cost over the useful life of the material (in the case of SPF, “useful life” is the entire life of the building). These and other cost savings can only be fully realized when they are incorporated at the project’s conceptual design phase with the assistance of an integrated team of professionals. The integrated systems approach ensures that the building is designed as one system, rather than a collection of stand-alone systems that may or may not work in unison for sustainability.
SPF Can be Used on Most Substrates:
- Gypsum board
- Galvanized steel
- Structural steel
- PVC plastics
- Asphalt and tar
- Urethane insulation
- Polystyrene insulation
The Building Material of the Future, Today
Spray foam might sound like a miracle material, and in many ways it is. SPF’s versatility and its malleability make it an ideal building material for new homes, renovation of older homes and buildings, non-traditional homes and buildings, DOE Solar Decathlon models, and prefab homes.
Doesn’t it make sense to use building materials that protect you, your occupants, your clients, and your community in the near and distant future?
Spray foam is increasingly recognized as a safe, healthy, affordable, versatile, and easy-to-work-with building material that’s the wave of the energy efficient future. Energy codes are changing rapidly, raising the bar for homeowners, contractors, carpenters, and applicators to meet or exceed code and help build a better, more sustainable future. When combined with spray foam’s affordable cost and availability, it’s easy to see why spray foam is replacing legacy insulation options and other old fashioned building materials. Already, most contemporary zero-energy homes are using spray foam insulation in their construction, and as more and more builders begin to recognize spray foam as the best solution to many of their construction needs, you can be sure that it’s truly the future of American building.
 US Dept. of Labor
 National Association of Homebuilders (NAHB)