Spray foams (insulation)

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Spray foam insulation or spray polyurethane foam (SPF) is an alternative to traditional building insulation such as fiberglass. A two-component mixture composed of isocyanate and polyol resin comes together at the tip of a gun, and forms an expanding foam that is sprayed onto roof tiles, concrete slabs, into wall cavities, or through holes drilled in into a cavity of a finished wall.

Spray foam insulation extruding from a duct.


Otto Bayer (1902-1982) is credited with the invention of polyurethane in 1937. He succeeded in synthesizing polyurethane foam by exploring his basic idea that mixing small volumes of chemical substances could create dry foam materials.[1]

Polyurethane was further developed for different applications, ranging from shoe soles and cushions to industrial uses. In the 1940s rigid foam was applied to airplanes,[2] and in 1979 polyurethane began being used as building insulation.[3]

Various systems are used to apply the spray foam. The two component high pressure system is generally used in new home construction. It is a quick expanding type of spray foam. The two component low pressure spray foam is another system that is used primarily for remodel jobs where there are existing walls with drywall already in place. This is also known as a slow rise formula and often referred to as injection foam.[citation needed]


Spray polyurethane foam (SPF) insulation can be categorized into two different types: light-density open-cell spray foam insulation and medium-density closed-cell spray foam insulation. Both types of SPF are thermoset cellular plastics comprising millions of small cells.[4]

Open cell spray polyurethane foam insulation being applied in wall cavities.

Medium-Density Closed-Cell Spray Foam (ccSPF)

Medium-density closed-cell foam insulation is often referred to as two pound (2 lb) foam. It is a rigid insulating material with an Long Term Thermal Resistance (LTTR) R-value that ranges between 5.1 - 6 per inch[5] When the required minimum thickness of 50 mm is installed, ccSPF is both a vapour barrier and an air barrier.

In Canada, the National Building Code references two standards that apply to the manufacturing and installation of ccSPF: the CAN/ULC S705.1 Material Standard and the CAN/ULC S705.2 National Application Standard. The installation standard requires that all installers of ccSPF in Canada be licensed and carry a photo ID card.[6]

Typically the foam's natural colour is yellow, however in Canada all ccSPF that have CCMC listings are required to have a unique colour for field identification.[7]

Light-Density Open-Cell Spray Foam (ocSPF)

Light-density open-cell SPF is commonly known as half-pound foam. It is a semi-rigid material with a sponge-like appearance that expands during installation and creates small, open cells that are filled with carbon dioxide. Due to its ability to expand during the application process, it fills cracks, crevices and voids and adheres to irregular surfaces or substrates to form an air sealing insulation.[8]

While the R value will vary, most ocSPF products have an R value of around 3.8 per inch. Unlike medium-density closed-cell SPF, ocSPF is not a vapour barrier. When installed at 5.5 inches or more, ocSPF does act as an air barrier. It is often used for interior walls because it provides sound reduction by blocking and absorbing air leakage. It is usually only recommended for indoor applications.


Spray foam insulation saves on energy costs and lowers utility bills. Studies by the US Department of Energy show that 40% of a home's energy is lost as the result of air infiltration through walls, windows and doorways. Buildings treated with spray foam insulation insulate as much as 50% better than traditional insulation products.

Insulation that is sprayed in buildings protects against moisture, which provides the benefit of reducing the chance of harmful mold and mildew. Eliminating mold growth reduces the likelihood of rotting wood in a home, and allergic reactions to mold spores.

In addition to building temperature and moisture control, spray foam insulation is often used to reduce noise. Foam insulation serves as a barrier to airborne sounds, and reduces airborne sound transfer through a building's roof, floor and walls.

In the United States, homes treated with spray foam insulation often qualify for state and federal tax deductions.[9]

Thermal resistance[edit]

R-value is the term given to thermal resistance to heat flow. The higher the R-value of an insulation product, the more effective the insulation properties. 1.8-2 pound polyurethane foam has the highest R-value of readily available insulation used in homes and buildings.[10]

Polyurethane is a closed-cell foam insulation material that contains a low-conductivity gas in its cells.[11] As a result of the high thermal resistance of the gas, spray polyurethane insulation typically has an R-value around R-5 to R-6 per inch.[11] In comparison, blown fiberglass typically has an R-Value of only R-2 to R-4 per inch.[12]

Foam insulation blocks all three forms of heat transfer:

Conductive heat transfer
The flow of thermal energy through a substance from a higher to a lower temperature region. Foam thermoset plastics block conductive heat transfer due in part to having very loose molecular bonds; In addition the cells of the installed spray foam are either filled with air in the case of open cell foam or 245fa in closed cell foam.
Radiant heat transfer
The process by which heat energy in the form of light (usually IR unless the substrate is hot enough to glow in the visible range) is emitted more strongly by warm surfaces and absorbed by other materials especially those of low IR reflectivity (think matte black finish). Radiant heat transfer does not require a medium. Thermoset foams, such as spray foam insulation, have the ability to reflect radiant heat. This is due to the reflective (shiny, in terms of IR) surfaces within the cell structure of the foam.
Convective heat transfer
Heat which is created elsewhere that is transported by means of a fluid, such as water or in our case air. Spray foam insulation's most important attribute is the ability to air seal creating a custom airtight envelope within the building structure. The added benefit to air sealing is the ability to block convective heat transfer from interior to exterior during heating months and vice versa during cooling months, as the heat cannot escape through gaps in the buildings envelope without the aid of air movement from infiltration as a means of transport.

Health effects[edit]

Spray foam insulation is typically non-toxic only after it has cured. While curing spray foam emits a gas that causes blurred vision and trouble breathing. Using full face and respiratory protection while applying the product is recommended.[13]

Isocyanates are powerful irritants to the eyes and gastrointestinal as well as the respiratory tracts. Direct skin contact with isocyanates can also cause marked inflammation. Some people say that their eyes feel like they have sand in them at the onset of problems. Some break out in a rash on their arms, chest, and neck.

Overexposure to isocyanates can sensitize workers, making them subject to asthma attacks if they are exposed again. Respiratory irritation may progress to a chemical bronchitis. Additional exposures can make the onset easier with less isocyanate necessary to start the attack.

Sporadic cases of hypersensitivity pneumonitis (HP) have also been reported in workers exposed to isocyanates. The symptoms may seem like the flu, with fever, muscle aches, and headaches. Other symptoms may include a dry cough, chest tightness, and difficult breathing. Individuals with chronic HP often experience progressively more difficult breathing, fatigue, and weight loss. Individuals with acute HP typically develop symptoms 4-6 hours after exposure.[14][10]

Environmental properties[edit]

Insulation of all types stops a good deal of energy loss. Some types including spray foams also seal air leaks. Insulation can also save energy in hot climates by reducing air conditioning use.

See also[edit]


  1. ^ AG, Bayer. "Otto Bayer – Important Personalities of Bayer's History". www.bayer.com. Retrieved 2016-08-03. 
  2. ^ Seymour, Raymond B.; Kauffman, George B. (1992). "Polyurethanes: A Class of Modern Versatile Materials". J. Chem. Ed. 69: 909. doi:10.1021/ed069p909. 
  3. ^ "Polyurethanes in Polyurethanes timeline". www.polyurethanes.org. Retrieved 2016-08-03. 
  4. ^ Spray Applied Rigid Polyurethane Insulation Installer Training Program Manual. CUFCA. 1 October 2014. p. 5. 
  5. ^ "Technical Documents | CUFCA". www.cufca.ca. Retrieved 2016-08-03. 
  6. ^ "What Foam Do I Ask For? / How Do I Know If I Received What I Asked For? | CUFCA". cufca.ca. Retrieved 2016-08-03. 
  7. ^ "CMC Registry of Construction Product Evaluations". National Research Council Canada. Retrieved 3 August 2016. 
  8. ^ Low Density Semi-Rigid Open Cell Training Manual. Canada: CUFCA. 2014. p. 3. 
  9. ^ Federal Tax Credits for Consumer Energy Efficiency
  10. ^ a b Insulation Alternatives: Sprayed Foam Insulation
  11. ^ a b Polyurethane Insulation Materials
  12. ^ Insulation Values For Selected Materials
  13. ^ Spray Foam Insulation: Installation, Tips and Best Practices
  14. ^ Foam Insulation vs Standard Insulations