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How Does Spray Foam Work

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 typically 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.

  • Lower energy cost

  • Stops drafts and condensation

  • Better indoor air quality

  • Does not settle or shrink

  • Quieter indoor environment

  • Fills irregular shapes

  • Increased comfort

  • Adds structural strength


Thermal Resistance

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. 8-2 pound polyurethane foam has the highest R-value of readily available insulation used in homes and buildings.
Polyurethane is a closed-cell foam insulation material that contains a low-conductivity gas in its cells.[7] 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. In comparison, blown fiberglass typically has an R-Value of only R-2 to R-4 per inch.
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.



Spray foam insulation has many advantages over alternative insulation products such as fiberglass and cellulose. If foam insulation is used throughout the entire home, it seals-off all air infiltration by sealing the voids throughout the insulated area. This helps to create a thermal envelope controlling the air inside the building allowing for the downsizing of the buildings HVAC systems lowering building costs.

  • Saves energy operating costs. 30-50% per year

  • Reduces air and moisture infiltration-resulting in a more consistent temperature

  • Reduces dust and pollen infiltration

  • Adds structural strength to the building

  • Reduces the likelihood of mold

  • Reduces noise

  • Reduces ice damages

  • Reduces HVAC capacity requirements

  • R-values remain stable over time

  • It has the highest performance of all insulation

  • It is permanent and will not sag or settle


Spray Foam as an Air Sealant

Air leaks can waste energy and drive up utility bills. Spray foam can be used to fill gaps and stop the leaks in many areas of a home or building. Some common spots for air leaks that can be sealed with spray foam include:

  • Behind knee walls

  • Attic hatches

  • Wiring holes

  • Plumbing vents

  • Open soffits

  • Recessed light, furnace flue or duct chaseways

  • Basement rim joists, windows and doors

“Cool roofs” are roofs designed to maintain a lower temperature than traditional roofs.6 They are light in color and reflect sunlight instead of absorbing it, which allows heat to escape. SPF applied to the roof of a home or building can provide cool roof performance when topped with a protective, reflective coating. Along with reducing air conditioning needs, spray foam helps protects the roof, potentially extending its lifetime.
Spray foam roofs also reduce thermal shorts or bridges. Traditional roofing materials must be nailed down or fastened to the roof deck with metal fastenings, creating a thermal short or bridge from the conditioned building interior to the outside roof deck, which can reach temperatures of up to 180 degrees in the summer. Spray foam roofing does not require metal fastening since the foam bonds directly to the roof deck in a continuous layer of insulation.
When having SPF insulation installed in your home or building, work with a professional contractor who can educate you on the installation process.


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