Spray foam building insulation is a polyurethane foam that expands and hardens to fill gaps. Spray foam is a chemical product created by two materials, isocyanate and polyol resin that reacts when mixed with each other and expand up to 30 to 60 times its liquid volume after it is sprayed in place. For large insulating jobs, professionals spray this insulation into place with special equipment. For small sealing jobs, spray foam is available in spray cans. 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 is also an informal term used to refer to various plastic foam materials that are used in building construction to provide thermal insulation and minimize air infiltration. Polyurethane and polyisocyanurate are two types of foam used in this application. 

Benefits of Spray Foam Insulation

• Best for hard-to-reach or oddly shaped areas and already insulated areas. 

• Can be used to fill small gaps and cracks or to insulate large spaces. 

• Ideal for sealing around doors, windows and vents. 

• Sets quickly and can be trimmed, painted or stained. 

• Has two types: open-cell foam and closed-cell foam.

• Closed-cell foam is denser and thus has a higher R-value.

• Closed-cell foam is usually more expensive than open-cell foam.

• Open-cell foam has an approximate R-value of R-3.7 per inch of thickness. 

• Closed-cell foam has an approximate R-value of R-6.2 per inch of thickness.

• Sheathing reduces heat conduction through structural elements like wood and steel studs. 

• Great insulation choice for cold climates. 

• DIY-friendly. Typically more expensive per square foot than other insulations.

• R-values range from R-4 to R-6.5 per inch of thickness.

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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.
Open cell spray polyurethane foam insulation being applied in wall cavities. Open cell insulation can be crushed in your hand and has a lower insulation value. Closed cell is rigid to the touch and each air cell is completely sealed. While closed cell foam has a higher R-value, it is more costly to buy.