Spray foam can be used as an insulating and air sealing product for residential wall and ceiling cavities. The insulation is sprayed, via special equipment, into wall cavities and expands to fill all the nooks and crannies in a wall cavity. Excess foam is scraped off the studs to form a uniform wall cavity. Spray foam insulation makes it easy to completely fill wall cavities with insulation and to perform air sealing in the same step.

There are two types of spray foam: open-cell (isocyanurate) and closed cell (polyurethane). The closed cell foams typically have a higher R-value than open-cell foam.

Sprayed foam insulation is applied as a liquid which contains a polymer (such as polyurethane or modified urethane) and a foaming agent. The liquid is sprayed through a nozzle into wall, ceiling, and floor cavities where it expands to fill every nook and cranny. Because it expands into tight areas, sprayed foam is ideal for insulating steel framing and around outlets. By acting as a wind and air barrier, it often eliminates the need for separate air-tightness detailing which can increase energy efficiency and allow downsizing of the heating and cooling system equipment. Sprayed foam insulation does not shrink, sag, settle, or biodegrade.