ABOUT SPRAY FOAM INSULATION
Spray polyurethane foam (SPF) is better than any other type of insulation at reducing air leakage.
With foamed-in-place insulation, it is relatively easy (though not inexpensive) to fill wall and ceiling cavities completely. Closed-cell spray foam provides a higher R-value per inch (6.5) than less expensive insulation types like cellulose and fiberglass (3.5 to 3.7).
Most spray polyurethane foam is called “two-component” foam. Two ingredients—conventionally called “A” and “B” components—are mixed on site using special equipment mounted in a trailer or truck. Heated hoses convey the components to a mixing gun that sprays the chemicals on the surfaces to be insulated.
A chemical reaction begins as soon as the chemicals are mixed. The liquid mixture foams, expands, and eventually hardens.