High-pressure systems can be used to spray all three types of spray polyurethane foam. Of the three types of spray foam used in building insulation and weatherization, the high-pressure, two-component spray foam is most likely to be used on larger projects such as a new building construction or renovations. SPF applied with a high-pressure system tends to adhere tightly to the entire structure which helps avoid sagging or detaching from its position. It can also provide a seal against air and insects.
For large jobs, professionals such as Dr. Energy Saver use two-part foam, which comes in larger containers. With 2-part spray foam, it's necessary to mix separate resin and catalyst compounds at the application nozzle. Combining these ingredients starts a chemical reaction that creates expanding foam. Contractors use small 2-part foam "kits" to air-seal an attic or to seal and insulate ductwork. To insulate an entire attic or wood-framed wall with spray foam, the resin and catalyst compounds are pumped to the application nozzle from 50-gallon drums in a specially equipped truck.