Can I use urethane to insulate an existing home?

Spray polyurethane insulation is used primarily to insulate new homes. This is because spray polyurethane must be applied to an open cavity. When spray polyurethane is injected into a closed wall cavity, the pressure of the expanding insulation may damage the wall. Consider insulating an existing home with spray polyurethane when you’re replacing the exterior siding or doing other major remodeling.