The average cost of foam board insulation is between $2.40 and $3.75 per square foot. Spray Foam Spray foam insulation, like blown-in, is great for adding insulation to existing finished areas and ...

A board foot is 144 cubic inches. With this unit as the standard to go by, open cell spray foam insulation costs between $0.45 and $0.65 per board foot. Closed-cell spray foam is more expensive ...