Foam type. Open-cell costs $0.44 to $0.65 per board foot installed; closed-cell runs $1.00 to $1.50. That gap adds up fast across a 1,500-square-foot attic.
Thickness. Closed-cell delivers R-7 per inch, so 2 inches gets you R-14. Open-cell is R-3.7 per inch, so you need close to 4 inches for the same value. More inches means more board feet, which means higher cost.
Area size. A 1,200-square-foot attic at 2-inch closed-cell is 2,400 board feet. Scale the area or the thickness and the number climbs steeply.
Access and prep. Tight rafter bays, old blown-in batts to remove, or ductwork in the way all add labor time and cost to the quote.
Condition of the space. Wet or moldy framing needs treatment before foam goes on. A clean, dry attic is faster and cheaper to spray.
Timing. Peak summer demand in Lake Charles can push lead times and prices up. Jobs scheduled in fall or early spring typically land faster and sometimes cheaper.