Insulation Cost Per Square Foot

Blown fiberglass attic (R-49): $1.55–$2.60 per sq ft. Blown cellulose attic (R-49): $1.60–$2.75. Fiberglass batts (walls, R-15): $1.10–$2.10. Mineral wool batts: $1.90–$3.20. Rigid foam board: $1.60–$3.40 per inch. Open-cell spray: $1.20–$2.20 per inch. Closed-cell spray: $1.75–$3.50 at 2 inches.

Blown cellulose: $0.55–$1.05 per sq ft at R-49. Fiberglass batts: $0.45–$1.15. Mineral wool: $1.05–$1.85. Rigid foam: $0.45–$1.30 per inch. Two-part foam kits: $0.85–$1.40 per board foot.

Attic access and headroom, whether old insulation must be removed, air sealing scope, roof pitch, number of penetrations, and the target R-value. Removal alone adds $1.00–$2.25 per sq ft.

Attic top-up on a 1,500 sq ft attic: $2,300–$3,900 installed. Full wall retrofit with dense-pack on a 2,000 sq ft home: $4,000–$8,500. Crawl space encapsulation with wall foam: $3,500–$9,000. Whole-house spray foam on new construction: $9,000–$22,000.