How much does it cost to insulate an attic?

Insulating a 1,500 sqft attic to current R-49 code costs $1,800–$4,500 in 2026, depending on existing insulation depth and the type added. Blown-in cellulose runs $1.00–$1.80/sqft; blown-in fiberglass $1.20–$2.00/sqft; spray foam $3.50–$7.00/sqft. The federal 25C credit (30% up to $1,200/year) expired Dec 31, 2025 — utility rebates of $200–$1,500 remain in most states. Payback is 1–4 years on heating-dominant homes — the fastest of any energy upgrade.