Attic Insulation: R-Value, Cost and Payback
Updated 2026-10-14. All figures were checked on that date.
Short answer: ENERGY STAR estimates that air sealing plus insulating attics, floors over crawl spaces and rim joists saves an average of 15% on heating and cooling (11% of total energy costs) (ENERGY STAR methodology, as of 2026-10-14). A typical pro attic job costs $1,700–$2,500, averaging $2,100 (Angi, as of 2026-10-14).
How much R-value do you need?
| Climate zone | Uninsulated attic | Attic with 3–4 in. already | Floor |
|---|---|---|---|
| 1 | R30 | R25 | R13 |
| 2 | R49 | R38 | R13 |
| 3 | R49 | R38 | R19 |
| 4A, 4B | R60 | R49 | R19 |
| 4C, 5, 6 | R60 | R49 | R30 |
| 7, 8 | R60 | R49 | R38 |
Source: ENERGY STAR recommended R-values (based on 2021 IECC), as of 2026-10-14.
Check what you have: fiberglass, cellulose and mineral wool give roughly R-3 to R-3.5 per inch, so inches × 3 ≈ your current R-value (ENERGY STAR). Six inches is about R-18, well short of R-49.
Installed cost by type
| Type | $/sq ft installed |
|---|---|
| Blown-in | $1–$4 |
| Batt | $2–$4 |
| Loose fill | $2–$5 |
| Spray foam | $2–$5 |
| Rigid board | $2–$5 |
| Reflective (radiant barrier) | $0.50–$2 |
Source: Angi, attic insulation cost, as of 2026-10-14. Also budget for air sealing ($250–$750) and old-insulation removal if needed ($1–$1.50/sq ft) (same source).
Payback calculator
Simple payback = cost ÷ (annual heating and cooling spend × savings %). The 15% default is ENERGY STAR's national average. Under-insulated homes in cold climates often do better, and already-insulated homes do worse. Subtract any utility rebate from the cost. For your annual spend, total 12 months of bills, or see our heating cost comparison.
DIY notes
- Air seal first: top plates, plumbing and wiring penetrations, the attic hatch. Insulation doesn't stop air leaks.
- Keep insulation clear of soffit vents (use baffles) and of non-IC-rated recessed lights and flues.
- Many big-box stores lend the blowing machine free with a minimum bag purchase. Check your local store.
- Older homes with vermiculite (grainy, gray-brown) insulation should have it tested for asbestos before anyone disturbs it.