How much does insulation cost in 2026?
Insulation runs $1 to $5 per square foot installed in 2026 depending on type. Blown cellulose and fiberglass are the budget options; closed-cell spray foam is the highest-performance choice.
| Type | R-value | Material/sf | Installed/sf |
|---|
| Radiant barrier | radiant only | $0.10-$0.30 | $0.50-$1.50 |
| Blown fiberglass | R-2.5/in | $0.40-$0.80 | $1.00-$2.30 |
| Blown cellulose | R-3.5/in | $0.50-$1.00 | $1.00-$2.50 |
| Fiberglass batt (wall) | R-3.2/in | $0.40-$1.20 | $1.20-$2.70 |
| Fiberglass batt (attic) | R-3.2/in | $0.80-$2.00 | $1.80-$3.80 |
| Mineral wool (Rockwool) | R-4/in | $1.00-$2.20 | $2.20-$4.20 |
| Rigid foam board | R-5/in | $0.50-$2.00 | $1.50-$4.00 |
| Open-cell spray foam | R-3.5/in | $1.00-$1.80 | $1.50-$3.00 |
| Closed-cell spray foam | R-6.5/in | $2.00-$3.50 | $3.00-$5.50 |
Frequently asked questions
How much does insulation cost in 2026?
Fiberglass batts run $1.50-$3/sf installed. Blown cellulose $1-$2.50/sf. Spray foam open-cell $1.50-$3/sf, closed-cell $3-$5/sf. A 1,500 sf attic top-up to R-49 with cellulose runs $1,500-$3,750.
What R-value do I need?
DOE recommends R-30 to R-49 in attic floors for southern climates and R-49 to R-60 for northern climates. Walls: R-13 to R-21. Floors over crawl: R-19 to R-30. The IECC 2024 climate-zone map sets local code minimums.
Spray foam vs cellulose - which is better?
Closed-cell spray foam delivers the highest R-value per inch (R-6.5/in) and air-seals at the same time, but costs 2-3x cellulose. Cellulose is cheap, dense, and a great attic top-up. Spray foam shines in cathedral ceilings, rim joists, and crawl spaces where moisture matters.
Can I install insulation myself?
Batts and rigid foam are very DIY-friendly. Blown cellulose is doable with a rented blower (often free with material purchase from big-box). Spray foam should always be pro-installed (PPE + cure-time off-gassing).
Do I need a vapor barrier?
Cold climates (zone 5+) often want one on the warm side. Hot-humid (zone 1-2) avoid them — they trap moisture. Mixed climates use a smart vapor retarder (MemBrain). Consult IECC 2024 + IRC for your zone.
Why does the calculator show a price range?
Material brand, attic access, R-value target, prep work (rotted, vermiculite), and pro vs DIY swing the total 30-60%. A range gives an honest planning estimate.
