Cost per square foot by material
Installed cost per square foot
At R-30. Bars show the typical range, so overlap is visible.
- $0.90–$2.10
- $1.05–$2.05
- $1.05–$2.10
- $1.35–$2.25
- $1.80–$3.20
- $3.00–$4.50
$0.00/sq ft$1.20/sq ft$2.40/sq ft$3.60/sq ft$4.80/sq ft
| Material | DIY material | Installed | DIY friendly? |
|---|---|---|---|
| Blown cellulose | $0.30–$0.48 | $1.05–$2.10 | Yes |
| Blown fiberglass | $0.33–$0.54 | $1.05–$2.05 | Yes |
| Fiberglass batts | $0.39–$0.72 | $0.90–$2.10 | Yes |
| Mineral wool | $0.84–$1.35 | $1.80–$3.20 | Yes |
| Open-cell foam | — | $1.35–$2.25 | No |
| Closed-cell foam | — | $3.00–$4.50 | No |
At R-30. Cost scales with R-value, so an R-60 attic costs roughly double these figures per square foot.
Cost by part of the house
| Project | Typical installed | Notes |
|---|---|---|
| Attic | $900–$2,800 | Best return of any insulation project |
| Crawl space | $1,500–$4,500 | Encapsulation costs more but solves moisture too |
| Walls (existing, dense-pack) | $1.50–$3.50 / sq ft | Drilled and filled from outside or in |
| Garage ceiling | $600–$1,800 | Only worth it with conditioned space above |
| Basement walls | $1,800–$5,000 | Usually rigid board or closed-cell foam |
What a professional quote should include
Quotes vary wildly partly because they cover different scopes. Before comparing numbers, confirm each one includes:
- Air sealing — often excluded, and it's the part that matters most
- Rafter baffles — required with blown insulation to keep soffit vents clear
- Attic hatch insulation — routinely forgotten
- Recessed light covers — needed where fixtures aren't IC-rated
- Target R-value in writing, not just "we'll top it up"
- Cleanup and disposal
A quote that's 30% cheaper but omits air sealing and baffles isn't cheaper — it's a different job.
Where the money goes furthest
In rough order of return per dollar for most houses:
- Air sealing the attic floor. Cheapest meaningful improvement available, almost always.
- Attic insulation to the recommended level. Straightforward, and material is cheap because depth is unconstrained.
- Crawl space or basement. Especially where floors are cold or humidity is a problem.
- Rim joists. Small area, disproportionate leakage. Good use of a spray foam kit.
- Existing walls. Real improvement but far more invasive and expensive per unit of benefit.
If your attic is already at the recommended R-value, adding more is near the bottom of that list, not the top. Diminishing returnsare steep.