Blown-in insulation cost: attic insulation per square foot, by attic size and by state
A mid-size attic, 1,200 sq ft: about $3,900 to $4,800, typically $4,300. That's blown-in insulation 20 inches deep, R50, over the attic floor, plus the contractor's overhead, profit and sales tax. Everything in, it runs $3.25 to $4.00 a sq ft of attic. The 2021 energy code's ceiling minimum is R30 in climate zones 0 and 1, R49 in 2 and 3, and R60 in 4 through 8.
Anthony Hicks30+ years in construction. Updated November 5, 2026.
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What it costs
| Job | Cost |
|---|---|
| A small attic, 800 sq ft | $2,600 to $3,200 |
| A mid-size attic, 1,200 sq ft | $3,900 to $4,800 |
| A large attic, 1,800 sq ft | $5,800 to $7,200 |
About $3.25 to $4.00 a sq ft of attic, everything in.
Totals include the contractor's overhead and profit (20%) and the state's average sales tax. Prices as of November 2026.
What’s in these numbers
Each total is a typical job, priced the way a contractor’s estimate is priced:
- Blown-in insulation, 20 inches deep, R50, over the attic floor.
- Overhead and profit: 20%, the standard markup on a contractor’s estimate.
- Sales tax on the materials, at the state’s average rate.
The sizes are the attic floor’s square feet, about the same as the floor below it.
Not in them: removing old or damaged insulation, air sealing, baffles at the eaves, an attic hatch cover, and work around recessed lights.
How much the code calls for
The 2021 International Residential Code’s ceiling minimums by climate zone (Table N1102.1.3):
| Climate zone | Ceiling R-value |
|---|---|
| 0 and 1 | R30 |
| 2 and 3 | R49 |
| 4 through 8 | R60 |
The figures here are R50. States adopt the energy code in different editions and amend it; the local building department says which applies.
Keep the vents open
Where the attic is vented at the eaves, insulation can’t block the free flow of air, and the code calls for at least 1 inch of space between the insulation and the roof sheathing at the vent (IRC R806.3). Baffles hold the insulation back. The guide to roof vents covers how much venting an attic needs.
What moves the price
- Depth. Each step in R-value takes more inches of insulation.
- What’s there now. Old, wet or rodent-damaged insulation is removed first.
- The material. Fiberglass and cellulose reach different R-values at the same depth.
- Access. Low or crowded attics are slower to work in.
- Where you live. Pick your state in the box above.
For foam sprayed under the roof deck instead, the spray foam insulation cost guide prices it by the square foot.
Common questions
How much does it cost to blow insulation into an attic?
About $3,900 to $4,800 for a 1,200 sq ft attic to R50, typically $4,300.
What does blown-in insulation cost per square foot?
$3.25 to $4.00 a sq ft of attic of attic for R50, with overhead, profit and sales tax.
How much insulation should an attic have?
The 2021 code’s minimum is R30, R49 or R60 depending on the climate zone. The bag’s coverage chart gives the depth for each R-value.