Attic Insulation Cost Calculator
| Attic (1,200 sq ft) | Band | Mid |
|---|---|---|
| Blown fiberglass | $1,800-3,600 | $2,700 |
| Blown cellulose | $1,800-4,200 | $3,000 |
| Fiberglass batts | $1,200-3,000 | $2,100 |
| Spray foam | $4,200-9,000 | $6,600 |
Attic insulation is priced by the square foot of floor and the material in it: blown fiberglass runs $1.50-3.00 per square foot installed, blown cellulose $1.50-3.50, fiberglass batts $1.00-2.50, and spray foam $3.50-7.50. A 1,200 square foot attic lands mid-band near $2,700 in blown fiberglass, $3,000 in cellulose, and $6,600 in spray foam.
The R-value target drives the depth: cold-climate zones want R-49 to R-60 in the attic floor, which is roughly 17-22 inches of loose-fill fiberglass or 14-18 inches of cellulose. Most existing homes under-insulated decades ago are sitting at R-19 or less - the top-up is where the math sings, because the first inches of insulation save more energy than the last.
The order that decides everything: air-seal first, insulate second. Insulation slows air movement but does not stop it - warm house air escapes through every top plate, wire hole and attic hatch unless they are sealed, and the ENERGY STAR program's whole attic protocol is built on that sequence. A $300 sealing pass is the difference between an insulation job and an insulation photo.
How to use
- Measure the attic floor area (length times width of the footprint) - most homes run 800 to 1,600 square feet.
- Pick the material honestly: blown cellulose or fiberglass for the standard top-up, batts for clean open bays, spray foam only where you want to condition the attic itself.
- Check your current depth with a ruler - 6 inches or less means you are in the top-up sweet spot where every added inch pays visibly.
- Get the air-sealing scope priced into the bid (top plates, wire holes, hatch), then compare the total against two installers with the R-value target in writing.
Frequently asked questions
How much does attic insulation cost?
For a 1,200 square foot attic: blown fiberglass lands mid-band near $2,700 installed, blown cellulose near $3,000, fiberglass batts near $2,100, and spray foam near $6,600. Bands run roughly 70-130 percent of mid depending on access, existing removal and depth target - and attic hatch, vents and air-sealing are the line items to see in writing.
What R-value should my attic be?
Cold zones (zones 5-7) target R-49 to R-60 in the attic floor; mixed zones R-38 to R-49; hot southern zones R-30 to R-38 where the goal shifts to keeping heat out. In depth terms that is 14-22 inches of loose fill depending on material - cellulose delivers about R-3.5 per inch, blown fiberglass about R-2.9. A ruler and a tape measure settle it in five minutes.
Is blown-in or batts better for attics?
Blown wins for attics almost always: loose fill flows around wires, joints and irregular framing where batts leave comfort-robbing gaps, and it tops up existing insulation cleanly. Batts make sense in wide-open new construction bays. Spray foam is a different product - it air-seals and insulates at once and is priced like it, usually only rational when conditioning the attic space itself.
How long does attic insulation pay back?
A top-up from R-19 to R-49 in a cold-climate home commonly trims 15-20 percent off heating and cooling combined - on a $2,000 annual energy bill, $300-400 a year against a $3,000 job: a 7-10 year payback, faster with rebates. The payback calculator on this site runs your exact numbers; the honest caveat is that the air-sealing half of the job carries most of the early savings.
Can I DIY attic insulation?
Yes, and blown-in is the DIY-friendly version: equipment rental runs $30-70 a day at box stores (often free with a bag minimum), and a two-person crew does 1,000 square feet in an afternoon. The catch is the prep - baffles at the eaves, the dam around the hatch, and the air-sealing underneath are where DIY jobs quietly underperform. Wear the respirator; loose fill in lungs is a lifetime souvenir.