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Attic Insulation Cost Calculator

Estimate attic insulation by area — with top-up vs. from-scratch pricing.

Quick answer

Blown-in attic insulation costs $1.50–$2.50 per sq ft for fiberglass, $1.75–$2.75 for cellulose, and $3.50–$6.00 for spray foam in 2026, installed — a 1,000 sq ft attic runs about $2,000 with blown fiberglass. Topping up existing insulation to R-38 costs about 40% less than a from-scratch job. The 25C tax credit expired at the end of 2025, so check your utility for 2026 rebates instead.

Calculator

sq ft

How it works

(Attic area × $/sq ft) × Existing-insulation factor, adjusted by Region = Total

Your attic floor area is multiplied by the 2026 installed rate — $2.00 blown fiberglass, $2.25 cellulose, $4.75 spray foam per square foot — times 1.0 for a from-scratch job or 0.6 for a top-up over existing insulation, then adjusted for your region.

Materials ≈ 40% · Labor ≈ 60%

Insulation material is the smaller share; blower labor, prep, baffles, and air-sealing carry the other 60%.

The low–high range follows each type's published installed band. The 25C credit expired Dec 31, 2025 — check your utility for 2026 rebates instead.

Worked example

1,000 sq ft attic, blown fiberglass, from scratch:

1,000 sq ft × $2.00 = $2,000

Materials (40%) = $800

Labor (60%) = $1,200

Range: $1,500 – $2,500

Budget around $2,000 for this project.

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Attic insulation is the highest-ROI project in home improvement — the EPA credits it with cutting heating and cooling costs up to 15%, and it routinely pays back in 2–4 years. It is also one of the cheapest projects per unit of comfort gained, which is why energy auditors recommend it before touching the HVAC.

The cost math is simple: attic square footage times a per-square-foot installed rate, adjusted for what is already up there. A top-up over existing insulation costs roughly 40% less than a from-scratch job — this calculator prices both.

How to measure an attic for the insulation cost calculator

  1. Measure the attic floor length × width in feet — the footprint you will insulate, not the roof slope.
  2. Check current depth with a ruler: fiberglass batts are ~3.5" (R-13), blown fills vary — under 10" total usually means a top-up pays.
  3. Note access: a full-size hatch or pull-down stairs is standard; scuttle-only access in a closet adds labor.
  4. Photograph the soffit vents — insulation must not block them, and baffles may be needed.

Attic insulation cost per square foot (2026 US average, installed)

Insulation typeLowMidHigh
Blown fiberglass — per sq ft$1.50$2.00$2.50
Blown cellulose — per sq ft$1.75$2.25$2.75
Spray foam — per sq ft$3.50$4.75$6.00
Top-up multiplier (existing insulation)—×0.6—
1,000 sq ft, fiberglass, from scratch$1,500$2,000$2,500

Blown or sprayed to DOE-recommended R-38, including prep and cleanup. Removal of old/damaged insulation is extra. Sources: energy.gov, angi.com, homeguide.com (2026).

Worked example: 1,000 sq ft attic, blown fiberglass

1,000 sq ft attic, blown fiberglass, no existing insulation, average-cost region:

  1. Attic area: 1,000 sq ft.
  2. Blown fiberglass rate: $2.00/sq ft; no existing insulation → ×1.0.
  3. Total: 1,000 × $2.00 = $2,000; region ×1.00 → $2,000.
  4. Materials (40%): $2,000 × 0.40 = $800. Labor (60%): $2,000 × 0.60 = $1,200.
  5. Range: 1,000 × $1.50 = $1,500 low; 1,000 × $2.50 = $2,500 high.

Total $2,000 — about $800 in materials and $1,200 in labor, with a realistic range of $1,500–$2,500.

Pro tips for insulation quotes

  • Air-seal first — caulk top plates and wire penetrations before insulating, or warm air bypasses the insulation entirely.
  • Don't block soffit vents — install baffles to keep airflow from eave to ridge.
  • Fall is the sweet spot: contractors discount 10–15% before the winter rush, and you feel the difference immediately.
  • Ask for the installed R-value in writing, not just inches — different materials need different depths for R-38.
  • Keep bath fans venting outside, not into the attic — moisture plus new insulation equals mold.

How to use the attic insulation cost calculator

Measure the attic footprint in square feet. Choose the insulation type: fiberglass for value, cellulose for green credentials, spray foam when air-sealing is the goal. Be honest about existing insulation — wet or moldy material must come out first. Set the region and read the range.

How attic insulation cost cost is calculated

The estimate multiplies the attic floor area by the 2026 installed rate — $2.00 blown fiberglass, $2.25 cellulose, $4.75 spray foam per square foot — times 1.0 for a from-scratch job or 0.6 for a top-up over existing insulation, then applies the region multiplier. Materials are about 40%; blower labor, prep, and air-sealing carry 60%.

What drives attic insulation cost cost the most?

Insulation type is the headline variable — spray foam costs 2–3x blown fiberglass. But the existing-insulation question moves the total nearly as much: a top-up skips prep labor and runs ~40% cheaper. Access difficulty (scuttle vs. full stairs), needed air-sealing, and baffle installation fill out the rest.

Attic Insulation Cost cost example

Insulating a 1,000 sq ft attic with blown fiberglass from scratch in an average-cost region estimates at $2,000 — about $800 in materials and $1,200 in labor, with a realistic range of $1,500 to $2,500.

Fiberglass vs. cellulose vs. spray foam

Blown fiberglass ($2.00/sq ft) is the default for a reason: cheapest installed, proven for decades, and DIY-friendly for top-ups. Blown cellulose ($2.25/sq ft) insulates slightly better per inch, uses recycled material, and settles less — worth the small premium for green-minded owners.

Spray foam ($4.75/sq ft) is a different product: it air-seals and insulates in one pass, hitting high R-values in thin roof decks where blown insulation can't fit. Pay for it when air-sealing is the problem (old leaky house, conditioned attic) — not as a blanket upgrade where fiberglass would do.

Frequently Asked Questions

How much does it cost to insulate an attic per square foot in 2026?+
Blown-in attic insulation costs $1.50–$2.50 per sq ft for fiberglass, $1.75–$2.75 for cellulose, and $3.50–$6.00 for spray foam in 2026, installed. A 1,000 sq ft attic runs about $2,000 with blown fiberglass — the most common choice.
Which attic insulation is best: fiberglass, cellulose, or spray foam?+
Fiberglass is cheapest and most common; cellulose (recycled paper) insulates slightly better per inch and is greener; spray foam wins on air-sealing and R-value per inch but costs 2–3x. For most attics, blown fiberglass or cellulose to R-38 is the value optimum.
How much cheaper is topping up existing insulation?+
About 40% less — topping up existing insulation to R-38 skips the air-sealing and prep labor of a from-scratch job. A 1,000 sq ft top-up runs roughly $1,200 versus $2,000 fresh. If existing insulation is wet, moldy, or vermiculite, remove it first.
Is there a tax credit for attic insulation in 2026?+
No — the 25C credit (30% of insulation and air sealing, up to $1,200 per year) ended for property placed in service after December 31, 2025. Work completed in 2025 can still be claimed on the 2025 return (IRS Form 5695). For 2026, many utilities still offer their own insulation rebates on top of contractor pricing.
What R-value should attic insulation be?+
R-38 (about 10–14 inches of blown insulation) is the Department of Energy recommendation for most US climate zones; R-49 for the coldest zones. More than that has sharply diminishing returns — the money is better spent on air sealing.

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