Exterior
Attic Insulation Cost Calculator
The price on the bag is for R-19. Multiply it by your attic size and you will under-budget by about three times, because a bag of loose fill covers less than half as much floor at R-49 as it does at R-19. This works from the manufacturers’ own coverage charts.
What to order
- Blown fiberglass to R-49 31 bags
| Line item | Low | High |
|---|---|---|
| Blown fiberglass to R-49 39.9 sq ft a bag, blown to 17 in. | $1,300 | $1,900 |
| Blow the insulation in Two-person crew: one at the hose in the attic, one feeding the machine. | $290 | $615 |
| Set up and clean up Arriving, running the hose, moving the machine and clearing up. The published blowing rates cover blowing only, so this is reconciled from contractors’ own job durations rather than measured. | $120 | $425 |
| Permit Insulation is on no city’s exempt list, though small jobs are often waved through in practice. | $0 | $200 |
| Total | $1,700 | $3,150 |
Compare real quotes near you
This is a research estimate. Actual pricing depends on your site conditions, so get at least three quotes from licensed pros and ask each to itemize against the line items above — that is the fastest way to see why two bids differ.
What drives the price
The price on the shelf is an R-19 price
A bag of Owens Corning AttiCat is advertised at about 61 cents a square foot. That is $67.58 divided by 110.7 square feet — the R-19 row of the coverage chart printed on the bag. At R-49 the same bag covers 39.9 square feet, so it costs $1.69 a square foot. Greenfiber’s 33 cents a square foot is the same trick with cellulose: the R-19 row, adjusted for 2×6 framing, which is the most generous cell in its table. Multiply a shelf price by your attic area and you will be short by roughly three times. The coverage chart is not marketing — the FTC requires it on every bag under 16 CFR 460.12, which means you can check this yourself in the aisle.
Fiberglass or cellulose changes the bag count threefold
To reach R-49 over 1,200 square feet takes about 30 bags of blown fiberglass or about 86 bags of cellulose, because cellulose is a denser, heavier product sold in smaller effective coverage. It gets there in fewer inches — roughly 13 settled against 17 — which matters in a shallow attic near the eaves. Labour runs the other way: a blowing machine moves about four times the weight of cellulose an hour that it does fiberglass, so the bigger pile of cellulose goes in faster. Any bag count you read that does not name the product and the bag weight is guesswork.
The federal tax credit for insulation has ended
Most of what you will read still says you can claim 30 per cent of an insulation job, up to $1,200, under section 25C. That was true through 2025. ENERGY STAR now states the credit applied to products "purchased and installed between January 1, 2023, and December 31, 2025", and the IRS credit table stops at 2025 — the July 2025 law brought the expiry forward from 2032. Utility rebates are a different matter and some are generous: Jacksonville pays 20 cents a square foot up to $200, and Denver’s utility pays up to $400 for attic insulation on a gas-heated house. Ohio has had no general-population utility rebate since 2020.
What the code wants and what your house needs are two numbers
Energy codes set R-values for new construction, and adding insulation to an existing attic is not held to them — the 2021 code exempts cavities that are not exposed, and Ohio publishes a separate existing-building table at R-38 against R-49 for a new house. The Department of Energy’s recommendation for an existing attic is the more useful figure: roughly R-49 to R-60 across the northern half of the country and R-38 to R-49 in the south. Where you sit matters less than people expect. Houston and Jacksonville share a climate zone, yet Houston asks for R-49 and Florida for R-38, purely because Houston adopted a newer code.
Doing it yourself barely pays with fiberglass
Both big-box chains lend the blowing machine free with a ten-bag purchase, which makes an attic look like a cheap weekend. Run the numbers: 30 bags of AttiCat at retail is about $2,050 in material alone, while contractors in the same market publish installed prices of $1,560 to $3,120 for that attic. A contractor buys the same material below retail and blows it in a morning. Cellulose is the exception — at about $16 a bag it is genuinely cheaper to do yourself, if you can carry 86 bags up a ladder and keep the depth even.
Sources
- Owens Corning AttiCat and ProCat coverage charts; Johns Manville Climate Pro attic cards · current fact sheets, retrieved September 2026 The coverage chart every bag must carry under FTC rule 16 CFR 460.12. AttiCat covers 68.5 sq ft a bag at R-30 and 39.9 at R-49 — coverage nearly halves as the R-value rises, which is why a shelf price per square foot means nothing without the R-value beside it.
- Greenfiber SANCTUARY attic card; National Fiber loose-fill coverage chart · Greenfiber revision G; National Fiber chart retrieved September 2026 Cellulose covers 25.9 sq ft a bag at R-30 and 14.1 at R-49 — roughly three times as many bags as fiberglass, in about four fewer inches. The charts already allow for settling: the quoted R-value is the settled one.
- North Dakota Department of Commerce, Weatherization Assistance Program — Final Condensed Labor Study; Krendl 425 machine specification · state labor study, retrieved September 2026 Blowing time measured per pound: 0.002 worker-hours a pound for cellulose, 0.16–0.24 an bag for fiberglass. Those rates reconcile almost exactly with the rated throughput of a blowing machine at a two-person crew — which also confirms the crew size, and shows the figures cover blowing only, not hose runs and clean-up.
- Published price lists from 14 insulation contractors in Texas, Florida, Ohio and Colorado · retrieved September 2026 Installed attic insulation runs about $1.30–2.60 a square foot at R-49, and published hourly rates of $50–100 a worker set the markup used here. Minimum jobs run $1,000–2,000.
- Craftsman Book Company, 2026 National Home Improvement Estimator (free preview), demolition section; published contractor descriptions of vacuum-out work · 2026 edition; contractor pages retrieved September 2026 Pulling batts out by hand runs 0.003 laborer-hours a square foot. Vacuuming blown-in is slower and needs a machine: contractors describe eight to twelve worker-hours for a typical attic.
- Published price lists from US insulation contractors (FL, TX, OH, CO) · retrieved September 2026 Containment and HEPA setup $0.30–0.75 a square foot, disposal $100–400 a load, sanitising $150–350 where there is rodent contamination. Removal quotes cluster at $1–2 a square foot all in.
- Published price lists from insulation contractors in Texas, Ohio and Colorado · retrieved September 2026 Air sealing an attic is sold as a flat job: $200–600 and $300–800 from two Texas firms, $300–1,000 in Denver. Only one contractor prices it by the square foot, and that is for whole-attic work on its own.
- District of Columbia DOEE weatherization price list; GETCAP (Texas) weatherization bid sheet · DC price list 2021; GETCAP 2025–26 bid sheet Per-item prices from weatherization programmes: a recessed light cover at $25–45, a chimney dam at $64, hatch weatherstripping at $28. These are programme rates, so they sit at the low end of what a private contractor charges.
- Permit fee schedules and exempt-work lists: Houston, Jacksonville, Columbus and Denver · retrieved September 2026 None of the four cities lists insulation as exempt work, and fees span $65 in Denver to $385 in Columbus. Enforcement is another matter — an insulation-only job is often waved through, which is why the low end of the national range here is zero.
- U.S. Bureau of Labor Statistics, Occupational Employment and Wage Statistics · May 2025 Hourly wages by state: 25th percentile (low), median (typical), 75th percentile (high).
Frequently asked questions
How many bags of insulation do I need?
Divide your attic area by the coverage figure on the bag for the R-value you want — not the headline figure on the shelf label. At R-49, a 27.5 lb bag of blown fiberglass covers about 39.9 square feet and a 25 lb bag of cellulose about 14.1, so a 1,200 square foot attic takes roughly 30 bags of fiberglass or 86 of cellulose. The calculator above does this from the manufacturers’ charts and shows the depth to blow it to.
How deep should attic insulation be?
Depth depends on the material. Blown fiberglass needs about 17 inches for R-49 and 20.5 for R-60; cellulose reaches R-49 at about 14.3 inches blown, settling to 13.3. Those are the manufacturers’ minimum installed thicknesses, and they already allow for settling — the R-value quoted is the settled one. Measure with a ruler stapled to a truss rather than by eye.
Do I have to remove the old insulation first?
Usually not. New loose fill goes straight over old insulation and the R-values add up. Removal is for a real reason — rodent contamination, water damage, smoke, or wiring work that needs the attic floor clear. It costs $1 to $2 a square foot because it is slow, dirty work with a vacuum and a containment setup, so it is worth being sure you need it.
Fiberglass or cellulose?
Cellulose is made from recycled paper, packs denser, reaches a given R-value in fewer inches and blows in faster. Fiberglass does not absorb water, does not settle meaningfully and weighs less on a ceiling. Cost per square foot installed is close enough that neither wins on price alone at R-49. In a shallow attic where depth near the eaves is the constraint, cellulose has the edge.
Is there still a tax credit for insulation?
No. The 25C credit covered 30 per cent of insulation and air sealing materials up to $1,200 a year, but it applied only to products installed through December 31, 2025. A law passed in July 2025 ended it early — it had been due to run to 2032, which is why so many pages still describe it as available. Check your utility instead, and if your household income qualifies, the federal Weatherization Assistance Program does this work free.
Do I need a permit to insulate an attic?
Read literally, yes in all four cities researched here — insulation appears on none of their lists of exempt work, and Denver goes further and requires an inspection of the insulation before it is covered. In practice an insulation-only job is often waved through. Fees are small next to the job: about $119 in Houston, $385 in Columbus, $65 to $100 in Denver.
Costs by state
The same job as above, priced with each state's wages, material price level and permit fees.