An under-insulated attic is one of the most expensive rooms in the house — you just pay for it through the heating and cooling bills instead of at the register. Adding insulation is also one of the few projects where the material is cheap, the math is simple, and the payback starts the first cold night. This guide prices attic insulation per square foot of attic floor, by material, so you can budget a top-up or a full install.
Prices are per square foot of attic floor area. Measure the attic’s length × width; the calculator below works from that same area and your target R-value.
Attic insulation cost per square foot
Typical US prices, checked November 2026. Depth is what you are really buying — the same material costs more per square foot as the target R-value rises, so these ranges assume a typical top-up to modern levels (about R-38).
| Cost item | Typical cost per sq ft |
|---|---|
| Blown-in fiberglass or cellulose, professionally installed | $1.10 – $2.30 |
| Fiberglass batts, professionally installed | $1.40 – $2.80 |
| Materials only, DIY blown-in | $0.45 – $1.00 |
| Materials only, DIY batts | $0.55 – $1.10 |
Spray foam is the outlier: professionally applied attic foam commonly runs $3.50 – $7.00 per sq ft and is priced as an air-sealing system as much as an insulation. It sits outside the ranges above and outside what most attics need.
How much insulation do you need? R-value, depth, and bags
Insulation is sold by R-value — resistance to heat flow. The US Department of Energy recommends roughly R-38 for attics in mild climates and R-49 to R-60 where winters are cold. Material piles up at different rates, so the depth and bag count for the same R-value differ:
| Target R-value | Blown fiberglass depth | Blown cellulose depth | Bags per 1,000 sq ft (approx.) |
|---|---|---|---|
| R-30 | 10 – 12 in | 8 – 9 in | 15 – 47 |
| R-38 | 13 – 15 in | 10 – 11 in | 20 – 61 |
| R-49 | 16 – 19 in | 13 – 14 in | 26 – 84 |
| R-60 | 20 – 22 in | 16 – 17 in | 33 – 46 |
Bag counts are approximate — every brand prints a coverage chart on the bag, and that chart is the final word for the product in your hands. If you are topping up existing insulation, its R-value counts: a settled R-19 layer plus R-19 of new material gets you to about R-38.
Total cost by attic size
| Attic floor area | DIY materials only (blown-in) | Professionally installed (blown-in) |
|---|---|---|
| 500 sq ft (small ranch) | $225 – $500 | $550 – $1,150 |
| 1,000 sq ft (typical single story) | $450 – $1,000 | $1,100 – $2,300 |
| 1,500 sq ft (large or two-story footprint) | $675 – $1,500 | $1,650 – $3,450 |
What changes the cost
- Target R-value. Going from R-38 to R-60 adds roughly half again as much material. In cold climates the extra depth usually pays for itself; in mild ones it often does not.
- Existing insulation. Topping up is the cheapest path. Removing old, damaged, or contaminated insulation first commonly adds $0.50 – $1.50 per sq ft including disposal.
- Air sealing. Sealing top plates, wire holes, and the attic hatch before insulating is unglamorous and highly effective. Pros often bundle it; as a line item it adds a few hundred dollars on a typical attic.
- Access and baffles. Tight hatches, low slopes, and ductwork slow the job. Soffit baffles to keep ventilation channels open add a small material cost per rafter bay.
- Material choice. Cellulose is denser, settles the air-leak penalty a bit better, and is often the cheapest blown option; fiberglass batts cost more in labor because every joist bay is fitted by hand.
DIY vs hiring an insulation contractor
Blown-in insulation is one of the best DIY bargains in home improvement: home centers commonly rent the blower free or cheap with a minimum bag purchase, and a two-person team (one feeding the hopper, one on the hose) can cover 1,000 sq ft in a few hours. Your cost lands at the materials-only range above. Batts are slower but need no machine.
Hire it out when the attic access is poor, when old insulation has to come out, or when you want air sealing and depth verified as part of the job. A pro crew also finishes in hours, not a weekend, and their per-square-foot price already includes the machine, the setup, and the cleanup.
Calculate your project
The Insulation Calculator turns your attic area and target R-value into a depth, a bag count, and a material estimate — run it here with your measurements:
FAQ
How much can attic insulation save on heating bills?
The US EPA estimates that air sealing and adding insulation in an under-insulated home can save around 15% on heating and cooling costs on average. The worse your starting point — many older homes sit at R-11 to R-19 — the bigger the winter difference tends to be, in both the bill and how evenly rooms hold temperature.
When is the best time of year to insulate an attic?
Late fall, before sustained cold arrives, is the sweet spot: you capture the whole heating season’s savings, and attics are still tolerable to work in. Spring is second best. Mid-summer attic work is genuinely hazardous in hot climates, and mid-winter installs mean the first weeks of savings are already gone.
What R-value should my attic have?
As a rule of thumb: about R-38 in mild climates, R-49 in cold ones, and up to R-60 in the coldest northern zones. Check your existing depth first — fiberglass batts are roughly R-3 per inch and blown materials less, so a ruler in the attic tells you where you stand.
Can I just add new insulation on top of old?
Usually yes, and it is the standard approach, as long as the old layer is dry and not moldy or pest-damaged. Never compress the new layer to fit — squashed insulation loses R-value. If the old material is wet or contaminated, removal comes first.
Does attic insulation help with ice dams?
It helps a lot. Ice dams form when heat escaping through the ceiling melts roof snow unevenly. Better insulation plus air sealing keeps the roof deck colder and more uniform, which attacks the cause rather than the symptom.
Related guides and calculators
Start with the area: the Square Footage Calculator measures your attic floor from room dimensions. For another winter-season project with a fast payback, the Interior Paint Cost per Square Foot (2026 Guide) prices a room refresh, and all of our pricing guides are collected on the Cost Guides page.
Estimates only. Prices are typical US ranges checked in November 2026 and vary by region, target R-value, and contractor. Bag coverage figures are approximate — follow the coverage chart printed on the product you buy, and get written quotes before committing to a project.