Blown-in attic insulation runs $1.50 to $3.50 per square foot installed by a pro, so a 1,200-square-foot attic typically lands between $1,800 and $4,200 with air-sealing included. Doing it yourself with a rented blower cuts that to roughly $0.70 to $1.20 per square foot. Of everything on the energy-upgrade menu, this has the cleanest math.
What You’re Buying
Blown-in means loose-fill fiberglass or cellulose, pneumatically blown over the attic floor to a target depth. It fills gaps and irregular joist bays that batts handle badly, which is why it’s the default for topping up older attics. Fiberglass delivers roughly R-2.5 per inch. Cellulose delivers roughly R-3.5 per inch and settles into a denser blanket, which makes it our default pick for retrofits.
| Cost component | Typical range | Notes |
|---|---|---|
| Loose-fill material | $0.50 - $1.00 per sq ft | Covers a typical R-19 to R-49 top-up |
| Pro labor and blower | $0.60 - $1.50 per sq ft | Varies by region and attic access |
| Air-sealing package | $300 - $800 per attic | The line item to insist on |
| Vent baffles at eaves | $2 - $5 each | Keeps soffit airflow open under new fill |
| Insulated hatch cover | $60 - $300 | Leaks like an open window if skipped |
| Old insulation removal | $1,000 - $2,500 | Only if wet, moldy, or contaminated |
Anchor on the two headline numbers: $1.50 to $3.50 per square foot installed all-in, or $0.70 to $1.20 DIY. If a quote lands far outside that band, ask what’s in it.
R-Value Targets by Climate, Simply
R-value measures resistance to heat flow. Here are the attic targets by standard climate zone: hot southern regions like Florida and south Texas aim for R-38 to R-49; the mixed middle of the country aims for R-38 to R-60; cold northern and mountain zones aim for R-49 to R-60, with R-60 worth paying for only in the coldest spots.
Translated to depth: cellulose at about R-3.5 per inch means R-49 is roughly 14 inches and R-60 is about 17. If your attic shows 6 inches of settled gray insulation, you’re near R-19 to R-21, and you’re likely 8 to 11 inches short of target. A tape measure in the attic tells you this in two minutes. Above R-60, returns diminish hard; below R-30, every added inch works at full value, which is why topping up beats starting over.
Air-Seal First: The Cheap Part Everyone Skips
Before any insulation goes down, the attic floor needs sealing. Every hole drilled for wire and pipe, every top plate where the drywall meets framing, bath fan housings, the chimney chase, and the hatch itself are the actual leaks. Warm air rises, and in winter a typical attic floor has dozens of one- and two-inch holes pumping heated air straight into the attic.
Air-sealing costs $300 to $800 professionally, or one weekend and $50 to $150 in fire-rated foam, caulk, and metal flashing if you do it yourself. Skip it and you’ll understand the complaint we hear constantly: “we blew in a foot of insulation and barely felt a difference.” Fluffy insulation slows air, but it doesn’t stop it. Sealing stops the air movement so the blanket on top can do its thermal job.
Two safety notes before anyone seals or blows. Old recessed lights need clearance or rated covers unless they’re IC-rated, and any knob-and-tube wiring must stay exposed and get inspected first. And bath fan ducts must run to a roof or gable vent, never end under where the new fill will sit.
Three Real-World Scenarios
1,200 sq ft ranch, Chicago, currently R-19. Target R-49, so about 8.5 more inches of cellulose. Material $850, pro labor and machine $1,100, air-sealing $500, baffles and hatch cover $300. Total: $2,750. The DIY version runs about $950 in bags plus $100 to $150 of sealing foam and caulk, so roughly $1,100 with the free loaner blower from the big-box store, plus a weekend and one itchy helper.
2,000 sq ft two-story, Atlanta, currently R-30 fiberglass. Topping up about 6 inches of blown fiberglass to approach R-49, with lighter air-sealing since the house is newer. Materials $900, labor $1,300, air-sealing $400, extras $250. Total: $2,850. In a hot climate this purchase trims cooling costs and, more noticeably, takes the furnace-of-an-upstairs feeling out of the bedrooms in August.
1,500 sq ft cape, Minneapolis, half-insulated at R-13 with ice dam history. Air-sealing is the star of this job: $700 of careful sealing at the eaves and top plates, vent chutes in every rafter bay, then 10 inches of cellulose across the whole floor. Materials $1,300, labor $1,400, extras $400. Total: $3,800. Here the sealing and venting matter more than the final R-value, because ice dams come from warm air leaking into a cold attic, not from cold weather itself.
The Payback Math
Here’s the physics, and you can check it. Heat flow through a surface scales inversely with R-value, so going from R-19 to R-49 cuts heat passing through the ceiling to about 39 percent of what it was, a 61 percent reduction on that surface alone. The ceiling typically accounts for 10 to 20 percent of a home’s heating-and-cooling load, so insulation alone recovers roughly 6 to 12 percent at the whole-house level. Air-sealing pushes the combined saving toward the 15 percent the EPA Energy Star program has long cited for this work.
Put dollars on it. A house spending $2,400 a year on heating and cooling in a cold climate, trimmed 15 percent, saves about $360 a year. Against the $2,750 pro job, that’s an eight-year payback on a product that lasts as long as the house. Against the $1,100 DIY version, it’s a three-year payback. In a mild climate with a $1,200 annual bill and a 12 percent saving, the same pro job takes closer to nineteen years, which is why hot-climate owners should still do it, just with honest expectations.
One note on incentives: the federal tax credit for insulation (Section 25C) expired on December 31, 2025, so ignore any article or sales pitch still promising 30 percent back. What survives are state and utility programs, and many utilities pay flat or per-square-foot rebates for attic upgrades. Check dsire.org and your electric or gas utility’s efficiency page before booking; a good rebate can move the payback math by years.
Insulation vs. Windows: Where the Dollar Works Harder
People reach for new windows when they feel drafts, and often the attic is the cheaper, better fix. A full window replacement commonly runs $8,000 to $20,000 with modest savings, while insulation plus air-sealing at $2,000 to $4,000 usually cuts more energy, because heat rises and the attic is where it leaves. Those first-floor drafts are often stack effect at work: warm air escaping the attic pulls cold air in through the bottom of the house, and sealing the top is what actually stops it.
We cover the window side in detail in when new windows actually save money, and the thermostat half of the equation in what a smart thermostat really saves. The order we’d spend in: insulation and air-sealing first, thermostat second, windows when they’re rotten or single-pane.
How to Pay Less
- Do the air-sealing yourself even if you hire the blowing. Sealing is a $100 material job and a Saturday; paying for it adds $300 to $800.
- Check dsire.org and your utility before you book. Rebates for attic work are common and change often, and some require using a listed contractor, which is worth knowing before you price the job.
- Borrow the blower for free. Big-box stores commonly lend the machine with a minimum bag purchase, which removes the $100-plus daily rental from the DIY math.
- Get two pro bids even if you plan to DIY. If the pro bid is close to your materials cost after the rebate, the decision writes itself.
Mistakes That Cost Homeowners Money
- Blowing insulation without air-sealing. You pay twice: once for performance that never shows up, and again later when someone has to move the fill to seal properly.
- Burying the soffit vents. Without baffles, new insulation dams against the eaves and shuts off intake air, which invites moisture and ice dams. Baffles cost a few dollars each.
- Leaving bath fan ducts dumping under the fill. Warm moist air into cold insulation means condensation, mildew, and stained ceilings within a season or two.
- Misreading the old insulation’s depth. Settled fiberglass reads thinner than its rated value. Measure and use settled R-values, or you’ll undershoot the target without noticing.
Bottom Line
Plan on $1.50 to $3.50 per square foot installed, or roughly half that if you’ll spend a weekend with a borrowed blower. Insist on air-sealing first, hit R-49 to R-60 in heating country, and check dsire.org and your utility for rebates since the federal credit is gone. In a cold climate this remains the best dollar-for-dollar energy upgrade on the menu, with payback measured in a few years, not decades.
FAQ
How many inches of blown-in insulation do I need?
Fourteen inches of cellulose gets you to about R-49, and seventeen gets you to R-60. Blown fiberglass runs about R-2.5 per inch, so the same targets need 20 to 24 inches. Measure what’s already up there and subtract.
Can I put new insulation over old insulation?
Yes, almost always, as long as the old material is dry and free of mold, and it’s not vermiculite, which in some older homes contains asbestos. Loose-fill over batts, or fill over fill, works fine. Test vermiculite before disturbing it; full removal is the exception, not the rule.
Is cellulose or fiberglass better for attics?
Cellulose performs slightly better per inch, settles less, and usually costs a bit less, which is why we default to it for retrofits. Fiberglass is lighter and doesn’t hold moisture if a roof leak happens. Honestly, either installed to the right depth beats the difference between them. Depth and air-sealing matter far more than what’s printed on the bag.
Should I do this myself or hire it out?
DIY makes sense on simple single-story attics with decent access: expect $0.70 to $1.20 per square foot and a weekend with a borrowed blower. Hire it out for tight or two-story attics, for air-sealing, or whenever ice dams, old wiring, or suspected vermiculite are in the picture.