Blown-in insulation costs about $0.84 to $2.40 per square foot installed across R-38 to R-60, per HomeGuide’s cost guide, or roughly $1,100 to $1,900 to bring a 1,000 square foot attic floor to R-49. Loose fiberglass or cellulose is machine-blown across the attic floor to a target R-value, usually R-38 to R-60 depending on climate zone. A confident DIYer can cut the cash cost to about $1,010 to $1,130 in bags at R-49, with the blower often free, but the trade-off is coverage consistency, air sealing, and getting the ventilation baffles right so the new insulation does not choke your roof.
This guide breaks down 2026 pricing, R-value math by material from current manufacturer coverage charts, the DIY-versus-pro decision, and the one thing most cost guides skip: how blown-in insulation interacts with your roof deck and attic ventilation. Get that part wrong and you trade a lower energy bill for a moisture problem.
How much does blown-in insulation cost in 2026?
Blown-in attic insulation runs $0.84 to $1.50 per square foot installed at R-38, $1.10 to $1.90 at R-49 and $1.40 to $2.40 at R-60, per HomeGuide. Price swings with material, target R-value, attic access, and whether the crew also air-seals and adds ventilation baffles before blowing.
Fiberglass and cellulose are the two common materials. A cellulose bag costs less than a fiberglass bag, but you need more of them, so in October 2026 retail listings cellulose ran slightly more per square foot at the same R-value. Fiberglass resists moisture better. The table below shows the raw material cost if you buy bags yourself, worked from each manufacturer’s coverage chart.
| Material | Material only / sq ft at R-38 | Material only / sq ft at R-49 | R-value per inch |
|---|---|---|---|
| Blown fiberglass (Owens Corning AttiCat, $40.34 per bag) | About $0.77 | About $1.01 | About R-2.8 to R-2.9 |
| Blown cellulose (Greenfiber SANCTUARY, $15.97 per bag) | About $0.84 | About $1.13 | About R-3.7 |
Sources: Owens Corning AttiCat product data sheet, Pub. No. 10011273-L (May 2026); Greenfiber SANCTUARY attic coverage chart; Home Depot (AttiCat) and Lowe’s (SANCTUARY) prices checked October 2026. Cost per sq ft is Roofing Brief arithmetic: bag price times bags per 1,000 sq ft, divided by 1,000. Prices vary by store, region and week.
Attic size drives the total. The next table estimates installed cost to reach R-49, a common target across much of the country, using HomeGuide’s R-49 range of $1.10 to $1.90 per square foot.
| Attic floor area | Typical installed cost (R-49) |
|---|---|
| 500 sq ft | $550 to $950 |
| 1,000 sq ft | $1,100 to $1,900 |
| 1,500 sq ft | $1,650 to $2,850 |
| 2,000 sq ft | $2,200 to $3,800 |
What R-value do you need, and how thick is that?
ENERGY STAR’s retrofit table, based on the 2021 IECC, recommends R-30 for an uninsulated attic in zone 1, R-49 in zones 2 and 3, and R-60 in zones 4 through 8. If the attic already has 3 to 4 inches, it recommends adding R-25, R-38 and R-49 for the same zones. R-value measures resistance to heat flow, so higher is better in both winter and summer, and many local codes set a minimum for insulation work that requires a permit.
R-value converts to a physical depth based on the material. Because fiberglass and cellulose deliver different R per inch, the same R-49 target lands at different fill depths. Follow the bag chart: cellulose is blown to an initial installed thickness that settles to the rated depth, while the AttiCat chart lists the same figure for installed and settled thickness.
| Target R-value | Fiberglass depth (AttiCat) | Cellulose depth, installed / settled (SANCTUARY) | ENERGY STAR use |
|---|---|---|---|
| R-38 | 13.5 in | 11.2 in / 10.4 in | Adding to 3 to 4 in, zones 2 to 3 |
| R-49 | 17 in | 14.3 in / 13.3 in | Uninsulated, zones 2 to 3; adding, zones 4 to 8 |
| R-60 | 20.5 in | 17.3 in / 16.1 in | Uninsulated, zones 4 to 8 |
Sources: Owens Corning AttiCat data sheet (May 2026); Greenfiber SANCTUARY coverage chart; ENERGY STAR, Recommended Home Insulation R-Values. Other brands publish different depths, so use the chart on the bag you buy.
How many bags of blown-in insulation do you need?
Bag count depends on your square footage and target R-value, because coverage per bag drops sharply as depth rises. One bag of Owens Corning AttiCat covers at most 39.9 square feet at R-49 and 31.8 square feet at R-60, per its May 2026 data sheet. Every bag prints a coverage chart on the label, so use that number for your exact product rather than a generic estimate.
To size a job, divide attic square footage by the maximum coverage per bag at your target R-value, or multiply by the chart’s minimum bags per 1,000 square feet. The chart is a minimum, so round up, and buy a few extra bags for fill around ducts and HVAC equipment if your store accepts returns.
| Target R-value | AttiCat max coverage / bag | AttiCat bags per 1,000 sq ft |
|---|---|---|
| R-13 | 169.8 sq ft | 5.9 |
| R-19 | 110.7 sq ft | 9 |
| R-30 | 68.5 sq ft | 14.6 |
| R-38 | 52.6 sq ft | 19 |
| R-49 | 39.9 sq ft | 25 |
| R-60 | 31.8 sq ft | 31.5 |
Source: Owens Corning AttiCat PINK Blown-In Insulation product data sheet, Pub. No. 10011273-L (May 2026), 27.5 lb nominal bag.
Example: a 1,000 square foot attic at R-49 needs at least 25 AttiCat bags. The same attic in Greenfiber SANCTUARY cellulose needs at least 68.5 bags at R-49 on Greenfiber’s chart (14.6 sq ft per bag, adjusted for 2×6 framing on 16-inch centers), because each cellulose bag weighs 25 lb and cellulose is denser.
Fiberglass vs cellulose: which blown-in material is better?
Fiberglass and cellulose both work well; the right pick depends on moisture, budget, and fill needs. Fiberglass does not absorb moisture (ASTM C1104), and the AttiCat chart lists no settling allowance, which suits humid or leak-prone attics. Cellulose packs denser and fills around wires and obstructions well, but it can absorb water, and Greenfiber rates its settled thickness at 90 percent of installed, so an under-filled job ends up short of target. For bag counts, rental terms and depth on the most common fiberglass product, see our Owens Corning AttiCat review.
| Factor | Blown fiberglass | Blown cellulose |
|---|---|---|
| R-value per inch | About R-2.8 to R-2.9 (AttiCat) | About R-3.7 (SANCTUARY) |
| Moisture behavior | Does not absorb water | Absorbs water, risks mold if wet |
| Settling | None listed on AttiCat chart | Settled is 90% of installed (about 10%) |
| Fill around obstructions | Good | Excellent |
| Material cost at R-49 | About $1.01 per sq ft | About $1.13 per sq ft |
| Fire behavior | Noncombustible (ASTM E136) | Treated with fire retardant |
For most attics in humid or mixed climates, fiberglass is the safer default because it does not absorb moisture from the occasional roof leak or condensation event. In dry climates or tight, wire-cluttered attics, cellulose earns its place.
Blown-in insulation vs batts: which should you use?
Blown-in loose fill usually wins on an existing attic floor because it flows around wiring, framing, and ductwork to leave no gaps, while fiberglass batts leave a thermal hole at every obstruction they get cut around. Attic-depth fiberglass batts carry a higher R-value per inch, about R-3.2 to R-3.5 (Owens Corning PINK Next Gen R-30 to R-49) versus about R-2.8 to R-2.9 for AttiCat blown fiberglass, but that label number only holds if the batt goes in with no gaps or compression, which is hard to pull off in a cluttered retrofit attic.
Coverage is the deciding factor. ANSI/RESNET/ICC 301-2022, the standard HERS raters use, grades both products by the area left with gaps, voids or compression, and its energy-model rule treats a Grade III install as 5 percent uninsulated. On that rule, an R-49 attic with 5 percent bare performs at roughly R-21 for the whole ceiling (Roofing Brief parallel-path arithmetic, including about R-1.7 for drywall and air films), less than half its label. Batts are more prone to those gaps than loose fill. Batts still make sense in a clean, open attic with uniform joist spacing and no obstructions, or when you want hands-on installation without a blower in an accessible space.
| Factor | Blown-in loose fill | Fiberglass batts |
|---|---|---|
| R-value per inch | About R-2.8 to R-2.9 (fiberglass); R-3.7 (cellulose) | About R-3.2 to R-3.5 (attic depths) |
| Gap and obstruction coverage | Excellent, flows around framing and wires | Poor, leaves gaps at every cut |
| Best for | Retrofit attics with wiring, ducts, odd bays | Open new-construction attics, uniform joists |
| DIY difficulty | Needs a rented blower and two people | Easiest DIY, roll and cut by hand |
| Real-world vs rated R-value | Holds close to rated R when depth is even | Can lose R to gaps and compression |
| Material cost / sq ft at R-49 | About $1.01 to $1.13 | About $2.27 |
| Installed cost / sq ft (HomeGuide) | $1.10 to $1.90 at R-49 | $0.80 to $2.60, all R-values |
Sources: Owens Corning AttiCat data sheet (May 2026) and PINK Next Gen submittal sheet (Pub. No. 10024913-C, September 2025); Greenfiber SANCTUARY chart; Home Depot, Lowe’s and HEP Sales listings, October 2026 (R-49 batt: Owens Corning BF93 at $108.98 per 48 sq ft bag); HomeGuide cost guides. HomeGuide’s batt range spans all R-values, so its low end reflects thin batts, not R-49.
For a flat, obstacle-filled attic floor, blown-in is the usual pick. To compare blown-in against spray foam, rigid board, and batts across every attic type and climate, see our best insulation for attic guide. If squeezing the most resistance into limited depth is the priority, our ranking of the highest R-value insulation by material shows where loose fill lands against foam boards. For the full head-to-head on cost, depth and install grading, see blown-in vs batt insulation compared.
DIY vs pro: which makes sense for you?
DIY blown-in insulation makes sense in an open, accessible attic with standard joists and no complications. Expect to spend about $1,010 to $1,130 on bags for a 1,000 square foot attic at R-49 (25 AttiCat bags or about 71 SANCTUARY bags at October 2026 prices), versus $1,100 to $1,900 for a pro on the same attic at HomeGuide’s R-49 rates. The cash gap is small at R-49, so the pro price mostly buys air sealing, depth verification, ventilation baffles, and cleanup that a rental machine and a Saturday do not guarantee.
The blower is often free. Owens Corning’s AttiCat rental guide lists Lowe’s and The Home Depot and gives 24 hours free with the machine when you buy 10 bags, with a daily fee if you need more time. Terms vary by store and product, so confirm before you load the car. The machine is a two-person job: one feeds bags into the hopper, one runs the hose in the attic.
The table below is the honest trade-off, including a cost that most guides leave out: uneven DIY coverage lowers your effective R-value even when the average depth looks right.
| Line item | DIY | Professional |
|---|---|---|
| Cash cost (1,000 sq ft, R-49) | About $1,010 to $1,130 in bags | $1,100 to $1,900 (HomeGuide) |
| Blower | Often free for 24 hours with 10 bags (AttiCat) | Included, higher pressure |
| Air sealing before blowing | Your responsibility | Usually included |
| Ventilation baffles at eaves | Buy and install yourself | Installed as prep |
| Depth consistency | Varies with skill | Verified with depth rulers |
| Effective R-value risk | Thin spots and voids lower effective R | Even fill holds rated R |
When to call a pro no matter the price
Some conditions turn a DIY attic job into a hazard or a wasted weekend. Hire a professional if any of these apply:
- Knob-and-tube wiring, which can overheat under loose-fill insulation and needs evaluation first.
- Vermiculite already present, which may contain asbestos and requires testing, not disturbance.
- Existing moisture, mold, or roof leaks, which must be fixed before you bury the deck under insulation.
- Very low headroom or a complex multi-level attic where even coverage by hand is impractical.
- Significant air-sealing work around chimneys, can lights, and top plates that should happen before blowing.
How to install blown-in insulation in an attic
Blown-in installation is straightforward on paper: seal, protect airflow, then blow to depth. The order matters, because air sealing and ventilation baffles must go in before insulation covers the attic floor. Skip them and you either lose the energy savings to air leaks or trap moisture against the roof deck. Before you climb in, see our guide to how to walk in an attic safely. Our step-by-step guide on how to blow insulation in an attic walks through each stage in order.
- Air-seal the attic floor. Caulk or foam the top plates, wiring penetrations, plumbing stacks, and around the chimney. Air leaks bypass insulation, so sealing first is what makes the R-value real.
- Install baffles at the eaves. Rigid vent chutes keep the new insulation from blocking soffit vents, preserving the intake side of your attic ventilation.
- Dam and protect fixtures. Build a metal or hardware-cloth barrier around non-IC-rated can lights and the attic hatch so insulation stays clear of heat sources.
- Set depth markers. Staple depth rulers to joists at several points so you can confirm the fill hits your target R-value everywhere, not just near the hose. The 2021 IECC requires at least one marker per 300 square feet for blown attic insulation. Our guide to attic insulation depth markers covers placement and which number to write on them.
- Blow to the chart depth and bag count. Fill evenly, working back toward the hatch. Blow cellulose to the chart’s initial installed thickness, since Greenfiber rates settled depth at 90 percent of installed, and check that you used at least the chart’s bags per 1,000 sq ft.
The roofing angle most cost guides skip: ventilation and ice dams
Blown-in insulation and attic ventilation are a package, not separate projects. Insulation slows heat loss into the attic; ventilation carries away the heat and moisture that still get through. Cover your soffit vents with loose fill and you cut off intake air, which can drive condensation on the roof deck and, in cold climates, feed ice dams at the eaves.
This is where a roofing lens beats a generic insulation quote. A balanced system keeps the attic cold and dry in winter so snow melts evenly instead of refreezing at the overhang. If your attic runs warm and damp after insulating, the fix is usually airflow, not more insulation. See our guide to attic ventilation and its 2026 calculation for the intake-to-exhaust math, and how soffit vents work for why baffles at the eaves are non-negotiable.
In snow country, the insulation-and-ventilation combo is your first line of defense against ice dams. Our guide to ice dam prevention methods that actually work covers how a cold, evenly vented roof deck stops the melt-refreeze cycle that no amount of gutter heat fully solves.
Is blown-in insulation worth it?
For most under-insulated attics, yes. ENERGY STAR estimates that air sealing and adding insulation saves homeowners an average of 15 percent on heating and cooling costs, and blown-in is the fastest way to add R-value over an existing attic floor without tearing anything out. It also installs over old batts, so you can top up rather than replace. Our cheapest-insulation ranking shows how blown-in compares on cost per R-value. The federal 25C insulation credit ended for work placed in service after December 31, 2025 (Public Law 119-21), so budget without it and check state or utility programs. In Florida, our guide to the best attic insulation for Florida covers rebates.
The payback stretches out if your attic is already near code or if you skip air sealing and ventilation, which are what turn rated R-value into real savings. If your roof is near end of life or you suspect a leak, sequence the roof work first. Insulating over a deck that is about to be torn off wastes the material. Our roof lifespan by material guide can help you time the two projects so you insulate once.
Frequently asked questions
How much does blown-in insulation cost per square foot?
Blown-in insulation costs about $0.84 to $2.40 per square foot installed across R-38 to R-60, per HomeGuide, or roughly $1,100 to $1,900 for a 1,000 square foot attic at R-49. Material for a DIY job runs about $1.01 per square foot at R-49 for AttiCat fiberglass and $1.13 for SANCTUARY cellulose at October 2026 prices, and the blower is often free with a 10-bag purchase.
How many bags of blown-in insulation do I need?
Divide your attic square footage by the maximum coverage per bag at your target R-value, or use the chart’s minimum bags per 1,000 square feet. One bag of Owens Corning AttiCat covers at most 39.9 square feet at R-49 and 31.8 square feet at R-60, so a 1,000 square foot attic at R-49 needs at least 25 bags. Always use the coverage chart printed on your specific bag.
Is fiberglass or cellulose better for blown-in attic insulation?
Fiberglass does not absorb moisture and Owens Corning’s AttiCat chart lists no settling allowance, making it the safer default in humid or leak-prone attics. Cellulose packs denser and fills around wires well, but it can absorb water, and Greenfiber rates its settled depth at 90 percent of installed. Choose fiberglass for moisture resistance, cellulose for tight, wire-cluttered attics in dry climates.
Can I put new blown-in insulation over old insulation?
Yes, in most cases you can add blown-in insulation over existing batts or loose fill as long as the old material is dry and free of mold. Never cover damp or moldy insulation, and fix any roof leak first. Do not compress existing batts, since compression lowers their R-value. Air-seal the attic floor before topping up for the full benefit.
Does blown-in insulation settle over time?
Cellulose settles: Greenfiber rates SANCTUARY’s settled thickness at 90 percent of installed, so the chart has you blow 14.3 inches to end at 13.3 inches for R-49. Owens Corning’s AttiCat chart lists the same installed and settled thickness for its blown fiberglass. Blow to the chart’s installed depth, use at least the chart’s bag count, and recheck cellulose depth against your markers after it settles.
How thick does blown-in insulation need to be for R-49?
Reaching R-49 takes 17 inches of Owens Corning AttiCat fiberglass, or 14.3 inches of Greenfiber SANCTUARY cellulose blown to settle at 13.3 inches, per each manufacturer’s chart. ENERGY STAR recommends R-49 for an uninsulated attic in zones 2 and 3, and R-60 in zones 4 through 8.
Is blown-in insulation better than batts?
For most existing attics, blown-in is better than batts because it fills gaps around wiring, ducts, and framing that batts leave exposed. Under the RESNET 301-2022 modeling rule, an R-49 attic with 5 percent of its area bare performs at roughly R-21 for the whole ceiling. Batts carry a higher R-value per inch and suit clean, open attics with uniform joist spacing.
Reviewed by The Roofing Brief Team. Last reviewed: October 2026.