Cellulose Insulation Cost: Blown-In Prices per Square Foot

Most homeowners overpay for attic insulation because they compare quotes by the job total instead of by the R-value delivered. Your cellulose insulation cost comes down to three numbers: how many bags it takes to reach your target depth, if you rent a blower or hire a crew, and how much prep the attic needs before anything gets blown in. Once you know those, a quote either makes sense or it does not.

Here is the short version. Professionally installed loose-fill cellulose in an open attic typically runs about $1.00 to $2.30 per square foot, depending on depth, with R38 sitting near the middle of that range. A DIY job using a rented blower usually lands around $0.45 to $1.10 per square foot in materials, since many home centers lend the machine free with a minimum bag purchase. Dense-packed cellulose in closed walls costs more, often $2.00 to $4.00 per square foot of wall area, because the work involves drilling, filling and patching every stud bay.

Those ranges shift with your region, attic access, and how much air sealing or cleanup happens first. With a few measurements and the bag chart, you can build your own estimate and check a contractor’s math.

Cellulose Insulation Cost per Bag and per Square Foot

Loose-fill cellulose is sold in compressed bags, usually around 25 pounds each, at roughly $13 to $20 per bag in most markets. The bag label is the most useful document in the whole project. It lists how many bags you need per 1,000 square feet to hit each R-value, plus the minimum settled thickness. Never estimate by eye; the coverage chart already accounts for settling.

Cellulose delivers roughly R3.2 to R3.8 per inch, so the depth you need climbs quickly as your target rises. Typical figures for an open attic look like this, though your specific bag chart rules:

Installed prices from a contractor generally run about double the material line, because labor, truck-mounted equipment, and overhead get folded in. Expect roughly $1.00 to $1.40 per square foot for R30, $1.20 to $1.70 for R38, $1.50 to $2.00 for R49, and $1.80 to $2.30 or more for R60. A 1,200 square foot attic topped up to R49 therefore tends to fall somewhere between $1,800 and $2,400 with a pro, while doing it yourself would cost closer to $800 to $1,150 in bags.

What Depth Do You Actually Need?

The right depth depends on climate. Warm southern climates generally aim for R30 to R49 in the attic. Mixed climates through the middle of the country typically target R49 to R60. Cold northern zones usually aim for R49 to R60 as well, and some homeowners there go deeper because heating seasons are long. Your local building department or utility can tell you what current energy code expects for new work, and that is a sensible floor for a retrofit.

Existing insulation counts. If you already have 4 inches of old fiberglass or cellulose that is dry and undamaged, it provides perhaps R10 to R13, and you only need to add the difference. That alone can cut the job by a third. Measure in several spots with a ruler pushed to the drywall, because old insulation is rarely even.

Why going deeper is usually cheap

Most of a professional quote is fixed cost: travel, setup, hose runs, and air sealing. Moving from R38 to R49 often adds only $0.25 to $0.40 per square foot to a pro bid. If the crew is already on site, deeper fill is one of the better values in home energy work, provided the attic has room for it without blocking soffit vents.

DIY With a Rented Blower vs Hiring a Pro

Doing it yourself is realistic for a simple, walkable attic with a decent hatch. Many home centers loan a blowing machine free when you buy 10 or 20 bags; otherwise, rental runs about $60 to $120 per day. The setup takes two people: one feeding bags into the hopper in the driveway or garage, one in the attic directing the hose.

Tools and materials for a DIY job

• Loose-fill cellulose bags (quantity from the bag chart)
• Insulation blower with 100 to 150 feet of hose
• Baffles (rafter vents) for each soffit bay
• Canned foam, fire-rated sealant, and foam board for air sealing
• Depth markers or rulers stapled to joists
• N95 or better dust mask, goggles, gloves, long sleeves
• Work light and boards or planks to kneel on across joists

Steps for blowing attic cellulose

1. Inspect for roof leaks, damp spots, or pest activity and fix those first.
2. Air seal top plates, plumbing and wiring penetrations, and the attic hatch. This step often saves as much energy as the insulation itself.
3. Install baffles at every soffit so blown material does not choke off intake ventilation.
4. Build dams around the hatch, and keep cellulose away from flues, chimneys, and recessed lights unless those fixtures are rated for insulation contact.
5. Staple depth markers to joists every few feet so you can see your target height.
6. Start blowing at the far end and work back toward the hatch, keeping the hose level so fill lands evenly.
7. Check depth markers, top off low spots, and confirm the bag count matches the chart for your square footage.

A pro still makes sense for many homes. Low-slope roofs with little headroom, attics full of old vermiculite, knob-and-tube wiring, or significant air sealing work all argue for a crew. Professionals also move much faster, often finishing an average attic in half a day, and many include an air-sealing package and a blower door test that helps you qualify for utility rebates.

Dense-Pack Wall Pricing

Existing closed walls cannot take loose fill poured from above, so cellulose goes in under pressure through holes drilled in each stud bay. Dense-pack installers blow the material to about 3.5 pounds per cubic foot, which fills cavities tightly enough to resist settling and slow air movement. A 2×4 wall ends up around R13 to R14.

Pricing usually runs $2.00 to $4.00 per square foot of wall, sometimes more. What drives the number is access. Drilling from the exterior means removing and reinstalling a course of siding or drilling through it and plugging the holes, while interior work requires patching, priming, and painting drywall. Fire blocking inside walls, old balloon framing, and plaster all affect how many holes the crew drills and how long the job takes. For a typical 1,500 square foot two-story home with about 1,600 square feet of exterior wall, total dense-pack bids commonly fall between $3,500 and $7,000.

Dense-pack is not a weekend DIY task. It needs a higher-pressure machine than most rental units, and getting the density right takes experience. Underfilled bays settle and leave cold voids at the top, which defeats the purpose.

Other Factors That Move the Price

Several line items show up on quotes that are worth understanding before you compare bids:

• Old insulation removal: Vacuuming out wet, rodent-contaminated, or failed insulation runs roughly $1.00 to $2.00 per square foot, sometimes more, and is a separate job from adding new fill.
• Air sealing: Expect several hundred dollars to over $1,000 depending on attic size and how leaky the ceiling plane is.
• Baffles and hatch insulation: Usually modest, often $150 to $400 combined.
• Access difficulty: Small hatches, low pitches, and long hose runs to a third-floor attic add labor.
• Region: Labor rates in high-cost metro areas can push installed prices to the top of every range.

Ask each contractor to list the target R-value, settled depth, number of bags, and air-sealing scope in writing. Two bids that look $600 apart sometimes deliver the same thing, and sometimes one of them quietly skips the air sealing.

Cellulose vs Fiberglass on Cost

Loose-fill fiberglass and cellulose land in a similar installed price range for attic work, so cost alone rarely decides it. Cellulose tends to resist air movement better at the same R-value, which is why many energy auditors like it, and it is made largely from recycled paper treated with borate for fire and pest resistance. It is heavier, though, and it settles more, which is why the label lists both installed and settled depth. Fiberglass is lighter, does not absorb water, and is preferred by some crews where ceilings are thin or roof leaks are a concern. If you want to compare full fiberglass pricing, look at blown-in options side by side using the same R-value target.

Troubleshooting Common Estimate Problems

The bag count seems low. Check whether the bid was calculated to installed depth rather than settled depth, or whether it assumes existing insulation you have not verified.

The attic has wet spots or stains. Fix the roof or bathroom fan venting before any insulation goes in. Cellulose that stays damp compresses and loses most of its R-value.

Energy bills did not drop much. Air leaks often matter more than added depth. A blower door test can show whether the ceiling plane is still leaking around fixtures, chases, and top plates.

Vents are blocked after a DIY job. Pull material back from the soffits by hand and install baffles. Restricted ventilation can raise attic moisture in winter.

When to Call a Pro

Bring in a professional insulation contractor if the attic has suspected vermiculite (gray-brown, pebbly granules), active leaks, mold, signs of rodents, or very old wiring. Hire out dense-pack walls in nearly every case. An energy auditor is also worth the fee if you plan a larger retrofit, since the audit report helps you rank work by payback and often unlocks utility incentives or tax credits. For a straightforward open attic, though, a careful DIY approach with a rented blower can cut the cellulose insulation cost roughly in half.