Blown-In Insulation Cost in 2026: Per Square Foot by Material and Depth
Blown-in insulation costs $1.50 to $3.50 per square foot installed professionally in 2026. A 1,000 sq ft attic runs $1,500 to $3,500 installed. DIY blown-in costs $0.60 to $1.20 per square foot in materials with free or low-cost machine rental from major home improvement retailers. The blown-in insulation cost depends on material type (fiberglass vs cellulose), target R-value (depth of material), and whether air sealing is performed before installation.
Blown-in insulation is the most accessible attic insulation upgrade for US homeowners, with a true DIY pathway that saves 50 to 70 percent versus professional installation. The big-box retailer programs (Owens Corning, Johns Manville, and Greenfiber all participate) offer free machine rental when you purchase a qualifying number of bags, removing the tool barrier entirely. The materials are available off the shelf, the technique is straightforward, and the energy savings are immediate and measurable on the next utility bill.
The R-value calculator gives you inches needed and bag count for your attic size and target R-value.
Open the R-Value Calculator →Blown-In Insulation Cost by Material in 2026
| Material | R-value per inch | DIY cost per sq ft (material) | Professional installed per sq ft |
|---|---|---|---|
| Blown-in fiberglass (e.g., Owens Corning) | R-2.2 to 2.7 | $0.65 to $1.00 | $1.50 to $3.00 |
| Blown-in cellulose (recycled paper) | R-3.2 to 3.8 | $0.50 to $0.85 | $1.50 to $3.50 |
| Blown-in mineral wool (rock wool) | R-3.0 to 3.3 | $0.90 to $1.50 | $2.00 to $4.00 |
Blown-In Insulation Depth by R-Value Target
| Target R-value | Fiberglass depth needed | Cellulose depth needed | Starting from zero |
|---|---|---|---|
| R-30 | 11 to 14 inches | 8 to 9 inches | Minimum for most warm climates |
| R-38 | 14 to 17 inches | 10 to 12 inches | DOE minimum for mixed climates |
| R-49 | 18 to 22 inches | 13 to 15 inches | DOE optimal for cold climates |
| R-60 | 22 to 27 inches | 16 to 19 inches | Very cold climates (Zone 6-7) |
DIY Blown-In Program: Step-by-Step
Home Depot, Lowes, and Menards offer free or discounted machine rental with purchase of qualifying insulation bags. The Owens Corning program at Home Depot requires purchasing 10 or more bags for free 24-hour machine rental; similar programs at other retailers require 10 to 20 bags minimum purchase. Steps to DIY blown-in insulation: call the store to reserve the machine (machines are limited; call 1 to 2 days ahead); air seal the attic penetrations before the installation day (can lights, plumbing pipes, attic hatch); install eave baffles to protect soffit ventilation; pick up the machine with the insulation bags; load bags into the hopper and blow to the depth shown on the bag depth chart (posted at the store and printed on bags); return the machine by the specified time. The entire process is feasible solo, though a second person feeding bags into the hopper while you direct the hose significantly speeds the work.
For the air sealing that should precede blown-in installation, our attic insulation cost guide covers the air sealing step in detail. For the spray foam comparison when deciding between materials, our spray foam vs blown-in guide covers when spray foam is worth its higher cost instead of blown-in.
Blown-In Fiberglass vs Cellulose: Side-by-Side
| Feature | Blown-in fiberglass | Blown-in cellulose |
|---|---|---|
| R-value per inch | R-2.2 to 2.7 | R-3.2 to 3.8 |
| Depth to reach R-49 | 18 to 22 inches | 13 to 15 inches |
| Settling over time | Minimal (5%) | 15 to 20% (install thick to compensate) |
| Moisture response | Does not absorb moisture; maintains R-value when wet | Absorbs moisture; R-value drops when wet |
| Fire resistance | Inherently non-combustible (glass fiber) | Borate-treated to meet Class 1 fire rating |
| Pest resistance | Not a food or nesting material | Borate treatment deters insects and rodents |
| Environmental | 20 to 30% recycled glass content | 75 to 85% post-consumer recycled newspaper |
| DIY availability | Widely available; Owens Corning, Johns Manville | Widely available; Greenfiber, Insulwise |
Three Real Blown-In Insulation Projects
Example 1: DIY cellulose in a 1,200 sq ft attic in Nashville, Tennessee
A homeowner upgrading from R-11 batts to R-49 in a 1,200 sq ft vented attic (Climate Zone 4). Additional cellulose needed: R-38 more at R-3.5/inch = 10.9 additional inches. At 1,200 sq ft and 11 inches of cellulose: required approximately 40 bags of Greenfiber cellulose at $25/bag = $1,000. Free machine rental with 40-bag purchase. Air sealing (DIY with foam cans): $85. Eave baffles (20 baffles): $38. Total DIY: $1,123. Professional quote for same scope: $2,800. DIY savings: $1,677. The homeowner completed the project in 5 hours with a helper loading bags; the hardest part was the attic access limited to a 25×54 inch hatch that the machine hose had to thread through.
Example 2: Professional blown-in fiberglass in a 2,000 sq ft attic in Denver, Colorado
A homeowner with a 2,000 sq ft attic floor and a large rooftop HVAC unit making DIY difficult (limited floor space to work around equipment). Hired professional insulation crew. Starting R-value: R-19 existing batts. Target: R-60 (Climate Zone 5). Additional R-41 needed at R-2.5/inch = 16.4 more inches of fiberglass. Air sealing by crew (12 can lights, plumbing penetrations): $680. Blown-in fiberglass (2,000 sq ft, 16 inches): $4,200. Total: $4,880. Federal 25C credit on material cost ($2,800): $840. Net: $4,040. Annual savings (Denver gas heat): $480/year. Payback: 8.4 years.
Example 3: Adding blown-in over existing spray foam air seal in Seattle, Washington
A contractor installing a hybrid system in a 1,600 sq ft attic with 22 recessed lights and a complex geometry. Day 1: spray foam crew sealed all penetrations, light covers, and the attic hatch (open-cell foam air sealing only): $1,440. Day 2: blown-in cellulose crew added R-49 of cellulose over the entire floor: $3,520. Combined: $4,960. The spray foam air sealing on Day 1 would have taken a DIYer an estimated 12 to 15 hours with foam cans and specialized can lights covers; the professional foam crew completed it in 3 hours. The blown-in cellulose on Day 2 added the bulk R-value at the lowest per-R-value cost. The homeowner saved approximately $8,000 over a full closed-cell spray foam system that would have cost approximately $13,000 for the same R-value.
The R-value calculator gives you bag count, depth, and total material cost for your attic size and R-value target.
Calculate Blown-In Insulation Cost →Frequently Asked Questions About Blown-In Insulation Cost
How much does blown-in insulation cost?
Professional blown-in insulation costs $1.50 to $3.50 per square foot installed in 2026. A 1,000 sq ft attic costs $1,500 to $3,500 professionally installed. DIY blown-in costs $0.50 to $1.00 per square foot in materials, with free machine rental from major retailers when you purchase qualifying bag quantities. A 1,000 sq ft attic to R-49 with cellulose costs approximately $800 to $1,200 in DIY materials and takes 4 to 6 hours to complete.
How many bags of blown-in insulation do I need?
The number of bags depends on your attic area, the target R-value, and the material. Bag depth charts (printed on the bags and posted at the retailer) tell you how many bags to buy for a given area and R-value. As a rough estimate: cellulose bags typically cover 40 to 50 sq ft per bag at R-49 depth; fiberglass bags cover 30 to 40 sq ft per bag at the same R-value. For a 1,200 sq ft attic to R-49 with cellulose: 1,200 sq ft / 45 sq ft per bag = approximately 27 bags. Always add 10 percent buffer (30 bags) for coverage variation and any thicker areas near the eaves.
How deep should blown-in insulation be?
Depth depends on the R-value target and material. To reach R-49 with blown-in fiberglass: 18 to 22 inches. To reach R-49 with cellulose: 13 to 15 inches. Install cellulose 15 to 20 percent thicker than the target depth to account for settling: target R-49 with cellulose, install to the equivalent of R-57 depth (15 to 17 inches) to end up at R-49 after settling. Fiberglass does not settle significantly; install to the chart depth without additional buffer.
Which is better, blown-in fiberglass or cellulose?
Cellulose provides higher R-value per inch (R-3.5 vs R-2.5 for fiberglass), which means you need fewer inches to reach the target R-value, producing a shallower total insulation depth. Cellulose also has higher post-consumer recycled content (75 to 85%) and better pest resistance from borate treatment. Fiberglass does not settle and does not absorb moisture, making it slightly more forgiving in attics with any moisture risk. Both materials perform excellently in standard dry residential attics; the choice in most applications is primarily preference and which brand is available locally at competitive pricing.
Can I blow insulation into walls?
Yes. Blown-in insulation for existing walls (closed-cavity wall insulation) is a common professional technique: small holes are drilled in the wall exterior (or interior for finished walls), blown-in material fills the existing cavity, and the holes are plugged and patched. This is called dense-pack installation because material is blown at higher density than attic installation to prevent settling in a vertical cavity. Wall blown-in insulation typically costs $2 to $5 per square foot of wall area and is significantly more disruptive than attic installation. Cellulose is the preferred material for wall dense-pack because it performs better at higher densities than fiberglass.
Do I need to remove old insulation before adding blown-in?
In most cases, no. You can blow new insulation directly over existing batts or old blown-in material (provided the existing material is dry and not moldy). The new material adds to the existing R-value. Remove existing insulation only if it is wet, moldy, contaminated with rodent droppings, or significantly compacted from age and moisture exposure. Adding over existing dry insulation saves the removal cost ($0.50 to $1.50 per square foot) and keeps the project simple.
How long does blown-in insulation last?
Blown-in fiberglass insulation lasts indefinitely with no degradation when kept dry; it is essentially permanent in a properly ventilated, dry attic. Blown-in cellulose settles 15 to 20 percent in the first few years and then stabilizes; the R-value after settling is lower than immediately after installation, which is why installers blow thicker than the target to account for settling. Cellulose in a damp attic can degrade; moisture control (proper ventilation or encapsulation) is essential for cellulose longevity. Neither material has a defined end-of-life; both will still be performing their insulating function decades after installation in proper conditions.
Is blown-in insulation safe?
Blown-in fiberglass requires eye protection, an N100 respirator, and skin coverage during installation; fiberglass particles irritate eyes, skin, and respiratory tract during active installation but are considered safe once settled and not disturbed. Blown-in cellulose has a lower airborne fiber hazard than fiberglass; it is made of paper with borate treatment and requires a dust mask rather than an N100 respirator during installation (though N100 is still recommended for best protection). Neither material poses ongoing health risks after installation when sealed under drywall or under the attic floor; the exposure risk is only during active installation with the blowing machine running.
Related Calculators and Guides
For blown-in insulation depth charts and R-value recommendations by climate zone, the DOE Energy Saver Insulation guide is the primary reference, and product-specific depth charts are available from manufacturers including Owens Corning and Greenfiber cellulose.