Blown-in insulation is the most cost-effective professional insulation upgrade for existing homes. It fills attic floors to R-49, retrofits enclosed wall cavities without removing drywall, and costs a fraction of what spray foam costs for the same square footage. This guide breaks down blown-in insulation pricing by material, by application, and by real project scenarios in central Illinois.
Here are the typical installed costs for blown-in insulation in central Illinois:
Blown-in cellulose, attic floor (R-49): $1.50 to $3.00 per square foot
Blown-in fiberglass, attic floor (R-49): $1.00 to $1.75 per square foot
Dense-pack cellulose, wall retrofit: $2.00 to $3.50 per square foot of wall area
Attic air sealing (add-on): $300 to $800
Old insulation removal (if needed): $1.00 to $2.00 per square foot
These are professional installation costs including material, labor, and equipment. The cost varies based on the material, the area being insulated, the existing insulation depth, and the accessibility of the space. We break down each scenario below.
| Factor | Blown-In Cellulose | Blown-In Fiberglass |
|---|---|---|
| Cost Per Sq Ft (R-49 attic) | $1.50 to $3.00 | $1.00 to $1.75 |
| R-Value Per Inch | R-3.2 to R-3.8 | R-2.2 to R-2.7 |
| Depth for R-49 | 14-15 inches (settled) | 16-20 inches |
| Settling | 15-20% in first 1-2 years | 5% or less |
| Moisture Behavior | Absorbs, can dry | Does not absorb |
| Air Movement Resistance | Higher (denser material) | Lower |
| Dense-Pack Wall Retrofit | Yes ($2.00 to $3.50/sq ft) | Not recommended |
Fiberglass is cheaper per square foot, but cellulose delivers better performance per dollar in most attic applications. Cellulose is denser, which means it resists air movement through the insulation layer more effectively. Research from the University of Colorado found that cellulose-insulated homes used 26% less heating energy than identical fiberglass-insulated homes, primarily because of this density advantage.
For attic floor upgrades, either material works well. For wall retrofits in existing homes, cellulose is the only practical blown-in option because it can be dense-packed to 3.5 lbs per cubic foot, which creates a solid thermal and air-retarding layer inside enclosed wall cavities.
Our recommendation for most central Illinois attic projects: cellulose. For attics with known moisture concerns (prior roof leaks, active condensation issues): fiberglass.
Starting from an uninsulated attic or one where old insulation has been removed.
| Project | Material | Target R-Value | Approx. Cost |
|---|---|---|---|
| 1,000 sq ft attic | Cellulose | R-49 | $1,500 to $3,000 |
| 1,500 sq ft attic | Cellulose | R-49 | $2,250 to $4,500 |
| 2,000 sq ft attic | Cellulose | R-49 | $3,000 to $6,000 |
| 1,000 sq ft attic | Fiberglass | R-49 | $1,000 to $1,750 |
| 1,500 sq ft attic | Fiberglass | R-49 | $1,500 to $2,625 |
| 2,000 sq ft attic | Fiberglass | R-49 | $2,000 to $3,500 |
Adding blown-in material on top of existing insulation that is dry and in good condition.
| Starting R-Value | Additional Depth Needed | Cost Per Sq Ft | Cost for 1,500 Sq Ft |
|---|---|---|---|
| R-7 (2-3") | 11-12" cellulose | $1.25 to $2.50 | $1,875 to $3,750 |
| R-11 (3-4") | 10-11" cellulose | $1.10 to $2.25 | $1,650 to $3,375 |
| R-19 (5-6") | 8-9" cellulose | $0.85 to $1.75 | $1,275 to $2,625 |
| R-30 (8-9") | 5-6" cellulose | $0.65 to $1.25 | $975 to $1,875 |
Note: Topping off is significantly cheaper than starting from bare joists because less material is required. This is the most common scenario we see in central Illinois homes built in the 1960s through 1980s.
Cellulose blown into enclosed wall cavities at 3.5 lbs per cubic foot through small access holes. No drywall removal required.
| Project | Approx. Cost |
|---|---|
| Per square foot of wall area | $2.00 to $3.50 |
| Typical ranch home (1,200 sq ft walls) | $2,400 to $4,200 |
| Typical two-story home (1,800 sq ft walls) | $3,600 to $6,300 |
Note: Wall area is calculated by multiplying the perimeter by wall height. A 30x50 ranch home with 8-foot walls has approximately 1,280 sq ft of exterior wall. Actual insulated area is typically 60-75% (windows, doors, areas with existing insulation are excluded).
Blown-in insulation in floor joist bays above unheated garages, cantilevered sections, or open basements.
| Project | Target R-Value | Approx. Cost |
|---|---|---|
| Per sq ft of floor area | R-19 to R-30 | $1.50 to $3.00 |
| 400 sq ft floor over garage | R-30 | $600 to $1,200 |
| Add-On Service | Approx. Cost | When It Applies |
|---|---|---|
| Comprehensive attic air sealing | $300 to $800 | Every attic insulation project (strongly recommended) |
| Old insulation removal | $1.00 to $2.00 per sq ft | Pest-contaminated, moldy, or water-damaged insulation |
| Rafter baffle installation | $5 to $15 per bay | Vented attics (prevents insulation from blocking soffit vents) |
| Bathroom vent extension to exterior | $150 to $400 per vent | Fans currently venting into the attic |
| Attic hatch or pull-down stair insulation | $50 to $200 | Uninsulated attic access points |
Air sealing is the most important add-on. Without it, warm air convects through gaps in the attic floor and bypasses the insulation entirely. We include air sealing in every attic insulation proposal because blown-in insulation without air sealing delivers only 50% to 75% of its potential performance. The $300 to $800 spent on air sealing typically generates more energy savings than the insulation itself.
Cellulose costs more per square foot than fiberglass but delivers better thermal performance due to its higher density. For most central Illinois attics, the cost difference is $0.25 to $1.00 per square foot. Cellulose is worth the premium in most applications.
Topping off an attic from R-19 to R-49 costs roughly half what insulating from bare joists to R-49 costs. We measure your existing insulation depth during the estimate and calculate material needs accordingly.
Larger attics cost more in total but less per square foot. The crew and equipment setup is the same for a 1,000-square-foot attic as for a 2,000-square-foot attic, so the setup cost is spread across more square footage.
Attics with tight access hatches, low clearance, or obstructions (HVAC equipment, ductwork, storage platforms) take longer to insulate. Walk-up attics with full standing height are the fastest and least expensive.
A 2000s home with few attic penetrations needs minimal air sealing. A 1950s home with open top plates, unsealed plumbing stacks, recessed lights, and a half-dozen HVAC chases needs significantly more sealing work.
Removal adds $1.00 to $2.00 per square foot. We recommend it only when existing insulation is genuinely compromised (pest damage, mold, water damage). Clean, dry insulation can stay in place with new material blown on top.
Attic floor blown-in is the least expensive application. Dense-pack wall retrofits cost more per square foot because the process is more labor-intensive (drilling access holes, inserting fill tubes, patching holes). Floor assemblies fall in between.
| Insulation Type | Cost Per Sq Ft (Attic, R-49) | Air Sealing | Best For |
|---|---|---|---|
| Blown-In Cellulose | $1.50 to $3.00 | Moderate (dense material) | Existing home attic floors, wall retrofits |
| Blown-In Fiberglass | $1.00 to $1.75 | Minimal | Attics with moisture concerns |
| Spray Foam (Roof Deck) | $1.90 to $4.50 | Excellent (built-in) | Attics with HVAC equipment |
| Fiberglass Batts | $1.25 to $2.00 | None | New construction only |
Blown-in insulation on the attic floor is the least expensive way to reach R-49 with professional installation. Spray foam on the roof deck costs two to three times more and is only justified when the attic needs to be conditioned space. For the vast majority of central Illinois homes with standard unconditioned attics, blown-in cellulose or fiberglass on the attic floor is the right choice.
Blown-in attic insulation is the single highest-ROI energy upgrade for most central Illinois homes. Here is why:
A 1,500-square-foot attic upgraded from R-19 to R-49 with air sealing costs approximately $2,500 to $4,500. That upgrade typically reduces annual heating and cooling costs by 15% to 25%. On a $2,500 annual energy bill, a 20% reduction saves $500 per year. The project pays for itself in 5 to 9 years. The insulation lasts 30 to 50 years.
Beyond energy savings, properly insulated attics eliminate ice dams, reduce temperature differences between floors, extend HVAC equipment life by reducing runtime, and make the home significantly more comfortable in both winter and summer.
For homes built before 1980 in the Mattoon, Champaign, and Decatur area, attic insulation is almost always the first upgrade we recommend. It delivers the most improvement for the least cost.
Learn more about our blown-in insulation servicesFor a 1,500-square-foot attic in central Illinois, blown-in cellulose insulation to R-49 typically costs $2,250 to $4,500. Blown-in fiberglass for the same attic runs $1,500 to $2,625. Adding comprehensive air sealing adds $300 to $800. If old insulation removal is needed, add $1,500 to $3,000.
Yes, significantly. Blown-in cellulose on an attic floor costs $1.50 to $3.00 per square foot for R-49. Spray foam on the roof deck costs $1.90 to $4.50 per square foot for R-20. Blown-in is the better value for standard unconditioned attics. Spray foam is justified only when the attic contains HVAC equipment or needs to be conditioned space.
For existing homes, blown-in is typically comparable in cost but far superior in performance. Batts cannot be installed in an attic with existing insulation, around obstructions, or in irregular joist bays without significant gaps. Blown-in fills every cavity completely.
Dense-pack cellulose wall insulation typically costs $2.00 to $3.50 per square foot of wall area in central Illinois. For a typical ranch home with approximately 1,200 square feet of exterior wall, the total cost is $2,400 to $4,200 including access hole drilling, filling, patching, and painting.
You can rent a blowing machine from Home Depot or Lowes for free with a minimum material purchase. The material cost is lower, but you will not get the air sealing that makes the insulation effective, you may not achieve uniform depth, and you risk blocking soffit vents. Professional installation costs $1.00 to $3.00 per square foot and includes air sealing, baffle installation, and depth verification.
Old insulation removal adds $1.00 to $2.00 per square foot. For a 1,500-square-foot attic, that is $1,500 to $3,000 for removal plus $2,250 to $4,500 for new cellulose at R-49. Total: $3,750 to $7,500. Removal is only necessary when the old insulation is contaminated, wet, or moldy.
Yes. We provide free, on-site estimates throughout our central Illinois service area. We enter the attic, measure existing insulation depth, identify air leakage points, and provide a written proposal with specific pricing. Call (217) 508-8095 or submit a request online.
Your actual cost depends on your attic size, existing insulation depth, material choice, and air sealing needs. We provide free, detailed estimates with exact pricing. No guesswork. No national averages. Just what your project will cost in central Illinois.