💨 Blown-In Insulation Cost Calculator

Cost by application (installed, per sq ft):

• Attic floor — cellulose: $1.00–$1.75/sq ft
• Attic floor — fiberglass: $1.00–$2.00/sq ft
• Crawl space: $1.00–$2.50/sq ft
• Wall cavities (exterior drill): $1.50–$3.50/sq ft
• Wall cavities (interior drill + finish): $2.00–$4.50/sq ft

Total project cost (1,000 sq ft attic floor):

• Blown-in fiberglass R-49: $1,500–$3,000
• Blown-in cellulose R-49: $1,400–$2,800
• Add air sealing: +$200–$600
• Add baffles: +$150–$350

Cellulose blown-in:

• R-3.5 to R-3.7 per inch — higher R/inch than fiberglass
• 80–85% recycled content (most eco-friendly option)
• Excellent air infiltration resistance
• Settles 5–7% over time — install slightly deeper
• Best in dry to moderate humidity climates
• Cost: $0.40–$0.65/sq ft for material

Fiberglass blown-in:

• R-2.5 to R-3.0 per inch — requires more depth for same R-value
• Does not settle or compact over time
• Moisture resistant — safer in humid environments
• Lighter weight, easier to handle in hot attics
• Best in humid climates (FL, Gulf Coast, Pacific NW)
• Cost: $0.45–$0.75/sq ft for material

Bottom line: Both are good choices. Cellulose slightly wins on performance and eco-friendliness; fiberglass wins in high-humidity environments.

Bags needed (coverage varies by manufacturer):

• Fiberglass blown-in to R-38 (~14 inches): 1 bag per 35–45 sq ft
• Fiberglass blown-in to R-49 (~18 inches): 1 bag per 25–35 sq ft
• Cellulose blown-in to R-38 (~10 inches): 1 bag per 30–40 sq ft
• Cellulose blown-in to R-49 (~13 inches): 1 bag per 22–30 sq ft

Example for 1,000 sq ft attic to R-49:

• Fiberglass: approximately 30–40 bags
• Cellulose: approximately 35–45 bags

Important: Always use the manufacturer's coverage chart printed on the bag. These charts specify minimum weight per sq ft at each R-value level accounting for settled vs. installed depth. Do not rely on generic estimates alone.

DIY blown-in attic floor — highly feasible:

• Home Depot and Lowe's loan blowing machines free when you buy 20+ bags of insulation
• 2-person job recommended (one person feeds bags, one directs hose)
• Install baffles at eaves first to protect soffit ventilation
• Air seal all penetrations before blowing (this is the most important step)
• Wear N95 or better respirator, full goggles, and a Tyvek suit
• Blow in multiple passes for even coverage
• Cost savings: $0.50–$0.90/sq ft in labor

DIY wall cavity blown-in — challenging:

• Requires drilling into each stud bay and proper fill technique
• Risk of missed cavities, bridging, and incomplete fill
• Patching holes requires finishing skill to be invisible
• Most homeowners hire a professional for wall work

Never DIY: Anything involving the electrical panel, gas lines, or attic spaces with suspected vermiculite/asbestos.

Section 25C Energy Efficient Home Improvement Credit:

• 30% of insulation material and installation cost
• Maximum $1,200 per year for insulation (separate from HVAC and window credits)
• Insulation must meet IECC requirements for your climate zone
• Air sealing materials also qualify under the same $1,200 cap
• Available tax years 2023–2032
• Claim on IRS Form 5695
• Must be installed in your primary residence

Examples:

• $2,000 blown-in project: 30% = $600 credit
• $3,500 blown-in + air sealing project: 30% = $1,050 credit (under the $1,200 cap)
• $5,000 blown-in + air sealing project: 30% = $1,200 credit (capped)

Also check your utility company at energystar.gov/rebate-finder — many offer $0.10–$0.25/sq ft or $100–$500 flat rebates for attic insulation upgrades.

DOE recommended attic R-values by climate zone:

• Zone 1–2 (FL, HI, Puerto Rico, southern TX): R-30 to R-38
• Zone 3 (Southeast, central TX, AZ, NM, southern CA): R-38
• Zone 4 (mid-Atlantic, TN, KY, CO, NM, Pacific NW): R-38 to R-49
• Zone 5 (Midwest, PA, NY, OR, WA, northern CA): R-49
• Zone 6 (upper Midwest, mountain states, ME, VT, NH): R-49 to R-60
• Zone 7 (northern MN, ND, SD, MT, WY, northern ME): R-60
• Zone 8 (Alaska): R-60+

How to determine your zone: Visit energystar.gov or search "DOE climate zone map" — enter your zip code to find your zone.

Diminishing returns above R-60: Each additional R-value unit saves less energy. The jump from R-0 to R-38 saves the most; from R-38 to R-49 is still very worthwhile; above R-60 the marginal savings are small.

Blown-in advantages for attics:

• Fills completely around joists, pipes, wires, and blocking — no gaps or voids
• Better air infiltration resistance than batts
• Faster to install for large attic floors
• Works well as a topping layer over existing batts
• Can be blown to any depth — easy to hit exact R-value target

Batt advantages:

• Easier to DIY without a blower machine (no equipment rental)
• Stays in place if the attic is accessed frequently
• Works well in perfectly clear, regular-joist-spacing attics

Verdict: For most attics, blown-in wins on performance. The only situation where batts are preferred is an attic that is accessed regularly (HVAC equipment, storage) where loose insulation would get disturbed. In that case, encapsulated batts or rigid foam make more sense.