How to Estimate Insulation Jobs: Attic, Wall, and Spray Foam Pricing per Square Foot

Insulation installation pricing depends heavily on the type. Blown-in cellulose or fiberglass for attics runs $1.50-$3.00 per square foot installed. Fiberglass or mineral wool batt insulation in walls runs $1.00-$2.50 per square foot. Closed-cell spray foam runs $4.00-$8.00 per board foot (2 inches thick) — significantly more expensive but with much higher R-value per inch and added air-sealing benefits. Open-cell spray foam runs $1.50-$4.00 per board foot — cheaper than closed-cell but lower R-value and less moisture resistance. The estimating workflow: (1) Determine the area to be insulated in square feet (attic floor area, wall surface area, etc.). (2) Determine the target R-value based on climate zone and the homeowner's energy goals. (3) Choose the insulation type that meets the R-value, fits the application, and matches the budget. (4) Calculate material and labor costs based on type and depth. (5) Add overhead, profit, and any disposal/prep costs. (6) Check current state and utility rebates before you mention any to the customer. The most common estimating mistake: assuming all insulation types are interchangeable. They are not. Blown-in works for attics but is impractical for walls (you would have to drill access holes). Batt works for walls but loses R-value if compressed or installed poorly. Spray foam is the only choice for irregular cavities, rim joists, and air-sealing applications. Picking the wrong type for the application produces poor performance and unhappy customers. Describe the job in ContractorIQ, for example a 1,500 sqft attic to R-49, and it itemizes the materials and labor, priced for your region; check the depth and the code minimum yourself. This content is for educational purposes only and does not constitute legal advice.

R-value measures thermal resistance. Higher R-value = better insulation. The 2021 IECC (International Energy Conservation Code) sets the prescriptive minimums below by climate zone. States and cities adopt different editions, often with amendments, so confirm which one applies to the job. The 2024 IECC lowers the attic values (R-38 in zones 2-3, R-49 in zones 4-8) but requires additional efficiency measures (section R408). Attic minimums by climate zone (R-value): - Zone 1 (South Florida, Hawaii): R-30 - Zone 2 (Gulf Coast, Phoenix): R-49 - Zone 3 (Texas, Carolinas, mid-Atlantic): R-49 - Zone 4 (Pacific Northwest, Tennessee, Virginia): R-60 - Zone 5 (Iowa, Pennsylvania, mountain west): R-60 - Zone 6 (Minnesota, North Dakota, Wisconsin): R-60 - Zone 7-8 (Alaska, far northern Maine): R-60 Wood-frame wall minimums (same in the 2021 and 2024 IECC): - Zone 1-2: R-13 cavity, or R-10 continuous - Zone 3: R-20 cavity, R-13 cavity + R-5 continuous, or R-15 continuous - Zone 4-8: R-30 cavity, R-20 cavity + R-5 continuous, R-13 cavity + R-10 continuous, or R-20 continuous These are MINIMUMS. Many homeowners want better-than-code insulation for energy savings or comfort. Always ask the customer what R-value target they want, then confirm against code. If they want code minimum, that is your floor — you cannot install less. R-value per inch by material: - Fiberglass batt (low density): R-2.9 to R-3.8 per inch - Fiberglass batt (high density): R-4.3 per inch - Cellulose (blown or dense-pack): R-3.2 to R-3.8 per inch - Mineral wool batt: R-3.0 to R-4.0 per inch - Open-cell spray foam: R-3.5 to R-3.7 per inch - Closed-cell spray foam: R-6.0 to R-7.0 per inch (best per inch) - Rigid foam (XPS): R-5.0 per inch - Rigid foam (Polyiso): R-6.0 to R-6.5 per inch Quick math: to hit R-49 in an attic, you need: 13 inches of fiberglass batt, 13 inches of cellulose, 14 inches of open-cell spray foam, 7-8 inches of closed-cell spray foam, or 8-10 inches of polyiso rigid foam. The required depth tells you whether the target is achievable with the chosen material in the available space.

Each insulation type has different material costs, labor rates, and equipment requirements. Here are the typical 2026 pricing ranges for common installations. **Blown-in cellulose (attics)**: Material cost roughly $0.30-$0.50/sqft for R-30 to R-49 thickness. Labor including blowing equipment, hose setup, dust containment, and cleanup runs $1.00-$2.00/sqft. Total installed: $1.30-$2.50/sqft. Most cost-effective option for open attic floors. Requires a blower truck or rental equipment ($150-$300/day rental for the blower). Time: 2-4 hours of blowing for a 1,500 sqft attic. **Blown-in fiberglass (attics)**: Material cost $0.40-$0.70/sqft (more expensive than cellulose). Labor similar to cellulose. Total installed: $1.50-$2.80/sqft. Lighter weight than cellulose so it does not settle as much over time, but higher material cost. Some customers prefer fiberglass for lower dust generation. **Fiberglass batt (walls)**: Material cost $0.30-$0.80/sqft depending on R-value and density. Labor $0.50-$1.00/sqft for cutting and installing. Total installed: $0.80-$1.80/sqft. Easiest to install in standard 16 inch on-center stud walls. Performance is good IF installed without compression and without gaps. Performance suffers if installed sloppily. Most common wall insulation in new construction. **Mineral wool batt (walls)**: Material cost $0.60-$1.20/sqft. Labor similar to fiberglass batt, slightly higher because mineral wool is denser and harder to cut. Total installed: $1.20-$2.20/sqft. Better fire resistance and sound dampening than fiberglass. Often specified in fire-rated assemblies and music studios. **Open-cell spray foam**: Material cost $1.00-$2.50/board foot (1 board foot = 1 sqft × 1 inch thick). Labor and equipment $0.50-$1.50/board foot. Total: $1.50-$4.00/board foot. To insulate to R-30 in walls, you need ~8.5 inches of open-cell, which translates to $12.75-$34/sqft of wall area. Open-cell expands rapidly after spraying, fills irregular spaces well, and provides air sealing. Lower R/inch than closed-cell but cheaper. **Closed-cell spray foam**: Material cost $2.00-$5.00/board foot. Labor and equipment $1.50-$3.00/board foot. Total: $4.00-$8.00/board foot. To insulate to R-30 in walls, you need ~5 inches of closed-cell, which translates to $20-$40/sqft of wall area. Closed-cell is the most expensive option but the only choice for: rim joists, basement walls, irregular cavities, applications requiring air sealing and moisture barrier, and space-constrained installations where high R/inch is needed. Spray foam jobs typically have a minimum charge of $1,500-$3,000 because of equipment setup, mobilization, and the size of the spray rigs. Small jobs can be uneconomical. Most spray foam contractors will not come out for less than $1,500 unless it is a callback or part of a larger project.

Scope: insulate a 1,500 sqft attic in climate zone 5 (target R-60, currently R-19 from old fiberglass batts that have settled). Add ~14 inches of blown-in cellulose on top of the existing batts. Located in a mid-cost market. Step 1: confirm R-value calculation. Existing R-19 + new R-41 from blown cellulose = R-60 total. (Cellulose at R-3.2/inch × 13 inches = R-42, rounding up.) Step 2: material takeoff. Cellulose for R-41 over 1,500 sqft: 1,500 sqft × 13 inches / 12 = 1,625 cubic feet. Bags of cellulose typically cover ~28-32 sqft at R-49 depth. For our R-41 target, slightly less depth, so ~35 sqft per bag. 1,500 / 35 = 43 bags. Bag cost: $13/bag × 43 = $559. Misc material (baffles for vents, dust masks for crew, blower hose extensions): $80. Total material: $639. Step 3: labor. Crew: 2 people. Time: 1 setup (45 min) + blowing (2 hours) + cleanup (45 min) = 3.5 hours total. 2 people × 3.5 hours × $40/hour = $280 raw labor. Blower rental: $250 (one day). Total labor + equipment: $530. Step 4: subtotal, overhead, profit. Subtotal: $639 + $530 = $1,169 Overhead 15%: $175 Profit 15% (insulation work has good margins): $202 Total customer price: $1,546 Per-sqft cost: $1,546 / 1,500 = $1.03/sqft. Lower than the $1.50-$3.00 typical range because the job is a top-up over existing insulation rather than a full removal-and-replace. Tax credit note for the customer: the federal 25C credit, which paid 30% of qualified insulation costs up to $1,200 a year, covers only improvements made through December 31, 2025, according to the IRS. Do not count it on a 2026 job like this one. Check your state energy office and the local utility for current rebates instead, and confirm any program's documentation rules before you promise a customer a lower net cost.