Cost Estimators · Interior Work
Insulation Cost Per Sq Ft Calculator
Enter your area and instantly estimate insulation cost — attic, walls, floors, or crawl space.
Insulation is one of the best investments in a home — reducing energy bills every single month for decades. But the right insulation type and R-value depends on the location in the home, climate zone, and budget. Use this calculator to understand what insulation costs per sq ft before calling contractors.
Enter an area above to see your estimate
Using national average: $1–$5/sq ft
Estimates are based on national averages and are for planning purposes only. Actual costs vary by location, contractor, and material choice.
Example: 1,000 sq ft insulation area
Area
1,000
sq ft
Low Estimate
$1,000
@ $1/sq ft
High Estimate
$5,000
@ $5/sq ft
Based on national average rates of $1–$5/sq ft. Actual costs will vary by location and contractor.
What does insulation cost per square foot?
Fiberglass batt insulation costs $0.50–$1.50 per sq ft installed — the most common and affordable option for walls and attic floors. Blown-in fiberglass or cellulose costs $1–$2.50 per sq ft and is ideal for attics and existing wall cavities. Spray foam insulation is the most effective air barrier at $1.50–$5 per sq ft for open-cell and $3–$8 per sq ft for closed-cell. Rigid foam board costs $1–$3 per sq ft. The right R-value for your climate zone is critical — under-insulating costs more in energy bills than the savings on materials.
Cost by project size
| Project size | Low estimate | High estimate |
|---|---|---|
| 500 sq ft (attic floor or crawl space) | $500 | $2,500 |
| 800 sq ft | $800 | $4,000 |
| 1,000 sq ft (full attic or wall cavities) | $1,000 | $5,000 |
| 1,500 sq ft | $1,500 | $7,500 |
| 2,000 sq ft (whole house walls) | $2,000 | $10,000 |
Approximate 2026 US national averages at $1–$5/sq ft installed. Actual costs vary by location, contractor, and project complexity.
What affects interior work cost per square foot?
Insulation type
Fiberglass batts are cheapest at $0.50–$1.50/sq ft installed. Blown-in cellulose runs $1–$2/sq ft. Open-cell spray foam costs $1.50–$5/sq ft. Closed-cell spray foam is the premium option at $3–$8/sq ft — also acts as a vapour barrier and adds structural rigidity.
R-value required
Higher R-values require more material thickness and cost more. Climate Zone 5–7 (cold climates) requires R-38 to R-60 in attics — nearly double the R-value needed in Zone 2–3. Using the correct R-value for your zone is more important than insulation type for energy performance.
Location in home
Attic floor insulation is the cheapest and most impactful location — easy access and large area. Wall insulation in existing construction requires injection or drill-and-fill methods. Basement rim joists and crawl space floors are critical for comfort but often neglected.
Air sealing requirement
Insulation alone does not stop air infiltration. Air sealing around penetrations, top plates, and rim joists adds $0.20–$0.50/sq ft but dramatically improves the thermal envelope. Professional energy auditors recommend air sealing before adding insulation for best results.
Old insulation removal
If attic insulation is contaminated with mould, pest droppings, or asbestos (pre-1980 homes), it must be removed before new insulation is added. Attic clean-out and removal costs $1–$3/sq ft and should be done by a certified contractor.
Access & difficulty
Open attic floors are the easiest insulation job. Finished walls require injection foam or removal and replacement of drywall. Crawl spaces with limited clearance add significant labour time. Difficult-access areas cost 50–100% more per sq ft than open, accessible spaces.
Frequently asked questions
How much does insulation cost per square foot installed?
Fiberglass batt insulation costs $0.50–$1.50/sq ft installed. Blown-in fiberglass or cellulose runs $1–$2.50/sq ft. Open-cell spray foam costs $1.50–$5/sq ft. Closed-cell spray foam costs $3–$8/sq ft. For a 1,000 sq ft attic floor, expect $1,000–$2,500 for blown-in insulation.
What type of insulation is best for an attic?
Blown-in fiberglass or cellulose is the most cost-effective choice for attic floors — it fills gaps and achieves high R-values easily. R-38 to R-60 is recommended depending on your climate zone. Spray foam is better for attic rooflines (creating conditioned attic space) but costs significantly more.
How much can insulation reduce energy bills?
Adding insulation to an under-insulated attic typically reduces heating and cooling costs by 10–20%. The US Department of Energy estimates proper attic insulation pays back its installation cost in energy savings within 3–7 years in most climates, making it one of the highest ROI home improvements.
What R-value do I need?
R-value requirements depend on your climate zone. Zone 1–2 (South): attic R-30 to R-38. Zone 3–4 (Mid-Atlantic): attic R-38 to R-49. Zone 5–7 (North): attic R-49 to R-60. Walls: R-13 to R-21 in most zones. The DOE Energy Star map shows your zone.
Is spray foam insulation worth the extra cost?
Closed-cell spray foam costs 3–5× more than fibreglass batts but creates a complete air and vapour barrier, adds structural rigidity, and achieves higher R-value per inch. It is particularly cost-effective in rim joists, crawl spaces, and unvented attic rafter bays where its air-sealing properties deliver the most benefit.