Quick Answer: Insulation costs $1–$7/sqft installed depending on type. Insulating an average attic (1,000 sqft) with blown-in fiberglass runs $1,500–$4,500. Spray foam costs more but delivers the best air-sealing results.
How Much Does Insulation Cost?
| Insulation Type | Cost per Sqft Installed | R-Value per Inch | Best Use |
|---|---|---|---|
| Fiberglass Batt | $0.50–$1.50 | R-3.1 to R-3.4 | Walls, floors, attics (accessible) |
| Blown-In Fiberglass | $1.00–$2.50 | R-2.9 to R-3.8 | Attics, hard-to-reach cavities |
| Blown-In Cellulose | $1.00–$2.00 | R-3.2 to R-3.8 | Attics, retrofit wall fills |
| Open-Cell Spray Foam | $1.50–$3.00 | R-3.5 to R-4.0 | Crawl spaces, rim joists |
| Closed-Cell Spray Foam | $3.00–$7.00 | R-6.0 to R-7.0 | Roof decks, exterior walls |
| Rigid Board (XPS/EPS) | $0.75–$2.50 | R-3.8 to R-6.5 | Basements, exterior sheathing |
Attic Insulation Cost
Adding blown-in insulation to an existing attic is one of the highest-ROI home improvements. The average 1,000–1,200 sqft attic costs $1,500–$4,500 depending on current R-value, access, and material. Most utility companies and states offer rebates of $200–$1,000 for qualifying upgrades.
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View on Amazon →Wall Insulation Cost
New construction walls insulated with fiberglass batt typically run $0.50–$1.50/sqft. Retrofit injection foam for existing closed walls costs $2–$5/sqft due to access drilling and patching. Blown-in dense-pack through small holes is the most common retrofit approach.
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Crawl Space and Basement
Insulating a crawl space floor (between joists) runs $1–$3/sqft. Encapsulation of a crawl space (vapor barrier + rigid board on walls) costs $3,000–$8,000 for an average home but dramatically reduces moisture issues and energy loss.
What R-value do I need for my attic?
The Department of Energy recommends R-38 to R-60 for most attics in the US (about 10–15 inches of blown-in fiberglass or cellulose). Climate zone determines the exact target.
Is spray foam insulation worth the extra cost?
Spray foam (open-cell or closed-cell) provides both insulation and an air seal in one step. It costs 3–5x more than batt but can cut HVAC load significantly in leaky homes.
Can I insulate my attic myself?
Blown-in insulation is DIY-friendly with a rented blower machine. Spray foam requires licensed applicators. Batt insulation is very DIY-accessible in walls and crawl spaces.
How long does insulation last?
Fiberglass batt and blown-in insulation last 80–100 years in undisturbed conditions. Spray foam is permanent. Cellulose can settle over time and may need a top-up after 15–20 years.
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