Spray Foam Cost Per Square Foot
Spray foam insulation is priced by board foot (1 sq ft × 1 inch thick). Installers typically quote by square foot at a specified thickness. Here are the 2026 installed price ranges in Connecticut:
| Type | Cost Per Sq Ft (installed) | R-Value Per Inch |
|---|---|---|
| Open cell spray foam | $1.00 – $2.00 | R-3.5 |
| Closed cell spray foam | $1.50 – $3.50 | R-6 to R-7 |
| Comparison: Fiberglass batts | $0.50 – $1.00 | R-2.9 to R-3.8 |
| Comparison: Blown-in cellulose | $0.75 – $1.50 | R-3.7 |
Cost by Project Type in Connecticut
| Project | Average CT Cost | Typical Size |
|---|---|---|
| Rim joist insulation | $800 – $1,800 | Full perimeter, standard home |
| Basement walls | $1,500 – $4,000 | 2" closed cell, full perimeter |
| Crawl space encapsulation | $2,000 – $5,000 | Walls + ground barrier |
| Attic (vented, air seal only) | $600 – $1,500 | Air sealing + minor spray |
| Attic (conditioned, spray foam) | $3,500 – $8,000 | 4–6" on roof deck |
| Garage walls + ceiling | $1,200 – $3,000 | 2 car garage |
| Exterior walls (retrofit) | $2,500 – $7,000 | 3" injected or open wall |
| New construction (full home) | $8,000 – $20,000 | 2,000–3,000 sq ft home |
Open Cell vs. Closed Cell: Cost Comparison
Open Cell: Lower Upfront
$1.00–$2.00/sq ft. But you need more of it (R-3.5/inch vs R-6.5/inch). For the same R-value, open cell may cost only 20–30% less than closed cell when you factor in thickness.
Closed Cell: Better Value Long-Term
$1.50–$3.50/sq ft. Higher upfront but provides vapor control, structural rigidity, and superior R-value per inch. Often the better choice when space is limited.
What Affects Spray Foam Cost
- Type: Closed cell costs 40–80% more than open cell per sq ft
- Thickness: More passes = more material = higher cost
- Accessibility: Tight crawl spaces or complex attics cost more to access
- Prep work: Removing old insulation adds cost
- Project size: Larger projects benefit from economies of scale
- Rebates: CT utility rebates can reduce net cost by 20–50%
Spray Foam vs. Fiberglass: True Cost Comparison
Fiberglass batts appear cheaper at $0.50–$1.00/sq ft installed. But they don't air-seal. An attic insulated with blown-in fiberglass but not air-sealed may save 10–15% on energy. The same attic air-sealed with spray foam and then blown-in may save 30–45%. Over 10 years, the spray foam approach often delivers 2–3× the total savings, making its higher upfront cost worthwhile.
Frequently Asked Questions
Does EcoFoam offer financing for spray foam insulation?
Yes. EcoFoam works with financing partners to offer low-interest payment plans for qualified CT homeowners. Ask about financing options when requesting your free estimate.
Can I get multiple quotes for spray foam insulation?
Absolutely — we encourage it. When comparing quotes, make sure you're comparing the same material, thickness, and scope. Lower quotes often mean thinner application or lower-quality material. Ask for R-value specifications in writing.