Professional
Spray Foam Insulation

Open-cell vs. closed-cell — which one?

Open-cell (typically $0.45–$0.75/board foot): lower density, higher expansion ratio. Best for interior walls, cathedral ceilings, and above-grade applications where you want maximum yield per can and sound-deadening benefits. R-3.6 per inch.

Closed-cell (typically $1.00–$1.75/board foot): higher density, built-in vapor barrier, structural rigidity. Best for rim joists, basement walls, crawl spaces, and any application where moisture is a concern. R-6+ per inch.

Most New England jobs are mixed: closed-cell where moisture matters, open-cell where yield matters.

Where spray foam earns its premium

• Attic roof deck — creates an unvented conditioned attic, eliminating ice dams and knob-and-tube concerns.
• Rim joists — the #1 air-leakage location in most homes. A thin closed-cell bead here pays off more than anywhere else.
• Crawl spaces — closed-cell on walls plus ground-sealing creates a conditioned crawl space, eliminating moisture and cold floors above.
• Cathedral ceilings — irregular cavities where batts fail. Open-cell fills and air-seals in one step.
• Bonus rooms over garages — where nothing else works.

Spray foam and state rebate programs

Here's the part other contractors don't tell you: Mass Save®, NHSaves®, and Efficiency Maine do not rebate spray foam specifically. They rebate approved cellulose, fiberglass, and rigid foam weatherization plus air sealing.

What this means in practice: if your job is pure spray foam (e.g., cathedral ceilings, crawl space), it's out-of-pocket. If your job mixes spray foam with air sealing and attic blown-in insulation, we can get the air sealing and attic portion rebated — cutting your effective cost meaningfully.

We tell you up front what's rebated and what isn't. No surprises.

Cost ranges (2026)

• Attic roof deck (1,500 sq ft): $4,500–$9,000 closed-cell, $2,500–$5,500 open-cell.
• Rim joist (whole house): $800–$1,800 closed-cell.
• Crawl space (800 sq ft): $2,500–$5,500 closed-cell.
• Cathedral ceiling (400 sq ft): $1,500–$3,500.
• Basement walls (1,500 sq ft): $3,500–$7,500 closed-cell.

Exact pricing depends on access, existing insulation removal, thickness, and electrical/mechanical prep. We give a firm written quote after walkthrough.

Safety and cure

Spray foam is chemically inert once cured — typically 24 hours. Occupants, pets, and plants must be out during spraying and cure. We follow manufacturer re-entry guidelines and won't return the home to occupancy until cured and ventilated. Properly installed, spray foam has an 80-year service life.