The Money Side
How Much Does Spray Foam Insulation Actually Cost?
Real cost-per-board-foot numbers, what drives the price, and how open-cell and closed-cell compare.
Spray foam insulation pricing questions are some of the most common searches homeowners run before starting a project — and the honest answer depends on several specific factors, not a single flat number. Here's a real breakdown.
Priced by the Board Foot
Spray foam is typically priced by the board foot — one square foot of coverage at one inch of thickness. This is a more precise pricing unit than a flat per-square-foot number, but it also means the final price depends on both the area covered and the thickness applied, not area alone.
Foam Type Is the Biggest Variable
Open-cell foam typically runs roughly $0.45 to $0.65 per board foot installed. Closed-cell typically runs roughly $1.00 to $1.50 per board foot installed — two to three times more, reflecting higher material density and a more expensive blowing-agent system, along with the higher R-value and vapor-barrier properties it delivers.
Job Accessibility and Prep Work
An open, easily accessible attic or new-construction cavity costs less to spray than a cramped crawlspace or a space requiring substrate prep before application. An accurate quote requires an in-person walkthrough, not just a square-footage number over the phone.
Typical Whole-Project Ranges
For context: a typical 1,500 sq ft attic insulated with open-cell foam at 6 inches often lands somewhere in the $4,000-$9,000 range; the same job with closed-cell at 3 inches often lands higher, reflecting the material cost difference. These are general ranges, not a quote — your specific project's price depends on the factors above.
Key Takeaways
- Spray foam is priced by the board foot (area x thickness), not area alone.
- Open-cell runs roughly $0.45-$0.65/board foot installed; closed-cell runs roughly $1.00-$1.50/board foot.
- Job accessibility and prep work materially affect the final price beyond the material cost alone.
- General ranges are a starting point — an in-person walkthrough is the only way to get an accurate number.
Common Questions
Real Cost Breakdown FAQs
Real questions people ask before starting a spray foam project.
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