Costs & R-Value
Spray Foam Insulation Cost
Spray foam is priced per board foot — one square foot at one inch thick. Knowing that unit makes every quote comparable.
Updated January 2026 · about 7 min read
Price per board foot (2026)
Open-cell installed: $0.45–$0.75 per board foot. Closed-cell installed: $1.00–$1.75. DIY two-part kits: $0.85–$1.40 per board foot before waste, and real-world yield usually comes in 10–20% under the printed figure.
Spray foam cost per square foot
Per square foot is per board foot times the inches sprayed, so the thickness decides the price as much as the foam does. Closed-cell is usually sprayed 1 to 3 inches; open-cell fills a 2x4 cavity at 3.5 inches or a 2x6 cavity or roof deck at 5.5 inches.
| Foam and thickness | R-value | Board feet per sq ft | Installed per sq ft | Calculator typical |
|---|---|---|---|---|
| Closed-cell spray foam, 1 in | R-6.5 | 1 | $1.00 – $1.75 | $1.35 |
| Closed-cell spray foam, 2 in | R-13 | 2 | $2.00 – $3.50 | $2.70 |
| Closed-cell spray foam, 3 in | R-19.5 | 3 | $3.00 – $5.25 | $4.05 |
| Open-cell spray foam, 3.5 in | R-13 | 3.5 | $1.57 – $2.63 | $1.93 |
| Open-cell spray foam, 5.5 in | R-20.4 | 5.5 | $2.48 – $4.13 | $3.03 |
Spray foam calculator: worked examples
Board feet = area × inches × 1.10 for overspray and trim (the calculator's default 10%). Then divide by the kit's rated board feet for DIY, or multiply by the installed rate for a contractor figure.
- Rim joists, 120 ft basement perimeter with 9.25 in rim (about 93 sq ft), 2 in closed-cell: 93 × 2 × 1.10 = 205 board feet, R-13. One 200 board ft kit is not enough — buy a 600, or two 200s at $400 each. A contractor at $1.35 per board foot: about $275 of foam, though most charge a trip minimum.
- Attic roof deck, 1,000 sq ft at 5.5 in open-cell: 1,000 × 5.5 × 1.10 = 6,050 board feet, about R-20. At $0.45–$0.75 per board foot that is about $2,720–$4,540 installed; DIY would take seven 1,000 board ft kits ($10,500), which is why big open-cell jobs are left to contractors.
- Crawl space walls, 400 sq ft at 2 in closed-cell: 400 × 2 × 1.10 = 880 board feet, R-13. One 1,000 board ft kit ($1,500) against about $880–$1,540 installed.
Gear for this job
Loctite Tite Foam Gaps & Cracks Spray Foam Sealant, White, 12 oz, 1 Pack
$6.28
Check price on Amazon
Professional Expanding Foam Spray Gun, 1 Insulation Guns + 9 Extenders
$19.99
Check price on Amazon
Wolline Spray Foam Insulation Gun, Heavy Duty Teflon-Coated, Yellow, 1 Pack
$18.99
Check price on Amazon
Great Stuff 157911 Insulating Foam Sealant, 20 Ounce, Ivory
$16.99
Check price on Amazon
As an Amazon Associate I earn from qualifying purchases. Product links on this page may earn us a commission at no extra cost to you.
Prices as of Oct 11, 2026, 4:41 AM UTC. Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.
As an Amazon Associate I earn from qualifying purchases. Product links on this page may earn us a commission at no extra cost to you.
Typical job totals
Rim joists in an average basement (2 inches closed-cell, ~200 board feet): $350–$700. Crawl space walls (1,000 board feet): $1,100–$1,900. Unvented attic roof deck on a 1,500 sq ft footprint with open-cell at 5.5 inches: $4,500–$8,500. Whole new-construction house: $9,000–$22,000.
DIY kit math
Kits are sold by advertised board feet (200, 600, 1,000). Calculate area × inches, add 15–20% for overspray and yield loss, and buy the next size up. Temperature matters: below 60°F substrate temperature, yield and adhesion both fall off.
Getting a fair quote
Ask for board feet and installed thickness in writing, not just 'spray the attic'. Confirm the product name and data sheet, the ignition barrier plan, and the re-entry period. Compare bids on board feet, because thickness is where quotes quietly differ.
Spray foam is the one job most people hire out; see DIY vs hiring an insulation contractor.
Run the numbers
Frequently asked questions
- How much does spray foam cost per square foot?
- Multiply the per-board-foot price by the inches sprayed. At $1.00–$1.75 per board foot, closed-cell at 2 inches is about $2.00–$3.50 per square foot installed (R-13). Open-cell at $0.45–$0.75 per board foot is about $1.58–$2.63 per square foot at 3.5 inches (R-13) and $2.48–$4.13 at 5.5 inches (R-20).
- How do I calculate how much spray foam I need?
- Board feet = square feet × inches of foam, plus about 10% for overspray and trimming. 500 sq ft of wall at 3.5 inches of open-cell is 500 × 3.5 × 1.10 = 1,925 board feet. Divide by a kit's rated board feet to count DIY kits, or multiply by the installer's per-board-foot rate to check a quote.
- How many square feet does a 600 board foot spray foam kit cover?
- 600 square feet at 1 inch, 300 at 2 inches or about 200 at 3 inches, before losses. Allow at least 10% for overspray and yield that falls short of the label, so plan on roughly 270 sq ft at 2 inches.
- Are DIY spray foam kits cheaper?
- For small areas like rim joists, yes. For large jobs the per-board-foot cost of kits approaches professional pricing without the equipment control.
- Why do spray foam quotes vary so much?
- Different installed thicknesses. Always compare board feet at a stated inch depth, not lump sums.
Insulation gear worth owning
The tools and materials that show up on almost every insulation job.
Spray Foam Insulation Kit, 12 Pack x 30 oz, Expanding Foam Sealant Spray
$214.99
Check price on Amazon
Loctite Tite Foam Gaps & Cracks Spray Foam Sealant, White, 12 oz, 1 Pack
$6.28
Check price on Amazon
3M Particulate Disposable Respirator 8210, N95, Pack of 20, NIOSH APPROVED
$22.89
Check price on Amazon
YIBER Hazmat suit, Disposable coveralls for Painting, Ideal Halloween Cosplay Hazmat Costume, White, Large, 1
$6.99
Check price on Amazon
As an Amazon Associate I earn from qualifying purchases. Product links on this page may earn us a commission at no extra cost to you.
Prices as of Oct 11, 2026, 4:41 AM UTC. Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.