Cost estimate · Spray foam
Spray Foam Insulation Cost Calculator
Price spray foam the way contractors do — in board feet (sq ft × inches). Pick open- or closed-cell, set thickness for walls, attic deck, rim joist, or crawl, and optionally add an ignition-barrier coating. Blown attic bag counts and ruler-to-R tools live on sibling pages.
Spray foam details
Fill stud bay depth — 3.5" for 2×4, ~5.5" for 2×6.
Lower $/board-ft; vapor-permeable; common in walls and attic decks. R ≈ 3.5–3.7/in.
Estimated spray foam cost
$1,470–$2,573
Typical ~$2,021 · $1–$3/sq ft
- Board feet
- 3,675 bf
- Approx R
- R-13
- Foam
- Open-cell spray foam
- R range
- 12–13
1 board-foot = 1 sq ft × 1 in thick. Contractors bid spray foam in board-feet, not bags.
Cost breakdown
- Open-cell spray foam (installed)3675 board-ft × $0.40–$0.70/bf (1000 sq ft × 3.5 in + 5% waste)$1,470–$2,573
Not included
- Framing repairs, mold remediation, or asbestos/vermiculite abatement
- New drywall, paint, or full thermal barrier assemblies beyond a coating allowance
- HVAC redesign, roofing, or whole-house air sealing outside the sprayed area
- Permit fees and sales tax
Price data updated . National US ranges from published supplier and contractor averages. Not a bid. Local quotes vary.
How spray foam cost is calculated
Board feet equal coverage area times thickness, plus a little waste. Installed cost multiplies board feet by a national $/board-foot band for open or closed cell. An optional coating line covers ignition/thermal barrier when foam stays exposed.
board_feet = area_sq_ft × thickness_in × (1 + waste %) foam_cost = board_feet × $/board-foot (by foam type) barrier = area_sq_ft × barrier $/sq ft (optional) total = foam_cost + barrier approx_R = thickness_in × r_per_inch
Worked example. 1,000 sq ft of 2×4 walls at 3.5" open-cell is 3,500 board-ft before waste (3,675 at 5%). At $0.40–$0.70/bf that is about $1,470–$2,570 for foam alone (~R-13). The same area at 3" closed-cell is 3,000 bf (~R-18–21) at $1.00–$2.00/bf → roughly $3,000–$6,000 before any barrier coating.
Spray foam board-foot cost & thickness to R
Contractors sell foam by the board-foot. Use this chart to translate thickness into approximate R and a planning dollar band before waste.
| Foam | R / inch | $ / board-ft | In for ~R-13 | In for ~R-21 | In for ~R-38 |
|---|---|---|---|---|---|
| Open-cell | 3.5–3.7 | $0.40–$0.70 | ~3.5" | ~6" | ~10.5" |
| Closed-cell | 6.0–7.0 | $1.00–$2.00 | ~2" | ~3.5" | ~6" |
- 1 board-foot = 1 sq ft of surface × 1 inch of foam thickness.
- Wall cavities are usually limited by stud depth (3.5" or 5.5") — you cannot always chase attic-level R inside a 2×4 bay.
- Closed-cell at ≥2" often acts as a Class II vapor retarder; open-cell stays vapor-permeable.
Installed $/sq ft at common thicknesses (foam only)
Multiply mid board-foot price × thickness for a quick $/sq ft check. Waste and ignition barrier are extra in the calculator.
| Thickness | Open-cell $/sq ft | Closed-cell $/sq ft | Typical use |
|---|---|---|---|
| 2" | $0.80–$1.40 | $2.00–$4.00 | Crawl / flash coat |
| 3" | $1.20–$2.10 | $3.00–$6.00 | Rim joist |
| 3.5" | $1.40–$2.45 | $3.50–$7.00 | 2×4 wall fill |
| 5.5" | $2.20–$3.85 | $5.50–$11.00 | 2×6 wall / attic deck |
| 7" | $2.80–$4.90 | $7.00–$14.00 | Higher attic R targets |
Spray Foam Insulation Cost calculator FAQ
- How much does spray foam insulation cost?
- National installed bands are often about $0.40–$0.70 per board-foot for open-cell and $1–$2 per board-foot for closed-cell. Convert with area × thickness: 1,000 sq ft at 3.5" is 3,500 board-feet before waste.
- What is a board foot of spray foam?
- One board-foot is one square foot of surface covered one inch thick. A 500 sq ft wall at 3" thick is 1,500 board-feet. That is how foam trucks meter and bid the job.
- Open-cell vs closed-cell — which should I choose?
- Open-cell costs less per board-foot and stays vapor-permeable. Closed-cell costs more but packs more R per inch and adds rigidity and moisture resistance. Walls with limited depth often prefer closed-cell to hit code R; large attic decks often use open-cell for $/R.
- Do I need an ignition or thermal barrier?
- When foam is left exposed in living space, storage attics, or some crawlspaces, code often requires a 15-minute thermal barrier (commonly 1/2" gypsum) or an approved ignition-barrier coating. Toggle the coating line for a planning allowance — drywall is a separate trade.
- Is this a contractor bid?
- No. It is a national US planning range from board-foot price rows. Access, prep, removal of old insulation, and local labor move the number. Compare local bids against this range.
- How is this different from the attic insulation cost calculator?
- Attic cost is built around blown/batt fill plus attic job add-ons (baffles, hatch dam, air sealing). This page is foam-only board-foot math for walls, roof decks, rim joists, and crawls.
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