The short answer
Spray foam is priced by the board foot: one square foot of surface, one inch thick. National cost guides put installed open-cell foam at roughly $0.44 to $1.60 per board foot and closed-cell at roughly $1.00 to $3.10 per board foot. Angi reports that most homeowners spend about $1,455 to $4,336 on a spray foam project, with a national average near $2,888, while whole-home jobs can reach about $8,000 or more.
Because price is tied to thickness, the number that matters for a Princeton home is how many square feet of surface get sprayed and how deep. A sealed attic roof deck needs several inches of open-cell foam; a rim joist or crawl space wall usually needs a couple of inches of closed-cell. Treat every figure on this page as a planning range, not a quote.
Typical spray foam price ranges
National ranges from published cost guides, plus worked examples using those per-board-foot rates.
| Item | Typical installed range | Notes |
|---|---|---|
| Open-cell foam | $0.44–$1.60 per board foot | Common for attic roof decks and interior walls |
| Closed-cell foam | $1.00–$3.10 per board foot | Denser; used for crawl spaces, rim joists, metal buildings |
| Broad planning range | $1–$5 per sq ft of surface | Depends mostly on foam type and depth |
| Example: 1,000 sq ft roof deck, ~5.5 in open-cell | About $2,400–$8,800 | 5,500 board feet at the rates above |
| Example: 200 sq ft rim joists or crawl walls, 2 in closed-cell | About $400–$1,240 | 400 board feet at the rates above |
| Typical project total (national) | About $1,455–$4,336 | Angi 2026 data; whole homes can run about $8,000+ |
Examples are simple arithmetic from published ranges. Real quotes add minimum charges, prep work and access and may not scale linearly.
What drives the price
- Foam type: Closed-cell uses more material per inch and costs roughly twice as much per board foot as open-cell.
- Thickness and R-value target: Every added inch adds another board foot per square foot, so the target R-value sets most of the material cost.
- Surface area, not floor area: A sloped roof deck is larger than the attic floor below it, and two-story homes have more wall and knee-wall area than their footprint suggests.
- Removing old insulation: Pulling out old batts or loose fill, or cleaning up rodent damage, is often priced separately.
- Access: Low-pitch roofs, tight attics, crawl spaces and second-floor work slow the crew down.
- Prep and code items: Air sealing, closing off attic vents for an unvented attic, and any required ignition or thermal barrier add cost.
- Job size: Small jobs often hit a minimum charge, so the per-board-foot price is higher.
Princeton and Collin County considerations
North Texas is in IECC climate zone 3, where the long cooling season is the main driver. In many newer Princeton subdivisions the ductwork and air handler sit in the attic, which can be far hotter than the outdoors on a July afternoon. Spraying open-cell foam under the roof deck brings that equipment inside the insulated space, which is why roof-deck jobs are the most common quote here.
Metal shops, barns and garages on acreage east of town are the other common project. Bare steel panels can drip condensation on humid mornings, and closed-cell foam sprayed directly on the panels is the usual fix. Those jobs are priced on wall and roof square footage, so measure both before you call.
If you're building new, insulation is cheapest before drywall goes up. Ask your builder what the insulation allowance is and compare it with a separate spray foam estimate.
Ways to save on spray foam
- Get two or three quotes that each list foam type, thickness, square footage and R-value so you're comparing the same job.
- Use closed-cell only where it earns its keep (crawl spaces, rim joists, metal) and open-cell elsewhere.
- Bundle areas such as the attic, garage ceiling and rim joists into one visit to avoid paying several minimum charges.
- Clear the attic and garage access yourself before spray day if the installer agrees.
- If the HVAC system is due for replacement, ask about re-checking the equipment size after the attic is sealed.
- For new construction, schedule foam before drywall rather than retrofitting later.
Call (469) 812-8909 for a free estimate
Sources checked 2026-10-29: Angi: spray foam insulation cost (2026); HomeAdvisor: spray foam insulation cost; HomeAdvisor: insulation cost; ENERGY STAR: recommended insulation R-values. National figures are adjusted by local labor, materials and site conditions; treat every number here as a planning range, not a quote.