Spray Foam Insulation Cost per Square Foot (2026)
By Your Name · Last updated · How we calculate
Professionally installed spray foam costs about $1.40–$3.50 per square foot for open-cell foam 3½" thick, and $2.00–$5.80 per square foot for closed-cell foam 2" thick. Contractors actually price by the board foot (one square foot, one inch thick), at roughly $0.40–$1.00 for open-cell and $1.00–$2.90 for closed-cell, and most charge a minimum of $1,000–$2,000 per job.
Key takeaways
- A square-foot price means nothing without a thickness. Always convert quotes to price per board foot.
- Closed-cell costs about 2.7 times as much per board foot as open-cell, but packs nearly twice the R-value per inch.
- Small jobs like rim joists often cost $1,000–$2,000 because of the job minimum. Bundle areas into one visit.
- DIY kits cost about as much per board foot as a pro’s closed-cell price, so they only save money on small jobs.
Run your own numbers: Spray Foam Insulation Calculator
Spray foam is the most expensive common insulation per square foot, and also the hardest to price, because the same job can be quoted at $1.50 or $5.00 per square foot depending on the foam and how thick it goes on. This guide breaks the price down the way contractors do: by the board foot, then by thickness, then by real projects. To price your own job, use the spray foam cost calculator.
Spray foam cost per square foot by thickness
Installed price per square foot of surface sprayed, at our 2026 board-foot rates. R-values use typical aged values of R-3.7 per inch for open-cell and R-6.5 for closed-cell.
| Foam and thickness | R-value | Typical use | Cost per sq ft |
|---|---|---|---|
| Open-cell, 3.5" | R-13 | 2×4 wall, full cavity | $2.10 $1.40–$3.50 |
| Open-cell, 5.5" | R-20 | 2×6 wall, full cavity | $3.30 $2.20–$5.50 |
| Open-cell, 8" | R-30 | Roof deck, unvented attic | $4.80 $3.20–$8.00 |
| Closed-cell, 1" | R-7 | “Flash” coat under batts | $1.60 $1.00–$2.90 |
| Closed-cell, 2" | R-13 | Rim joists, basement walls, 2×4 wall | $3.20 $2.00–$5.80 |
| Closed-cell, 3" | R-20 | 2×6 wall, roof deck | $4.80 $3.00–$8.70 |
That’s why published averages vary so much. HomeGuide’s $1.50–$3.50 for open-cell and $3.00–$5.00 for closed-cell are typical cavity-fill thicknesses. A 1" flash coat of closed-cell can come in under $2.00, and a thick roof deck can top $6.00.
Spray foam cost per board foot
A board foot is one square foot of foam one inch thick. It’s how foam comes out of the drum and how every installer prices. Board feet = square feet × inches; there’s no dividing by 12. Read more inspray foam board feet explained.
| Open-cell | Closed-cell | |
|---|---|---|
| Installed price per board foot | $0.40–$1.00 (avg $0.60) | $1.00–$2.90 (avg $1.60) |
| R-value per inch | R-3.5–3.8 | R-6–7 |
| Price per R per sq ft (avg) | $0.16 | $0.25 |
| Density | about 0.5 lb/cu ft | about 2 lb/cu ft |
Per unit of R-value, closed-cell costs about 52% more than open-cell at average prices. You’re also paying for things open-cell doesn’t do: closed-cell is a vapor retarder at about 2", doesn’t absorb water, and stiffens the framing. See open-cell vs. closed-cell spray foam for when each is worth it.
Spray foam cost by project
Contractor prices for common jobs, using the same model as our calculator. They price the foam actually sprayed and apply a job minimum where it kicks in:
| Project | Board feet | Contractor cost | Per sq ft |
|---|---|---|---|
| Rim joists, 160 ft of perimeter × 10" deep Closed-cell, 2.5" (R-16) | 333 | $1,500 $1,000–$2,000 | $11.28 |
| Crawl space walls, 500 sq ft Closed-cell, 2.0" (R-13) | 1,000 | $1,600 $1,000–$2,900 | $3.20 |
| 2×4 exterior walls, new build, 1,600 sq ft Open-cell, 3.5" (R-13) | 5,075 | $3,045 $2,030–$5,075 | $1.90 |
| Roof deck (unvented attic), 1,800 sq ft Open-cell, 8.0" (R-30) | 13,500 | $8,100 $5,400–$13,500 | $4.50 |
| Roof deck, closed-cell R-38, 1,800 sq ft Closed-cell, 5.8" (R-38) | 9,865 | $15,785 $9,865–$28,610 | $8.77 |
| Pole barn walls + roof, 4,000 sq ft at 2" Closed-cell, 2.0" (R-13) | 8,000 | $12,800 $8,000–$23,200 | $3.20 |
For a sanity check, HomeGuide’s contractor data puts a typical attic at $3,000–$8,000, all exterior walls at $4,000–$10,000, a crawl space at $2,000–$4,000 and a whole house at $8,000–$20,000. Walls and roof decks in new construction are the cheapest per square foot because the cavities are open. Existing homes need drywall or siding removed, or a different foam injected through holes, which adds labor.
Why small spray foam jobs cost so much
A spray foam crew arrives with a truck-mounted rig: a heated proportioner, a generator and a long heated hose. Setting up, heating the chemicals, masking, spraying and cleaning out take about the same time whether the job is 300 board feet or 3,000. So most companies charge a minimum of $1,000–$2,000.
The rim joist job in the table needs only 333 board feet, worth about $532 at the average rate, but you’ll pay the minimum. Two ways around it: bundle the rim joists with the crawl space or attic in one visit, or do small jobs yourself with a kit.
DIY spray foam kits vs. hiring a pro
Two-component DIY kits are almost all closed-cell and come in nominal 200 and 600 board-foot sizes. HomeGuide lists 200-board-foot kits at $300–$500 and 600-board-foot kits at about $700–$850, or $1.17–$2.00 per board foot. That’s close to a contractor’s installed closed-cell price, before you buy a suit, respirator and spare nozzles ($75–$200).
- DIY makes sense for jobs under the contractor minimum: rim joists, a small crawl space wall, a shed, sealing around a bump-out.
- Hire a pro for whole walls, roof decks and anything open-cell. Kits rarely yield their full rating, are limited in thickness per pass, and mistakes like poor mixing or too-thick passes cause odor and shrinkage that are expensive to fix.
- Kits only work within the chemical and surface temperature range printed on the box, and you’ll need to keep everyone out of the area while it cures. Read the kit’s data sheet before you buy.
Our spray foam calculator tells you how many 200 and 600 board-foot kits a job needs, and the cost calculator compares the kit price with a contractor’s.
Extra costs to budget for
- Removing old insulation: about $1.00–$2.50 per sq ft. Foam needs a clean, dry surface, so old batts on a roof deck or rim joist have to come out.
- Thermal or ignition barrier: building codes require foam in living spaces to be covered, usually by ½" drywall. Exposed foam in attics and crawl spaces entered only for service needs an ignition barrier or a foam/coating that’s been tested for it. Ask whether a coating is included.
- Vapor-retarder coating: open-cell foam on an unvented roof deck in cold climates (zones 5–8) usually needs one; ArmorThane puts it at $0.65–$1.00 per sq ft.
- Access in existing homes: removing drywall, siding or a ceiling and putting it back. ArmorThane estimates existing homes run about 15% more.
- Time away: plan to stay out of the house during spraying and for at least 24 hours after, or as long as the product’s instructions say.
How to compare spray foam quotes
- Get the foam type, thickness and area in writing for every surface. If a quote won’t state thickness, that’s a red flag.
- Convert to price per board foot: total ÷ (square feet × inches). Then compare with $0.40–$1.00 for open-cell and $1.00–$2.90 for closed-cell.
- Check the R-value against code for your climate zone and location (roof, wall, floor).
- Ask what’s included: removal, coatings or barriers, masking, cleanup, and any warranty on the foam and the installation.
- Ask about the product. Get the manufacturer, its evaluation report, and whether the crew is trained or certified on it.
Frequently asked questions
How much does it cost to spray foam a 1,000 sq ft area?
At 3½" of open-cell, about $2,100 ($1,400–$3,500). At 2" of closed-cell, about $3,200 ($2,000–$5,800). That’s 1,000 sq ft of sprayed surface, not floor area.
Is closed-cell spray foam worth the extra cost?
Where you need a vapor retarder, water resistance or the most R-value in a thin space (basement and crawl space walls, rim joists, roof decks in cold climates, 2×4 walls), usually yes. In interior walls and many attics, open-cell does the job for less.
How much is spray foam per square foot compared with fiberglass?
HomeGuide puts fiberglass batts at $1.00–$2.60 per sq ft installed and blown-in at $1.00–$2.80, against $1.50–$5.00 for spray foam. Spray foam also air-seals, which fiberglass doesn’t, so compare against fiberglass plus air sealing.
Does spray foam pay for itself?
It depends on what it replaces, your climate and energy prices. The biggest gains come from sealing leaky areas such as rim joists, attics with ductwork and crawl spaces. Be skeptical of fixed payback promises in a quote.