Most of our projects run between $3,500 and $12,500. On a spray foam job the number follows how much foam goes in, counted in board feet (the area sprayed times the inches), whether it is open or closed cell, how hard the space is to work in, and what comes before and after: old insulation out, air sealing, a fire barrier over the foam.
National cost guides quote spray foam by the square foot, and they disagree. HomeGuide’s, updated December 2025, puts it at $1.50 to $5.00 per square foot installed; Fixr’s, updated January 2025, at $2.75 to $6.50 in new construction and $3.15 to $7.50 in existing homes. Both are national averages that vary by region, neither is our price, and a square-foot figure means little until you know how many inches it buys.
Spray foam insulation cost per square foot and per board foot
A board foot is one square foot covered one inch deep, the unit Fixr’s guide says spray foam is sold and installed by. So 400 square feet of roof deck at 3 inches is 1,200 board feet, and at 7 inches it is 2,800.
The national figures, none of them a quote for your house or our price:
- Installed, per square foot: HomeGuide (December 2025) lists open cell at $1.50 to $3.50 and closed cell at $3.00 to $5.00, and counts the treated surface area, not the floor area of the house.
- Installed, per board foot: HomeAdvisor (updated June 2026) lists open cell at $0.60 to $1.60 and closed cell at $1.30 to $3.10.
- Material only, per board foot: Fixr (January 2025) lists open cell at $0.44 to $0.65 and closed cell at $1 to $1.50.
How to estimate what your project needs
A spray foam cost calculator multiplies area, inches and a price per board foot. You can pin down the first two:
- Measure the surface, not the floor. A sloped roof deck is bigger than the attic floor under it, and gable walls add more. Basement and crawl space walls are height times perimeter.
- Set the inches from the R-value. Divide the target by R-6.9 to R-7.1 per inch for closed cell, or R-3.9 to R-4.2 for open cell.
- List what isn’t foam: the fire barrier, vapor retarder paint where required, prep, and taking the old insulation out.
What does spray foam cost for a 1,500 or 2,000 square foot house?
Floor area doesn’t say how much foam a house takes. HomeAdvisor’s (June 2026) says a 1,500-square-foot home usually costs $1,500 to $7,500. Fixr’s (January 2025) puts the national average range to fully insulate a home at $10,000 to $30,000, and around $20,000 for open and closed cell 6 inches thick in an existing 2,000-square-foot home. What gets sprayed, and how deep, is the difference.
Open cell vs closed cell spray foam cost
Closed cell costs more per inch because each inch holds more foam. The EPA describes professional open cell as low density, half-pound foam, and closed cell as medium density, 2-pound foam: roughly four times the material in every board foot. The Department of Energy’s Building America insulation guide puts it simply: open-cell foam costs less than closed-cell foam, but has a lower R-value per inch.
What you are buying is R-value. Two inches of closed cell, about R-13.8 to R-14.2, matches a full 3 1/2-inch 2x4 bay of open cell, about R-13.7 to R-14.7. The sources split on what that does to the price: HomeGuide’s installed figures put open cell lower, while Fixr’s guide argues that because open cell needs more inches, there is little to no difference once installed. The space usually decides:
- Deep framing, such as 2x10 and 2x12 rafters, has room for open cell’s inches, and its lower price per inch counts.
- Shallow framing, such as 2x6 and 2x8 rafters, needs closed cell. R-49 takes about 7 inches of closed cell, or 11 3/4 to 12 1/2 inches of open cell.
- Water, vapor or below grade, meaning rim joists and crawl space and basement walls: closed cell, whatever the price. The same guide calls it the best moisture control of all interior foundation insulations.
One code cost falls on open cell. In climate zone 5 and colder, foam under an unvented roof must be a Class II vapor retarder or carry a Class II coating (IRC Section R806.5, in the 2021 edition Connecticut uses and the 2024 edition New Jersey and New York adopted). That is all of Connecticut, New Jersey’s seven zone 5 counties from Bergen to Warren, and most of the Hudson Valley beyond Westchester. The Department of Energy notes closed cell is a vapor retarder and open cell is not, so open cell there gets a sprayed vapor retarding paint, one more line on the quote. See open cell vs closed cell spray foam.
What drives the price of a spray foam job
- Area and depth. Board feet set the material; the R-value the code or the assembly needs sets the depth.
- Access. HomeGuide notes installation costs less in open attics and unfinished basements than in tight crawl spaces or finished walls. Low eaves, knee walls and rim joists above a finished ceiling all add hours.
- Prep. Belongings moved, surfaces masked, and the heating and cooling shut down with vents sealed; the EPA lists skipping that among the practices that affect curing.
- Old insulation and wiring. Foam goes onto clean, dry framing, sheathing or masonry, so batts in rafter bays, rim joists and crawl space walls come out first. We do that removal ourselves, bagged out under containment with a HEPA insulation vacuum, and it is its own line on the quote; HomeGuide (December 2025) puts the national average at $1.00 to $2.50 per square foot. Wet or settled insulation comes out the same way, but mold itself is work for a remediation company, vermiculite for a licensed asbestos professional, and active knob-and-tube wiring, which the Department of Energy says should be replaced before insulation work begins, for an electrician.
- The fire barrier. The International Residential Code requires foam to be separated from the inside of the house by a thermal barrier such as 1/2-inch gypsum wallboard (Section R316.4 of the 2021 IRC, which Connecticut uses; R303.4 of the 2024 IRC, adopted in New Jersey and New York). An attic or crawl space entered only for repairs or maintenance needs only an ignition barrier, or foam tested for that use (R316.5.3 and R316.5.4; R303.5.3 and R303.5.4); one used for storage doesn’t qualify.
- Setup, travel and small jobs. The EPA explains that professional foam is pumped from drums through heated hoses at high pressure, so the rig, heating and cleanup come with every job, one rim joist or a whole roof. Small jobs cost more per square foot, HomeGuide notes most spray foam companies set a minimum job fee, and distance adds travel time.
Spray foam cost by project
Attic roofline
The area is the underside of the roof deck plus the gable walls. The depth follows the ceiling requirement: R-49 under New Jersey’s 2024 energy code and New York’s 2025 code, which is about 7 inches of closed cell or 11 3/4 to 12 1/2 inches of open cell, and R-60 under Connecticut’s 2021 IECC, about 8 1/2 to 8 3/4 inches of closed cell. Add the ignition barrier (a thermal barrier if the attic holds storage), vapor retarder paint on open cell in zone 5, old batts out of the rafters, and the vents sealed.
The Department of Energy’s guide says enough foam for the recommended R-value under a cold-climate roof may be expensive, and that adding inexpensive fiberglass or dense-pack cellulose under closed cell foam cuts the cost; the code sets the foam minimum for that hybrid at R-15 in zone 4A and R-20 in zone 5 (IRC Table R806.5). The guide also calls roofline foam much more expensive than batts or blown fiber, possibly cost-effective when reroofing or creating an attic room. With no ductwork up there, blown-in on an air-sealed attic floor usually costs far less; see attic insulation.
Rim joists
Priced on the foundation perimeter and joist bays, and slowed by pipes, wires, ducts and finished ceilings. Closed cell up to 3 1/4 inches, about R-22 to R-23, can stay exposed if it meets the code’s density and flame-spread limits (R316.5.11, R303.5.11), so there is usually no drywall. A small area, and worth doing while the rig is set up for basement or crawl space work.
Crawl space walls
Priced on wall height times perimeter, plus the rim. The Department of Energy’s guide lists 3 inches of closed cell for crawl space walls. A crawl space used for storage needs a thermal barrier, not just an ignition barrier. We install the ground liner and encapsulate the space, and can talk through a dehumidifier; drainage work is a waterproofing contractor’s. See crawl space insulation.
Basement walls
Priced on wall area, and the cost people miss is the thermal barrier: a basement is inside the house, so foam on its walls gets covered, typically with 1/2-inch drywall. A leaking wall needs a waterproofing contractor first. Closed cell earns its price on rough stone and block; on flat poured walls, rigid foam board with taped seams is worth pricing too, and we install both. See basement insulation.
New construction and gut renovations
Open framing is the easiest spray foam there is: nothing to remove, nothing finished to protect, and the drywall that serves as the thermal barrier goes up anyway. The price moves with framing depth, the R-value the energy code requires, and trimming, since open cell can expand past the studs and gets cut back, as the EPA notes. HomeAdvisor (June 2026) puts new construction at about $1 to $4 per square foot nationally, against about $3 to $5 in existing homes.
Existing, closed walls
Standard spray foam needs open cavities, so drywall or siding comes off first. HomeGuide notes siding matters: vinyl comes off and goes back easiest, brick and wood take the most labor. Fixr’s guide says the patching and finish work is why most people insulating existing wall cavities choose blow-in insulation. We dense-pack blown-in insulation through small holes, and we install injection foam, a different product made for closed cavities; either way it is our line item, not a trade to line up separately. See wall insulation.
How to compare spray foam quotes
- Foam type, inches and R-value for every area, in writing. “Spray foam the attic” is not a scope. HomeGuide advises getting the areas, estimated R-value, depth, and foam brand and type. With area and inches you can work out board feet and compare like with like.
- Air sealing. Foam seals what it covers; ask what else gets sealed. If a quote specifies a depth of insulation and never mentions air sealing, it is half a job.
- The fire barrier. Which one each area needs and whether it is in the price. Bare foam where the code requires a barrier is not a cheaper quote but an incomplete one.
- Exclusions. Mold remediation, drywall, electrical work. Removal and vapor retarder paint are in our scope; line the rest up before comparing totals.
- Who sprays it. HomeGuide’s questions for spray foam companies include whether the work will be subcontracted. Our crew is in-house and never subcontracts.
Price is a poor tiebreaker: HomeGuide lists spray foam as difficult and expensive to remove.
Is spray foam insulation worth the cost?
ENERGY STAR says sealing air leaks and adding insulation can provide up to a 10% savings on your annual energy bills. That covers sealing and insulating generally, not spray foam in particular.
The Department of Energy’s Building America guide sets the test. If your insulation is already adequate, adding more may not save enough to recoup the cost; if the house is poorly insulated or the bills are high, added insulation is likely to pay for itself over time. Its yardstick is simple payback: the cost of the work divided by the estimated annual savings, in years.
The same guide rates open and closed cell spray foam at four dollar signs for relative cost, against one for fiberglass batts and cellulose. So foam pays best where its air seal does what cheaper insulation can’t: rim joists, crawl space and basement walls, a roofline over attic ductwork, and the wall between garage and house, which the guide names as a place a perfect air barrier is needed.
Spray foam vs fiberglass, cellulose and rigid board cost
Installed per square foot, HomeGuide’s December 2025 national figures are $1.50 to $5.00 for spray foam, $1.00 to $2.60 for fiberglass batts, $1.00 to $2.80 for blown-in and $1.20 to $3.70 for rigid foam board, thickness again unstated. The Department of Energy calls loose-fill fiber and fiberglass batts the least expensive types of insulation.
Those numbers leave out air sealing: fiberglass and cellulose slow heat but let air through, so sealing is a separate step, while foam seals where it goes. On an open attic floor, blown-in still wins. In Connecticut, where the code calls for R-60, open cell under the roof would need 14 1/4 to 15 1/2 inches; blown cellulose on a sealed attic floor gets there for far less. See types of insulation.
DIY spray foam kits
The EPA sorts spray foam three ways. Two-component high-pressure foam is a professional system that should only be used by a trained applicator. Two-component low-pressure kits and one-component cans are available to do-it-yourselfers, and professionals use them largely for air sealing and filling holes and gaps; the cans are for gaps of about half an inch to 3 inches.
The EPA says homeowners using them should learn the precautions professionals use, notes do-it-yourselfers are often unaware of the inhalation and skin hazards, lists asthma, sensitization and lung damage among the effects of exposure, and asks homeowners to consider having a trained professional install the product. DIY foam still needs the code’s thermal or ignition barrier. A can around pipes and wires is a homeowner job; a kit on a roof deck or basement wall is not. More in is spray foam safe.
Rebates and tax credits
State and utility programs offer incentives for insulation and air sealing, depending on your utility and the work; see New York and New Jersey insulation rebates and Connecticut insulation rebates. The federal 25C tax credit ended for anything placed in service after 31 December 2025.
Common questions about spray foam insulation cost
How much does spray foam insulation cost?
Most of our projects run between $3,500 and $12,500. The price follows the board feet of foam, open or closed cell, access, prep and the fire barrier. HomeGuide (December 2025) quotes $1.50 to $5.00 per square foot installed, a national average that varies by region and thickness.
How much does spray foam insulation cost per square foot?
It depends on the source and the thickness. HomeGuide (December 2025) lists $1.50 to $3.50 installed for open cell and $3.00 to $5.00 for closed cell; Fixr (January 2025) lists $2.75 to $6.50 in new construction and $3.15 to $7.50 in existing homes. Both are national averages, not our prices.
How much does closed cell spray foam cost per board foot?
HomeAdvisor (June 2026) lists $1.30 to $3.10 per board foot installed for closed cell and $0.60 to $1.60 for open cell. Fixr (January 2025) lists the material alone at $1 to $1.50 for closed cell and $0.44 to $0.65 for open cell. A board foot is one square foot, one inch thick.
Is open cell or closed cell spray foam cheaper?
Open cell; the Department of Energy’s guide says it costs less but has a lower R-value per inch. For equal R-value the gap narrows, since 2 inches of closed cell matches about 3 1/2 inches of open cell. Where depth is short or moisture is a risk, closed cell is the one that works.
How much does it cost to spray foam an attic?
Most of our projects run between $3,500 and $12,500. A roofline is priced on the roof deck and gable area and the depth to code: for R-49, about 7 inches of closed cell or 11 3/4 to 12 1/2 inches of open cell. The ignition barrier, and taking the old batts out, add to the total.
Why does spray foam insulation cost so much?
It is made on site from two chemical components pumped through heated hoses at high pressure, the house is emptied while it cures, and it insulates and air seals in one step. The Department of Energy rates it at the top of its relative cost scale.
Is spray foam insulation worth the cost?
Where its air seal matters: rim joists, crawl space and basement walls, a roofline over attic ductwork. ENERGY STAR says sealing and insulating can save up to 10% on annual energy bills; the Department of Energy notes more insulation in an adequately insulated house may not recoup its cost.
Can I save money with a DIY spray foam kit?
For small gaps, a can of one-component foam is a homeowner job. For insulating, the EPA says high-pressure two-component foam should only be used by a trained applicator, and kit users need the same precautions as professionals. DIY foam still needs the code’s thermal or ignition barrier.
Spray foam quotes in New Jersey, Connecticut, the Hudson Valley and Long Island
We price spray foam after we have been in the space: the area and depth of each part, what is in the rafters or rim bays now, access, water, wiring, how the attic or crawl space is used, and whether foam is the right material at all. You get a written scope with the foam, the inches and the fire barrier for each area. The energy audit is free.
Call 914-825-6824 or use the contact form, 8am–8pm, seven days. The Home Insulators is family-owned, based in New Rochelle, NY since 2015, with a 100-plus-person in-house crew that never subcontracts. We work across all of New Jersey, all of Connecticut, New York’s Hudson Valley and Long Island; see our service area.