The short answer
Angi and HomeAdvisor put professionally installed open-cell spray foam at $0.60 to $1.60 per board foot, where a board foot is one square foot one inch thick. Spraying 1,000 square feet to 3.5 inches is 3,500 board feet, or $2,100 to $5,600 at that range before minimum charges and extra work. Open-cell costs less per board foot than closed-cell but needs more thickness for the same R-value.
For example, spraying 1,000 square feet to 3.5 inches requires 3,500 theoretical board feet. At Angi’s broad published range, the corresponding installed foam-volume price is $2,100–$5,600, before any separately charged work. Your actual bid could differ substantially with job size, location and scope.
Quick answer: Open-cell generally costs less per board foot than closed-cell foam, but it usually requires more thickness to achieve a comparable nominal R-value. It also has different water-vapor characteristics, so cheapest and best are not automatically the same thing.
Pricing reviewed October 19, 2026. Figures are US planning ranges, not a live local quotation. For costs across both foam types see our spray foam insulation cost guide.
Open-Cell Spray Foam Cost at a Glance
| Item | Planning figure or explanation |
|---|---|
| Open-cell installed unit price | $0.60–$1.60[1][2] per board foot (Angi) |
| 500 sq ft at 3.5 inches | $1,050–$2,800 before separately charged extras |
| 1,000 sq ft at 3.5 inches | $2,100–$5,600 before extras |
| 1,500 sq ft at 3.5 inches | $3,150–$8,400 before extras |
| 1,000 sq ft at 5.5 inches | $3,300–$8,800 before extras |
| Typical nominal R-value | Roughly R-3.6 to R-4.5[3] per inch; consult product data |
| Key price drivers | Thickness, treated area, mobilization, removal and access |
How to read the table: The figures are arithmetic applications of Angi’s published installed board-foot range, not independently surveyed prices for those exact project sizes.
Why Other Sites Show Lower Open-Cell Prices
Not every 2026 source reports the same rates. For example, a calculator site, SprayFoamCalc[4] publishes an open-cell planning range of $0.48–$1.08 per board foot installed, while a contractor, ThermoSeal USA[5] lists approximately $0.44–$0.65 per board foot for its stated assumptions.
Some regional contractors also publish narrower bands than national cost aggregators. These sources use different markets, project assumptions and scope definitions. Treat them as separate pricing references, not numbers to average together without a common methodology.
A local contractor’s written bid with product, area, depth and all exclusions identified is more useful than any national average.
How Much Is Open-Cell Spray Foam per Square Foot?
Multiply the board-foot rate by the thickness. At $0.60–$1.60 per board foot[1][2], open-cell costs $2.10–$5.60 per square foot at 3.5 inches and $3.30–$8.80 at 5.5 inches. Headline prices like “$1.50–$3.50 per square foot” mean little without a stated thickness. The full table by thickness is on the cost per square foot page.
Open-Cell Spray Foam Cost by Project Size
These calculations assume the area of the surface being insulated, not the floor area of the home. That distinction makes a big difference for attics and roof decks.
| Actual surface treated | Thickness | Board feet | Calculated installed range |
|---|---|---|---|
| 250 sq ft | 3.5 in | 875 | $525–$1,400 |
| 500 sq ft | 3.5 in | 1,750 | $1,050–$2,800 |
| 750 sq ft | 3.5 in | 2,625 | $1,575–$4,200 |
| 1,000 sq ft | 3.5 in | 3,500 | $2,100–$5,600 |
| 1,500 sq ft | 3.5 in | 5,250 | $3,150–$8,400 |
| 2,000 sq ft | 3.5 in | 7,000 | $4,200–$11,200 |
The low end for very small installations is particularly easy to underestimate. Many installers have a mobilization or minimum-job charge. If the calculated foam volume produces a $525 estimate but the crew’s minimum is higher, the minimum is what you pay. Ask for that figure before using any advertised rate.
Worked Example: 1,000-Square-Foot Project
Imagine a homeowner has measured 1,000 square feet of actual framing cavities and a contractor specifies 3.5 inches of open-cell foam.
- Board feet: 1,000 × 3.5 = 3,500.
- At an illustrative $0.80 per board foot: $2,800.
- At an illustrative $1.20 per board foot: $4,200.
- Add any quoted prep, removal, fire-protection or access charges that are not included.
The rates in that example are intentionally hypothetical within the published price band. They are not promises of contractor pricing.
Use our spray foam insulation cost calculator to change the area, depth, rates and additional project costs.
How Much Does Open-Cell Spray Foam Cost for an Attic?
Open-cell foam is commonly considered for suitable attic roof decks and other enclosed building cavities, but attic prices are particularly prone to misleading square-footage estimates.
The first decision is where the thermal boundary belongs: at the attic floor or along the roof deck. These are different insulation designs, with different areas, moisture implications and heating/cooling consequences.
If the work involves 1,200 square feet of actual roof deck at a hypothetical 5.5-inch depth:
- Board feet = 1,200 × 5.5 = 6,600.
- At $0.60 per board foot = $3,960.
- At $1.60 per board foot = $10,560.
Those are calculated installed foam charges based on the broad national unit range, not a recommendation to use 5.5 inches on every roof deck. Your roof geometry, climate, existing ventilation, air-conditioning ducts, code requirements and chosen foam’s vapor performance all affect the correct design.
An unvented attic system must be designed as an assembly. Open-cell’s vapor permeability can be an advantage in some contexts and a liability in others. Roof leak detection, roof sheathing drying and vapor control deserve explicit consideration before installation.
Our attic spray foam insulation guide covers attic-specific decisions in more detail.
Open-Cell Cost for Walls, Garages and Other Areas
Exterior Walls
Open-cell is often considered for framed above-grade walls where there is sufficient cavity depth. Unit pricing can be attractive because the foam expands and air-seals irregular spaces. However, you need a wall design that addresses bulk-water management and vapor control, not just nominal R-value.
New-build open framing is generally simpler to access than finished walls. Existing drywall removal and reinstatement can change the total economics.
Interior Partition Walls
Homeowners sometimes choose open-cell for air sealing and sound absorption. If noise control is the primary objective, compare the complete wall assembly, including drywall layers, framing, gaps and acoustic isolation. Foam alone cannot deliver a guaranteed sound rating.
Garage Walls and Ceilings
The garage’s intended use determines whether insulation is worthwhile and what protection is required. Attached-garage separation, ignition and thermal barriers, and temperature-control goals all matter. Ask contractors to price the finished compliant assembly, not exposed foam alone.
Rim Joists and Crawl Spaces
A cheap unit price is not enough to justify using open-cell in an area that might see dampness or restricted drying. Lower-permeance closed-cell products may be more suitable in some rim-joist and below-grade assemblies, but the answer depends on the construction and moisture conditions.
Read the open-cell versus closed-cell comparison rather than making the decision on cost alone.
Seven Factors That Change an Open-Cell Quote
Installed thickness and the measured spray area matter most, followed by minimum and mobilization charges, preparation, old-insulation removal, fire or ignition protection, and access. Each is explained in the main cost guide.
Is Open-Cell Spray Foam Cheaper Than Closed-Cell?
Per board foot, yes: $0.60–$1.60 for open-cell against $1.30–$3.10 for closed-cell[1][2]. But open-cell needs more thickness for the same R-value, so compare at equal R-value on the open-cell vs closed-cell cost page.
What R-Value Do You Get for the Money?
At an illustrative R-3.7 per inch, 3.5 inches of open-cell gives about R-13 and 5.5 inches about R-20, before framing and other layers. Use the R-value on the quoted product’s data sheet; the open-cell spray foam guide explains the ranges.
Is Open-Cell Spray Foam Worth the Cost?
It can be, particularly where air leakage is a major issue, suitable cavities are accessible and the assembly has been designed for the material.
But there’s no universal payback period. The outcome depends on existing insulation, climate, energy rates, heating and cooling equipment, installation quality and how much air leakage is actually reduced.
Ask what you’re paying for beyond the foam volume. If an expensive proposal does not explain coverage, moisture design, fire protection and expected improvements, more bids are sensible.
What About Tax Credits in 2026?
Do not rely on outdated articles promoting the former US federal Energy Efficient Home Improvement Credit for new work. Under the 2025 legislative changes, the federal Section 25C credit generally does not apply to eligible property placed in service after December 31, 2025. Check the current IRS Form 5695 instructions[6] and look separately for any applicable state, utility or local incentives.
DIY Open-Cell Spray Foam vs Professional Installation
DIY kit prices are materials only and their coverage figures are theoretical, so they aren’t comparable with installed bids. Two-component foam also carries chemical-exposure risks during spraying. See DIY spray foam insulation before buying a kit.
How to Compare Open-Cell Contractor Quotes
Compare total prices for the same completed work. Example: Contractor A quotes $0.75 per board foot for 4,000 board feet ($3,000) but excludes a $700 protective coating; Contractor B quotes $0.90 ($3,600) with the coating included. B is $100 cheaper overall. Use the quote checklist.
Questions owners ask
How much does open-cell spray foam cost per board foot?
Angi's guide reports roughly $0.60–$1.60 per board foot professionally installed. Some regional contractors publish narrower or lower ranges. Ask what's included.
How much does open-cell spray foam cost per square foot?
Multiply the board-foot rate by thickness. At 3.5 inches, Angi's range translates mathematically to approximately $2.10–$5.60 per treated square foot, before separately charged extras.
How much is 1,000 square feet of open-cell spray foam?
At 3.5 inches, 1,000 treated square feet requires 3,500 theoretical board feet. Multiplying by $0.60–$1.60 produces a broad $2,100–$5,600 installed foam-volume estimate.
How much does open-cell spray foam cost for a 2,000-square-foot house?
A home's floor area is not enough to price the project. You must measure the actual surfaces being sprayed and specify their thickness. A 2,000-square-foot attic floor and a house with 2,000 square feet of living area may have very different insulation quantities.
Is open-cell foam cheaper than closed-cell foam?
Usually per board foot, yes. But open-cell generally supplies less nominal R-value per inch and has different vapor behavior. Compare complete suitable assemblies, not unit price alone.
Is open-cell spray foam suitable for attics?
It can be suitable in correctly designed attic assemblies. Roof-deck applications require attention to climate, moisture control, sheathing drying, code compliance and existing ventilation arrangements.
Sources
- How Much Does Spray Foam Insulation Cost?, Angi. Accessed October 19, 2026. National consumer cost guide from a survey of Angi customers. No update date shown; title says "2025 Data". Its installed per-board-foot ranges match HomeAdvisor's page updated June 17, 2026.
- How Much Does Spray Foam Insulation Cost?, HomeAdvisor. Accessed October 19, 2026. National consumer cost guide, updated June 17, 2026. Installed cost per board foot; national ranges, not quotes.
- Frequently Asked Questions, Spray Polyurethane Foam Alliance (SPFA). Accessed October 19, 2026. Industry trade association. Page metadata shows modified April 27, 2026. Typical density, R-value per inch, air-barrier thickness and vapor permeance ranges.
- Spray Foam Insulation Cost Per Square Foot: 2026 Price Chart and Guide, SprayFoamCalc. Accessed October 19, 2026. Calculator-site article updated October 7, 2026; contains affiliate links.
- Spray Foam Cost Guide, ThermoSeal USA. Accessed October 19, 2026. Contractor blog dated April 10, 2026. A business with a commercial interest.
- Instructions for Form 5695, Internal Revenue Service. Accessed October 19, 2026. Last reviewed April 30, 2026. Credits end for property placed in service after December 31, 2025.