Spray foam insulation is typically priced at $1 to $5 per square foot installed for a U.S. residential project in 2026. Most single-area projects, including an attic, crawl space or basement, cost about $1,100 to $9,000. A whole-home installation can cost $4,000 to more than $29,000, depending on the foam type, thickness, accessibility and preparation required.
The key pricing detail is that spray foam is usually sold by the board foot, not only by square foot.
Spray Foam Insulation Cost at a Glance
| Project or material | Typical installed cost |
|---|---|
| Open-cell spray foam | $0.60 to $1.60 per board foot |
| Closed-cell spray foam | $1.30 to $3.10 per board foot |
| Attic | $1,100 to $9,000 |
| Crawl space | $1,200 to $6,900 |
| Basement | $1,500 to $6,200 |
| Garage | $1,500 to $9,400 |
| Whole home | $4,000 to $29,000+ |
These are broad U.S. planning ranges from current cost guides. Local labor rates, project size and job complexity can change the final quote.
What Is a Board Foot?
A board foot equals one square foot of insulation applied one inch thick.
Use this formula to estimate the material quantity:
Insulated area × foam thickness in inches × price per board foot = estimated cost
For example, insulating 1,000 square feet at 2 inches thick requires about 2,000 board feet:
- Open-cell foam: about $1,200 to $3,200
- Closed-cell foam: about $2,600 to $6,200
These are planning estimates before unusual preparation, minimum service charges or repairs.
A quote that lists only "$3 per square foot" leaves out two important details: the foam type and the applied thickness.
Open-Cell vs. Closed-Cell Spray Foam Cost
Open-cell spray foam costs less. Closed-cell spray foam provides a higher R-value per inch and better moisture resistance.
| Feature | Open-cell spray foam | Closed-cell spray foam |
|---|---|---|
| Installed cost | $0.60 to $1.60 per board foot | $1.30 to $3.10 per board foot |
| Typical R-value per inch | About R-3.5 to R-3.7 | About R-5 to R-7 |
| Structure | Soft and flexible | Dense and rigid |
| Moisture resistance | Limited | High |
| Common applications | Dry wall cavities and some attic assemblies | Crawl spaces, basements, roofs and areas with limited depth |
Closed-cell foam costs more because it uses more material per unit of volume. U.S. Department of Energy Building America guidance identifies typical closed-cell foam at approximately R-6 per inch and describes it as rigid and highly resistant to water vapor at commonly applied thicknesses.
Open-cell foam can be a better value where moisture exposure is controlled and there is enough cavity depth to reach the required insulation level. Closed-cell foam is usually the better fit where moisture control, rigidity or a higher R-value in a shallow cavity matters.
How Much Does It Cost to Spray Foam an Attic?
Spray foam attic insulation costs $1,100 to $9,000. Other published guides place many attic projects between approximately $1,500 and $7,400. The final price depends on the attic's size, roof geometry, required thickness, ventilation changes and whether old insulation must be removed.
Roof-deck applications can cost more than attic-floor applications because the installer may need to:
- Seal the attic as part of a conditioned roof assembly
- Work around electrical wiring, ductwork and roof penetrations
- Install baffles or modify ventilation
- Apply a thermal or ignition barrier
- Remove existing insulation or damaged materials
Compare attic quotes by the surface being sprayed, not floor area alone. A contractor may be pricing the roof deck, gable walls, knee walls or attic floor. Each has a different surface area.
How Much Does Spray Foam Cost for a Crawl Space or Basement?
A crawl space typically costs $1,200 to $6,900, while basement spray foam commonly costs $1,500 to $6,200. Closed-cell foam is often selected in these locations because it provides air sealing and greater resistance to moisture.
The quote may increase if the crawl space or basement has:
- Standing water or drainage problems
- Mold or mildew
- Damaged wood
- Difficult access
- Existing insulation that must be removed
- Plumbing, wiring or ductwork that complicates installation
Spray foam should not conceal an active water problem. Correct moisture intrusion before installing insulation.
Why Does Spray Foam Insulation Cost So Much?
Spray foam insulation costs more when the project requires more material, more preparation or more difficult access.
Foam Thickness
Thicker foam requires more board feet. One inch of open-cell foam provides roughly R-3.5, while one inch of closed-cell foam may provide approximately R-6 to R-7. Doubling the thickness usually increases material cost, although larger projects may receive different contractor pricing.
Existing Homes Cost More
New construction typically costs about $1 to $4 per square foot, while existing-home installations can cost approximately $3 to $5 per square foot. Existing homes may require drywall removal, work around existing insulation and repairs to finished surfaces.
Installing spray foam during a renovation is usually less expensive than opening finished walls later.
Preparation and Removal
Old insulation removal, surface cleaning, air sealing and disposal can add to the project cost. If mold is present, published estimates place professional mold remediation at roughly $1,125 to $3,345 before new insulation is installed.
Vapor Control and Code Requirements
Open-cell foam does not provide the same vapor resistance as closed-cell foam. Depending on the climate, wall or roof assembly and local building code, the project may require a separate vapor retarder or another layer in the assembly. Angi estimates vapor-barrier installation at approximately $0.65 to $1 per square foot.
Access and Job Size
Small jobs can have higher per-square-foot pricing because the contractor still has travel, setup, equipment and cleanup costs. Tight crawl spaces, steep roofs and complicated framing can also increase labor costs.
Is Spray Foam Insulation Worth the Cost?
Spray foam insulation can be worth the cost when a project needs both insulation and air sealing, especially around rim joists, difficult gaps, rooflines and irregular cavities. The Department of Energy explains that air sealing can reduce drafts, improve comfort and reduce unwanted heat transfer. Spray foam can perform both functions in one application.
Spray foam may not be the most economical choice for every large, accessible wall or attic area. Targeted air sealing combined with fiberglass or cellulose insulation can cost less while still meeting the project's performance requirements.
The right choice depends on:
- Whether the main problem is air leakage, low R-value or moisture
- The required insulation depth
- The local climate and building assembly
- Whether walls or ceilings are already finished
- How long you expect to remain in the property
What Should a Spray Foam Quote Include?
A spray foam quote should list:
- Open-cell or closed-cell foam
- Thickness in inches
- Target R-value
- Total square footage being sprayed
- Total board feet
- Material and labor costs
- Old insulation removal and disposal
- Mold, water-damage or surface preparation
- Required vapor, thermal or ignition barriers
- Ventilation plan and re-entry time
- Product warranty and installer warranty
The U.S. Environmental Protection Agency recommends controlling ventilation during and after spray polyurethane foam installation and following the product manufacturer's re-occupancy instructions. Occupants should not remain in the work area during installation.
Bottom Line
If a quote does not state the foam type, thickness and total board feet, ask the contractor to revise it before comparing the bid with other prices.