Spray foam insulation is a critical component in modern commercial construction and retrofitting. For property owners and project planners, understanding the differences between Closed-Cell and Open-cell spray foam determines long-term performance, compliance, and building durability. Selecting the wrong type—or using it in the wrong location—can lead to code violations, moisture problems, or reduced energy efficiency.
This guide outlines the functional differences between Closed-Cell and Open-cell spray foam insulation for commercial applications. It clarifies where each performs best, what limitations to consider, and how to align your choice with building type, climate, and code.
Closed-Cell and Open-cell Foam Differ in Density, Structure, and Performance
The core difference between the two spray foam types lies in their cellular structure. That structural variation drives differences in thermal resistance, moisture control, expansion behavior, and code compliance.
Foam Cell Structure and Density
Closed-Cell spray foam uses tightly packed cells that are sealed off from one another. This structure makes it dense, rigid, and water-resistant. Open-cell foam has interconnected cells that allow air and moisture vapor to pass through.
R-Value and Thermal Resistance
Closed-Cell foam offers about twice the R-value per inch compared to Open-cell. This matters most in buildings with space constraints or stricter efficiency requirements.
Expansion Rate After Application
Open-cell foam expands rapidly—up to 100 times its volume—allowing it to fill irregular cavities easily. Closed-Cell expands less, which gives it a more controlled, dense application.
| Feature | Closed-Cell Foam | Open-cell Foam |
|---|---|---|
| R-value per inch | ~6–7 | ~3.5–4 |
| Water resistance | High – acts as vapor retarder | Low – vapor permeable |
| Density | 1.75–2.2 lb/ft³ | 0.4–0.5 lb/ft³ |
| Expansion rate | Low (30x) | High (100x) |
| Sound dampening | Moderate | High |
| Structural reinforcement | Adds rigidity to walls | Does not contribute structurally |
Closed-Cell Foam Is Better for High-Stakes Commercial Environments
Closed-Cell spray foam insulation is typically the better choice for commercial structures where moisture control, structural integrity, or energy performance is a concern.
Suitable for Metal Structures, Warehouses, and Cold Storage
Metal walls and roofing panels conduct heat easily. Closed-Cell foam helps limit energy loss and offers a rigid surface that reinforces panel strength. It also helps prevent condensation—critical in storage environments.
Moisture Protection for Ground-Contact and Roof Systems
Commercial buildings in humid climates or flood-prone areas benefit from Closed-Cell’s low vapor permeability. It limits water intrusion and meets many code requirements for below-grade or roof applications.
Code-Driven R-Value in Limited Wall Space
Tighter energy codes often require R-20+ in commercial walls. Closed-Cell’s high R-value per inch helps meet those targets even in narrow cavities or retrofit projects where additional space isn’t available.
Open-cell Foam Works in Interior Walls and Conditioned Cavities
Open-cell spray foam performs well in commercial settings where moisture resistance and structural contribution aren’t primary concerns. It’s often used for sound control and interior comfort.
Ideal for Office Interiors, Demising Walls, and Acoustic Separation
Open-cell foam offers excellent sound dampening. It’s used in conference rooms, mixed-use units, or demising walls to reduce acoustic transfer between tenants or departments.
Best in Above-Grade, Dry Environments
Open-cell foam should only be used where wall systems remain dry and are not exposed to bulk water or vapor drive. It is not a suitable air barrier where high humidity or moisture intrusion exists.
Cost-Effective for Large Volume Applications
Its lower material cost and faster application rate make it attractive for insulating large, conditioned cavities that don’t require water resistance or added wall strength.
Moisture and Vapor Control Are Major Differentiators
One of the most misunderstood aspects of spray foam selection is how the two types manage moisture.
Closed-Cell Blocks Bulk Water
Its impermeable structure resists water absorption and can even serve as a Class II vapor retarder. This makes it useful in roofing systems, below-grade walls, and environments subject to periodic moisture exposure.
Open-cell Allows Moisture Vapor to Pass
While it doesn’t absorb bulk water easily, Open-cell foam allows vapor transmission. In the wrong setting, this leads to condensation and mold. It must be paired with a separate vapor barrier in many commercial wall systems.
Fire Rating and Building Code Considerations Vary
Each type of spray foam requires different treatments and approvals for commercial code compliance.
Thermal Barriers and Fire Resistance
Both foam types require a thermal barrier—such as gypsum board—when exposed to interior occupied space. Closed-Cell often meets ignition barrier requirements more easily due to its density.
Compliance for Commercial Structures
Local codes may restrict Open-cell in certain applications, especially near metal panels, unvented roofs, or below-grade walls. Always review the ICC-ES reports or material testing documents before specifying.
Installation Quality Affects Both Foam Types
Regardless of type, spray foam performance depends on proper installation. Problems include over-expansion, off-ratio mixes, shrinkage, or poor adhesion.
Closed-Cell Requires Skilled Application
Its chemical mix must be accurate and carefully applied to prevent cracking or separation. Overapplication can create pressure on walls.
Open-cell Expands Rapidly—Overspray Is a Risk
Open-cell foam can overflow cavities or coat unintended surfaces if not controlled. Overspray must be removed before it interferes with electrical boxes or HVAC ducts.
Conclusion
Both Closed-Cell and Open-cell spray foam serve distinct purposes in commercial building insulation. Closed-Cell is stronger, more resistant to moisture, and delivers better thermal performance per inch. It’s best for metal buildings, roofing systems, and exterior walls exposed to the elements. Open-cell foam works well inside conditioned spaces where sound control, flexibility, and cost efficiency are the priorities.
Choosing the right foam starts with knowing the building type, moisture exposure, required R-value, and code demands. Apply each material where it aligns best with the building’s functional and compliance needs. This approach avoids costly remediation and delivers reliable performance long term.
FAQs
Where should Closed-Cell spray foam be used in commercial buildings?
Closed-Cell foam performs well in exterior walls, metal structures, unvented roofs, and areas exposed to moisture. It’s also effective in achieving code-required R-values where wall depth is limited.
Can Open-cell foam be used in commercial buildings?
Yes, but only in above-grade, dry interior spaces. It’s often used for sound insulation between offices or in wall cavities where moisture is not a concern.
Does Open-cell foam require a vapor barrier?
Yes. Open-cell allows moisture vapor to pass, so it often needs a separate vapor retarder or air barrier to prevent condensation in mixed-humidity environments.
What is the main risk of using the wrong spray foam type?
Using Open-cell in areas exposed to moisture can lead to mold, wall damage, and building envelope failure. Choosing the wrong type can also violate code and reduce insulation effectiveness.
Are both types of spray foam fire-rated for commercial use?
Both require a thermal barrier like drywall to meet fire codes. Closed-Cell may offer more consistent ignition resistance, but both must comply with local building standards and testing protocols.
Reviewer: Sophia White has 8 years of experience in spray foam insulation. She reviewed this post and gave clear guidance on aligning business messaging with what customers actually care about.