Open Cell Insulation: Definition and What it is

What is Open Cell Insulation?

Open-cell spray foam is a lighter, more flexible type of spray foam insulation with interconnected cells that allow some air and moisture permeability. It provides R-3.5 to R-3.7 per inch and expands significantly more than closed-cell foam, typically reaching 3 inches when applied at 1 inch thickness.

Open-cell foam gets its name from the structure—cells are open and filled with air, creating a spongy texture. This makes it less dense (about 0.5 lbs per cubic foot) than closed-cell foam and more affordable. The material still provides excellent air sealing and fills cavities completely, but it's vapor-permeable and doesn't add structural strength. Open-cell foam works exceptionally well for interior applications like walls between conditioned spaces, and it provides superior soundproofing compared to closed-cell foam.

Open-Cell Foam Applications

• Interior Walls: Sound dampening between rooms, no moisture concerns
• Cathedral Ceilings: In climates where vapor permeability is acceptable
• Attic Roof Decks: Combined with proper vapor barrier in appropriate climates
• Sound Studios: Excellent acoustic absorption properties

When to Use Open-Cell Foam

Open-cell foam is ideal when you need air sealing and sound control at a lower cost than closed-cell. It works well in interior applications where moisture isn't a concern. In cold climates, open-cell foam typically requires a separate vapor barrier on the warm side. Avoid using open-cell in below-grade applications, flood-prone areas, or where moisture resistance is critical. The material's expansion properties make it excellent for filling irregular cavities, but overfilling can cause framing distortion—professional installation is essential to achieve proper density and thickness.

Benefits of Open Cell Insulation

• More affordable than closed-cell spray foam (40-50% less)
• Excellent air sealing properties
• Superior soundproofing and acoustic dampening
• Expands more than closed-cell, filling cavities thoroughly
• More flexible and less rigid than closed-cell
• Good thermal performance (R-3.5 to R-3.7 per inch)

Open Cell Insulation Cost

Open-cell foam costs significantly less than closed-cell while still providing excellent air sealing.

• Installation cost typically $1.50-$3.00 per square foot
• Target R-value and required thickness
• Project size (larger projects get better rates)
• Application area and accessibility
• Regional contractor availability
• Need for separate vapor barrier in cold climates

Related Services and Resources

Related Terms

• Spray Foam Insulation: Definition and What it is
• Closed Cell Insulation: Definition and What it is
• Polyurethane Foam Insulation: Definition and What it is

References

• Energy.gov - Foam Insulation Types
• Wikipedia - Spray Foam
• Wikipedia - Thermal Insulation
• Energy.gov - Insulation (Energy Saver)
• National Insulation Association - Insulation Basics
• ICAA - Insulation for Consumers