Open-cell spray foam is a lighter, less dense polyurethane foam insulation with tiny open cells within its structure, allowing some air and moisture vapor to pass through, offering good thermal performance and effective air sealing at a generally lower cost than closed-cell alternatives.
This open cellular structure gives the material a softer, more flexible texture compared to closed-cell foam’s rigid, dense composition, along with somewhat lower R-value per inch of thickness.
Because open-cell foam allows some vapor permeability, it’s often chosen for interior wall applications where this characteristic helps a wall assembly manage moisture through controlled drying rather than trapping it entirely, though this same permeability makes it less suitable for below-grade or high-moisture exposure applications.
What Does Open-Cell Spray Foam Involve?
- Tiny open cells allowing some vapor permeability
- Lower density and softer texture than closed-cell foam
- Generally lower cost per board foot
- Good sound dampening due to its softer structure
Why Is Open-Cell Spray Foam Important?
The combination of effective air sealing, good sound dampening, and lower cost compared to closed-cell foam has made open-cell spray foam a popular choice for interior wall and attic applications where its vapor permeability characteristics align well with the wall assembly’s intended moisture management strategy. This practical fit for common residential applications has sustained open-cell foam’s popularity despite closed-cell’s superior R-value per inch.
Because open-cell foam’s vapor permeability isn’t appropriate for every application, particularly below-grade or high-moisture exposure areas, consulting with an insulation professional about the specific location and climate helps ensure the correct foam type is selected for each particular use. This guidance helps ensure the material performs as intended in its specific application.
Open-Cell Spray Foam vs. Closed-Cell Spray Foam
Open-cell spray foam offers lower cost, softer texture, and vapor permeability. Closed-cell spray foam provides higher R-value per inch, moisture resistance, and rigid structural contribution, better suited to below-grade or high-moisture applications.