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Open-Cell vs. Closed-Cell Spray Foam Insulation

Spray foam insulation is one of the most effective ways to seal gaps, stop drafts, and lock in conditioned air. However, not all spray foam is built the same. Choosing the right type depends on your project goals, budget, and climate.

Tiger Foam, Innovative Polymer Systems, Frontier Basement Systems, Johns Manville, Oakridge Foam and Coating System, RetroFoam Injection Insulation

10/12/20261 min read

a man standing on a ladder going into attic with spray foam insulation
a man standing on a ladder going into attic with spray foam insulation

What is Open-Cell Spray Foam?

Open-cell spray foam is a soft, spongy, and flexible insulation material.

  • How it’s made: During the chemical reaction, the gas bubbles inside the foam break or rupture, leaving the cell structure open and porous.

  • Texture & Density: It has a low density (about 0.5 lbs per cubic foot) and expands rapidly (up to 100 times its liquid volume).

  • R-Value: Roughly R-3.5 to R-3.8 per inch.

Benefits of Open-Cell Foam

  • Cost-Effective: It uses fewer chemicals and yields more coverage per pound, making it cheaper to install.

  • Great for Sound Damping: Its porous, sponge-like structure absorbs sound waves much better than closed-cell foam.

  • Allows the House to "Breathe": It is vapor-permeable, meaning moisture can pass through rather than getting trapped in the wood framing.

  • Reaches Tight Spaces: High expansion allows it to fill awkward, hard-to-reach cavities easily.

What is Closed-Cell Spray Foam?

Closed-cell spray foam is a dense, hard, and rigid plastic material.

  • How it’s made: The gas bubbles remain completely sealed and intact, pressing tightly together so air and moisture cannot penetrate the pockets.

  • Texture & Density: It has a high density (about 2.0 lbs per cubic foot) and a rigid, rock-solid finish once cured.

  • R-Value: Much higher, typically R-6.0 to R-7.0 per inch.

Benefits of Closed-Cell Foam

  • Superior Thermal Performance: Because it packs roughly double the R-value per inch compared to open-cell, you need a much thinner layer to hit high thermal resistance goals.

  • Built-in Vapor and Moisture Barrier: It is moisture-impermeable and stops water vapor, making it ideal for basements, crawl spaces, and exterior roof decks.

  • Adds Structural Strength: Its rigid final state bonds to framing members, increasing the racking strength and overall rigidity of walls and roofs.

  • Stops Air Leaks Dead: It creates a rock-solid airtight seal at a much thinner application depth (often effective at just 1 to 2 inches).

Open-cell and closed-cell spray foam insulation comparisons
Open-cell and closed-cell spray foam insulation comparisons