Sprayfoam Insulation: Open Cell vs Closed Cell

When it comes to insulating your home or commercial space, spray foam is one of the most effective and versatile options on the market. But not all spray foam is created equal. The two main types—open cell and closed cell—have distinct characteristics, performance benefits, and best-use scenarios. Understanding the difference can help you make a smarter investment in energy efficiency, comfort, and durability.

Open Cell vs. Closed Cell Spray Foam Insulation: What’s the Difference?

What Is Spray Foam Insulation?

Spray foam insulation is a liquid material that expands into a solid foam when sprayed, filling gaps and sealing leaks far better than traditional insulation methods like fiberglass or cellulose. It’s especially valued for its ability to provide both insulation and air sealing in one application.

Now, let’s break down the differences between open cell and closed cell spray foam.

Open Cell Spray Foam: Light and Airy

Structure:

Open cell spray foam is made up of cells that are intentionally left open. This makes the foam softer, more flexible, and less dense.

R-Value:

R-value measures thermal resistance. Open cell foam typically has an R-value of about 3.5 to 3.9 per inch, which is lower than closed cell.

Air Barrier:

While it does provide an air seal, open cell foam is not a vapor barrier. It can allow moisture to pass through, which can be a pro or a con depending on the application.

Best Uses:

  • Interior walls (helps with soundproofing)

  • Attics (especially in moderate climates)

  • Places where moisture permeability is acceptable

Pros:

  • Less expensive than closed cell

  • Great for sound dampening

  • Expands more, filling gaps effectively

Cons:

  • Lower R-value per inch

  • Can absorb moisture if not properly managed

Closed Cell Spray Foam: Dense and Durable

Structure:

Closed cell spray foam is made of completely closed cells, packed tightly together. This results in a more rigid, dense material.

R-Value:

Closed cell foam boasts a higher R-value—around 6 to 7 per inch—making it one of the highest-performing insulation options available.

Air & Vapor Barrier:

It not only provides an air seal but also acts as a vapor barrier and adds to the structural integrity of the building.

Best Uses:

  • Exterior walls

  • Crawlspaces

  • Basements

  • Metal buildings

  • Areas prone to moisture or needing extra rigidity

Pros:

  • High insulation value

  • Resists water and moisture

  • Adds structural strength

Cons:

  • More expensive

  • Rigid and less flexible

  • Requires more careful application

So, Which One Should You Choose?

The right spray foam depends on your project’s goals, climate, and budget.

  • If you’re insulating an attic in a mild climate and want good soundproofing at a lower cost? Open cell is a great choice.

  • If you’re sealing a basement or exterior wall and need moisture protection and maximum R-value? Closed cell is the way to go.

Final Thoughts

Both open and closed cell spray foam have their advantages, and in many buildings, a combination of both types may be the best solution. Working with a knowledgeable contractor can help you determine the best option for your specific needs.

Still unsure which spray foam is right for your project? Reach out to a local insulation expert to get a tailored recommendation—and start saving on energy bills the smart way.