Open Cell vs Closed Cell Spray Foam: What’s the Difference and Which Should You Choose?

Spray foam insulation is one of the most effective ways to improve a home’s energy performance, comfort, and air sealing. But many homeowners and even some contractors are unsure whether open-cell or closed-cell spray foam is the better choice for a specific project. Understanding the differences helps ensure the right product is used in the right place.

What Is Spray Foam Insulation?

Spray foam is applied as a liquid that expands into a solid insulating layer. As it expands, it fills gaps, cracks, and voids, helping the home retain heat during colder periods and reject heat during warmer seasons. This expansion also creates an air seal, which helps reduce unwanted air movement through walls, ceilings, and attic surfaces.

There are two primary types of spray foam: open cell and closed cell.

Open Cell Spray Foam

Open-cell foam expands significantly when applied and forms a lighter, softer insulation with tiny interconnected cells. Because of this structure, it is excellent at filling irregular spaces and creating a strong air seal.

Open-cell foam is often used for:

• attic rooflines• interior wall cavities• sound reduction between rooms• projects where large expansion helps fill complex framing

Its flexibility allows it to expand deeply into small cracks and voids, making it a strong choice for interior applications where moisture resistance is not the primary concern.

Because it uses less material density, open-cell foam is typically more economical per square foot than closed-cell foam.

Closed Cell Spray Foam

Closed-cell foam expands less than open-cell foam but cures into a dense, rigid insulation with tightly packed cells. This structure provides a higher insulation value per inch and creates a strong moisture-resistant barrier.

Closed-cell foam is commonly used for:

• exterior walls• crawl spaces• metal buildings• areas where additional structural rigidity is beneficial• locations exposed to humidity or potential moisture

Because of its density, closed-cell foam delivers a higher R-value in thinner applications and adds strength to the surfaces it adheres to.

Key Differences at a Glance

Open Cell Foam• lighter and more flexible• expands more when applied• typically lower cost• excellent for interior air sealing and sound control

Closed Cell Foam• dense and rigid• higher insulation value per inch• stronger moisture resistance• suitable for demanding environments and exterior assemblies

Which Spray Foam Is Right for Your Project?

The right choice depends on the structure of the building, moisture conditions, available space, and project goals. In many homes, both types may be used in different areas to achieve the best overall performance.

A proper evaluation of the structure helps determine which foam type will help the home retain heat more effectively in winter, reject heat in summer, and support the long-term performance of the heating and cooling system.

Need Help Choosing the Right Spray Foam?

At Insulation Discounts, we help contractors and homeowners understand which insulation materials fit their project needs and supply the products required for professional installation.

If you’re planning a spray foam project and want guidance on material selection or availability, contact our team today to discuss your options.