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

If you’ve started researching insulation options for your home or building project, you’ve likely come across two terms that seem to show up everywhere: open cell and closed cell spray foam. At first glance, they sound similar, but the differences between them can significantly impact your comfort, your energy bills, and even your budget. At Husky Insulation Pros, we get asked about this comparison almost every single day, so we put together this guide to break it down in plain language.

What Is Spray Foam Insulation?

Before diving into the differences, it helps to understand what spray foam actually is. Spray foam insulation is a liquid material made from two components — typically a polyol resin and an isocyanate — that are combined and sprayed into place. When these chemicals meet, they react and expand, filling gaps, cracks, and cavities as they harden into a solid insulating layer. This expansion is what makes spray foam so effective at sealing spaces that traditional insulation, like fiberglass batts, often misses.

The key distinction between open cell and closed cell spray foam comes down to the structure of the foam itself once it cures.

Open Cell Spray Foam: The Basics

Open cell spray foam is made up of tiny cells that are, as the name suggests, left open. This gives the foam a soft, spongy texture. Because the cells aren’t fully encapsulated, air can fill the tiny pockets within the material, which makes open cell foam lighter and more flexible than its closed cell counterpart.

Key characteristics of open cell spray foam:

• Lower density — It expands significantly, often up to 100 times its original volume, making it a cost-effective option for filling large areas.
• Lower R-value per inch — Typically around R-3.5 to R-3.6 per inch, meaning you may need a thicker application to achieve the same insulating performance as closed cell foam.
• Sound dampening — Its spongy structure makes it excellent at reducing noise transmission between rooms or floors.
• More affordable — Because it uses less material to cover the same square footage, open cell foam is generally less expensive upfront.
• Vapor permeable — It does not act as a vapor barrier, so it’s often used in climates or applications where moisture needs to be able to pass through and dry out naturally.

Open cell foam is a popular choice for interior walls, attics, and areas where soundproofing is a priority, particularly in moderate climates where an added vapor barrier isn’t a strict necessity.

Closed Cell Spray Foam: The Basics

Closed cell spray foam, on the other hand, is composed of tightly packed cells that are fully closed off from one another. This creates a denser, more rigid material. Instead of air, these cells are filled with a gas that helps improve the foam’s insulating properties even further.

Key characteristics of closed cell spray foam:

• Higher density — It expands less than open cell foam (roughly 30 to 40 times its original volume), resulting in a much more rigid, sturdy finished product.
• Higher R-value per inch — Typically around R-6 to R-7 per inch, making it significantly more efficient at insulating in tighter spaces.
• Moisture and vapor barrier — Its closed structure makes it naturally resistant to water and moisture, which helps prevent mold growth and water damage.
• Adds structural strength — Because of its rigidity, closed cell foam can actually add strength and stability to the walls or surfaces it’s applied to.
• More expensive — The denser material and higher performance come at a higher upfront cost compared to open cell foam.

Closed cell foam is often the go-to choice for exterior walls, basements, crawl spaces, roofing applications, and any area exposed to moisture or extreme temperature swings.

Comparing the Two Side by Side

When deciding between open cell and closed cell spray foam, it typically comes down to a few core considerations: budget, climate, moisture exposure, and the specific area being insulated.

If you’re insulating an interior space where soundproofing matters more than moisture resistance, open cell foam is often the more practical and budget-friendly choice. But if you’re working on an exterior wall, basement, or any area where water infiltration or extreme weather is a concern, closed cell foam’s moisture resistance and higher R-value make it the stronger long-term investment.

It’s also worth noting that closed cell foam’s added rigidity can contribute to a building’s structural integrity, which is a benefit that open cell foam simply doesn’t offer in the same way.

Spray foam insulation can generally be sprayed, foamed-in-place, poured, or injected directly into building cavities, which is part of what makes it such a versatile solution across different applications — but the right formula for the job still depends on the specific goals of your project. For more general background on insulation types and performance, resources like the U.S. Department of Energy’s insulation guide can be a helpful starting point.

Which One Is Right for Your Project?

There’s no universal “better” option between open cell and closed cell spray foam — the right choice depends entirely on your project’s needs. Factors like your local climate, the area of the home being insulated, your budget, and your long-term energy efficiency goals all play a role in determining which type of foam will serve you best.

This is exactly why working with an experienced, licensed insulation contractor matters. A professional installer can evaluate your space, account for local building codes, and recommend the foam type — or combination of both — that will deliver the best performance for your investment.

Trust Husky Insulation Pros for Expert Guidance

Choosing between open cell and closed cell spray foam doesn’t have to be overwhelming. The team at Husky Insulation Pros has years of hands-on experience helping homeowners and builders select the right insulation solution for their specific needs, budget, and climate. Whether you’re insulating a new build, retrofitting an older home, or tackling a moisture-prone basement, we’re here to walk you through your options and deliver a professional installation you can count on.

Ready to find out which spray foam solution is right for your home? Visit our website to learn more about our services and request a free consultation today.