If you've researched spray foam insulation, you've probably seen people claim that closed cell spray foam is always the better option.
That sounds convincing, until you learn the full story.
The truth is, closed cell vs open cell spray foam isn't a "better or worse" debate. It's about using the right material in the right place. In some applications, closed cell spray foam insulation is exactly what you want. In others, it can actually create problems down the road.
At RetroFoam of Michigan, we've installed both open cell and closed cell spray foam for more than two decades. Our crews are manufacturer-trained, and our project managers know when each material makes sense and when it doesn't.
Let's clear up these spray foam misconceptions and walk through the difference between closed and open cell spray foam, starting with the basics.
• Closed cell spray foam has a higher R-Value per inch, but R-Value alone doesn't determine comfort or efficiency.
• Open cell and closed cell both create an air seal, which is more important than R-Value alone.
• Closed cell spray foam is rigid and moisture-impermeable, making it ideal for exposed or harsh environments.
• Open cell spray foam expands more, making it better for filling wall cavities in homes.
• Closed cell foam isn't always better than open cell -- it depends on how and where it's used.
Both open cell and closed cell spray foam insulation stop air movement, which is one of the biggest contributors to energy loss in a home.
Where the pair differ is in density, expansion, moisture behavior, and sound control.
Closed cell spray foam is dense and rigid once cured.
Because of this, it's commonly used in areas where the insulation will remain exposed or could take abuse.
Key characteristics of closed cell spray foam:
This makes closed cell a great choice for:
Open cell spray foam is much softer and boasts a much higher expansion rate when installed.
That expansion rate is what allows open cell spray foam to fill every nook and cranny in exposed and open cavities.
Key characteristics of open cell spray foam:
This is why open cell spray foam is commonly used in:
One of the biggest reasons people believe closed cell spray foam is superior is its R-Value per inch.
Closed cell foam R-Values typically fall around R-6 to R-7 per inch, which is higher than open cell spray foam.
That sounds impressive, but R-Value doesn't tell the whole story.
Spray foam's biggest advantage isn't its R-Value. It's the air seal it creates. Stopping air leakage does far more for comfort and efficiency than adding more R-Value alone. A slightly lower R-Value with an excellent air seal often outperforms higher R-Value insulation that still allows air movement.
Another common claim is that closed cell spray foam adds structural integrity to a building.
While closed cell is rigid, it should never be relied on as structural reinforcement. If a building needs insulation to improve its structural strength, that's a framing issue, not an insulation solution.
That rigidity does make closed cell useful in workshops and barns, but it can be problematic in homes.
Homes move. They settle. They shift over time.
Closed cell spray foam does not move easily once cured. That means:
Because closed cell foam is moisture-impermeable, water can travel behind it unnoticed until a much larger problem develops. Open cell foam, on the other hand, allows moisture to pass through, making leaks easier to identify early.
If sound control matters, open cell spray foam usually wins.
The soft, spongy structure of open cell absorbs sound waves much more effectively than dense closed cell foam. This makes open cell ideal for:
Not always.
Closed cell spray foam insulation is excellent for specific applications, but it is not a universal solution. Open cell spray foam performs exceptionally well in residential homes when installed correctly.
The idea that closed cell is "the best insulation" often comes from:
Both materials are effective when used correctly.
At the end of the day, open cell vs closed cell spray foam isn't about which is better -- it's about which is right.
Your home, building, or project has unique needs. The best insulation choice depends on:
If you want to learn more about spray foam insulation and how it works in different applications, visit our Learning Center. You'll find in-depth resources to help you make an informed decision for your insulation project.
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