If you’ve been researching spray foam insulation, you’ve probably heard people say closed cell spray foam is the best.
But the better question is… best for what?
Closed cell spray foam is a powerful insulation material, but it’s not the right fit for every project. Good insulation decisions aren’t about hype – they’re about using the right building science for your space.
Let’s break it all down so you can understand what closed cell spray foam insulation is, how it works, where it shines, and where it doesn’t.
• Closed cell spray foam is a low-expanding, rigid insulation that creates an air seal.
• It has a high R-Value of about R-6 to R-7 per inch.
• Commonly used in pole barns, vans, tiny homes, and commercial buildings.
• It acts as an air barrier and moisture barrier.
• Closed cell spray foam rejects bulk water and does not absorb moisture.
• It is durable, mold-resistant, and ideal for tight spaces.
• Not every home or project requires closed cell – application matters.
Closed cell spray foam is a low-expanding, rigid spray foam insulation that creates an air seal wherever it’s installed.
Unlike fluffy or fibrous insulation materials, closed cell foam hardens after application. That rigid structure is what gives it its strength, durability, and high insulating performance.
One of the biggest reasons homeowners and builders are drawn to it is its impressive R-Value.
The R-Value of closed cell spray foam is one of its biggest selling points.
This high R-Value makes it especially useful in projects where space is limited, but insulation performance still matters, like van walls, tiny homes, or commercial retrofits.
Closed cell spray foam insulation really shines in environments that demand strength, moisture control, and efficiency.
You’ll commonly see it used in:
While open cell spray foam is usually recommended for residential homes, there are situations where closed cell is the better fit, especially when moisture resistance or added rigidity is required.
Closed cell spray foam is sprayed directly into wall cavities, ceilings, or other building assemblies.
Because it has a low expansion rate, it expands just enough to:
Once cured, it forms a strong air barrier and moisture barrier, helping reduce drafts, condensation, and moisture-related issues.
Here’s an important, but often misunderstood, fact:
FEMA classifies closed cell spray foam as highly resistant to floodwater.
This doesn’t mean it’s waterproof in every situation or that you should buy it just for that reason. What it does mean:
The result is more consistent indoor temperatures and fewer condensation and moisture problems over time.
Closed cell spray foam has some clear advantages when it’s used in the right application.
Closed cell foam is rigid and tough.
In areas like pole barns or vans, it can often be left exposed and still hold up to everyday wear and tear.
Mold and mildew need moisture to grow.
Since closed cell spray foam doesn’t absorb water, it doesn’t provide the conditions that mold needs to thrive.
That controlled expansion makes closed cell spray foam ideal for tight or shallow cavities, like:
The bottom line: closed cell spray foam is built for environments that need strength, moisture control, and efficiency.
Closed cell spray foam insulation is created on-site using two liquid components:
When the “A” side and “B” side combine, a chemical reaction occurs. The foam is formed and sprayed into place, where it expands slightly and seals the cavity.
Any time spray foam insulation is involved, it’s smart to ask the right questions.
Before installation, ask your insulation contractor:
An experienced contractor should be able to answer these clearly and confidently.
The installation process is straightforward, but there is prep involved.
A good contractor will:
Not necessarily.
Closed cell spray foam is excellent at what it’s designed to do, but that doesn’t mean it’s the best insulation for every home or every project.
The right choice depends on:
Closed cell spray foam insulation is durable, moisture-resistant, and high-performing when it’s used in the right place.
The key isn’t choosing insulation based on what’s “best.” It’s choosing what’s best for your specific space.
If you want to learn more about foam insulation, building science, and making smarter comfort decisions for your home, check out our Learning Center for more articles, videos, and resources.
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Closed cell spray foam insulation is best used in environments that need high R-Value, moisture resistance, and durability, such as pole barns, vans, tiny homes, and commercial buildings.
The R-Value of closed cell spray foam is typically R-6 to R-7 per inch, making it one of the highest-performing insulation materials available.
Closed cell spray foam is water impermeable, which means it doesn’t allow water or moisture to move through it; it also rejects bulk water and does not absorb moisture.
In some applications – such as pole barns and vans – closed cell spray foam can be left exposed, depending on local building codes and use of the space.