When choosing foam for upholstery or marine projects, one of the most common questions is open cell vs closed cell foam. The difference comes down to how each foam material handles air, moisture, pressure, and long-term use.
Both open cell foam and closed cell foam are widely used across industries, including spray foam insulation for walls, roof deck applications, and exterior walls. These two different types of foam have distinct cell structure properties that affect durability, moisture resistance, and overall performance.
What Is Open Cell Foam?
Open cell foam has a breathable open cell structure. The cells inside the foam are not fully sealed, which allows air, water vapor, and even sound waves to pass through.
This makes it soft, flexible, and better suited for interior walls, furniture, and comfort layers like seat cushions or back cushions. Open cell foam typically has a lower density compared to closed cell foam, which means it compresses more easily and is often used where soundproofing and noise reduction are important.
However, because of this open cell structure, it can absorb liquid water and moisture. This makes it less suitable for humid environments, crawl spaces, or applications where water damage is a concern.
What Is Closed Cell Foam?
Closed cell foam has a sealed cell structure. Each cell is closed off, which prevents air, water vapor, and liquid water from passing through.
This creates a rigid, firm material with higher density and stronger structural integrity. Closed cell foam insulation is commonly used in spray foam insulation systems for exterior walls, roof decks, and areas where an air barrier and vapor barrier are required.
In upholstery and marine use, materials like closed cell marine foam sheets provide strong moisture resistance and durability. A common example is 1/8" closed cell foam, which is often used in panels, backing layers, and thin applications where water resistance and structural support matter.
Breathability vs Water Resistance
The key differences between open cell and closed cell foam come down to how they handle air and moisture.
Open cell foam allows airflow and is vapor semi permeable, meaning water vapor can pass through. This can help regulate air inside interior spaces and reduce trapped heat.
Closed cell foam acts as an effective barrier. It is vapor semi impermeable, resists water absorption, and works as both an air barrier and moisture barrier. This makes it ideal for marine environments and exterior applications.
If your insulation goals or project involve exposure to water, closed cell foam makes sense as the more durable option.
Compression and Recovery
Open cell foam is soft and compresses easily. It’s designed for comfort, making it a good fit for cushions, furniture, and interior applications where flexibility matters.
Closed cell foam is firmer and more rigid. It provides better structural strength and holds its shape under pressure, even in high use areas.
Because of its higher density closed cell foam structure, it offers better support and durability over time compared to open cell foam.
Heat and Environmental Performance
Heat flow and temperature changes affect how foam performs.
Open cell foam insulation has a lower R value, meaning it provides less thermal insulation. It can trap air but does not block heat as effectively.
Closed cell foam insulation has a higher R value per inch, which improves energy efficiency and helps reduce energy costs. It also performs better in humid environments and maintains its structure under changing conditions.
This is why closed cell spray foam is commonly used in high pressure insulation systems for homes and buildings across the USA.
Side by Side Comparison
Here’s a simple example of the differences between open cell vs closed cell foam:
Open Cell Foam
- Soft, flexible, and breathable
- Lower density and lower R value
- Allows air and water vapor to pass through
- Better for interior comfort and soundproofing
- Common in furniture, walls, and insulation for noise control
Closed Cell Foam
- Rigid, firm, and durable
- Higher density and higher R value
- Acts as an air sealing and moisture barrier
- Better for exterior walls, marine use, and structural support
- Resists water damage and performs well in humid environments
Choosing the Right Foam for Your Project
Choosing between open and closed cell foam depends on the application.
For interior use, open cell foam is often the better choice. It works well for sound control, comfort layers, and areas where breathability is important.
For marine, exterior, or high moisture areas, closed cell foam is the clear option. It provides moisture resistance, structural support, and long-term durability.
If you’re working on a marine project, pairing foam with materials from the marine vinyl collection or marine fabric collection helps create a complete system that performs well in wet conditions.
Where Thin Closed Cell Foam Fits In
Thin foam sheets like 1/8 closed cell foam and 1/4 inch closed cell foam are commonly used for panel work and backing layers.
They add a protective barrier, improve durability, and help with air sealing in tight spaces. Because they are lightweight and easy to handle, they are ideal for detailed upholstery work and marine panels.
These foam products are often sold in sheets with consistent width and length, making them easy to cut and install depending on the design and application.
Making the Right Call
Open cell and closed cell foam each serve a specific purpose. One focuses on comfort, airflow, and noise control, while the other focuses on durability, moisture resistance, and structural performance.
Understanding the differences between open cell vs closed cell foam helps you choose the right material for your project. Whether you're working on furniture, a boat, or even insulation in a house, matching the foam type to the environment is what delivers better results.