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Foam insulation serves as a vital component in various applications, providing thermal insulation, moisture control, and structural support. When it comes to choosing between open cell and closed cell foam, understanding their cellular structure and characteristics is fundamental.

Table of Contents:

Understanding Foam Cells

Foam cells are the microscopic building blocks that form the structure of foam insulation materials. These cells are essentially tiny pockets or bubbles within the foam, and understanding their nature is crucial in determining the properties and functionalities of different types of foam.

There are two primary classifications of foam cells: open cell and closed cell.

Open Cell Foam Cells

Open cell foam has connected cells, leaving open spaces between them like a honeycomb. This makes it soft, bouncy, and breathable, and good at absorbing sound. However, it also absorbs moisture more easily.

Closed Cell Foam Cells

Closed cell foam has cells completely sealed off from each other, creating a dense and compact structure. This prevents air and moisture from getting inside, making it sturdy, long-lasting, and water-resistant. It also has better insulation properties and can handle more weight.

Differences Between Open and Closed Cell Foam

Their different cell structures lead to distinctive properties and applications for open and closed cell foam.

Cell Structure

Open cell foam features linked pockets of air instead of fully enclosed cells, creating air channels throughout the material. In contrast, closed cell foam has sealed-off cells, resulting in a dense and compact structure without interconnected spaces.

Density and Rigidity

Closed cell foam’s tightly packed cells make it denser and sturdier, while open cell’s air pockets give it a softer, more flexible feel.

Insulation Properties

Closed cell foam provides superior insulation thanks to its cells that keep air still inside, helping it keep heat in or out. Open cell’s structure allows air to move freely, reducing its insulation performance.

Moisture Resistance

Closed cell foam’s sealed structure acts as a barrier, making it highly resistant to water. Open cell foam can easily absorb moisture due to its linked air channels.

Strength and Durability

Closed cell foam’s compact structure gives it greater strength and resistance to damage, making it suitable for situations needing strong support. Open cell, while less durable, is still ideal for flexible uses.


Open cell foam shines in indoor insulation, soundproofing, and applications where flexibility is important. Closed cell foam excels outdoors, in wet areas, and situations requiring strong insulation and support.

Properties of Open and Closed Cell Foam

Open cell foam boasts a porous structure with linked air pockets. This gives it a soft, flexible feel and exceptional sound absorption capabilities. It’s also budget-friendly and offers decent insulation. However, its openness makes it more susceptible to moisture absorption, so it might not be the best choice for high-moisture areas.

In contrast, closed cell foam packs a denser punch. Its tightly sealed cells create a rigid, robust structure that effectively resists moisture infiltration and provides superior insulation. While its cost is higher, its durability and strength make it ideal for demanding environments like outdoors or wet areas.

Which is Better: Open Cell or Closed Cell Foam?

Choosing between open cell and closed cell foam depends on several factors, each impacting the foam’s performance and suitability for different applications.

Insulation Needs

  • High Insulation Requirements: If superior insulation is the priority, especially in areas with extreme temperatures, closed cell foam might be the better choice due to its higher insulating properties.
  • Moderate Insulation Needs: For areas where less insulation is required, open cell foam could suffice while offering cost-effective solutions.

Moisture Exposure

  • Moisture-Prone Environments: Closed cell foam acts as a moisture barrier and is ideal for areas prone to moisture, such as basements, bathrooms, or exterior applications.
  • Limited Moisture Exposure: In drier environments or interior spaces where moisture isn’t a significant concern, open cell foam can be suitable.

Budget Considerations

  • Initial Cost: Open cell foam is generally more cost-effective upfront compared to closed cell foam, making it an attractive option for those with budget constraints.
  • Long-Term Cost: Despite the higher initial cost, closed cell foam’s durability and superior insulation might lead to long-term savings due to its extended lifespan and better performance.

Specific Applications

  • Flexibility and Soundproofing: Open cell foam’s softer and more flexible nature makes it suitable for soundproofing or areas where flexibility is essential.
  • Structural Support and Durability: Closed cell foam’s rigidity and durability make it a better choice for applications requiring structural support or areas prone to wear and tear.

Environmental Considerations

Open cell foam may use fewer chemicals, but its longevity might be shorter compared to closed cell foam.


Choosing the perfect foam, open cell or closed cell foam, is like finding the ideal puzzle piece for your project. Understanding your needs and the distinct strengths of open and closed cell foam is key. For superior insulation and moisture resistance in demanding environments, closed cell foam shines. Open cell foam, with its budget-friendly warmth and sound-dampening abilities, thrives in drier spaces.

Since there’s no one-size-fits-all answer when it comes to foam insulation, contact an insulation expert like Ener-Spray  to guide you finding the perfect match for your project.

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