knowledge Tips & Tricks

Open Cell or Closed Cell Spray Foam?


If you’ve locked in on spray foam for insulation of your property, there’s yet another decision you’ll have to make. 

You need to decide between open cell and closed cell varieties – a decision that can influence the usefulness of your insulation based on your specific needs.

We go over the main differences between open cell and closed cell spray foam insulation, helping you make an informed choice depending on your goals like moisture resistance, air sealing, soundproofing, etc.

Understanding the Cellular Structure

The basic difference between open cell and closed cell spray foam is their cellular structure. 

Open cell foam is composed of cells that are not entirely encapsulated. Air can flow through the material. In contrast, closed cell foam features tightly packed, sealed cells that create a dense, rigid structure.

This difference in structure has a big effect on how each type of insulation works and what its properties are.

1. Density and R-Value

Most notable differences between open cell and closed cell spray foam is their density and insulation value. This is well-known as the R-value. 

Closed cell foam has a higher density (typically ranging from 1.75 to 2 pounds per cubic foot) while open cell foam has a lower density (around 0.5 pounds per cubic foot).

A higher density means better R-value for closed cell foam of R-6 to R-7 per inch, compared to an R-value of approximately R-3.5 per inch for open cell foam. 

A higher R-value means better thermal resistance. So closed cell foam is a clear winner for areas with extreme temperature fluctuations or where maximum insulation is needed.

2. Moisture Resistance and Air Sealing

Closed cell spray foam is better than open cell spray foam at keeping out moisture and air. 

It is perfect for places that tend to get wet, like crawl spaces, basements, and outside walls, because the closed cell structure makes an impermeable barrier that keeps air and moisture out.

On the other hand, open cell foam lets air and moisture in, which can cause problems like mold growth and energy loss if not fixed properly. 

However, the fact that it breathes well can be helpful in some situations where controlling moisture is not as much of a priority.

3. Soundproofing Capabilities

For soundproofing, open cell spray foam might be a better choice. Because it has open cells and is less dense, it is a great sound absorber that stops noise from moving from one room to another or from outside sources.

Open cell foam is better at blocking out noise than closed cell foam (though closed cell foam does block out some). Its rigid structure can actually make sound waves stronger, which could cause echoes or sound transfer.

4. Expansion and Application

Another thing to think about is how each type of spray foam is applied and how fast it expands. Open cell foam often grows up to 100 times its original size, which is a lot more than closed cell foam. Its high expansion rate makes it perfect for filling in cracks, holes, and hard-to-reach places, making sure that the whole area is covered.

If you compare it to closed cell foam, it has a lower expansion rate, around 30 times its original volume. 

This might seem like a bad thing, but it makes it easier to apply and control, so it can be used in places that need a higher R-value and structural integrity.

Isothane is an expert in polyurethane foam solutions and works with companies in TV, film, and construction. The company promises to provide high-quality materials and provides full technical support. Isothane is known as a reliable manufacturer and problem-solver in the polyurethane foam technology sector. They are always adding new products to their line to meet customers’ needs.For more information, visit



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