Choosing Spray Foam Insulation: Closed-Cell vs. Open-Cell

spray foam equipmentIf you are new to the Spray Polyurethane Foam (SPF) insulation space, you may be wondering why two different types of spray foam exist on the market. The two variations, closed-cell and open-cell, are available simply due to different needs.

Open-cell foam is half the weight of closed-cell foam and, therefore, is an ideal material for specific areas of a home or building needing more dense insulation. Open-cell expanding foam has a lower R-value, which means it has a lower resistance to heat transfer. Some SPF contractors choose this type of foam if they do not need the resistance and strength that closed-cell foam offers.

With open-cell foam, the cells within the material break up, allowing air to fill the spaces within. As a result, the foam has a low-density and a soft, sponge-like appearance. Open-cell foams typically require substantially less material per square inch to manufacture, making them less expensive.

Alternatively, closed-cell foam weighs twice as much as open-cell foam. However, with higher density comes more resistance to heat transfer.

Closed-cell foam is a smart choice for use in homes and commercial buildings that need greater protection from both heat transfer and moisture buildup. It is also an ideal material for roofing, where you typically need more R-value per square inch.

As the name suggests, with closed-cell foam, the cells inside the material remain just that: closed. What does this mean? It means that there are no gaps in the foam for the air to fill, so air is unable to pass through the material, creating an airtight barrier. Closed-cell foam has a much higher density than open-cell and is much more solid in structure.

Common Spray Foam Types and Applications

Here are some of the most common SPF types and applications:

  • High-Density Foam. SPF contractors often use high-density foam for exterior and roofing applications, situations where high insulation values and durability are important. High-density foam, which has a seamless, monolithic quality, boasts a dense cell structure that does not expand as much as other varieties. It also requires more material to cover and insulate a space.

One advantage of high-density foam is that it can reduce energy costs over a roof’s lifetime thanks to its thermal resistance properties. Also, it can provide maximum protection against air and water.

  • Medium-Density Foam. Contractors often use closed-cell, medium-density foam for continuous insulation, unvented attic applications, and interior wall cavity fill. You can use this type of SPF as low or high-pressure, two-component insulation.

The majority of applicators use medium-density foam when there is a need for the greatest possible R-value insulation per cubic inch. A major advantage of this foam variety is that it acts as an air, vapor, and water barrier and can help reduce noise.

  • Low-Density Foam. SPF applicators typically utilize low-density foam, also known as open-cell foam, for interior wall cavity fill and unvented attic applications.

The open cell structure of low-density foam gives some flexibility to the end product. Most SPF contractors use low-density foam to fill cavities in walls during construction. Because it has a large cell structure, it stays softer and more flexible than other SPF varieties after it cures, boosting the chance of its continuing to provide high insulation value even as a building shifts over time.

Low-density foam also can absorb sound thanks to its open-cell structure and softer texture.

Why Should You Choose Closed-Cell Foam?

For starters, closed-cell foam has better thermal characteristics than open-cell foam. This type of foam also offers significantly better insulation properties due to it having a lower thermal conductivity. While open-cell foams have a thermal conductivity of about 0.039 W/mK, closed-cell foams can offer a value as low 0.025 W/mK.

Here are three more reasons why we believe SPF contractors should pick closed-cell foam for their spray foam needs:

  1. Water resistance. Closed-cell foams are more water resistant.
  2. Higher water vapor resistance. Closed cell foams allow only low levels of water vapor to pass through thanks to their unique cell structure.
  3. Enhanced compressive strength. Due to the higher core density of closed-cell foam, it is essentially rigid. On the other hand, open-cell foam tends to have a very soft, spongy feel. You can use closed-cell foam in specific scenarios to enhance the structural stability of a building’s framework.

The Bottom Line

Now that you know the key differences between open-cell and closed-cell SPF foams, you now may be wondering which one is best for customers’ projects. A thorough discussion with one of the experts on the Intech Equipment & Supply team can help you determine the exact type of spray foam insulation you need to get the job done.

Our team’s resume includes designing and building hundreds of mobile spray rigs for commercial roofing and SPF insulation contractors around the world, as well as deep industry relationships with the best in manufacturers and equipment dealers.

Check out our online store for your spray foam insulation equipment and spray foam kit needs.