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What is the Difference between Open-cell and Closed-cell Polyurethane Foams?

This may be one of the most important pages on the website if your interest is in spray foam insulation. When it comes time to actually put the foam product in your home or commercial building structure, you must identify whether you will use 0.5 lb./cu. ft., open cell foam, or 2.0 lb./cu. ft. closed cell foam. This makes a big difference in cost, application methods, and performance.
With the open-cell vs. closed-cell issue, there are two major factors to understand and consider. The first is the nature of the foam. It is either open-cell foam, where the tiny cells of the foam are not completely closed. They are broken and air fills all of the “open” space inside the material. This makes the foam weaker or softer feeling than closed-cell foam.

Closed-cell foam differs in that all of its tiny foam cells are closed and packed together. They are filled with a gas that helps the foam rise and expand and become a greater insulator. These cells can be formulated to obtain many characteristics, the most common being size and density.

Density is measured by weighing one solid cubic foot of foam material. Open cell foams typically weigh in at 0.4 to 0.5 lb./cu. ft. Closed cell foam for insulation applications range in density from 1.7 lb./cu. ft. to 2.0 lb./cu. ft. Roofing applications typically use a 2.8 to 3.0+ lb./cu. ft. to support traffic and loads better. The higher the density the foam, the heavier, or stronger it becomes. Some polyurethane foams are molded into decorative interior molding and painted or stained for a simulated wood effect. These “higher density” foams are typically in the 30 lb./cu. ft. to 40 lb./cu. ft. density range.

The advantages of closed-cell foam compared to open-cell foam include its strength, higher R-value, and its greater resistance to the leakage of air or water vapor. The disadvantage of the closed-cell foam is that it is denser, requires more material, and therefore, is more expensive. Even though it has a better R-value, typically the cost per R is still higher than open-cell foam. The choice of foam can also be based on the requirements for the other performance or application specific characteristics such as strength, vapor control, available space, etc.  Open-cell SPF has an R-value around 3.5 per inch and typically uses water as the blowing agent.  Closed-cell SPF has an R-value of around 6.0 per inch (aged R-value) and uses high R-value blowing agents.

Both types of foam are commonly used in most building applications and the choice for which to use can depend on many of the factors discussed above. Some foams are inappropriate in specific applications. For example, you typically would not use open-cell foam below grade or in flotation applications where it could absorb water; this would negate its thermal performance because water is a poor insulator compared to air. Closed-cell foam would be a good choice where small framing sizes need the greatest R-value per inch possible. Closed-cell foam would be used for roofing applications

Q: How can I tell the difference between close cell and open cell when I am doing inspections?

A: Here we will discuss insulation spray foams.  Roofing spray foams are all closed cell and any suspicion that the membrane foam has open cells from an “off ratio” mis-application will require sample analysis in a lab.

The first item for an inspection should be the Installer’s Certificate listing the type system being inspected.

With no other documentation or evidence of system properties, the simplest means is by gently touching the foam surface, with open cell having a soft cushion feel and closed cell having a harder rigid feel.  One should take care not to push on the foam surface enough to damage the open cell membrane.  Unlike flexible cushion polyurethane foams used for bedding and furniture cushions (which can be squeezed and spring back into shape) spray foams do not have the same recovery properties and may be compressed beyond the recovery point.   This is particularly true with open cell systems.

Open cell systems with a density measurement of 0.5 pounds per cubic foot are very soft.  By comparison, closed cell insulation systems have a density measurement of 2.0 pound per cubic foot and are much stronger and harder.   Lately, some alternate products are being introduced to the market with higher density open cell 2.0 systems and lower density closed cell 1.7 to 1.2 systems.  As these systems find wider acceptance in the construction industry, inspector may be required to rely more on the Certifications by the installer.

Q: What R-Value does spray foam provide?

A: There are several types of foam and several manufacturers. Each type and manufacturer differs slightly. Open cell foam has R-values of 3.4-4 per inch. Closed cell foam has R-values of 6.2 to 7.0 per inch. Both open and closed cell foam provide the benefit of air seal. Closed cell foam provides a complete moisture vapor barrier.

Q: What brand of Spray Foam does American Spray Foam use?

A: American Spray Foam is an independent insulation service provider. Therefore we are not tied to a specific brand of foam. This gives us the freedom to install products from a variety of manufacturers. Our product offerings include:
Bayer, Demilic, Dow, Lapolla, Gaco Western,

American Spray Foam handles many other important home energy needs such and complete Air-Sealing Packages which will eliminate drafts, increasing comfort and lowering energy costs.

Q: Can you insulate non-vented roof decks and attics with foam?


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