Spray foam insulation is widely regarded as one of the best forms of building insulation. It is widely used in a number of commercial and residential building applications. There are several leading brands of spray foam available on the market. Within each brand, there are also several different types of spray foam that are used for specific applications. Two of the most common types of spray foam are open cell and closed cell spray foam. To understand which type of spray foam is suitable for your insulation application, it is helpful to define and compare the two types in more detail.

What Is Closed Cell Spray Foam?

Closed cell spray foam is the most widely used type of spray foam on the market today. Closed cell spray foam also comes in a variety of different types which are used for various applications.  In addition to the standard type of Class I spray foam, you can get closed cell spray foam that is high density which provides the maximum level of insulation. This is typically used for flooring insulation and roof repairs. It is also an effective soundproofing measure. You can also get a type of slow-rise spray foam which is useful for insulating existing walls and soundproofing. The latest developments are of a microbial type of closed cell spray foam. This type of spray foam actually retards bacteria and microorganisms, preventing them from getting into your home. When set, closed cell spray foam generally forms an airtight and moisture-tight barrier in your home. In addition, closed cell spray foam does not retain water. It also resists the buildup of mold and has proven to be an effective barrier against pests. The closed cell spray foam is rigid when it sets. Because of this, it provides additional structural support in your home.

What Is Open Cell Spray Foam?

Open cell spray foam has a much lower density than closed cell spray foam. Because of this, it is lighter in weight. The open cell spray foam holds its form but does not settle to a completely rigid structure. Open cell spray foam therefore does not form a barrier against pests. While it forms an effective air barrier, the open cell structure is capable of retaining water. Because of this, it is not an effective moisture barrier.  Open cell spray foam is most often used in flash and fill applications in both interior and exterior walls. It can also be used in attic rafters, attic floors and open stud cavities. Interestingly enough, it is also very effective when used for sound proofing.

Major Differences Between Open Cell and Closed Cell Spray Foam

The main difference between closed cell and open cell spray foam is that closed cell spray foam solidifies into a rigid structure whereas open cell spray foam does not. Because of this, closed cell spray foam is more durable and therefore more resistant to moisture and mold buildup. It also forms a barrier to pests and insects which open cell spray foam does not. In terms of density, closed cell spray foam has a density of between two and three pounds. Open cell spray foam has a much lower density of only three-quarters of a pound. The R-value rating of open cell spray foam is also much lower than that of closed cell spray foam. The R-value of open cell spray foam is 4 whereas the R-value rating of closed cell spray foam is between 6 and 7.7.

As you can tell from these figures, closed cell spray foam is therefore viewed as the more effective type of insulator.  Closed cell spray foam also has more applications than open cell spray foam. While open cell spray foam applications are generally limited to flash and fill applications, closed cell applications are much more diverse.  Closed cell spray foam can also be used for flash and fill applications in attic rafters, floors and on internal and external walls. In addition, it can be used to insulate basements, floors, sill plates, crawlspaces and cathedral ceilings. Closed cell spray foam is also very effective at adding structural support and used extensively to insulate metal building structures. If you want to use spray foam for soundproofing a room or building, you will be pleased to know that both open cell and closed cell provide effective soundproofing. Your choice will largely depend on the structure of the room as well as the climate of the area.