Understanding the Difference Between Closed Cell vs. Open Cell Foam Insulation

Open cell vs. Closed Cell Foam Insulation

We often are asked to explain the difference between open cell and closed cell Polyurethane Foam types.

When you want to put foam insulation into your home you should understand the differences so that you can decide whether to use the .05 pound/cu.ft. open cell foam or the 2 pound/cu.ft. closed cell foam. There are some very important differences between these two types of foam. They have different prices, different application techniques and different performance.

In order to choose properly between the Closed Cell vs. Open Cell Foam insulation you need to understand the nature of the materials and how they are structured. In an open cell foam, the cells of the foam do not close completely. The space where they are open is filled with air. This gives the open cell foam a much weaker structure than the closed cell foam.

The structure of closed cell foam is quite different. The tiny cells in the foam are closed and they are packed very tightly against each other. They have been filled with a gas to make the foam expand. For this reason this foam is a good insulator. The cells can be formulated to control their size and density. To determine the density of the foam, a cubic foot of solid foam is weighed. The open cell foams tend to weigh about one half pound per cubic foot. The closed cell foams are more dense and they tend to weigh 1.7 – 2.0 pounds per cubic foot of foam. The higher density foams are stronger and heavier. Foams that are used for roofing insulation often weigh 2.8 to 3 pounds or more per square foot. This enables them to bear the weight of the roof more effectively. Very high density foam is heavier and stronger than the less dense foam materials.

Occasionally polyurethane foams are molded to simulate wood or molding. These high density foams may be thirty to forty pounds per cubic foot. Closed cell foam is far superior to open cell foam for most uses. It is much stronger, it is a much better insulator, and water vapor is less likely to leak through it. The main disadvantage of closed cell foam is the expense. Because there is literally more material in each cubic foot, it is more costly. The cost per R is higher than when open cell foam is used. We regularly use both types of spray foam as insulating materials.

When choosing between closed cell vs. open cell foam insulation, it is important to understand how each type works. For instance, if you are going to use foam insulation in an area where there will be a lot of water present, you would not use open cell foam in that situation. It would absorb water and then it would lose its insulating value. Where a lot of R value per inch is required such as in small framing areas, closed cell foam is the better choice. It is also better as an insulator in the roof area.

If you still have questions, give us a call, and we can show you examples of each and discuss which type of spray foam insulation will be best for your project.