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Open Cell vs. Closed Cell Spray Foam: What is the Best Choice For You?

Both open and closed cell spray foams work and do a great job at insulating a building. They both have strengths and weaknesses. It is important to understand those strengths and weaknesses to decide which type of spray foam will work best to meet your needs.
Residential Home requiring open-cell or closed-cell spray foam

At RetroFoam of the Carolinas, we get a lot of phone calls from people requesting closed-cell spray foam because they have heard that it is better than open-cell spray foam. The truth is that both types of spray foam work and do a great job at insulating a building. They both have strengths and weaknesses. It is important to understand those strengths and weaknesses to decide which type of spray foam will work best to meet your needs.

Open-Cell Spray Foam

The name “open-cell” refers to the structure of the spray foam. The foam is made up of many cells. These cells are designed not to close up all of the ways. The texture of the foam is soft and pliable. Here are some other things to know about open-cell spray foam:

  • It blocks the movement of air, which means that it effectively creates an air seal for your building envelope.
  • It has a high expansion rate. When installed, the open-cell foam will expand more than 100 times its size to fill in all of the nooks and crannies. This helps create an airtight home. 
  • Open-cell foam offers an R-value of around 3.5 per inch.
  • Because the cells are open, this type of foam is less dense. It weighs only ½ lb per cubic foot.
  • Open-cell spray foam is not a vapor barrier. This means that water can pass through it. It is, however, a vapor retarder. Most vapor is carried by air, and since open-cell spray foam blocks air movement, it will also block the condensation carried in the air. (It is important to note that not all open-cell spray foams are equal when it comes to how they react with water. They can range. Ask your contractor about the type of open-cell spray foam they use.)
  • Because of its structure, it absorbs sound. This will help with dampening the sounds coming in from outside.
  • It is more affordable than closed cell spray foam.

Closed-Cell Spray Foam

The structure of closed-cell spray foam comprises many cells, and each of these cells is closed and pressed tightly together. The texture of this foam is hard and rigid. Here are some things to know about closed cell spray foam.

  • Like open-cell spray foam, closed-cell spray foam blocks air movement and can create an air seal for your home when applied.
  • The expansion rate of closed-cell foam is less than that of open-cell foam, meaning that it doesn’t expand nearly as much as open-cell foam. However, this does allow you to put on multiple layers in a smaller space.
  • It has an R-value of around 6 per inch.
  • It is a dense product and weighs around two pounds per cubic foot.
  • Closed-cell spray foam is a vapor barrier, meaning water cannot pass through it.
  • Because of its structure, it is strong and can help increase wall strength.
  • It is more expensive than open-cell spray foam.

Applications of Open-Cell and Closed-Cell Spray Foam

Now we can take what we know about each type of foam and put it into a few scenarios where it would perform best. 

Open-cell spray foam performs well in a residential home. The pliability of the open-cell foam makes it easy if you need to do any electrical or plumbing work. The expansion rate is beneficial in this aspect because as it expands, it fills in all of the many hard-to-reach places and creates an airtight seal.

A roof deck is another place where installing open cell foam is beneficial. If there is a roof leak, the water will seep through the foam, indicating where the leak is happening. If you were to use closed-cell foam, the water could pool and/or drain off of the foam to another area of the house, causing more damage. Let’s say it causes water damage to a wall. You will have no idea that the real problem is a leaky roof.

Closed-cell foam is excellent in outbuildings such as a pole barn where the walls will be left exposed. If the walls are exposed, and tools are laid up against them, the durability of closed-cell foam will keep it from being damaged and compromising the integrity of the insulation.

Both open and closed cell spray foams have strengths and weaknesses. It depends on what your project entails. Talking with your contractor will help you decide which type will work best for you to cash in on the strengths of the spray foam type you choose. If you still have questions about closed and open-cell spray foam, contact one of our specialists today. They will be happy to help you find out which one will work best for you.

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