Open Cell vs Closed Cell Spray Foam: What’s the Difference?

So, you’ve done research on spray foam insulation and you’ve decided is the best out there. But now the question, open cell or closed cell?

What’s the difference between open cell and closed cell spray foam you ask? The obvious answer might be that one is more expensive than the other. Actually, that is true. Closed cell can be more expensive than open cell, but there are other differences to consider besides just the price.

You will need to know what makes these two types of insulation unique in order to decide what kind is the best for your specific application. Let’s look at the differences between open cell spray foam and closed cell spray foam.




What are the differences?

Open and closed cell foam insulation are two different types of spray foam that have different benefits. Open-cell is the cheaper option, but it has a lower R-value. Open cell foam has a composition which is pourus, making it more flexible, and it is also permeable to water but not air. This makes it ideal for use on wood, allowing it to breathe. The open cell structure of the foam allows moisture to escape through evaporation.

Open cell is easier to work with after it has been applied. For example, if you need to do any plumbing or electrical work, you can easily bore a hole in open cell insulation.

Closed-cell spray foam is denser and therefore provides more value for your money. It has a higher R-value than open cell spray foam, which means that it will keep your home warmer in the winter and cooler in the summer. Essentially, the closed cell structure just makes it a more effective insulator. It is not permeable to either air or water.

Closed cell is more rigid and compact than open cell, and because of this, it can actually act to increase the structural soundness of a building like a pole when it is applied to the walls, making them stouter and more capable of withstanding extreme weather conditions.


Density is the real difference between the two types of insulation. Open cell spray foam has a density of around 0.5 pounds per cubic foot, while closed-cell foam can be more than triple, at about 1.75 pounds per cubic foot or more. Open cell foam is made up of porous cells that are interconnected, and this makes it more flexible and allows for water to pass through it. However, the fact that it is porous also means that it has a lower R value, and its effectiveness as an insulator is decreased.

The density of closed-cell spray foam makes it much more effective at sealing your home to keep out the cold or prevent heat from escaping. It also makes it a much more durable material because it is not as likely to experience air leaks, even after it has been installed for some time.


R-Value is the measurement of insulation’s ability to resist heat flow. Open cell spray foam has a relatively low R-value, usually around 2.5 per inch, while closed cell foam can have a much higher R-value of up to 7 per inch. You can see that even though closed cell insulation can be a bit more costly, the higher price can be well worth the money due to the significantly higher r-value and resulting energy savings.

How much do they expand?

Open cell insulation can expand up to 100 times its original size after application. Closed cell spray foam does expand as well, but not nearly as much. The open cell material expands so much that it is very easy to get into small, hard to reach areas like the nooks and crannies of an attic or exterior walls and ceilings, creating a very effective air seal.

Closed-cell insulation will only expand by about 10 times its original size. This may not sound like much, but it is enough to make a significant difference in the durability of your home and its ability to resist pressure from outside forces.

What is used for propellant?

Closed cell and open cell spray foam do have different blowing agents. Closed-cell, or foamed in place insulation is typically sprayed with an industrial chemical agent that can give off a temporary odor when the product first sets up (or dries). Open cell uses water as its blowing agent which means it will not smell like chemicals during the installation process. The products we use produce minimal off gassing so, you don’t need to worry about any chemical smells sticking around for long.

Water Permeability

Water permeability is another aspect of spray foam insulation that you should be aware of. Open cell spray foam will allow water to pass through it, making it a poorer insulator than closed cell. Closed-cell insulation has the benefit of being waterproof and providing an excellent vapor barrier, which greatly improves its overall performance as an insulator. This keeps your home warmer in the winter and cooler in the summer, but it also protects your insulation from being damaged by moisture.

Open cell may be appropriate in areas where it is important to identify leaks quickly, such in a roofing application. While the open cell insulation will show signs of a leak immediately, closed cell will conceal the leak allowing the water to accumulate elsewhere over time. This could potentially lead to major problems down the road.

Sound Reduction Qualities

Open cell spray foam is typically a bit more soundproof than closed cell spray foam. The spongy open cell structure absorbs the energy from sound waves, will the rigid closed cell structure conducts the energy easily. This makes closed cell a better choice for areas where sound reduction is highly valued.


The installation methods for open cell and closed cell insulation are both very similar. They both require you to seal all air leaks in the structure using a high quality spray foam product. After this process is completed, you should be left with an environmentally sound and long lasting insulation that will do its job properly. However, because of the lower density in open cell spray foam it is often easier to work with, making it a slightly less labor intensive product.

Air Sealing Properties

One advantage to open cell insulation is that it very good at getting inside of hard to reach nooks and crannies, creating a good seal. However, since open cell insulation has a lower r-value than it’s closed cell counterpart, you will need more inches of open cell in order to achieve the proper air seal necessary for good insulation.

Typically, 2 inches of closed cell insulation is recommended for as an absolute minimum, as compared to 3 inches ifor open cell.

For best results, 6-10 inches of open cell insulation should be applied to the ceiling and 3 inches to the walls. For closed cell, 4-5 inches is recommended for the ceiling while 2-3 inches is appropriate for walls.

Closed cell spray foam will provide superior air seal when compared to open cell spray foam. Both types of insulation must be properly installed, but in areas where increased durability is necessary closed-cel may be the better option.


This article has discussed the differences between open cell spray foam and closed cell spray foam. The major distinctions between these two products is their ability to expand in size, their density, permeability to water, and how much they conduct heat and sound energy.

Whatever type of insulation you choose, whether it is open cell or closed cell, make sure you do a little research on the products that are available in your area and talk to an expert at Evergreen Insulation when you are ready for an installation!