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

After doing some due diligence, you may have stumbled upon spray foam insulation and you realize it’s the best option available. But now you find yourself asking what’s better, open cell or closed cell?

While there are many differences between open-cell and closed-cell spray foam, the most important difference to the end consumer is cost. Obviously one variety is going to be more costly than the next. Although it is true that closed-cell is often more expensive than open-cell, there are other differences to be considered besides price alone.

If you want to make a well informed decision about which type of spray foam is best for you, you will need to be aware of the qualities that make these two types of insulation unique.

What are the Differences?

Open-cell and closed-cell spray foam are the two varieties available to homeowners, and they each have their own unique qualities. While open-cell is often cheaper, it has a lower insulation value. Open-cell spray foam has a porous composition which allows it to be flexible, and also allows it to be permeable to water while sealing out air. This can be ideal for use on wooden surfaces, allowing the wood to breathe. The open-cell structure of the foam allows for some level of evaporation to take place.

Open-cell foam is also easier to modify after it’s been installed. If you find that you need to do any plumbing or electrical work after installation, you can easily modify open cell foam to accommodate your new projects.

Closed-cell spray foam it’s much more dense, therefore providing a higher insulation value and thus more bang for your buck. It has a higher R-value when compared to open cell spray foam, meaning that it has the ability to insulate better and keep your home warmer in the winter and cooler in the summer. This type of foam is not permeable to either air or water.

Closed-cell foam is much more compact and durable than open-cell foam, and can actually act to increase the structural soundness of a building. This makes it ideal for structures like pole barns, making them more robust and capable of withstanding extreme weather conditions.


Density is the biggest thing that sets these two types of insulation apart. The typical density of open-cell spray foam is around 0.5 pounds per cubic foot, while closed-cell foam can come in at more than triple that, roughly 1.75 pounds per cubic foot. The porous cells of open cell foam are interconnected, making the material flexible and allowing for the passage of water. However, this fact also decreases its effectiveness as an insulator, leaving it with a lower overall R-value.

The higher density of closed cell spray foam makes it a much more effective insulating material, sealing out cold air from the outside and preventing the warm air inside your home from escaping. It is also much more durable overall and less likely to develop air leaks, even after having been installed for an extended period of time.


R-value measures an insulation material’s ability to slow the flow of heat energy. While open cell spray foam generally has a lower R-value of around 2.5 per inch, closed-cell foam’s R-value tends to be much higher, up to 7 per inch. It’s easy to see that even though closed cell foam can be a bit more costly, the higher price can be well worth the investment, due to the significantly higher R-value and the resulting energy savings.

How Much Do They Expand?

Open cell insulation can quickly expand as much as 100 times its original size. While closed cell spray foam does expand, its rate of expansion is not nearly as high as open cell. The expansion rate of open cell foam makes it great for getting into small hard-to-reach areas, especially the small nooks and crannies in the attic or exterior walls, creating a very effective air barrier.

Closed-cell insulation typically expands about 10 times its original size. While this may not sound like much when compared to open cell foam, it is enough to make a significant difference in your home’s durability, and its ability to resist pressure from outside forces.

What is Used for Propellant?

Open-cell and closed-cell spray foam both have different propellants, otherwise known as blowing agents. Closed-cell foam typically uses an industrial chemical agent that may give off fumes temporarily while the foam is allowed to set. Open-cell foam most often uses water as this blowing agent, meaning that it will not give off any chemical smells during the installation process. The products we use at Evergreen Insulation produce minimal off-gassing, so you won’t need to worry about prolonged chemical smells after installation.

Water Permeability

Differences in the permeability to water is another aspect of spray foam that you may need to consider. Open cell spray foam tends to be permeable to water, making it a less effective overall insulator.

Closed-cell insulation is great because it comes with the added benefit of being an excellent vapor barrier, which means that it can be used for waterproofing areas like the basement, or roof.

Sound Reduction Qualities

When it comes to soundproofing, open-cell spray foam typically performs better than closed-cell foam. The open cell structure acts as a sponge, absorbing the energy from sound waves, while the rigid closed cell structure tends to conduct sound energy more easily. If soundproofing is a major priority in your insulation project, open-cell foam may be a better choice fo you.


The method for installing both types of spray foam are very similar. They both generally involve spraying of the liquid insulation into the desired area and allowing for it to expand and set. After completion of the project, you should be left with a sturdy insulation installation that will last for many years. However, the lower density of open-cell spray foam generally makes it easier to work with, making it ideal for DIY projects.

Air Sealing Properties

One of the biggest advantages to open cell spray foam is its ability to expand and get inside of hard-to-reach areas, creating an airtight seal. While open-cell foam may be very good at getting into these tight spaces, it also has a lower R-value than it’s closed cell counterpart, meaning that you will need to apply it more liberally in order to achieve the same result.

2 inches is generally recommended for applications of closed-cell foam, compared to 3 inches or more which is generally recommended for open-cell foam.

Closed-cell foam will generally provide a superior air seal when compared to open-cell foam. Keep in mind that an adequate air seal can only be achieved when either type of insulation is installed properly. Also, be sure to consider that in areas where increased durability is desired, closed-cell foam is definitely 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 lie in 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!