Closed Cell vs Open Cell: Which One is Best for Me?

Which type of foam should I use?

When you ask anyone about which spray foam you should use for your job, you're bound to get a few different answers. It seems that you can always find someone saying one is better than the other and vice-versa. The truth is, one is not necessarily better than the other. It typically comes down the specific application and the goals you are trying to reach with your insulation, all while trying to maintain your budget. In this guide we will dive into the differences and similarities of open cell and closed cell spray foam so that you are able to pick out which is best for your project!

What's the Difference?

Cell Structure

Spray foam is referred to as either closed cell or open cell due to the structure of the material itself and the makeup of the cell structure.

Open Cell foam is called so because there is room left inside each cell of the foam - think of it as a little air bubble. Because of this, open cell foam tends to be softer and more flexible. While open cell will allow water to pass through, our Icynene open cell spray foam is hydrophobic, meaning that it will only retain less than 5% of any water it comes into contact with and will retain its shape, cell structure and insulating properties as it dries naturally. Other brands of open cell spray foam can retain up to 75% its weight in water.

Closed Cell foam is the exact opposite of open cell foam. There is no space in the cells and they are densely packed together. This causes the foam to be more rigid than open cell while not allowing any air or moisture to get inside or past the foam. Because of the cell structure and the rigidity that it creates, this will also help the structural integrity of the building that it is being installed into.

Based on this, why would I ever choose open cell over closed cell? Well, this is only part of the story and we will continue to expand on this as we talk further on the differences and similarities of each. However, with Icynene open cell spray foam, you are still able to achieve an air barrier - which is the most vital part when it comes to the building envelope of your home.

Density

The density of each spray foam is a direct correlation to the cell structure of each. Open cell foam is softer and more flexible, this means that the core density is lower. Typically, open cell foam has a core density around 0.5 pounds per cubic foot. Conversely, closed cell has a much higher core density due to the makeup of the cell structure. Closed cell foam is typically three to four times heavier than open cell foam, typically ranging from 1.75 to 2.2 pounds per cubic foot.

Due to the lighter density of open cell foam, it will perform much better than closed cell when it comes to sound dampening. The thicker, softer material of open cell will reduce sound waves much more efficiently than that of the tight, dense closed cell foam.

Expansion and R-Value

Because open cell foam has a lighter density and has a bigger cell structure, does that mean that it will expand more than open cell? Yes! Because of these things, open cell foam will expand 100 to 120 times its size while closed cell will typically only expand to about 33 times its size.

When you look at the culmination of the expansion, density, and cell structure of each type of spray foam, the relevant R-Value of each will make a bit more sense. Sprayed-in-place closed cell foam typically has an R-Value of 7 per inch while open cell foam normally has an R-value around 3.5 to 4 per inch sprayed.

So, based on this I should go with closed cell spray foam because a higher R-Value is better, right? Well, not necessarily. The biggest reason for heating and cooling loss in a home is due to not controlling air leakage properly. With Icynene spray foam, we are able to create an air barrier with closed cell foam at an installed thickness of 1.25". We can also achieve an air barrier with open cell foam at 3-3.5".

As an example, in a typical wall cavity application, closed cell foam installed at 2” would have an R-Value of approximately R14. A typical wall installation with the open cell foam at 3.5” yields an R-value of approximately R13. However, since they are both creating an air barrier, you won't see any of your conditioned air leaving your home or being infiltrated by the outside, un-conditioned air. Therefore, the thermal performance of the two products is virtually identical.

Cost

Due to the chemical makeup and the expansion rates of closed cell and open cell foam, there is a difference in cost. Since closed cell foam is denser than open cell foam, it will take more material to cover the same amount of space so it will ultimately cost more. Because there is more material being used, there also could be more labor cost to get it installed.

What are the benefits of each?

Before we dive into the benefits of each type of spray foam, let's take a second to recap what we learned above about the science behind them.

Open cell spray foam is lighter, less dense and expands 100-120 times its size. Because of this, it has a lower R-Value of around R3.5-4 per inch installed.

Closed cell spray foam is heavier, denser and expands up to 33 times its size. This leads to closed cell foam having a higher R-Value, typically around R7 per inch that is sprayed.

Open Cell Spray Foam Benefits

There are many benefits to using open cell spray foam for your home or project. One of the biggest is that the overall cost is considerably less than that of closed cell spray foam. This is due to the material itself costing less to manufacture as well as the expansion and cell composition of open cell spray foam. Because it expands much more than closed cell spray foam, it will take less material to insulate the same amount of space, thus potentially saving on labor costs as well.

Also, since open cell spray foam expands at a much higher rate than closed cell spray foam, it fills every nook and cranny of your home much easier. This ensures that there is a proper air barrier in difficult to reach spaces, which ultimately helps keep your conditioned air inside of your home.

Another great benefit of open cell spray foam is that it can be hydrophobic, meaning that it will retain less than 5% of its weight in water. What does this mean for you? It means that if there is a leak somewhere and the insulation is exposed to water, it won't need to be replaced if it is allowed to dry. Traditional insulation, like fiberglass, will not do this as it will soak up the water and can then lead to mold. Not all open cell spray foams are hydrophobic so be sure to verify the product that you are getting is indeed hydrophobic, like Icynene’s Classic Ultra Open Cell Spray Foam.

Pests and rodents do not like it. While open cell spray foam is not a deterrent of pests or rodents, it offers no food value to them. This means that you won't find critter homes in your attic or crawlspace!

Due to the cell structure and makeup of open cell foam, it effectively dampens soundwaves. This means that it will not only insulate and seal your home, but make it quiet as well!

Closed Cell Spray Foam Benefits

There are also a lot of benefits to using closed cell spray foam for your home or project. One of the biggest benefits is that it has a higher R-Value than that of open cell foam. This means that in situations where there are challenges to meet building code R-value requirements due to the depth of the wall, you are able to achieve a higher R-Value with less space and still maintain compliance.

At appropriate thickness and applications, closed cell spray foam does not allow any vapor or water to pass through due to its tightly packed, closed-off cells. In fact, FEMA recognizes closed cell spray foam as flood-resistant and acceptable to use in areas that are prone to flooding as it can effectively reject bulk water and not deteriorate under these conditions.

Since closed cell foam can act as a vapor retarder and doesn’t allow bulk water to pass through it, it can also be sprayed onto the exterior of buildings. Therefore, if there are applications where it is best or easiest to apply insulation on the exterior of the building, closed cell foam would be the best solution for this type of situation.

Because of the rigidness and cell structure of closed cell foam, it will also add to the structural rigidity of the structure that it is being applied to. Do you have a pole barn in an area with high winds and are worried about the flex that it could cause on the metal? Closed cell foam can help to combat this!

Benefits of Both Open Cell and Closed Cell Foam

While open cell and closed cell spray foams both have their own unique advantages, they also share a lot of the same qualities that provide tremendous benefit and value for the consumer.

Open cell and closed cell spray foam will create an air barrier for your home. This is the most important factor when it comes to the insulation and energy efficiency of your home. Having an air barrier will effectively keep the interior conditioned air from moving out of your home. Homes installed with Icynene spray foam typically have an ACH (Air changes per hour) of less than 3, which is substantially less than what most typical building codes call for.

Since both open and closed cell foams create an air barrier in your home, that means that it will dramatically help the quality of the air inside of your home. Say goodbye to allergens and irritants!

In most new construction homes, using either open cell or closed cell foam will mean that you can save even more money by downsizing the HVAC system that's being put in. Not only will this save on the upfront costs, but also on the monthly cost of keeping it running.

Since both open and closed cell foams adhere to the substrate that they are being applied to (instead of sitting in the cavity), there is zero chance for there to be any sagging or settling of the insulation over time. Our Icynene foam is guaranteed for the life of the structure!

So, which one should I use?

As we said at the beginning of this post, it all comes down to what the application will be. If you're in an area that has a building code that calls for a higher R-Value in certain areas, you may need to go with closed cell foam in order to meet those code requirements as it has a higher R-Value per inch sprayed that open cell foam does.

If you are wanting the benefits of spray foam and the application allows for it, there could be significant cost savings realized by using open cell spray foam instead of closed cell due to the reduced material and labor cost. This could allow a significantly reduced overall budget for your project.

If your building is needing to be sprayed on the exterior or has the opportunity to be exposed to continuous water, then you would need to go with closed cell foam as it will not allow any water to pass, can reject bulk water, and is FEMA approved.

If you have a building with tough areas to insulate with a lot of nooks and crannies that may be difficult to access, open cell foam might be the best choice due to its high expansion rate as it will effectively seal those areas very effectively and efficiently.

While there are specific applications and projects that we would recommend one spray foam product versus another, it really comes down to is what you, the consumer, is looking for and what is important for your project. At their core, both open cell and closed cell foams achieve the same thing - they seal up your home, last for the life of the structure, and will drastically reduce your heating and cooling costs!

Still have questions about your home or project that you would like some help with? Contact us today!

Superior Insealators is an ABAA (Air Barrier Association of America) Certified Insulation Contractor.

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