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Open Cell vs Closed Cell Spray Foam | Koala Insulation of West Florida

Open Cell vs Closed Cell Foam: Which Should I Choose? 

Which type of foam should I use? 

When you ask anyone about which spray foam you should use for your job, you'll likely get a few different answers. 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 to the specific application and the goals you are trying to reach with your insulation while maintaining your budget. In this guide, we will dive into the differences and similarities between open cell and closed cell spray foam so that you can pick out which is best for your project! 

What's the Difference? 

Cell Structure 

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

Open Cell foam earned its name because there is room inside each foam cell – 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 open cell spray foam is hydrophobic. It will only retain less than 5% of any water it encounters and retains its shape, cell structure, and insulating properties as it dries naturally. Other open cell spray foam brands can retain up to 75% of their weight in water. 

Closed Cell foam is the exact opposite of open cell foam. This densely packed foam leaves no space in the cells, causing the foam to be more rigid and not allowing any air or moisture to get inside or past the foam. A side effect of this cell structure and the rigidity created will also help the structural integrity of the building. 

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 about the differences and similarities of each. However, you can still achieve an air barrier with open cell spray foam, which is the most vital part of your home's building envelope. 

Density 

The density of each spray foam directly correlates to each cell structure. Open cell foam is softer and more flexible; therefore, the core density is lower. Open cell foam has a core density of 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, usually ranging from 1.75 to 2.2 pounds per cubic foot. 

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

Expansion and R-Value 

Because open cell foam has a lighter density and a larger cell structure, does that mean 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 cells will typically only expand to about 33 times. 

When you look at the culmination of each type of spray foam's expansion, density, and cell structure, 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 traditionally has an R-value of 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 not controlling air leakage properly. We can 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″. 

For example, in a typical wall cavity application, closed cell foam installed at 2" would have an R-Value of approximately R14. A standard wall installation with the open cell foam at 3.5" yields an R-value of roughly R13. However, since they create an air barrier, you won't see any of your conditioned air leaving your home or infiltration by the outside, nun-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, ultimately costing more. Because more material is used, there could also be more labor costs 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, having a higher R-Value, typically around R7 per inch per area 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 the overall cost is considerably less than closed cell spray foam as the material costs less to manufacture and 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. 

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. Using open cell spray ensures a proper air barrier in difficult-to-reach spaces, which ultimately helps keep the conditioned air inside 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? If there is a leak somewhere with insulation exposed to water, it won't need replacing if it is allowed to dry. 

Traditional insulation, like fiberglass, will soak up the water and can then lead to mold. Not all open cell spray foams are hydrophobic, so verify that your product is indeed hydrophobic. 

Pests and rodents do not like it. While open cell spray foam is not a deterrent to pests or rodents, it offers no food value to them. 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. Meaning 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 most significant benefits is that it has a higher R-Value than that of open cell foam. In situations where there are challenges to meet building code R-value requirements due to the depth of the wall, you can achieve a higher R-Value with less space and still maintain compliance. 

Close cell spray foam does not allow any vapor or water to pass through at appropriate thickness and applications due to its tightly packed, closed-off cells. FEMA recognizes closed cell spray foam as flood-resistant and acceptable in areas 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, a technician can spray it 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. 

Closed cell foam also adds to the rigidity of a structure due to its rigidness and cell structure. 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 have their unique advantages, they also share many 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, a most critical factor in your home's insulation and energy efficiency. An air barrier will effectively keep the interior's conditioned air from moving out of your home. Since both open and closed cell foams create an air barrier in your home, it will dramatically help the air quality inside 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. Not only will this save on the upfront costs, but also on the monthly cost of keeping it running. 

As open and closed cell foams adhere to the substrate to which they are applied (rather than inside the cavity), there is zero chance of sagging or settling the insulation over time. 

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 with a building code calling for a higher R-Value in certain areas, you may need to go with closed cell foam to meet those code requirements as it has a higher R-Value per inch sprayed than open cell foam. 

If you want 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. Choosing open cell foam could significantly reduce your project's overall budget. 

Buildings that require spraying on the exterior or endure exposure to continuous water should choose a closed cell foam as it will not allow any water to pass, can reject bulk water, and is FEMA approved. 

Suppose you have a building with challenging areas to insulate with many nooks and crannies that may be difficult to access. In that case, open cell foam might be the best choice due to its high expansion rate as it will effectively seal those areas quickly and efficiently. 

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

Still have questions or need help with your home or project? Contact us today!