Closed Cell VS Open Cell Attic Spray Foam Insulation

Spray foam comes in two different types; closed and open cell. Which type should you be using to insulate your attic?

Spray foam is a chemical-based insulation mixed on-site by certified attic specialists before spraying on attic surfaces using a spray foam gun. Ceiling cavities, floors, and walls are all popular places to utilize spray foam insulation. Foam insulation is an excellent alternative for insulating your house since it does not compress, droop, or settle over time. Whether it's open or closed-cell spray foam, can last for decades. 

There are two types of spray foam insulation: closed-cell and open-cell. Both are highly efficient insulating materials despite their very different characteristics. So how do you choose which type to use for your attic? Consider the differences of open-cell vs. closed-cell insulation below.

What Are The Differences?

Open Cell

Open-cell foam insulation immediately expands when applied, while closed-cell foam expands more slowly. As a result, you'll need fewer materials to cover the same amount of ground. It insulates hard-to-reach spots like corners, holes, and other crevices.

That said, open-cell spray foam insulation is somewhat less effective than closed-cell spray foam insulation in terms of R-value. Open-cell foam's R-value varies from 3.5 to 3.8 per inch, depending on the density. Thermal conductivity, or R-value, measures a material's resistance to heat movement. A building's insulating power increases with height.

Depending on the manufacturer, open-cell spray foams may hold anywhere from 5% to 70% of their weight in water. If you reside in an area with a high humidity level, open-cell insulation may not be the best option since it allows moisture from the outside in. Having a vapor barrier or vapor-retardant sprayed on insulation may help reduce this issue, however.

As mentioned above, one benefit of open-cell insulation is that it enables water to flow through it. The efficacy of the insulation is unaffected once it has dried. If you're looking to get rid of excess moisture, this is the best way to go. Mold cannot develop on it because it's not made of organic material.

Compared to closed-cell insulation, which expands more slowly, open-cell insulation has a more open, bubble-like appearance. As a result of its "openness," this insulation is more pliable.

Besides being more flexible, open-cell insulation is much lighter than closed-cell foam. That same pliability makes it simpler to remove when needed.

Open-cell spray foam insulation is also an excellent choice for sound absorption, and open-cell is less expensive than closed-cell.

Closed Cell

Closed-cell has a tight structure created by its air pockets that cluster closely together.

Closed-cell spray foam has a lower expansion rate than open-cell insulation. To fully insulate a large area, you'll need a lot more material. This, of course, entails a substantially higher cost. Additionally, you can expect the price of installation to rise.

Closed-cell has a substantially greater R-value (about 6.0 per inch) than open-cell spray foam, absorbing roughly twice as much heat. As a result, it is instrumental in climates with intense heat and humidity.

Water vapor can't quickly go back and forth due to the tight air seal created by closed-cell spray foam. On the other hand, this might be a negative since it could hide a leak until the water has built up, resulting in a far more severe situation.

Closed-cell's rigid structure makes it more long-lasting than other options. It may even strengthen your house's framework. Closed-cell weighs between 1.75 and 2.25 pounds per cubic foot.

Pros & Cons Of Open Cell And Closed Cell Spray Foam Insulation

Open Cell

The fact that open-cell foam expands so much after application means that it may effectively insulate even the most difficult-to-reach areas of a house. Closed-cell foam has difficulty insulating these sorts of spaces. Open-cell foam is typically ideal also for soundproofing because a single application may entirely cover the distance between studs.

This foam is more cost-effective, but it doesn't insulate a home as effectively as closed-cell foam. It might be inappropriate for places with harsh weather conditions.

Open-cell foam installation necessitates the use of personal protective equipment since chemical resins and blowing agents are used. There are several options for flame-resistant foams as far as building regulations go. Toxic fumes may be released while burning foam.

During installation, it's crucial to keep an eye out for open-cell foam that can accidentally go into electrical areas or coat surfaces. This includes everything in the wall cavity, such as pipes and cables. The open-cell foam may also complicate future electrical and plumbing repairs.

Closed Cell

If you ask most folks, they'll tell you that using closed-cell spray foam is the only way to go for any given job.

The rigidity of closed-cell makes it an excellent choice for pole barns with exposed walls. In addition, its moderate expansion rate makes it ideal for applications like cargo trucks.

There is a greater R-Value for closed-cell spray foam, but you should not rely exclusively on these values when making a choice. If you're looking at spray foam insulation, R-Value isn't going to give you the complete picture.

Closed-cell insulation has the potential to provide a little structural integrity in some situations. Adding a thin layer of closed-cell spray foam to the roof deck can strengthen a metal roof, for example. If a tree limb or other object strikes your roof, this is a big deal. By using a closed-cell, the weight is prevented from bending the metal.

On the other hand, the impermeability of closed-cell spray foam can be a risk. If there is a leak, the closed-cell foam will provide nowhere for the moisture to escape, so you won't notice a leak until it's too late. A contractor will have a tough time cutting through the closed-cell foam insulation to patch the leak since it is not malleable and has a stiff composition.

When it comes to the attic, closed-cell spray foam is a fantastic substance, but it isn't going to work well for all situations and structures.


So which is better: open-cell or closed-cell foam? While open-cell and closed-cell spray foam have their own advantages and disadvantages, both offer several common benefits, such as establishing an air barrier for your house, reducing energy bills, and lasting longer than fiberglass or other types of insulation. Given these benefits, there are just a few things to consider in the end.

While open-cell is far less expensive than closed-cell, it lacks the same lifespan and capacity to insulate harsh temperatures. When deciding on the ideal investment, take into account both of these factors.

Do you desire a safer building with thicker walls and better security? Your best bet is a closed-cell foam. It may reinforce anything because of its incredible density and hardening characteristics.

Attic or wall places that are difficult to access? Open-cell foam can get into places where closed-cell foam cannot. 

Is there a certain R-value that you are looking for or need? Closed-cell foam, which has a higher R-value of 7, may be a good investment if you live in an area that requires a specified R-value.

It’s a choice that requires the weighing of many factors. Calling upon a certified attic specialist can help you navigate this tricky process, but fortunately, you won’t go wrong with such a durable product – open or closed-cell.

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