Open Cell vs Closed Cell Spray Foam Insulations: Here Are Things You Didn’t Know

Now that you’ve finally decided to go for spray foam insulation, another decision awaits your verdict. You’re confused about whether to go for open-cell spray foam or closed-cell. Unlike what most would assume, spray foam insulation’s two common types have quite a few significant differences between them. Choosing the right type is essential because you don’t want to end up spending so much money on spray foam to end up with the wrong cell. 

The core difference between these two can be summed up by their names. Open-cell spray foam has cells that have an expansive arrangement. On the contrary, closed-cell spray foam has cells that are tightly packed together. You’ve probably got a physical representation of this cellular composition in your mind, but is it really that simple? In this article, you’ll be learning everything you need to know about spray foam’s cell types including which should work best for you. So, without further ado, let us dive into the comparison of open-cell and closed-cell spray foam.

Open-cell Spray FoamClosed-cell Spray Foam
EffectivenessModerateVery High
Expansion RateCan expand 100xCan expand 33x
TextureSoft and FoamyRigid and Firm
Air SealYesYes
open cell vs closed cell spray foam insulation

Composition and Density

When it comes to composition, open-cell foam has, as stated previously, a composition based upon cells that are not confined altogether. These cells or bubbles are wide apart from each other and have a lot of space that results in a soft foamy texture that expands easily. Due to its roomy composition, open-cell foam is also lightweight and seems to be larger in volume. This makes it one of the top contenders when it comes to filling tight spaces and leaks. The density of the open-cell foam is approximately 0.5 pounds for a single cubic foot.

As for closed-cell spray foam, it has a highly dense composition. The cells are tightly sealed together eliminating any chances of air from making its way in. It is because of closed-cell spray foam’s dense composition that gives it a stiff and tough texture. Unlike its counterpart, closed-cell foam can form a very strong line of defense against damage of any type. This is why closed-cell foam is considered to be a rigid solution for combatting airflow. In terms of density, it has around 1.7 pounds for a cubic foot.


Let us now come to the most important part of the comparison. Generally speaking, spray foam is definitely amongst the best in terms of performance. Open-cell foam in specific does not disappoint if you use it at the right place; especially when it comes to insulating places where the insulation might have trouble reaching, such as small openings. Thanks to its rapid expansion properties, open-cell can make its way into tight spaces with ease.

Closed-cell spray foam, on the other hand, specializes in setting up a vigorous barrier between the outside world and the inside of a structure. Simply put, it has its focus on quality over quantity. Closed-cell foam’s performance best stands out when you’re in need of extra strength for insulation. This is because it has a powerful composition that does not go down without a fight. Therefore, in places where space is short and you need to achieve maximum R-value, then closed-cell foam is an ideal solution.

The thermal insulation of open-cell and closed-cell foam is quite similar. Both types put up a strong seal that does not let air in or out. However, for ensuring that the air barrier is set up properly, the minimum thickness requirements of both cell types must be met. These requirements may vary from region to region and are also subjective to the place which needs to be insulated. To sum it up, open-cell and closed-cell foam are both highly effective in trapping air inside a structure and stopping air from creeping inside.


The R-value of a material tells how good it is at insulating. Open-cell foam has an R-value of 3.5 for every inch. Whereas closed-cell foam has a higher R-value of 6 per inch. Depending upon the brand, closed-cell spray foam can easily go up to 7 for an inch. As you can tell, open-cell foam’s R-value is just slightly more than half of the closed-cell foam’s R-value. Although the value might vary due to several factors, the difference we mentioned will probably remain the same between these two types. So, in regards to R-value, closed-cell spray foam takes the easy win.


Cost is a leading factor in determining the final verdict for insulation. In general, spray foam is expensive, but since we’re comparing its two types, we’ll be focusing on their cost relatively. Open-cell foam spreads like a wildfire and covers a lot of area as its volume multiplies. This means that less material is used for achieving the desired R-value and hence, it is relatively cheap. As for closed-cell foam, it has a dense texture and requires a lot of volume to insulate the complete area. Therefore, the need for more material obviously means more cost. To put it straight, closed-cell foam is more expensive than open-cell.


Although sound resistance is not usually the top reason behind one going for spray foam insulation, it’s a benefit worth appreciating. Open-cell spray foam boasts decent sound resistance properties. The science behind this sound insulation lies in the composition. Since open-cell foam has a spacious cell assembly, soundwaves tend to become trapped in the foam. However, things are different in closed-cell foam. It is nowhere near the level of open-cell foam in dampening sound levels because soundwaves cannot be trapped within its closely-packed bubbles. In conclusion, open-cell foam is a great option if you want your insulation to suppress noise.

Moisture Resistance

We all know that moisture resistance is an exceptional characteristic of insulation materials. It preserves the life of insulation and prevents the growth of mold. Now, open-cell foam’s moisture resistance is not really the best. Due to its spacious composition and fluffy foam, water can find a way through. However, many see this quality as an advantage instead of a disadvantage. This is because despite being prone to moisture, the open-cell foam does not influence the increase of mold due to the foam being inorganic. Nonetheless, if you find this quality to be threatening to the insulation’s performance, don’t forget that you can always opt for a vapor barrier.

Coming to open-cell’s counterpart, closed-cell foam is pretty much the opposite in regards to resisting moisture. Once again, due to its bubbles having no space amongst them to let air – let alone moisture through, closed-cell foam is completely impenetrable. This means that no matter how severely water hits the dry foam, it will neither budge nor let it through. However, this could be considered a drawback since, in the case of pipe leakage, water leaking would be hard to detect due to the insulation being in the way.

Expansion Rate

The expansion rate of open-cell spray foam is relatively high as compared to closed-cell foam. Remember, the more the foam expands, the less material is needed to insulate an area. When we look at it from a perspective of size, open-cell spray foam can expand up to a whopping 100+ times its actual size. That is why for insulating spacious areas, open-cell foam is highly recommended. As for closed-cell foam, its expansion rate is relatively less than open-cell. Call it a miracle if closed-cell foam expands more than 30 times its actual size. So, you’ll eventually be needing a lot more closed-cell foam for the same area that open-cell foam would cover.

Now that we’ve covered the main aspects of the comparison between open-cell and closed-cell foam, let us now discuss the pros and cons of both options.

Pros of Open-cell Spray Foam

High Expansion Rate

As we discussed earlier, a small amount of open-cell spray foam can cover a large area with ease because of its extraordinary expansion rate. If you have places that are hard to reach and they need insulation, open-cell foam can handle the problem. Despite its high expansion rate and soft texture, open-cell can also deliver an effective air barrier that will keep airflow at bay.

Excellent Sound Resistance

Now we know that sound resistance might not be your priority but opting for open-cell spray foam will only make things quieter. The spacious arrangement of bubbles discourages sound waves to reflect and thus they are forced to be absorbed into the insulation.


Open-cell spray foam is cheaper as compared to closed-cell. However, it still does a great job of restricting airflow. You’re using less material to insulate a structure. Moreover, the material makes its way into every leak by itself, saving you from giving special attention to miniature openings. Open-cell spray foam also costs less to install.

Cons of Open-cell Spray Foam

Not Ideal for Extreme Weather

Temperatures that go above and beyond normal cannot be handled by open-cell spray foam. Though it boasts a fair R-value for an inch, you’ll need extra insulation strength to hold off severe weather conditions. Unfortunately, open-cell is just too light and soft to handle anything more than moderate.

Pros of Closed-cell Spray Foam

Extremely Effective

So, what truly makes closed-cell spray foam special? Well, it has to be its effectiveness in restricting airflow. Due to the high-level density of the material, handling extreme temperatures would be a piece of cake for closed-cell foam. For regions where cold/heat strikes hard, closed-cell foam is a perfect fit.

Highly Resistant to Moisture

Moisture poses a great threat to insulation’s durability. However, moisture should be the least of your worries if you go for closed-cell spray foam. The material is simply excellent at battling wetness. Even if a leak occurs in the place, it’s improbable that it would affect closed-cell foam insulation.

Easier to Achieve the Required R-value

Since an inch of closed-cell foam can deliver a rating of R-7 with no effort, achieving the desired higher ratings should be no problem. This means that in areas where the suggested R-value goes above 20, closed-cell foam can get the job done without needing too much of the material.

Cons of Closed-cell Spray Foam

Quite Expensive

Although for some people the cost would be justified due to the return, for most closed-cell foam would be enough to break the bank. Yes, it’s meant for delivering a little extra to the table, but simply put, the price of closed-cell is exorbitant. It’s a drawback that impacts the end decision to a great extent.

The Final Verdict

We’ve analyzed all the factors that must be taken into account before the final verdict is given. It seems that open-cell foam is the winner here due to its popular usage and significant benefits. However, it probably holds no weightage in regions where soft foam simply won’t be enough to tackle the rough climate. 

Charles John

Experienced HVAC technician with 8 years of experience in the industry. Capable of handling all sorts of heating and cooling equipment as well as proficient in operational management, construction-related techniques such as preventative maintenance, electrical troubleshooting and AutoCAD

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