Two photo frames showing closed-cell spray foam insulation and open-cell spray foam insulation up close with the caption "Open-Cell vs. Closed-Cell Spray Foam Insulation"

We updated this post on April 25th, 2023 to add a pros and cons list and a helpful FAQ section so you can choose the best type of spray foam insulation for your home.

Choosing the type of insulation to use when putting insulation in your home is an important decision. If you’re considering installing spray foam, there are two main types: open-cell and closed-cell.

Open-cell spray foam insulation is cheaper, expands more, and allows more air circulation than closed-cell spray foam. Closed-cell foam is more expensive, doesn’t expand as much, and seals well enough to act as a vapor barrier. It also has about twice the R-value of open-cell spray foam insulation.

In this post, we will break down the differences to help you decide which will work better in your situation.

What Is Spray Foam Insulation?

Rim joist insulation using spray foam to form an airtight seal.

Spray foam is an insulation that is chemical-based and mixed on the worksite by insulation contractors, then applied to the desired location with a sprayer.

The foam is typically used to insulate walls, floors, and ceiling cavities. Because of its structure, foam insulation doesn’t compress, sag, or settle over time, making it a strong choice for insulating your home.

Both open-cell and closed-cell spray foam can last for an extremely long time.

The Differences Between Open-Cell and Closed-Cell Spray Foam Insulation

The difference between open-cell and closed-cell spray foam insulation is in the small cells, similar to bubbles.

As the names suggest, the bubbles in open-cell spray foam insulation are open, allowing both air and water to pass through and lending an overall softer structure.

The bubbles in closed-cell spray foam are closed, blocking air and water movement and making it more rigid.

Both can provide an air seal, but only with an applied thickness of two inches for closed-cell spray foam and three inches for open-cell foam.

Possible Problems With Spray Foam Insulation

One thing that isn’t as good about spray foam is that it’s much more expensive than fiberglass or cellulose insulation.

Closed-cell foam is the more expensive of the two foam-based insulation types, mainly because it doesn’t expand as much, so it requires much more to get the job done.

Open-cell spray foam is shown in use on a ceiling

Spray foam can also be a big fire hazard because of spontaneous combustion that can occur. An exothermic reaction begins if the foam is not applied correctly.

If a house catches on fire from another cause, spray foam is extremely flammable and also creates toxic smoke.

If it’s not mixed and applied properly, off-gassing (when something gives off a typically harmful chemical in the form of a gas) could cause health issues or aggravate conditions like asthma.

Interested in a healthier option? Click here.

It’s important to understand these downsides to spray foam. While it’s extremely popular because of its effectiveness, it won’t be appropriate for every situation.

Open-Cell Foam Insulation: The Basics

Spray foam insulation is applied in a home


Open-cell foam insulation, as mentioned above, expands more rapidly. This creates a much more open, bubble-like structure.

This openness in the structure makes open-cell foam insulation more flexible. In addition to being more pliable, open-cell insulation is much lighter.

Because of its pliability, it’s also easier to remove. Plus, it can insulate places that are harder to reach, like corners, holes, and other types of nooks.


Another quality of open-cell foam insulation is that it allows the movement of water through it. However, it’s not an organic material, so it does not encourage mold growth.

Once the insulation is dry, the effectiveness remains uncompromised. It simply allows a pathway where water and water vapor can move in and out of a specific area.

Good brands of open-cell spray foam can retain anywhere from 5% to 70% of their weight in water.

If you live somewhere with consistently high humidity, open-cell foam insulation may be less beneficial because it will allow outdoor moisture into your house.

You can spray a vapor retardant over the insulation, which will help minimize this problem.


One great thing about open-cell spray foam insulation is that it absorbs sound well. This comes back to its structure once again.

Remember your elementary school science classes? Sound waves travel through the air until they bounce off of something.

When they enter all the little spaces inside open-cell spray foam, they bounce back and forth until absorbed, never reaching your eardrums.


As mentioned earlier, open-cell spray foam insulation has a smaller R-value than closed-cell foam.

The R-value ranges from 3.5 to 3.8 per inch for open-cell foam.

R-value stands for the capacity the material has to resist heat flow. The higher it is, the greater the insulating power.


Its cost of open-cell insulation is also much more affordable than closed-cell. Open-cell expands pretty much as soon as it’s applied and expands much more than closed-cell foam.

Because of this, you need less to cover the square footage of the area you want.

Closed-Cell Foam Insulation: The Basics

Closed-cell spray foam insulation is applied to a wall


Closed-cell insulation is called this because the air pockets are grouped closely together, creating a denser structure.

The expansion rate of closed-cell spray foam is minimal compared to open-cell insulation. This lack of expansion and its rigid structure makes it much more durable.

It won’t easily be damaged, even while it’s still exposed. It can even make the structure of your home stronger. It has a medium density of about 1.75 to 2.25 lbs. per cubic foot.


The closed structure makes it much more difficult for water vapor to travel back and forth. This can actually be a bad thing because it could conceal a leak until the water builds up, causing a much bigger problem later on.


Closed-cell foam insulation has a much higher R-value, usually around 6.0 per inch, absorbing about twice as much heat as open-cell spray foam. This makes it very effective in areas with extreme temperatures and high humidity.


The lack of expansion means it takes much more material to insulate an entire area completely. Obviously, it is much more expensive to use. Installation costs are going to be higher as well.

Open vs. Closed-Cell Spray Foam Insulation Pro and Cons

Before you make up your mind between open and closed-cell spray foam, review this handy pros and cons section.

Open-Cell Spray Foam Insulation

Let’s begin with the pros of choosing open-cell spray foam for your home:

  • Light and flexible
  • Reduces noise
  • Covers large areas
  • A little goes a long way since it expands
  • Can get into areas you struggle to reach

Make sure you keep these downsides in mind as well:

  • Sometimes shrinks
  • Dries fast, so you must work faster
  • Cannot withstand extreme temperatures

Closed-Cell Spray Foam Insulation

Now let’s switch gears and assess the pros and cons of closed-cell insulation, beginning with these benefits:

  • Strong, so it can lend structural support to walls
  • Lasts a long time
  • Mold and water-resistant
  • Energy efficient

Carefully contemplate these issues with closed-cell foam:

  • Also shrinks
  • Hard to work with, especially if you want an even layer
  • Too heavy in some applications
  • Doesn’t absorb shocks that well

Which Type of Foam Insulation Is Better For You?

In general, foam insulation is a great solution for filling in all kinds of cracks and spaces. It can also be added to existing walls without tearing them open.

Because open-cell spray foam has a much lower R-value, it’s not as suitable for places with extreme temperatures. Heat and humidity can get through it more easily.

Open-cell foam is better for smaller, inaccessible areas because of its soft structure and expanding ability. It also dampens sound really well.

Closed-cell spray foam has a higher R-value, so it works well in places with more extreme temperatures. It does not allow water to pass through it, but this means it could conceal leaks.

Ultimately, whether you go with open-cell or closed-cell spray foam will depend on where you live, your budget, and your goals for the space you are insulating.

Spray Foam Insulation FAQs

Do you have more questions about spray foam insulation? Don’t worry, as we’ve got answers!

What Is a Blowing Agent? What Is Its Role in Spray Foam Insulation?

Blowing agents make spray foam more insulating than it would be without them. Hydrofluoroolefin or HFO is a popular blowing agent for this type of insulation, as it doesn’t deplete ozone and is non-flammable.

How to Tell the Difference Between Open and Closed-Cell Spray Foam Insulation?

To determine if you’re using open or closed-cell spray foam insulation, simply check the density. Closed-cell foam has a denser feel compared to the bubbly open-cell spray foam!

Does Spray Foam Insulation Decrease Home Value?

Spray foam insulation can improve a home’s curb appeal, but the job must be done correctly. If you feel like applying foam insulation is out of your depth, you can always hire a contractor to do it for you!


  1. Hi Erin,

    If I go with foam spray in my attic and a company sprays it on my roof plywood, what happens when I need to have my roof replaced and the roofers pull off the plywood. Does the foam come off with it?

    Would you mind emailing me your answer? Thanks, Elise

    1. Hi Elise,

      Thanks so much for your question. I can’t say for sure in your particular situation whether the foam comes off with it. I think it depends on many factors for your particular house. My best suggestion is to call three or more spray foam companies to ask them and hopefully they will give a consistent answer on that, perhaps after coming out to take a look at the attic and roof. Good luck! – Erin

  2. i spray foamed the rim joists and end joists in my basement . we live in minnesota and temps can be very hot and extremely cold during the season. i used 75 cans of open cell foam for each wall menards is the best deal at $4.00 a can i used the highest expanding foam they sell 3 inches the cavity of a rim or end joist is around 12 inches deep i completely filled the entire cavity 12inches thick . i installed plastic as a vapor barrier over it and it has warmed up our non heated basement tremendously it was alot of work but well worth it i used open cell because it can breathe closed cell cant do that and doing it yourself you can go at your own pace

Leave a Reply

Your email address will not be published. Required fields are marked *