You’ve decided to go with spray foam insulation because you feel it’s the best insulation choice for your home, but now you have to decide on the different types of spray foam insulation - open cell vs closed cell foam.

You already know foam insulation doesn’t just block heat flow, but it also stops airflow, which keeps your home or pole barn more comfortable while reducing your energy bills.

While open cell and closed cell are both types of spray foam insulations, there are differences between the two as far as how they are applied, their efficiency in homes compared to other structures, and how they work in general.

RetroFoam of Michigan has been insulating homes and pole barns across the lower peninsula for more than 17 years. As foam insulation is our specialty, we know quite a bit about what type of spray foam will work best in what areas of the home and for different buildings.

In this article, we will discuss some of the key differences between open cell vs closed cell spray foam, as well as the characteristics that make either a great choice for your home or pole barn.

Open Cell vs Closed Cell Foam

Let’s walk through closed cell foam vs open cell foam to figure out which type of spray foam insulation is better for you and your application.

For example, you might think closed cell spray foam is the best choice for your roof deck, but that’s not the case in most situations.

Before we dive in here, it’s important to note that both of these materials are incredible insulators and both create the air seal that will make your structure more comfortable and energy-efficient. With that being said, once you take a look at the differences between the open cell foam and closed cell foam you’ll have a better understanding of which one will best meet the needs of your project.

Now let’s get started.

Open Cell vs Closed Cell Spray Foam Composition

Open cell foam insulation is lightweight, pliable, and easy to work with, whereas closed cell foam is rigid and very dense.

For example, if you needed to run new wiring, open cell spray foam is going to be much easier to work with because it is so pliable. All you need to do is use fish tape and push it through the foam to get it where you want it to go.

Now you can’t fish wiring through closed cell, but that durability is great when the foam is left exposed. Closed cell’s rigid structure and durability make it ideal for exposed walls because it won’t be damaged if it is bumped by machinery or tools.

How Much Do Open Cell Foam and Closed Cell Foam Expand?

Open cell and closed cell foam insulation have very different expansion rates.

Open cell spray foam has a very high expansion rate, sometimes as much as 100 times over. This makes it an ideal option for homes because it gets in the nooks and crannies in attics, crawl spaces, open wall cavities, and rim joists.

Closed cell spray foam has very minimal expansion when applied as it is denser material. While closed cell does have a lower expansion rate, it still creates the same air barrier and has the same great benefits spray foam is known for.

We will get more in-depth in how thick spray foam should be down below.

What are the Blowing Agents for Closed Cell and Open Cell Spray Foams?

Closed cell and open cell spray foam do have different blowing agents.

Open cell spray foam is it typically uses water as its blowing agent.

Closed cell spray foam uses a chemical agent that can give off a temporary odor with some brands. The products we use have minimal off-gassing, which means less of a smell.

Another thing of note that is important to add is that both the open cell and closed cell spray foams used at RetroFoam of Michigan are deemed environmentally safe, Class One Fire Rated, and safe to have in the home.

What is the Moisture Permeability of Open Cell and Closed Cell Foam Insulations?

One spray foam will allow water to move through it and the other will block it completely.

Open cell foam is inherently moisture permeable, meaning water can move through it. Depending on the spray foam brand there are differences in whether or not free-standing water can be absorbed.

For example, a good spray foam may only retain up to 5 percent of its weight in water. Other open cell spray foam brands can retain as much as 75 percent of its weight in water. 

Closed cell spray foam, on the other hand, is 100 percent moisture impermeable, meaning it doesn’t allow water to move through it. While the moisture impermeable option might sound better, one scenario where open cell can be beneficial is on a roof deck of an attic. 

If a leak were to occur the foam would be discolored and let you know immediately where the leak was happening so it could be quickly repaired.

Closed cell spray foam will conceal the leak until the water builds up somewhere else and causes much bigger problems and headaches.

What is the Sound Dampening Qualities for Open Cell and Closed Cell Spray Foams?

Before answering this question it’s important to understand what sound dampening means.

Sound dampening isn’t the same as soundproofing. If a room is soundproof that means it’s impervious to sound. Sound dampening means reducing sound transmission.

The thicker, softer material of open cell reduces sound waves much better than the tight, dense closed cell.

If you want to completely soundproof a room or structure, you’ll need special sound panels, noise and isolation foams, sound barrier materials, and noise absorbers.

Does Open Cell and Closed Cell Spray Foams Create an Air Seal?

Both open cell and closed cell spray foams provide an air seal that is going to help eliminate drafts, heat loss, and moisture from getting into your home. 

That air seal can only be achieved with a minimum recommended thickness of 2 inches of closed cell and 3 inches of open cell. These are the minimum amounts, but the recommended amounts vary.

The thickness of spray foam really depends on where it’s being applied and what you’re trying to accomplish.

We usually recommend open cell spray foam to be 6- to 10-inches on a roof deck or ceiling depending on where you live and 3-inches in the walls. Closed cell foam insulation should be 4- to 5-inches on the ceiling and 2- to 3-inches in the walls.

This might come as a surprise, but honestly, this is all the spray foam it takes to get the biggest bang for your buck with the air seal and thermal resistance needed for certain areas of the home.

Some people believe that the more foam they have installed, the higher the R-Value, but that’s not how that works either. R-Value does matter, however thermal resistance is what R-Value measures. If you have an air seal, that’s the most important thing. After you reach a certain threshold, like the amount required to create an air seal, you don’t see any more return on investment by adding the extra foam.

Open Cell vs Closed Cell R-Value

The R-Value of spray foam insulation can vary depending on the product, manufacturer, and a few other variables.

Open cell foam R-Value is typically in the range of R-3.6 to R-3.9 per inch.

The common range of closed cell foam R-Value is R-6 to R-7 per inch.

There are several factors that affect the R-Value of spray foam, including the type of foam, the age of the foam, and how well it is resistant to moisture.

Open Cell Spray Foam vs Closed Cell Cost

The cost to insulate an entire existing home with spray foam varies by factors such as the size of the insulated area, the difficulty of the job, the thickness of foam applied, and the type of foam used.

Let's take an apples-to-apples look at a cost comparison between open cell and closed cell spray foam.

Say you have a 1,000-square-foot attic that you'd like to get spray foamed. The cost for 7-inches of open cell, including removal of old insulation, would be in the ballpark of $5,250. Now if you were to install closed cell into the same attic at the same depth, it would cost upwards of $10,350. It's important to note here that for closed cell spray foam we would normally recommend 5-inches of the product which would come in around $8,350.

Here's another open cell spray foam vs closed cell cost comparison using a crawl space.

To install open cell spray foam on the walls of an average 800-square-foot crawl space at 3-inches would cost around $2,350. For the same crawl space installing the same depth of closed cell spray foam would run $3,700, but we would normally recommend 2-inches of the material which would be in the $2,900 range.

Installation of open cell spray foam is much easier and the foam itself is less expensive to produce, therefore the cost of open cell is less expensive.

Closed cell spray foam, besides being more expensive to make, must be applied in thinner coats, often requiring several passes which can drive up installation time and cost.

Which Type of Spray Foam Insulation Meets Your Needs?

Spray foam insulation, regardless of what type, is going to create an air seal and insulate your home. 

Like most things, it’s not as easy as picking one over the other, it’s about what’s right for your home.

Balancing the pros and cons of each type of spray foam insulation isn’t hard if you’ve got all the information in front of you. Hopefully, this article has helped you with that and with deciding which spray foam is best for you.

If you’d like to learn even more about spray foam insulation, check out the Learning Center on our website.

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