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Open Cell or 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.


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. 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.


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 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 are deemed environmentally safe, 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. 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 are 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 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 really depends on where it’s being applied and what you’re trying to accomplish. We usually recommend open cell spray foam to be 5-inches on a roof deck or ceiling and 3-inches in the walls. Closed cell foam insulation should be 3 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 anymore return on investment by adding the extra foam.


Open Cell vs Closed Cell R-Value

The R-value of spray foam 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 the entire structure varies by factors such as the size of the insulated area, difficulty of the job, thickness of foam applied, and type of foam used.

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.



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