Spray Foam Insulation

Open and closed cell foam are two different types of spray foam insulation. They have different strengths and weaknesses, and one is not necessarily better than the other. It comes down to understanding the benefits of open cell vs closed cell foam and choosing the type that fits your needs.

Let’s start by looking at the differences between open and closed cell foams.

Spray foam is referred to as either closed cell or open cell due to the structure of the material itself and the makeup of the cell structure.

Open cell foam is is called this because the cells are left "open". Meaning there is room left inside the cell and it is not full. Think of a circle and only part of the circle has a solid matter, the rest is expansion that is full of air. This makes the foam a softer, more flexible material. While open cell will allow water to pass through, our open cell spray foam is hydrophobic, meaning that it will only retain less than 5% of any water it comes into contact with and will retain its shape, cell structure and insulating properties as it dries naturally. Other brands of open cell spray foam can retain up to 75% its weight in water. 

Closed cell foam is called this because the cells are "closed". That means the cell is completely full of product. So if you are thinking of the circle again, the circle is now solid and full. The cells are pressed densely together, so air and moisture are unable to get inside the foam. Because of this, closed cell foam is much more rigid and stable than open cell foam.  This will also help the structural integrity of the building that it is being installed into.

Closed cell foam is much denser than open cell foam. Open cell foam is softer and more flexible, making the core density lower than closed cell. Typically most open cell foam has a density of about 0.5 pounds per cubic foot. Closed cell foam can be over three times that, with a density of  1.75 to 2.2  pounds per cubic foot.

Due to the lighter density of open cell foam, it performs much better at sound dampening than closed cell. The thicker, softer material of open cell reduces sound waves much more efficiently than the dense closed cell foam.

A foams R-value is its resistance to heat flow or, in other words, how well they insulate.

Closed cell foam has a higher R-value than open cell foam, usually about 6.0 per inch. This higher rating makes closed cell foam better at keeping heat in or out of a structure.

Open cell foams have an R-value of around 3.5 to 4 per inch sprayed. This is significantly lower than closed cell foams, which can limit open cell insulations usefulness in extreme temperature conditions. 

As an example, in a typical wall cavity application, closed cell foam installed at 2” would have an R-Value of approximately R14. A typical wall installation with the open cell foam at 3.5” yields an R-value of approximately R13.The thermal performance of the two products is virtually identical.

This is one of the biggest differences from an application standpoint. Closed cell foam is designed to expand to about 1″ of thickness when sprayed. With each inch offering an r-value of 7, multiple applications can be applied to achieve higher total r-values. Open cell foam is designed to expand to 3″ of thickness, meaning only one application is possible in most standard walls. 

Here’s a quick summary of open cell vs closed cell foam and the best applications for each:

Benefits of Closed Cell Foam
Closed cell foam is the best choice for robust insulating where there is limited space. It can reach 2x the R-Value of  open cell inside a standard wall. The closed cell also acts as a vapor barrier, so water and moisture is less likely to get inside the home, and the foam itself is undamaged by water. Its rigid nature also adds to the structural integrity of the building and E84 fire rated versions are available. 

Benefits of Open Cell Foam
Open cell foam is more affordable than closed cell foam. Open cell foam won’t insulate a house as well as closed cell foam, so it’s not ideal for locations with extreme weather temperatures. One of the biggest benefits of open cell foam is it's amazing expansion after install. It really fills all the cracks and crevices'. These types of areas can be harder to insulate with closed cell foam. Open cell foam is excellent for sound dampening and proofing where a single application can completely fill the area between the studs.

Due to the chemical makeup and the expansion rates of closed cell and open cell foam, there is a cost difference. Since closed cell foam is denser than open cell foam, it takes more material to cover the same amount of space and cost more. Since there is more material being used with closed cell, there could also be more labor cost to get it installed. 

There are lots of variables that come into play here. It can depend on where a house is located, what the insulation goals are, and what the budget is. Need some more help deciding between open cell vs closed cell foam? Give us a call! 928-536-4031