The Difference Between Open-Cell and Closed-Cell Spray Foam

Not sure which spray foam is the right fit? This should help!


After weighing the benefits of spray foam over fiberglass, it’s pretty clear that spray foam is a powerful method of insulation for your home. Spray foam can help regulate your house temperature, keeping the indoors cool during the summer and warm during the winter. However, when going out to buy spray foams, there’s one small obstacle that people face: Do I buy open-cell or closed-cell?

Yes, there are two different types of spray foam, and they have two very different purposes. The differences have to do with the type of job that the foam will do once sprayed onto a surface.

What is Closed-Cell?

Closed-cell polyurethane spray foam is known to be the most common of the two. It’s considered a “closed” cell due to its high R-value. The R-value is the material’s capacity to insulate and resist heat flow. The higher the R-value results in greater insulation. Due to its high resistance, closed-cell spray foams can help resist water from seeping into the insulation, which creates moisture build-up. Moisture build-up will promote bacterial and mold growth, something you do not want inside your walls.

Since closed-cell spray foam is a denser material, it is meant to insulate buildings and appliances. It helps to insulate the air within (and outside) of the insulated object, prevents mold growth, and can even strengthen the wall.

What is Open-Cell?

As you may have expected, open-cell spray foam is similar to closed-cell in nature. It just has a lesser R-value. While most closed-cell spray foams will be above 6.0 per inch, open-cell is much lower at 3.6 to 3.8 per inch range. Open-cell will expand as soon as it’s applied, making it the perfect foam for hard to reach areas. Those nooks and crannies can easily be filled with an open-cell foam.

However, open-cell spray foam isn’t as water resistant as closed-cell. The lighter quality of this foam provides less support for walls, is permeable to vapor and air, and will lower noise frequency ranges.

So if you are looking for a strong insulation, a closed-cell spray foam is what you want to grab. As for smaller fill-ins, an open-cell foam will do just fine.