Differences Between Closed and Open Cell Foam Insulation


Deciding what type of spray foam insulation to use for a job can be tough. Homeowners are best off asking their insulation installers for recommendations. However, it’s still wise to perform some due diligence and learn what options are available. This article will focus on one specific distinction between different spray foam products. Read on to find out about the differences between open cell and closed cell foam insulation.

The Cells

All foam is made up of small bubbles, or cells. If the foam has open cells, those cells aren’t fully encapsulated. Manufacturers deliberately leave the cells open to make the material softer and more flexible.

Closed-cell materials are different. Each bubble is closed off, and they’re all pressed together to form a more rigid, stable material. Air and moisture cannot get into the foam’s cells, but the material won’t be as flexible as a result.

The Density of the Foam

Open-cell foam is much less dense than closed-cell alternatives. Open-cell foams have a density of just half a pound per cubic foot. Closed-cell foams are about three times as dense, at 1.75 pounds per cubic foot.

Insulation Effectiveness

The effectiveness of insulation at preventing heat transfer is measured using R-values. The R-value is the material’s ability to resist heat flow. The higher the R-value, the more effective the insulation material is at keeping heat from moving in and out of the home’s walls, ceilings, and floors.

Generally speaking, the R-values are higher for closed-cell insulation than they are for open-cell alternatives. Closed-cell insulation has an average R-value of around 6.0 per inch, with some advanced formulas boasting R-values of 7.0 or higher. Open-cell foams only have an average R-value of around 3.5 per inch, which means they’re not as efficient. More open cell foam will be required to provide the same level of insulation.

Foam Expansion

It may be tempting to assume that closed-cell is always better than open-cell foam given its higher R-value. From an application standpoint, that’s not the case. Open-cell foam has three times the expansion rate of its closed-cell cousin, which means only one application may be needed in some walls. Open-cell foam can also be better for applications that require filling in large gaps.

Common Applications

The most common application for closed-cell insulation is insulating areas where space is an issue. There isn’t always enough room to use closed-cell foam insulation, but since closed-cell options are denser, they can provide adequate insulation even in very small spaces. Closed-cell can also act as a vapor barrier, helping to prevent moisture from getting into the home. The foam itself will not be harmed by water exposure.

The most common applications for open cell foam are difficult-to-reach nooks and crannies. Open foam is also a good option for walls that require soundproofing but do not need extensive insulation. In areas with mild climates, some homeowners insulate their entire houses with open-cell foam to save money, but that’s not a great solution for colder climates.

The Bottom Line

Both closed and open-cell foams offer effective solutions for insulating homes. They have different applications, though, so choose carefully. When in doubt, ask an insulation contractor for advice. In most cases, using a combination of closed and open-cell foam is the best solution.