What Is the Difference Between Open & Closed Cell Foam?

Structure

• Foam said to be closed- or open-cell, refers to the structure of the material. Closed-cell foam includes many tiny bubbles filled with a special gas. However; in open-cell foam, these bubbles are perforated, allowing the air to move in and out like a sponge.

R-Value

• Both closed- and open-cell foams are used as insulation in homes, but have different R Values, or resistance to heat flow. Closed-cell foams are better at stopping heat from escaping the house, or allowing warmth to come in on hot days, as it has a relatively high R Value of around 6.0. Open-cell foam has a lower R Value of about 3.5, which means it is not as efficient an insulator.

Water Resistance

• Closed-cell foam absorbs less water than open-cell foam, because it does not have the sponge-like texture of open-cell foam. For this reason, open-cell foams are not appropriate to use where they are in direct contact with water, and should not be fitted on the exterior of a home.

Sound Resistance

• Open-cell foam is a better material for absorbing and blocking out normal frequency level sound than closed-cell foam, which may make it more appropriate for use on the inside of the house to stop noise from traveling. However, closed-cell foam is a better insulator of sounds with a low frequency, like bass tones.

Air Barrier

• Both foams can serve as an air barrier to stop drafts getting in, but closed-cell foam is more effective at this than open-cell foam. However, open-cell foam can serve as a good air barrier if it is used in relatively large amounts, particularly if it is used to a fill a space the thickness of a wall.

Rigidity

• Closed-cell foam is a more rigid, hard and strong substance than open-cell foam, which is more malleable. The rigidity of closed-cell foam can increase the strength of the walls to which it is applied.

Price

• Closed-cell foam is more expensive than open-cell foam and, although it has a much better R Value, the cost per R is higher than for open-cell foam. For this reason, it is more economic to use open-cell foam in places where it is not in contact with water, and a strong and dense material is not necessary.