Open Cell and Closed Cell Foam Insulation Structure

Polyurethane spray foam (PSF) is a widely used and accepted method of providing insulation for a broad range of applications, from refrigerator interiors to attic crawlspaces. The benefits of spray foam insulation versus traditional insulations such as fiberglass include quick application, the ability to insulate hard to reach spots, and generally robust resistance to a multitude of environmental conditions.

There are two primary types of PSF, known as open cell and closed cell. They differ in densities as well as other aspects, knowing which type to use can be beneficial and avoid costly mistakes and re-insulations.

open cell vs. closed cell foam insulationOpen Cell Spray Foam Insulation

Open cell spray foams are much less common than closed cell because open cell was originally only produced by one manufacturer. Also, their R-value is much lower than closed cell sprays. However, as their strengths were slowly discovered, other companies began to manufacture them. Installation is similar to closed cell spray foam, but the effects are different from their closed cell counterpart. Open cell foam expand once applied allowing them to be installed in hard to reach, out of the way places such as wall and ceiling cavities that can sometimes be difficult to seal with closed cell foams. This expansion feature will hermetically seal the area and provide a complete insulation. However, like we mentioned above, open cell has a lower R-value, usually 3.6 to 3.8 per inch. This means its heat resistance level is lower, which can cause the insulation to fail in extreme temperatures. Additionally, open cell spray foam does not have the water resistance that its closed cell counterpart has, and it does not provide as much support to walls as closed cell does.

However, open cell polyurethane foam is less costly than closed cell, but, caution should be taken. While it is more affordable, you should make sure that the less expensive alternative doesn’t lead to more costly repairs down the road.

Closed Cell Polyurethane Spray Foam

Closed cell is the denser and more common of the two types of PSF. Closed cell foam has higher R-values than it’s open cell counterpart, with R-values between 6.0 to 7.0 per inch, although there are some with higher R-values than that. Closed cell foams feature better insulation because of this resistance, and are also more resistant to water degradation or penetration, which includes moisture build-up. Moisture can and will eventually attract bacteria growth, which in turn promotes mold, which can be detrimental to your home. Preventing this moisture build-up can help greatly curb mold growth.

Closed cell foams are also dense enough to insulate air, which will help prevent drafts and keep your house warmer and temperatures regulated. This density is another feature of the foam that helps prevent mold growth, because well regulated temperatures can cut down on humidity, which can help create the environment that promotes mold growth. In order to maintain their resistance, closed cell foams are usually dense and strong, and resemble solids when they fully form. This density and strength not only helps insulate building and appliances, but can also strengthen your walls wherever the foam insulation is applied.

Open Cell vs Closed Cell

Closed Cell Open Cell
Liquid Water Resistant Yes No
FEMA approve flood zone insulation Yes No
Air Barrier Yes Yes
Structural Strength Yes No
Sound Absorption Yes Yes (better)
Vapor Retarder Yes No
Interior use Yes Yes
Exterior use Yes No
Mold resistant Yes Yes
R value per inch 7.0 3.81
Density 1.7lb+ .05lb-1.6lb
Difference greater than 90% Closed Cells less than 90% Closed Cells