The spongy and light feel of open cell foam should not fool you, it will seal very well, but it will allow moisture vapor to pass through

Ideal areas to apply Open-Cell

• Cavities inside walls
• Underneath roofs
• Sound Barrier

The light, sponginess of open-cell spray foam pop/break as the foam expands right before it sets and hardens. Similar to closed-cell insulation- it will be an air barrier but the difference is this type allows water vaper to enter and pass through it.

At a mere .4 to .5 lb. percubic foot, open cell spray foams lightens does not affect the loads of the structure. It is also a greener option because of the use of water to blow the foam. Open-cell foam also provides a good sound barrier.

The Application Process

First, open cell spray foam is mixed from the two other components. Because of its lightness it can fill a lot larger areas with less product than the closed-cell foams, almost 3-4 times as much. The R-value of open-cell spray foam, however is only 3.5-4 per inch and is much lower than closed cell foams. It is however less expensive.

The producers of both foams have been trying to make their product greener. Some have natural materiels like soy oil, but at a low percentage. Usually open-cell foam is considered freener because it uses water, which does not contribute to globel warming. Closed-cell foams, which have chemicals that give it a higher global warming potential (GWP).

Pros  

• Can cover high rates
• Cost per R-value lower than closed cell
• Creates air barrier
• Sound Barrier
• Uses Water- Greener option

Cons

• Lower R-value means that small areas are not a good fit
• Should be avoided where contact with water is possible
• May need house wrap and a vapor barrier
• Shrinkage of material may reduce effectiveness