Northeast Spray Foam, LLC uses two kinds of foam, Closed-Cell Foam (two-pound foam) and Open-Cell Foam (half-pound foam). Both options are great insulators and both provide excellent thermal and air barriers. But what's the difference?

Closed-Cell vs. Open-Cell Foam
Understanding the difference between open-cell and closed-cell foam insulation is an important step in determining which product is best for your next insulation project. Closed-cell foam is waterproof and will not let moisture move through it. Open-cell foam will allow moisture vapor to move through it and dry. A house should not rely on the insulation to stop moisture. Roof, wall, and crawlspace assemblies are designed to keep water out. If water somehow does get into those assemblies, it needs to be able to dry out, especially in wood structures.

Closed-Cell Foam
Closed-cell foam is highly dense and when sprayed expands up to 30 times its original size producing an aged R-value of 6.8 per inch. In closed-cell spray foam, cells or bubbles in the foam are compacted together, are not broken and each is filled with an inert gas selected to make the insulation value of the foam as high as possible.

The advantages of closed-cell foam include its strength, higher R-value, and greater resistance to the leakage of air or water vapor making it ideal for windy, damp and water prone locations, such as coastal areas, below grade, crawlspaces, or for the whole house. For many of our clients, closed-cell foam is the product of choice. While more expensive than open-cell foam because of its density, at one 1 inch thickness closed-cell foam develops the all important air barrier and at 2 inch moisture barrier.

Open-Cell Foam
Open-cell foam is soft, like a foam cushion in a pillow and is an excellent air and sound insulator. Unlike closed-cell foam, open-cell foam is less dense, with each cell in the foam being broken, thus allowing air to fill all of the spaces in the material. Upon spraying, open-cell foam expands up to 150 times its original size, thereby filling all nooks and crannies in the wall cavity. When spraying is complete, the excess foam is shaved off the studs, leaving a flat surface over which finish materials can be applied. With an aged R-value of 3.9 per inch, open-cell foam gives you an air barrier at 4.5” inches of thickness.

Uses for open-cell include spraying directly to all walls of a house, and as sound proofing for media rooms. Open-cell foam may also be direct sprayed to roof decks.