Open and closed cell foam are two different types of spray foam insulation. They have different strengths and weaknesses, and one is not necessarily better than the other. It comes down to understanding the benefits of open cell vs closed cell foam and choosing the type that fits your needs.
Open cell foam is full of cells that aren’t completely closed. Hence the name “Open Cell”, these cells are deliberately left open. This makes the foam a softer, more flexible material. Open-cell is superior as an air barrier, and is sponge-like in appearance.
Applications that typically use open-cell spray foam include residential construction insulation, under roof trusses for “conditioned attics”, as a spray foam sound insulation in media rooms or interior walls to minimize outdoor sound intrusion and ambient noise.
Another positive attribute of open cell polyurethane foam is its cost. It is less expensive and more affordable than closed cell.
Open cell foam expands once applied, allowing it to be installed in hard to reach, out of the way nooks and crannies. This includes wall and ceiling cavities that can be difficult to seal with other types of insulations and even closed cell foams. The expansion feature will hermetically seal the area and provide proper insulation.
Closed cell foam is made up of cells that are, as the name suggests, completely closed. The cells are pressed together, so air and moisture are unable to get inside the foam. Because of this, closed cell foam is much more rigid and stable than open cell foam.
The advantages of closed-cell foam compared to open-cell foam include its strength, higher R-value, and its greater resistance to the leakage of air or water vapor. The disadvantage of the closed-cell foam is that it is denser, requires more material, and therefore, is more expensive. Even though it has a greater R-value, typically the cost per R is still higher than open-cell foam. The choice of foam can also be based on the requirements for performance or application specific characteristics.
Closed cell foam is used in water-prone areas such as below grade, wet rooms or outdoors – i.e. crawlspaces, since it is a waterproof foam. While it isn’t a waterproofing product it won’t get damaged by water or allow water to seep through. It’s ridged-like texture makes closed cell the perfect candidate for places where it might stay exposed and will therefore not get damaged.
Closed cell foam has a higher R-value than open cell foam, usually about 6.7 per inch. But some closed cell foams have even higher ratings that go up to almost 7 per inch. This higher rating makes closed cell foam better at keeping heat in or out of a structure.
Open cell foams have an R-value of around 3.5 per inch. This is significantly lower than closed cell foams, which can limit open cell insulations usefulness in extreme temperature conditions.
A foams R-value, is its resistance to heat flow or, in other words, how well they insulate.
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