When it comes to the question of closed cell foam vs open cell foam, the two types of polyurethane foam used for roofing and insulation are not the same, even though they often look similar and can be difficult to distinguish by simple appearance.
These two families of polyurethane foam products bring very different advantages to the table and are utilized for very different purposes.
Let’s discuss the difference between closed cell foam and open cell foam so that, hopefully, you’ll see why we most often recommend closed cell foam for commercial building applications.
Insulation 101 — How Insulation Works
First, here’s some information about insulation in general — for example, what gives typical spun fiberglass batt its insulative properties?
“Insulation” happens when air is trapped in the many tiny air pockets formed among the fibers of spun fiberglass — remember that warmer air naturally mixes with cooler air until there is no longer a difference in temperature.
Those pockets hold air at a certain temperature, so they form a barrier that slows the mixing of warmer air and cooler air (also called heat conduction).
That barrier’s effectiveness can be increased by a tight seal that further restricts air flow.
Open Cell Foam vs Closed Cell Foam — What’s the Difference?
When it comes to open cell foam vs closed cell foam, the primary difference is the number of bubbles or air pockets each type contains and the rigidity of those pockets.
Open cell foam contains fewer linked air pockets that are comparatively larger in size, and it has an approximate density of 0.5- 0.75 pounds per cubic foot. It is somewhat moisture absorbent and air permeable, and it has an R-value of around 3.5.
Closed cell foam, on the other hand, has a high number of tiny, strong air pockets that resist air movement, which increases its insulative properties — its R-value is typically 6-6.5.
Closed cell foam has a density of 2 to 3 pounds per cubic foot, resists air permeation, and is highly moisture resistant. Another major difference between the two types of foam is what is contained within the pockets — closed cell foam is filled with inert gas that further reduces heat conduction.
Why We Recommend Closed Cell Foam
When it comes to commercial buildings, you need the increased R-value, water resistance, and strength that closed cell foam provides — those qualities add up to some serious advantages.
Closed Cell Foam Protects Well Against Weather
SPF, particularly closed cell foam, performs well against hurricane-force winds, hail, and torrential rain, and has been used as a commercial roofing system successfully for more than 50 years.
It forms a chemical and mechanical bond with surfaces to further prevent air and water leaks in tricky areas like joints and fixtures, in addition to the reduced air and water permeability that I mentioned above.
Closed Cell Foam Provides Crush Resistance and Tensile Strength
Closed cell foam is very strong and has a much higher compressive and tensile strength than an open cell foam. SPF roofs made of closed cell foam can be walked on — they also absorb impact from debris well.
Closed cell spray foam insulation can increase the strength of walls by as much as 300%.
In other words, by combining closed cell foam insulation with a closed cell SPF roofing system, you are enclosing (enveloping) your commercial building, sealing it together with a durable, high-R-value wrapper that is also highly water-resistant.
It’s usually the best option for commercial buildings that money can buy.
There are many other reasons SPF systems are so fantastic — you can read more about them here.
Closed Cell Foam or Open Cell Foam— Which Do You Need?
If you’re looking for the best insulation and roofing for your money and are willing to invest a little up front, we strongly recommend closed cell foam, especially when you consider its higher R-value.