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Variations in Spray Foam Density

Which Type of Spray Foam is Right for You?

The answer to that question depends on what type of performance you want out of your roof. There are many benefits that can be achieved through spray foam, but they all depend on the density of the foam that you install.

Low-Density Spray Foam

Low-density, AKA open-cell foam, has lower R-values per inch and is not as effective at sealing off air from the surface being foamed. Low-density foam also provides lower vapor and moisture barriers. The advantage of low-density foam is price; if your job doesn’t require high insulation values and strong wind resistance, you can save some money going with low-density foam.

Low-density spray foam is common in interior uses, in attics and walls. We don’t work on the interior of buildings often, but this is an option with spray foam.

Medium-Density Spray Foam

Spray foam density variations

Also known as closed-cell foam, medium-density spray foam is generally used as insulation on the exterior of the building envelope. It is often used to insulate tanks or vessels resting on the roof surface. With medium-density foam, you get high R-values, water resistance, and excellent durability.

If this foam is applied to the outside of a building, it will be protected by the siding or other cladding materials on the building. If medium-density foam is applied to outdoor tanks or other vessels, it will need some sort of additional coating or covering to protect it from the damaging effects of UV light.

High-Density Spray Foam

In applications where the foam is applied to the outside of the roofing surface, high-density spray foam should be used. Just like medium-density foam, this is considered closed-cell foam. High-density spray foam has been formulated to expand less than medium-density when applied, which makes it more manageable and capable of building proper slope into the roof surface.

Because of its flexibility, high-density spray foam can also conform very closely to any angles and protrusions your commercial roof may have. High-density foam also needs to be coated, typically with silicone, to be protected from UV light.


When making a decision on your foam roof, it is extremely important that you consider not only all roof type options, but also the different types of foam available to you. Depending on each specific application of your roofing system, you may require multiple types of foam. You can read more about the different densities of foam at the Spray Polyurethane Foam Alliance’s website; click here and scroll to “Installation, Performance & Benefits”.

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