SPF could come in either closed-cell or open cell form. Each form has its own pros and cons depending on application. As SPF highly adaptable it can be used in a variety of applications as required based on awareness about the difference between both the forms. Let’s know the difference between both forms of SPF.
Insulation is measured as R-value where R = resistance to heat. With one of the highest R-value ranging from 6.5-7 per inch closed-cell SPF is a very superior insulating material available in the markets today. Its strength is derived from the principle of retention of insulating gas within cells (blowing agent) and its closed structure blocks air, moisture retention (referred as “Perm” rating) and is water resistant. With about 2.0 pounds per cubic feet density, which falls in the range of optimal insulation capacity as per several researchers the rigidity and wall racking strength is increased manifold.
With densities ranging from 0.4 to 1.2 lbs per cubic feet open-cell SPF has an economical yield as yield and density and inversely related to each other. With an R-value of 3.5 inch this foam does had great thermal capacity and has some permeability allowance for moisture with “Perm” ratings about 16 per 3 inches thickness. Also the builder/architect does have control over how to diffuse the foam with desired moisture level just making sure that it does not openly come in contact with water; not recommended for hybrid applications. Comparatively, Open-cell has a spongier, softer texture, lower strength and rigidity.
Builders should use either closed or open cell SPF keeping in mind the local code requirements in terms of permeability, R-value and ignition barriers.