Insulation can be referred to as either open or closed cell insulation. Cell structures of closed-cell insulation are completely closed. Whereas open-cell insulation is made up of cells that aren’t completely closed – cell walls are open or shared.
Both insulation types are generally used for specific purposes. Spray foam insulation is available as an open-cell (in addition to a closed-cell) useful for sound attenuation and filling hard-to-reach areas. Rigid insulation such as XPS, EPS and GPS are closed-cell insulation products, which are denser and offer higher R-values than open cell insulation.