Open cell spray foam has an open cell structure where the cells are filled with air. The open-cell structure renders soft, flexible foam.
Still air is the primary insulation medium in open cell foam, similarly to fibreglass. These insulations work by reducing the natural air movement within these materials thereby reducing the ability of the material to conduct heat. Unlike fiberglass, the fine cell structure of open cell makes it air-impermeable at certain thicknesses.
The air-impermeability of open cell qualifies it as an air-barrier, dramatically reducing air leakage through the building envelope, significantly lowering the building’s heating and cooling costs.
Open cell spray foam, like fibre glass insulation, is moisture-permeable, and may require the installation of a vapor barrier in certain applications.