definition
strict definition
foam insulation
Thermal wall insulation applied as foam by spraying or injection, rather than as rigid boards.
Foam insulation materials are forms of wall insulation consisting of lofty foams, which are not installed as rigid sheets or wrapping, but which are generally sprayed into their place between or behind layers of the wall.
The foam takes its place within the wall during application rather than arriving as a finished rigid sheet. Its cellular structure provides the insulating material.
A rigid foam board belongs to panel insulation. The difference concerns the installed form, even where related substances can be used in both forms.