Disclosed is an apparatus and a method for at least partially encapsulating a fiber batt or other highly porous substrate by applying a polymeric foam layer to one or more surfaces of the fiber batt. The foam application assemblies are arranged and configured to extrude a polymeric foam or a foaming mixture onto the surface(s) of the fiber batt to be coated. A combination of foam application assemblies may be provided in either fixed or moveable configurations for coating one or more sides of the fiber batt. The encapsulation of the fiber batt may also include a premanufactured material layer on one or more surfaces that may be exposed or may also be encapsulated below the polymeric foam layer.