Apparatus for impregnating surfaces, including edge surfaces, of fiberglass insulation batts with synthetic fibers, comprising a conveyor for advancing the batts in a common direction and, initially, in a side-by-side orientation. Separators thereafter interrupt the side-by-side orientation, exposing the edges of the batts. Extrusion heads located in the area of side edge exposure impregnate the exposed edges with synthetic fibers while other extruder heads apply synthetic fibers to one or optionally both of the top and bottom surfaces.