Abstract: Apparatus for filling the cells of an expanded cellular core member with granular insulation. The core member may be secured to a base sheet thereby capping lower ends of the cells and may have a film of adhesive material on upper ends of the cells. The apparatus includes hopper means having a lower discharge opening therein, and conveyor means arranged to transport the core member along a rectilinear path of travel, past the discharge opening. Adjustable barrier means is provided for adjusting the cross-sectional area of the discharge opening. Valve means controls the flow of granular insulation through the discharge opening into the core cells. Brush means positioned downstream of the discharge opening removes excess granular insulation from the cells and renders the film of adhesive material substantially entirely free of the granular insulation. Pan means is positioned to receive excess granular insulation from the core member.