Abstract: The window sash of this invention employs strips of extruded plastic materials which are connected together by mechanical fasteners into an inner sash. The inner sash has barbed protrusions formed on the interior and the exterior which define interior and exterior channels into which wooden or metal trim members may be engaged in snap-fit relation. In operation, individual trim strips are first combined with interior sash elements. These sub-assemblies are then joined with L-shaped injection molded keys. The trim members, plastic keys, and plastic inner sash are then clamped in a frame and stapled together. The exterior sash trim or ring is assembled separately and brought together for assembly with the inner sash. A mastic adhesive is applied to the inner sash, a thermopane window light assembly is disposed on the adhesive, and a bead of adhesive is applied to the rabbet of the exterior ring which is then press-fit into engagement with the inner sash.