Abstract: A rectangular window frame includes a pair of vertical jamb members rigidly connected by a head member and a sill member all formed from extrusions of rigid plastics material. Each jamb and head member includes an inner section which snap-fits laterally into an outer section, and each outer section has a cross-sectional profile corresponding to that of the sill member to provide the frame with rigid fusion-welded mitered corner joints and a sill member with a low profile. The inner sections of the jamb and head members define channels for slidably receiving window units including a pair of rectangular sash frames each formed from extrusions and including snap-fit extruded cap members. The sash frames also receive removable extruded glazing strips which retain glass window panels within the sash frames.

Abstract: A rectangular window frame includes a pair of vertical jamb members rigidly connected by a head member and a sill member all formed from extrusions of rigid plastics material. Each jamb and head member includes an inner section which snap-fits laterally into an outer section, and each outer section has a cross-sectional profile corresponding to that of the sill member to provide the frame with rigid fusion-welded mitered corner joints and a sill member with a low profile. The inner sections of the jamb and head members define channels for slidably receiving window units including a pair of rectangular sash frames each formed from extrusions and including snap-fit extruded cap members. The sash frames also receive removable extruded glazing strips which retain glass window panels within the sash frames.