A sash (62) of a window opening up to 180° and capable of tilting is mounted onto a fixedly installed frame profile (63) and houses a pair of superimposing sashes that fit tightly therein when in closure position, i.e. an upper stationary sash (65) and a lower movable-divertible sash (64), each of the sashes (64,65) provided with laterally extending shafts (49) for connection with sash (62), roller wheels (50) provided onto the shafts (49) of sash (64) that roll within a predefined path created by insert guide profile members (19) and diverter guide members (66,68) to alternately bring sash (64) in a position of superimposing sash (65) and a position of alignment with the same. Lifting mechanisms (46) provided with a regulatory screw (84) for adjusting the pretension of a spring component thereof and thereby the force required by the user for moving the sash (64) are installed within the vertically extending sides of the sash (62).