Abstract: Sash window unit, at least comprising a frame with a sash window which is slidable vertically therein, the frame being provided with a guideway which can interact with one or more guide parts on the sash window, sealing means between the sash window and the frame, and means for holding the sash window balanced in an open position, the guide parts being stationary relative to the sash window, and closing means are present on the frame for, at least near a closed position of the sash window, placing said sash window in sealing contact with the frame, with the interposition of the sealing means, and on release to make the sash window slidable without appreciable friction.