A sash window is made of one or more movable panels or “sash” that form a frame to hold panes of glass, which are separated from other panes by narrow muntins. Any window with this style of glazing is technically “a sash”. This term is used almost exclusively to refer to windows where the glazed panels are opened by sliding vertically, or horizontally.

Traditional problems with old wooden sash windows include rot, swelling or distortion of the woodwork or rattling in the wind, due to shrinkage of the wood. It is also difficult to paint them properly.

Today, the latest designs and innovations in sash windows aim to replicate the aesthetic qualities of traditional sash windows, while overcoming many of the shortcomings, especially regular maintenance and energy inefficiency.One significant advantage of sash windows is that they provide efficient cooling of interiors during warm seasons. Opening the top and bottom of a sash window equally allows warm air at the top of the room to escape.

The basic form and purpose of this window is to be as sympathetic to the aesthetics of the original sash windows.