A single-hung sash window is a window that has one sash that is movable (usually the bottom one) and the other fixed. This is the earlier form of sliding sash window, and is also cheaper.
A sloped window used for daylighting, built into a roof structure. It is one of the few windows that could be used as an exit. Larger roof windows meet building codes for emergency evacuation.
Double-hung sash windows were traditionally often fitted with shutters. Sash windows can be fitted with simplex hinges that let the window be locked into hinges on one side, while the rope on the other side is detached—so the window can be opened for fire escape or cleaning.
Double-paned windows have two parallel panes (slabs of glass) with a separation of typically about 1 cm; this space is permanently sealed and filled at the time of manufacture with dry air or other dry nonreactive gas. Such windows provide a marked improvement in thermal insulation (and usually in acoustic insulation as well) and are resistant to fogging and frosting caused by temperature differential. They are widely used for residential and commercial construction in intemperate climates. Triple-paned windows have been commercially manufactured and marketed with claims of additional benefit but have not become common. In the UK double-paned and triple-paned are referred to as double-glazing and triple-glazing.