A single hung window is a window with a fixed upper sash and a movable lower sash. The lower sash can be raised to allow a free flow of air, and the sash may also be designed to tilt so that it can be easily cleaned from the inside. Double hung windows, in which both sashes are movable, tend to be much more common, but a few manufacturers still produce single hung windows in a variety of sizes and styles, and they can be used to replace existing windows or in new construction.
People sometimes confuse a fixed window with a single hung window. A fixed window has a single pane of glass which is not movable. Fixed windows are used when it will not be necessary to open the window for ventilation, and they can provide more insulation from noise and the elements because they are more tightly sealed than a movable window. The big disadvantage to fixed windows, of course, is that they do not open to allow air into the room.
Manufacturers produce single hung windows and accompanying frames which can simply be dropped into place, and it is also possible to purchase the windows as standalone items to fit in an existing frame. The primary advantage to this window design is that it can be significantly less expensive than a double hung window or other designs. The lower cost may be viewed as an acceptable tradeoff for some of the inconveniences associated with a single hung window.
With a sing hung window, the outside of the fixed upper sash cannot be reached from the inside for cleaning, which can be inconvenient. On the ground level, it may be relatively easy to clean the window, but windows on higher floors necessitate access with a ladder. The fixed sash also limits options in terms of ventilation, as people cannot lower the upper sash to allow air to flow across the upper part of the room.
A number of styles can be used for a single hung window. Some manufacturers create a mullioned style with multiple panes of glass in one or both sashes, to make the window more visually interesting. It is also possible to purchase double paned glass for extra insulation, which improves energy efficiency for the structure a window is installed in and cuts down on noise from the outside. Manufacturers are often willing to create custom single hung window designs and sizes by request.
