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A sash window typically has one or more wood-framed glass panels that slide up and down vertically. These movable panels are known as sashes and generally have multiple panes of glass in them. Certain types such as a Yorkshire light move horizontally instead of vertically. These windows first began to appear in England during the 17th century, but have become widely used in other countries over the years.
The most common type of sash window has both an upper and lower sash that moves vertically in separate grooves within the side jambs of the window frame. Metal weather stripping is sometimes installed in the side jambs of the frame to help hold the sash in place. A heavy counterweight is usually attached to the sash by a cord and pulley assembly to help it maintain a particular vertical position when opened. The cord and pulley assembly is typically hidden inside of the window frame for aesthetic purposes. Some sash windows employ a spring balance system in place of the cord and pulley assembly.
Sash windows can be installed in both double hung and single hung configurations. Double hung configurations allow both the upper and lower sashes to be opened for ventilation. Double hung sash windows are typically referred to as hung sash windows. Single hung sash windows also have two sashes, but only the lower sash can be opened; the upper sash remains in a fixed position. Triple and quadruple hung sash windows are sometimes installed in churches and other structures with very tall window openings.
Double hung sash windows provide an excellent method of ventilating an individual room because of their ability to create an incoming and outgoing stream of air when the upper and lower sashes are opened in equal amounts. This type of sash window is particularly useful on the upper floors of a structure because the inside and outside panes can be cleaned from within the room. Since these windows are typically constructed of wood, they are often subject to swelling, rotting, and distortion problems, however. Sash windows often become stuck due to improper painting methods and also have a tendency to rattle during windy conditions. Additionally, problems sometimes occur with the metal weather stripping as well as the cord and pulley balancing system.
Sash windows were first used in England in the late 1600s. English inventor Robert Hooke is credited with designing the first sash window. They have been frequently used in both Victorian and Georgian style houses. The classic style of sash window consists of two horizontal rows containing three individual panes in each row. Early mass produced versions of this window were used in Edwardian style houses built in the suburbs of England.