A sash window or hung sash window is made of one or more movable panels or
"sash" that form a frame to hold panes of glass, which are often separated from
other panes by narrow muntins. Although any window with this style of glazing is
technically "a sash", the term is used almost exclusively to refer to windows
where the glazed panels are opened by sliding vertically, or horizontally in a
style known as a "Yorkshire light", sliding sash, or sash and case. The
oldest surviving examples of sash windows were installed in England in the
1670s, for example at Ham House. The invention of the sash window is
sometimes credited, without conclusive evidence, to Robert Hooke.
The sash window is often found in Georgian and Victorian houses, and the
classic arrangement has three panes across by two up on each of two sash,
giving a six over six panel window, although this is by no means a fixed
rule. Innumerable late Victorian and Edwardian suburban houses were built in
England using standard sash window units approximately 4 feet in width, but
older, hand-made units could be of any size, as the image illustrates.
To facilitate operation, the weight of the glazed panel is usually balanced by
a heavy steel, lead, or cast iron sash weight or counter-weight concealed
within the window frame. The sash weight is connected to the window by a braided
cotton sash cord, or chain, that runs over a pulley at the top of the frame,
although spring balances are sometimes used. Breakage of this cord requires
disassembly, or destruction, of the trim pieces to gain access for repair.
Sash windows may be fitted with simplex hinges, which allow the window to be
locked into hinges on one side while the counterbalance on the other side is
detached, allowing the window to be opened for escape or cleaning.
The name "hung sash window" is more usual in the United States, and
typically refers to a double-hung window with two sash that can move up and down
in the window frame. These windows are commonly found in older buildings in
warmer climates as they are easy to clean and promote airflow.
A single hung window has two sash but normally the top sash is fixed and only
the bottom sash slides. Triple and quadruple hung windows are used for tall
openings, common in New England churches.
Construction is usually of softwood, and these sash were traditionally only
single-glazed. Modern double-glazed sash windows are now available, but depending
on their aesthetic style, can be frowned upon. Traditionally styled double-glazed
sash windows will often attempt to mimic the original appearance through the use
of non-functional muntins or "glazing bars", which are applied to the surface
of the glazing, and give the appearance that the sash is made up of several
smaller panes, whereas in reality, each sash consists of only one, large, double
glazed unit. Traditional problems with solid wooden
sash windows include rot, swelling or distortion of the woodwork or rattling
in the wind. It is also a common problem for inexperienced painters to paint the
sash stuck. The sliding mechanism makes sash windows more vulnerable to these
problems than traditional casement windows. Sash windows are relatively
high maintenance, but offer advantages in return, natural resources etc.),
however well-maintained sash windows should last generations without needing
parts replaced. It is also possible to clean all the glass from within the
building by sliding the two panes to different positions.
In recent years, uPVC sash windows have become available. These aim to replicate
the aesthetic qualities of traditional sash windows, while overcoming many of
the shortcomings—especially regular maintenance and painting, and energy
inefficiency. A significant advantage of sash windows
is that they provide efficient cooling of interiors during warm weather.
Opening both the top and bottom of a sash window by equal amounts allows warm
air at the top of the room to escape, thus drawing relatively cool air from
outside into the room through the bottom opening.
See also Witch window
Fortochka References
External links Historic Scotland's Sash Maintenance
Guide Research into the thermal performance of
traditional sash windows Installing Wooden Sash Windows
How to repair and upgrade sash windows sympathetically
The History of the Box Sash Window uPVC Sash Window Fitting Guide