Windows Glossary
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Antique Glass: Hand-rolled mouth-blown clear or colored glass made by old glass blowing methods.
Argon: An inert, nontoxic gas used in insulating windows to reduce heat transfer.
Armature: The iron, bronze or wood framework fixed in a window opening to support panels of stained glass.
Art Glass: Commercially designed and mass-produced windows, employing mainly Opalescent Glass.
Back-Painting: Painting on the back or outer surface of glass.
Bay: Window usually made up of three individual window units.
Beveled Glass: Plate glass with edges ground on an angle that extends beyond the flange of the Came. Often glazed with zinc instead of lead came.
Bottom Rail: The bottom horizontal member of a window sash.
Bow: Like a bay, this window combines a more rounded curve than the angled step style of the related bay window type.
BTU: An abbreviation for British Thermal Unit--the heat required to increase the temperature of one pound of water one degree Fahrenheit.
Bull's Eyes: The center of a piece of Crown Glass that includes the mark where the pontil was attached.
Came: Extruded lead strip, usually H-profile, used to hold together the individual pieces of glass in stained glass window.
Casement: A window sash that opens on hinges at the sides.
Clerestory: A wall of a room or building and contains windows along the top.
Confetti Glass: Hand-rolled glass to which chips of multi-colored glass have been added in the blowing process.
Check Rail: The bottom horizontal member of the upper sash and the top horizontal member of the lower sash which meet at the middle of a double-hung window.
Condensation: The deposit of water vapor from the air on any cold surface whose temperature is below the dew point, such as a cold window glass or frame that is exposed to humid indoor air.
Divided Light: A sash that is divided into multiple smaller panes of glass with muntins.
Double Glazing: In general, two thicknesses of glass separated by an air space within an opening to improve insulation against heat transfer and/or sound transmission. In factory-made double glazing units, the air between the glass sheets is thoroughly dried and the space is sealed airtight, eliminating possible condensation and providing superior insulating properties.
No glossary entries at this time.
Fanlight: A semicircular window (often placed above a door or another window).
Flashing: Sheet metal or other material applied to seal and protect the joints formed by different materials or surfaces.
Frame: The fixed frame of a window that holds the sash or casement as well as hardware.
Gas Fill: A gas other than air, usually argon or krypton, placed between window or skylight glazing panes to reduce the U-factor by suppressing conduction and convection.
Gothic: May be angular, commonly pointed, or feature lancet arch – a tall narrow window with pointed arch at the top, shaped often like a spear.
Grid/Patterned: The design of the divided lights on a sash, usually referred to as 'eight-over-one' (meaning that the upper sash has eight panes of glass divided by muntins while the lower sash is a single pane of glass).
Heat Gain: The transfer of heat from outside to inside by means of conduction, convection, and radiation through all surfaces of a house.
Heat Loss: The transfer of heat from inside to outside by means of conduction, convection, and radiation through all surfaces of a house.
Infiltration: The movement of outdoor air into the interior of a building through cracks around windows and doors or in walls, roofs, and floors.
Insulating Glass: Two or more pieces of glass spaced apart and hermetically sealed to form a single glazed unit with one or more air spaces in between. Also called double glazing.
Jalousie: Consists of parallel glass, acrylic, or wooden louvers set in a frame
Jamb: A vertical member at the side of a window frame, or the horizontal member at the top of the window frame, as in head jamb.
No glossary entries at this time.
Light: Window opening bounded by frame. Usually in series with Mullions between.
Low-Emittance (Low-E) Coating: Microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface primarily to reduce the U-factor by suppressing radiative heat flow. A typical type of low-E coating is transparent to the solar spectrum (visible light and short-wave infrared radiation) and reflective of long-wave infrared radiation.
Meeting/Check Rail: The rail where the two sashes come together.
Mullion: A major structural vertical or horizontal member between window units or sliding glass doors.
Muntin: A secondary framing member (horizontal, vertical, or diagonal) to hold the window panes in the sash. This term is often confused with mullion.
No glossary entries at this time.
Oculus: Circular window with no stone tracery .
Opalescent Glass: Glass developed in the late 19th century by La Farge and Tiffany, in which streaks of color, when fused, give a milky, iridescent appearance.
Oriel: Projecting bay windows, usually on an upper story and not extending to the ground.
Palladian Window: A tall window rounded at the top and flanked by two smaller windows.
Pane: One of the compartments of a door or window consisting of a single sheet of glass in a frame; also, a sheet of glass.
Patina: A film produced by chemical action, oxidization or sulphurization, during the course of time.
Polyvinylchloride (PVC): An extruded or molded plastic material used for window framing and as a thermal barrier for aluminum windows.
Putty: Material forced between the leading and the glass to make the window watertight.
Queen Anne: Usually larger square or diamond panes of glass surrounded by small glass squares.
Rail: Horizontal part of sash.
Rose Window: Circular window with tracery radiating in petal-like shapes.
Roundel: Circular pane of white glass with a complete composition painted on it. See Medallion.
R-Value: A measure of the resistance of a glazing material or fenestration assembly to heat flow. It is the inverse of the U-factor (R = 1/U) and is expressed in units of hr-sq ft-°F/Btu. A high-R-value window has a greater resistance to heat flow and a higher insulating value than one with a low R-value.
Sash: The portion of a window that includes the glass and the framing sections directly attached to the glass, not to be confused with the complete frame into which the sash sections are fitted.
Sill: The lowest horizontal member in a door, window, or sash frame.
Simulated Divided Lights: Placing muntins/grids to the outside of the window, placing a spacer bar between the glass, and affixing grids on the inside of the window.
Single Glazing: Single thickness of glass in a window or door.
Slag Glass: Opaque pressed glass with colored streaks, usually white and/or cream streaks. The name derives from the belief that these colors were achieved by adding "slag" from iron smelting works to the glass.
Solder: A mixture of tin and lead that is sweated onto lead joints of a window.
Stile: Vertical part of sash.
Support Bars: Iron bars set in the frame of the exterior of the window, to which the Panels of glass are attached on the inside by Flanges and metal keys.
Thermal Break: An element of low conductance placed between elements of higher conductance to reduce the flow of heat. Often used in aluminum windows. Triple glazing. Three panes of glass or plastic with two air spaces between.
Tracery: Ornamental stonework in the upper part of a GOTHIC window with openings for glass.
Transom: A window above a door (or a horizontal crossbar in a window or between a door and a window).
U-Factor (U-Value): A measure of the rate of non-solar heat loss or gain through a material or assembly. The U-factor may be expressed for the glass alone or the entire window, which includes the effect of the frame and the spacer materials. The lower the U-factor, the greater a window's resistance to heat flow and the better its insulating value.
Vinyl-Clad Window: A window with exterior wood parts covered with extruded vinyl.
Weather Stripping: A strip of resilient material for covering the joint between the window sash and frame in order to reduce air leaks and prevent water from entering the structure.
No glossary entries at this time.
No glossary entries at this time.
No glossary entries at this time.
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