Glossary
Awning: A single (or double) operating window in which the bottom of the sash swings outwards for ventilation
Astragal: The exterior center post or moulding on a double door (attached to the secondary or inactive door panel)
Bay: Three connected windows (usually made up of a larger fixed window in the center and two smaller operating windows on either side) in a 30 degree or 45 degree angle formation
Bow: Four or more connected windows (fixed or operating) in a 10 degree or 15 degree angle formation
Brickmould: An exterior moulding around the window (to seal and cover the exposed window opening, insulation, interior jambs etc…)
Casing: The interior decorative moulding/trim that covers the inside edge of the jambs and the rough openings between the window and the wall
Double glazing: The use of two panes of glass (in a window frame) to increase energy efficiency and to provide other performance benefits
Double hung: A window with two vertical operating sashes that slide up-and-down for ventilation
Drip cap: An exterior aluminum moulding placed on the top of the brickmould or capping of a window frame
Egress window: A window large enough for exit in case of an emergency
Fixed: Non-opening or non-operating window
Flashing: Aluminum attached to the outside of the head or side jambs of a window to provide a weather barrier (preventing leakage between the frame and the wall)
Gasket: A weatherstrip used to create a watertight seal between the sash and the window frame
Glazing: The glass panes in the sash of a window
Glazing stop: The moulding (or part of the window sash) which holds the glass in place
Grill: A bar used to visually separate glass into multiple lites (also named internal grid, muntin bar or window pane divider)
Header: A heavy beam extended across the top of the rough opening to help support the weight of the building
Lite: Glazing framed by muntin bars and/or sash in a window or door
Low-E glass: A commonly used term referring to a low emissivity coating placed on the glass surface to restrict the passage of radiant heat
Moulding: A trim installed around the exterior perimeter of a window frame
Mullion: The connectors installed between individual windows in a multiple unit window
Muntin: A bar used to visually separate glass into multiple lites (also named internal grid, grill or window pane divider)
Operator: A metal arm and gear which allows for easy opening or closing of projecting windows
Pitch: The degree of the slope in a roof
Rails: The horizontal parts of a window sash or door panel
Rough opening: The opening in a wall to accommodate the installation of a window or door
Sash balance: A system of weights or coiled springs which assist in the raising and lowering of single hung and double hung windows
Seat: A wooden board installed on the bottom contour of a bow or bay window (to provide a seat or shelf space)
Shims: Wooden wedges that are used to secure and level windows in the rough opening
Sidelites: Tall and narrow fixed glass on either (or both) sides of an entry door
Sill: The horizontal part that forms the bottom of a window or door frame
Sill course: The row of bricks across the bottom of a rough opening
Simulated divided lite: A method of constructing windows in which grills are attached to the inside and outside of glass panels to simulate the look of true divided lites
Single Hung: A window in which the top sash is fixed (or inoperable) and the bottom sash slides vertically up-and-down for ventilation
Solar gain: The amount of heat which has passed through the glass of windows and doors and has collected inside of the home
Stud: Wood installed vertically and horizontally to build a frame or wall
Transom: A smaller window attached above a door or another window
Triple glazing: A window glazed with three panes of glass (enclosing two separate air spaces)
U-Factor: A measure of heat transmission through a wall or window (the lower the U-Factor, the better the insulating value)
Vapor barrier: A watertight material used to prevent the passage of moisture through floors, walls and ceilings
Venting unit: A window or door that opens or operates
Wind Load: Force exerted on a surface by moving air