Glossary

Term

Definition

AwningA single (or double) operating window in which the bottom of the sash swings outwards for ventilation
AstragalThe exterior center post or moulding on a double door (attached to the secondary or inactive door panel)
BayThree 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
BowFour or more connected windows (fixed or operating) in a 10 degree or 15 degree angle formation
BrickmouldAn exterior moulding around the window (to seal and cover the exposed window opening, insulation, interior jambs etc…)
CasingThe interior decorative moulding/trim that covers the inside edge of the jambs and the rough openings between the window and the wall
Double glazingThe use of two panes of glass (in a window frame) to increase energy efficiency and to provide other performance benefits
Double hungA window with two vertical operating sashes that slide up-and-down for ventilation
Drip capAn exterior aluminum moulding placed on the top of the brickmould or capping of a window frame
Egress windowA window large enough for exit in case of an emergency
FixedNon-opening or non-operating window
FlashingAluminum 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)
GasketA weatherstrip used to create a watertight seal between the sash and the window frame
GlazingThe glass panes in the sash of a window
Glazing stopThe moulding (or part of the window sash) which holds the glass in place
GrillA bar used to visually separate glass into multiple lites (also named internal grid, muntin bar or window pane divider)
HeaderA heavy beam extended across the top of the rough opening to help support the weight of the building
LiteGlazing framed by muntin bars and/or sash in a window or door
Low-E glassA commonly used term referring to a low emissivity coating placed on the glass surface to restrict the passage of radiant heat
MouldingA trim installed around the exterior perimeter of a window frame
MullionThe connectors installed between individual windows in a multiple unit window
MuntinA bar used to visually separate glass into multiple lites (also named internal grid, grill or window pane divider)
OperatorA metal arm and gear which allows for easy opening or closing of projecting windows
PitchThe degree of the slope in a roof
RailsThe horizontal parts of a window sash or door panel
Rough openingThe opening in a wall to accommodate the installation of a window or door
Sash balanceA system of weights or coiled springs which assist in the raising and lowering of single hung and double hung windows
SeatA wooden board installed on the bottom contour of a bow or bay window (to provide a seat or shelf space)
ShimsWooden wedges that are used to secure and level windows in the rough opening
SidelitesTall and narrow fixed glass on either (or both) sides of an entry door
SillThe horizontal part that forms the bottom of a window or door frame
Sill courseThe row of bricks across the bottom of a rough opening
Simulated divided liteA 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 HungA window in which the top sash is fixed (or inoperable) and the bottom sash slides vertically up-and-down for ventilation
Solar gainThe amount of heat which has passed through the glass of windows and doors and has collected inside of the home
StudWood installed vertically and horizontally to build a frame or wall
TransomA smaller window attached above a door or another window
Triple glazingA window glazed with three panes of glass (enclosing two separate air spaces)
U-FactorA measure of heat transmission through a wall or window (the lower the U-Factor, the better the insulating value)
Vapor barrierA watertight material used to prevent the passage of moisture through floors, walls and ceilings
Venting unitA window or door that opens or operates
Wind LoadForce exerted on a surface by moving air

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