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Actual DimensionThe outside horizontal and vertical measurements of a window or door excluding the nailing fins. Also referred to as make size and overall dimension.
Adjustment ClipHardware on hung window jambs to align jamb after window installation. Also referred to as jamb adjusters.
Air ChambersSmall honeycomb spaces within the sash and frame which help to insulate and strengthen the window.
Air InfiltrationThe amount of air that passes between a window sash and frame. In windows it is measured in terms of cubic feet or air per minute, per square foot of area. The lower the number, the less air the window lets pass through.
Air LatchLatch mechanism on the interior face of the sash that retains the window in a partially open position for ventilation. Also referred to as night locks, or vent locks.
Air Leakage (AL)Heat loss and gain occur by infiltration through cracks in the window assembly. Air leakage is expressed in cubic feet of air passing through a square foot of window area. The lower the AL, the less air will pass through cracks in the assembly. While many think that air leakage is extremely important, it is not as important as U-factor and the Solar Heat Gain Coefficient.
AirspaceThe measured distance between the inner surfaces of the two pieces of glass in an insulated glass unit. Also used in reference to the thickness of the spacer bar.
Ambient TemperatureThe outdoor temperature.
American Architectural Manufacturers Association (AAMA)A window industry organization that establishes voluntary standards, certification to those standards, and designations.
Angle TopAny window with a horizontal sill, vertical jambs, and a straight sloping head.
Angled ExteriorA sloped extension from the frame that adds an aesthetically-pleasing dimension to the exterior of the window.
Annealed GlassNon-tempered glass. The most common glass used in window products.
Antique BrassFinish on hardware that has a dark brown color, also denoted by industry as US5.
Applied MuntinA muntin in a glazed window that does not actually separate individual lights of glass. This muntin may be of a material different than the main frame- work of the window. The applied muntin may be attached to the glass with an adhesive or placed over the glass and held in place by the glazing bead.
ApronFlat trim piece placed horizontally just beneath the window stool.
Arch TopAny window with a horizontal sill, vertical jambs, and a head that is curved upward.
AssembledA condition of a sliding glass door when all of the parts are in place, as opposed to Knocked Down (KD).
AstragalThe center member of a double door, which is attached to the fixed or inactive door panel.
AwningA type of window with a top-hinged sash that swings out at the bottom. Lets in fresh air while keeping rain out.
Awning WindowA window with the sash hinged at the top that can be opened outward. Awning windows can have more than one sash and allows for a maximum venting area.
