Air Infiltration: Industry test that measures the amount of air leakage through a window or door (the lower the number the better).
Annealed Glass: Standard float glass. Glass without internal stresses caused by heat treatment.
Apron: Decorative trim positioned directly underneath a window stool and installed flush against the wall.
Arch Window: Four-sided unit with a curve at the top.
Argon Gas: Colorless, odorless gas used in the air space of double pane Low-E glass to increase the insulating performance.
Art Glass: Decorative glass in a variety of colors/shapes/patterns used to accent a window or door.
Astragal: Center post of a double door attached to the fixed or inactive door panel.
Awning Window: Unit with hinged sash that swings outward from the bottom; allows ventilation at the bottom.