Glossary of Terms

A-B        C-D        D-F        E-F        G-K        L-P        Q-S        T-W
Air Infiltration

The amount of air leaking in and out of a building through cracks in walls, windows, and doors.


A mechanical device, normally spring loaded, used in hung windows to counterbalance the width of the sash during opening and closing.


Inside flat trim member that is used under the stool at the bottom of a window.

Bay Window

A combination of three or more windows consisting of central picture or fixed window and flanked by two flanking units at 30°, 45° or 90° angles to the wall.


A colorless, odorless, non-flammable, non-reactive, inert gas which acts as an insulator between the panes of glass in a sealed unit.

Bow Window

A combination of four or more window units attached at an angle to give the impression of a curve.

Awning Window

An operating style of window with a sash hinged on the sides, and swings open at the bottom towards the exterior.

Brick Mould

Outside casing around a window to cover jambs and through which nails are driven to install the window.