| Accessory Groove |
A shape included on a fenestration product frame that is designed for accessories to be snapped or fit into. |
| Air Barrier |
The assembly of materials used in building construction to cut down on passage of air in and out of the building. |
| Air Leakage/Air Infiltration |
Uncontrolled air passage through cracks or openings in a building, its envelope, or components when subject to differential air pressure. |
| Air Space |
The space between the two panes of glass which make up an insulating glass unit (IG unit) that is fitted into a high performance window sash. The depth of airspace affects overall window performance. A ½" to ¾" space is considered optimal. |
| Annealed Glass |
Raw glass which is easy to cut and is used as a glazing product. Additional processing transforms annealed glass into safety glass or laminated glass. |
| Anti-Lift Vinyl Inserts |
Components added to the main frame of slider window and sliding patio door to prevent the operating sash or door panel from being removed unless it is in the full open position. |
| Apron |
A molding applied horizontally to the wall, directly below the window sill. Trim used to hide the rough edge of the drywall or plaster directly below the window framing. |
| Argon Gas |
A safe, odorless, colorless, non-toxic, non-flammable inert gas used to fill insulated glass units to increase thermal performance. |
| Astragal |
The center member of a double door, which is attached to the fixed or inactive door panel. |
| Awning |
A window unit in which the bottom of the sash swings outward. |