Window & Door Terms, Explained

Clean, alphabetized definitions for homeowners

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Air Infiltration

The amount of outside air that leaks into a home through and around a window or door, usually measured under standardized test conditions.

Air Leakage Rating

A performance value that indicates how much air passes through a window or door assembly; lower numbers mean tighter, more efficient units.

Aluminum Window

A window with frames made primarily from aluminum, known for strength and slim profiles but typically less efficient without thermal breaks.

Annealed Glass

Standard untreated float glass that has been slowly cooled to relieve internal stresses; more likely to break into large shards than safety glass.

Argon Gas

An inert gas commonly used between panes of insulated glass to reduce heat transfer and improve energy efficiency.

Awning Window

A window hinged at the top that opens outward from the bottom, allowing ventilation even during light rain.

Bay Window

A window configuration that projects outward from an exterior wall, typically made of a fixed center unit flanked by angled side windows.

Bottom Rail

The lower horizontal part of a window sash or frame, providing structure and support for the glass.

Bow Window

A multi-panel window that curves outward from a wall, usually made of four or more equal-sized units to create a gentle arc.

Brickmould

Exterior trim that surrounds a window or door frame, creating a finished transition between the unit and the siding or brick.