Glossary

Air Infiltration The amount of air that passes through a window or door. Lower air infiltration rates indicate better energy efficiency.

Annealed Glass A basic type of glass that is cooled slowly to remove internal stresses. It is less strong than tempered glass but can be cut and worked with more easily.

Argon Gas A non-toxic gas used between window panes to improve insulation and energy efficiency by reducing heat transfer.

Awning Window A type of window hinged at the top, opening outward from the bottom to allow ventilation, even in light rain.

Bay Window A window style that extends outward from the home, typically made of three windows—a large center window with two smaller side windows angled toward the wall.

Bow Window A window style similar to a bay window but with a curved shape, typically composed of four or more windows for a more rounded look.

Cameo Window A small fixed window used as a decorative feature, often found in areas where a full-sized window is not needed.

Casement Window A window hinged on the side, allowing it to open outward like a door, providing excellent ventilation and easy cleaning.

Cladding The material that covers the exterior of a window or door frame, offering added protection from the elements and enhancing durability.

Condensation The moisture that forms when warm, humid air contacts a cooler surface, such as a windowpane. Proper window insulation and installation can help reduce condensation.

Double Glazing A type of window with two glass panes separated by a spacer, often filled with an insulating gas like argon for improved energy efficiency.

Double-Hung Window A popular window style with two operable sashes that slide vertically, allowing for ventilation from the top, bottom, or both.

Egress Window A window designed for providing an emergency exit, typically required in bedrooms and basements to meet building codes.

Energy Star® A certification indicating that a product meets energy efficiency guidelines set by the U.S. Environmental Protection Agency.

Fusion-Welded Frame A frame construction method where the corners are heat-fused, making the window or door stronger and more resistant to air and water leakage.

Gas Fill An insulating gas, such as argon or krypton, placed between window panes to improve thermal performance.

Glazing Refers to the glass in a window or door. Single glazing has one pane, double glazing has two panes, and triple glazing has three panes for added insulation.

Hurricane Impact Glass Specially designed glass with a laminated interlayer that withstands high winds and debris impact, offering extra protection for homes in hurricane-prone areas.

Insulated Glass Unit (IGU) A window unit made up of two or more panes of glass separated by a spacer and sealed to create an insulating layer, improving energy efficiency.

Krypton Gas An inert gas used as an insulating filler between panes in high-performance windows, similar to argon but offering even better thermal resistance.

Low-E Glass Glass coated with a thin layer that reflects heat while allowing light to pass through, helping to keep homes warmer in the winter and cooler in the summer.

Mullion A vertical or horizontal piece that separates window panes within a single window frame or connects multiple windows.

Muntin A decorative or functional divider placed between the glass panes to create the appearance of multiple smaller panes within a larger window, often used in traditional and colonial-style windows.

Obscure Glass Textured or frosted glass that provides privacy while still allowing light to enter a room, commonly used in bathrooms.

R-Value A measure of thermal resistance. Higher R-values indicate better insulation, which contributes to energy efficiency.

Sash The part of a window that holds the glass and can move or tilt for ventilation. Double-hung windows have two operable sashes, while casement windows have one.

Solar Heat Gain Coefficient (SHGC) Measures how well a window blocks heat from sunlight. Lower SHGC values mean less heat is transmitted, contributing to cooler indoor temperatures during hot weather.

Spacer A component used to separate the panes in an insulated glass unit (IGU). Spacers can be made from various materials and their quality can affect the window’s overall thermal performance.

Sound Transmission Class (STC) A rating that indicates how well a window reduces noise. Higher STC ratings are desirable for minimizing sound from outside.

Tempered Glass A type of safety glass that, if broken, shatters into small, less harmful pieces. It’s stronger than standard glass and is often required by building codes for doors and windows near floors.

Triple Glazing A window with three panes of glass, often filled with gas, offering superior insulation and energy efficiency.

U-Factor A measurement of how well a window insulates. Lower U-factors indicate better insulation and energy efficiency.

Vinyl Clad A type of window or door frame made with vinyl on the exterior for added durability and weather resistance.

Weatherstripping Material applied around windows or doors to seal gaps, reducing air infiltration and increasing energy efficiency.

Window Frame The structure that surrounds and supports the entire window system. Frames can be made from various materials including wood, vinyl, aluminum, and fiberglass, each offering different levels of durability, maintenance, and insulation.