Glossary of Window Industry Terms

Educate yourself on window industry terms and processes.

Below are terms and descriptions that will help you navigate your way through your window installation project from beginning to end.

aluminum windows
Glazed windows with aluminum sash and mullions. Aluminum windows are known for strength, value and flexibility in installation configurations to maximize views.

Also known as: aluminum storm windows, aluminum window frames, aluminum replacement windows, aluminum clad windows, aluminum window replacement, aluminum window repair, residential aluminum windows, aluminum frame windows

awning windows
These windows have a hinged upper sash that swings outward for ventilation.

Also known as: ventilation windows, awning window replacement, awning replacement windows

bay windows
A unit of three windows, usually made up of a large, center-fixed window unit and two flanking windows positioned at 30-, 45- or 90-degree angles that project out from the wall. Bay windows may increase the size of a room or may give the appearance of a larger room depending on the construction. Some bay windows have built-in seating and are used as window seats.

Also known as: bow windows, angle bay windows, window seat windows, bay bow windows, bow bay windows, replacement bay windows

casement windows
Windows that are side-hinged or pivoted. Casement windows have a single sash that cranks outward to the right or left.

Also known as: crank out windows, casement replacement windows, vinyl casement windows, casement window repair, wood casement windows, steel casement windows, aluminum casement windows, double-hung casement windows, French casement windows, metal casement windows

dormer windows
These windows protrude from the roof of a house. Dormer windows usually include one or more window panes.

Also known as: gable fronted dormer windows, hipped roof dormer windows, flat roof dormer windows, shed dormer windows, wall dormer window, link dormer window, window dormers

double-hung windows
Windows that have two operable sashes that slide vertically in the frame to open and close

Also known as: sash windows

double glazing windows
Any window made with two thicknesses of glass that are separated by airspace. Double-glazed windows increase energy efficiency and insulate against heat transfer and sound transmission.

Also known as: dual glazing windows, double glazed windows, insulated glazing, insulated glazing windows, double glazing sash windows, double glazed sash windows, energy efficient windows, conservatory windows, Energy Star windows, insulated glass, double-pane windows

dual-action windows
Windows with sashes that open for ventilation and swing open from the top or the side to allow cleaning of the outside glass

Also known as: sliding windows, swinging windows

Energy Star windows
Energy Star is a government program that established a set of guidelines for energy efficiency. Windows that are Energy Star Qualified meet efficiency requirements and can save seven to 15 percent on home energy bills compared to non-Energy Star windows. Most Energy Star windows are insulated or double/triple-paned, which keeps temperature-controlled air in the home and heat or cold out.

Also known as: energy efficient windows, insulated windows, energy efficient vinyl windows, energy efficient window replacements, energy efficient glass windows, energy efficient home windows, energy efficient wood windows

fixed windows
Nonventing or nonoperable windows made of fixed glass. Fixed windows are also known as picture windows and can be reglazed and replaced onsite.

Also known as: picture windows, fixed casement windows, fixed picture windows, fixed vinyl windows

hopper windows
Windows with a top sash that swings inward. Hopper widows are often used in basements and other areas where ventilation is desired but large windows are not required.

Also known as: casement windows, ventilation windows, basement hopper windows, hopper style windows, vinyl hopper windows

insulating glass
A combination of two or more panes of glass with a sealed airspace between the panes that’s filled with an inert gas, which increases insulation properties. Most major window companies offer insulated windows as part of their standard catalog.

Also known as: insulated windows, energy efficient windows, Energy Star windows,  insulated glazing, insulated glass, IG, double insulated glass, insulating glass, insulated replacement glass, insulated window glass, insulated glass windows, low-e insulated glass, insulated glass units, window glass insulation

jalousie windows
Windows with a series of overlapping, horizontal louvers that move together. Window louver panels open to maximize airflow through the openings.

Also known as: venetian blind windows, shutter windows, blind windows, aluminum jalousie windows, jalousie windows replacement

mullions
A vertical structural element that divides window panes and separates side-by-side windows

Also known as: window divider, window column, aluminum mullions, aluminum window mullions, mullion replacement, replacement mullions, removable mullions, wooden mullions, wood window mullions

picture windows
Also know as fixed windows, picture windows only consist of window frames and glass. Most picture windows are double-paned or insulated to be more energy-efficient since they have such a large surface area.

Also known as: fixed windows, non-opening windows, plate glass windows, picture replacement windows, vinyl picture windows

R-value
Thermal resistance to the transfer of heat through windows. Windows with higher R-value have greater insulating properties.

replacement windows
These are custom ordered to fit inside the jambs and sill of your existing windows. Replacement windows are usually less expensive to install than new windows that require new frames, jambs and window sills.

Also known as: window replacements, vinyl replacement windows, wood replacement windows, aluminum replacement windows, window pane replacements

single glazing
A single pane of glass installed in a window sash. Single-glazed windows are not as energy-efficient as double-glazed windows.

Also known as: conservatory windows, sun room windows,

single-hung windows
These look similar to double-hung windows, except the top sash is fixed and stationary, so only the bottom section opens.

storm windows
Mounted outside or inside the main glass, storm windows are often found in cold climates or as a retrofit of existing windows. They increase the efficiency of glass windows and can be mounted temporarily or permanently.

Also known as: replacement storm windows, aluminum storm windows, interior storm windows, home storm windows, vinyl storm windows, triple track storm windows, custom storm windows, combination storm windows, exterior storm windows

vinyl windows
Windows made with vinyl, a plastic material, cladding and window units. Vinyl windows are popular because they’re relatively inexpensive and maintenance-free.

Also known as: replacement windows, vinyl home windows, vinyl casement windows, maintenance-free windows, vinyl bay windows,

window casing
Also known as window trim, window casing is exposed molding of various widths, thickness and shapes that covers the framework of window and door units.

Also known as: window trim, interior window casing, flexible window casing, decorative window casing, exterior window casing, window interior casing, window molding

window cladding
Material applied to the outside faces of windows to provide a durable, low-maintenance exterior surface. Cladding often provides protection from the elements and adds an aesthetic touch. It may also be referred to as window capping, which is a specialized field offered by few window contractors.

Also known as: cladded windows, clad windows, vinyl-clad windows

wood windows
Windows with wooden frames. They’re a natural option, so they require more maintenance than vinyl windows and must be protected from moisture to avoid warping and rot.

Also known as: wooden windows, wood replacement windows, wood clad windows, custom wood windows, wood casement windows, wood double-hung windows, wood storm windows, aluminum-clad wood windows, exterior wood windows, wood window replacements, historic windows, historic wood windows