Common terms for consumers and contractors
Air infiltration: The amount of air leaking in and out of a building through cracks in walls, windows, and doors.
Airspacer: Component placed at the perimeter of an insulating glass unit to separate the two lites of glass.
Argon: An inert, non-toxic gas used in insulating glass to reduce heat transfer.
Bay: A combination of window units which projects to the exterior. Usually features a large center unit with two flanking units at 30° or 45° angles to the wall.
Bottom rail: The bottom horizontal member of a window sash or door panel.
Bow: A combination window which projects to the exterior. Usually features four or more window units in a radial or bow formation.
Box bay: A combination of window units which projects to the exterior. Usually features a large center unit with two flanking units at 90° angles to the wall.
Brickmould: A type of external casing for windows and doors.
Caming: The metal used in construction of decorative glass panels - usually zinc or brass. Caming is also applied to single-glass lites to create a decorative appearance.
Casement: Window with sash cranking outward, to the right or left.
Casing: Exposed moulding or profile around a window or door, on either the inside or outside, to cover the space between the window frame or door jamb and the wall.
Caulking: A compound for filling joints and sealing cracks to prevent leakage of water and air.
Cladding: Material placed on the exterior of wood frame and sash components to provide ease of maintenance. Common cladding materials include vinyl and extruded or roll-formed aluminum.
Clerestory: A window in the upper part of a high-ceilinged room that admits light to the center of the room.
Combination door: A screen or storm door used in combination with a primary door. Storm windows are also referred to as combination windows.
Composite: A term used for window or door components which consist of two or more materials, such as wood and plastic. The term is also used for windows and doors which combine two or more materials in the frame or sash construction, such as a product with a wood interior and a vinyl or aluminum exterior.
Condensation: Water vapor from the air deposited on any cold surface which has a temperature below the dew point. Sometimes a problem on cold (and poorly insulated) window glass or framing that is exposed to humid indoor air.
CRF: Condensation Resistance Factor. A rating of a window's ability to resist condensation. The higher the CRF, the less likely condensation is to occur.
Double glazing: Use of two panes of glass in a window to increase energy efficiency and provide other performance benefits. May or may not refer to an insulating glass unit.
Double-hung window: Window featuring two operable sash which move vertically in the frame.
ENERGY STAR®: The international ENERGY STAR symbol is a simple way for consumers to identify products that are among the most energy-efficient on the market. Only manufacturers and retailers whose products meet the ENERGY STAR criteria can label their products with this symbol. Choosing an ENERGY STAR-labelled product over a conventional model could save you hundreds of dollars in energy costs. Canada's ENERGY STAR website.
Extension jamb: A trim component which extends from the interior of the window frame to the interior wall.
Fanlight: A half-circle window over a door or window with radiating bars.
Fixed lite: Non-venting or non-operable window.
Fixed panel: Non-operable door usually combined with operable door unit.
Flashing: A thin strip of metal or other material that diverts water away from
a window, door, or skylight.
Float glass: Glass produced by a process in which the ribbon is floated across a bath of molten tin. The vast majority of flat glass is now produced using this method. The terms "plate" glass and "sheet" glass refer to older manufacturing methods still in limited use.
Flush door: Door produced using two skins or faces separated by a stile-and-rail frame construction at the perimeter. Flush doors may produced with a hollow core or solid core.
French door: Generally refers to a pair of hinged doors which open from the middle. Also incorporates wider stile and rail components around the glass than typical glazed doors.
Glazing: Glass (and other materials) in a window or door. Also, the act or process of fitting a unit with glass.
Glider: A window with a movable sash that slides horizontally. Also referred to as a horizontal sliding window.
Grille: A term referring to window pane dividers or muntins. It may be a type of assembly fitted to the interior of the window or door unit which can be detached for cleaning. Also can be fitted inside the sealed insulating glass unit, when it is also referred to as a grid.
Head: Main horizontal frame member at the top of a window or door.
Header: Horizontal framing member placed over the rough opening of a window or door to prevent the weight of wall or roof from resting on the frame. Also known as a lintel.
Hollow-core door: Flush door constructed with two skins or door faces separated by stiles and rails at the perimeter. Generally a honeycomb type support is used inside the door between the two faces.
Insulating glass (IG): Two or more lites of glass with a hermetically sealed airspace between the lites. The sealed space may contain air or be filled with an inert gas, such as argon.
Jamb: Main vertical members forming the sides of a window or door frame.
Lineal: A standard length profile or shape which is cut and processed to make window and door components.
Lintel: A structural component or beam above a window or door opening that supports the wall above. Also referred to as a header.
Lite: A piece of glass. In windows and doors, refers to separately framed panes of glass (as well as designs simulating the look of separately framed pieces of glass). Sometimes spelled "light."
Low-emissivity (Low-E) glass: A coated glass product which reflects heat.
Masonry opening: Area in a masonry wall left open for windows or door.
Mullion: A component used to structurally join two window or door units.
Multipoint lock: A locking system, operated with one handle, which secures a window or door at two or more locking points.
Muntin: Profile or moulding, either vertical or horizontal, used to separate glass in a sash into multiple lites. Generally refers to components used to construct divided lite grids or grilles simulating a divided lite look.
Nailing fin: An accessory component or integral extension of a window or patio door frame which generally laps over the conventional stud construction and through which nails are driven to secure the frame in place.
Palladian: A large, arch-top window flanked by smaller windows on each side.
Panel: Component, usually wood, mounted within stile and rail members of door. Also used to refer to entire door.
Panning: In replacement window work, the outside aluminum trim that can extend around the perimeter of the window opening; used to cover up the old window material.
Picture window: Large, non-operating window. It is usually longer than it is wide to provide a panoramic view.
Pivot window: A unit with a sash that swings open or shut by revolving on pivots at either side of the sash or at top and bottom.
Plate glass: Flat glass produced by grinding and polishing to create parallel plane surfaces affording excellent vision. Although the term is still used commonly, most window glass is now produced using the float process. See float glass.
Radiation: The transfer of heat in the form of electromagnetic waves from one separate surface to another. Low-E glass is designed to reduce this type of heat transfer by reflecting electromagnetic waves.
Rail: Horizontal member of the framework of a window sash or door.
Reflective glass: Window glass coated to reflect visible light and solar radiation striking the surface of the glass.
Roof window: An operable unit similar to a skylight placed in the sloping surface of a roof.
Rough opening: Framed opening in a wall into which a window or door unit is to be installed.
Round-top: One of several terms used for a variety of window units with one or more curved frame members, often used over another window or door opening. Also referred to as arch-tops, circle-tops, and circle-heads.
R-value: Resistance to thermal transfer or heat flow. Higher R-value numbers indicate greater insulating value. R-value is frequently used by insulation industry and is the recipricol of U-value, a value more generally used in the window industry.
Sash: An assembly of stiles and rails (vertical and horizontal members) made into a frame for holding glass.
Sash cord: Rope or chain in double-hung windows which attaches the sash to the counter balance.
Sash lift: Protruding or recessed handle on the inside bottom rail of the lower sash on a double- or single-hung window.
Sash weights: Concealed cast-iron weights used to counterbalance the sash of older double-hung windows.
Sheet glass: A transparent, flat glass found in older windows, now largely replaced by float glass.
Sidelites: Narrow fixed units mulled or joined to operating door units to give a more open appearance.
Sill: The main horizontal member forming the bottom of the frame of a window or door.
Simulated divided lites (SDLs): A type of grille or grid design that creates the appearance of a number of smaller panes of glass separated by muntins, but actually uses larger lites of glass with the muntins placed between and/or on the surfaces of the glass layers.
Single glazing: Use of single lite of glass in a window. Generally not as energy efficient as insulating glass or other forms of double glazing.
Single-hung: A window resembling a double-hung, or vertically sliding window, with a fixed top sash.
Stile: The main vertical frame members of a sash or door.
Thermal break: A thermally insulating or low-conductance material used between interior and exterior aluminum (or other conductive material) window and door components.
Tilt window: A single- or double-hung window whose operable sash can be tilted into a room to allow cleaning of the exterior surface on the inside.
Transom: Window used over the top of a door or window, primarily for additional light and aesthetic value.
Ultraviolet light (UV): Invisible rays of solar radiation at the short-wavelength violet end of the spectrum. Ultraviolet rays can cause fading of paint finishes, carpets, and fabrics, as well as deterioration of some materials.
Vinyl: Generic term for polyvinylchloride or PVC, an extruded material used for window and door framing.
Warm-edge: A type of insulating glass construction using an airspacer offering lower thermal conductance than traditional aluminum spacer. Warm-edge i.g. units typically offer higher resistance to condensation and an incremental improvement in window energy performance.
Weatherstripping: A material or device used to seal the openings, gaps, or cracks of venting window and door units to prevent water and air infiltration.
Weep hole: A small opening in window or sill member through which water may drain to the building exterior.
Weld: A term used for a type of corner construction, used with vinyl and other types of windows and doors, in which a small amount of material at the two pieces are melted or softened, then pushed together to form a single piece. This is also referred to commonly as a fusion-weld.
