Glossary
| A | |
| AAMA | An acronym for the American Architectural Manufacturers Association, a group that sets the voluntary standards for window, door and skylight manufacturers. |
| AAMA Gold | A certification program of the American Architectural Manufacturers Association relating to the areas of air leakage, water and structural performance in doors and windows. |
| AAMA Silver | A certification program of the American Architectural Manufacturers Association relating to the thermal performance of doors and windows. |
| Absorptance | In a glazing system, absorptance is the ratio of radiant energy absorbed compared to the total incident radiant energy. |
| Acrylic | A thermoplastic used as a glazing material that improves clarity, shatter resistance and weather resistance. |
| Active panel | The main, operable door leaf in paired or double doors. |
| Aerogel | A silicate foam that is microporous and transparent, and used for filling a glazing cavity. It is known for its excellent thermal performance. |
| Air Infiltration | A measurement of the amount of air that leaks between a window frame and sash. A low air infiltration number is best. |
| Air Latch | A mechanism attached to the interior of the window sash that allows a window to remain partially open for the purpose of allowing air flow. |
| Air Leakage (AL) | Also known as air infiltration, it is the measurement of the amount of air that leaks between a window frame and sash, with a low AL rating being best. |
| Airspace | The space between the sheets of glass in double or triple paned windows or doors. |
| Airspace Grilles (or Grilles in the Airspace) | Aluminum bars known as grilles that are sealed in the space between the sheets of glass in double or triple paned windows. |
| Airspacer | The mechanism that separates the two lites of glass in insulating glass. |
| Aluminum Surround | The frame surrounding a screen. |
| Annealed Glass | Glass that has been treated to withstand temperature change and impact. |
| ANSI | An acronym for the American National Standards Institute, which is an organization dealing with all types of product specifications and standards. |
| Apron | The trim attached to the wall beneath the interior window sill. |
| Arch or Arch-top Window | Also know as round-top, it is a window unit that is curved at the top. |
| Argon Gas | An inert, non-toxic gas that is both odorless and colorless and used to in the space between glass panes to reduce the transfer of heat. |
| ASHRAE | An acronym for the American Society of Heating, Refrigeration and Air Conditioning Engineers, a group responsible for setting the standards for the energy performance of buildings. |
| ASTM | An acronym for the American Society for Testing and Materials. An association that sets standards and testing methods for materials including glass. |
| Astragal | The center post fitted to the fixed door panel in a set of double doors. |
| Authentic Divided Lites (ADL) | Also known as True Divided Lites (TDL), it refers to windows that have multiple panes of glass separated by muntin bars. |
| Awning Window | A window with a hinge at the top of the sash, allowing the window to swing out from the bottom. |
| B | |
| Backband | Molding that is used in conjunction with window or door casings to provide additional decorative detail. |
| Backbedding | A sealant applied to a window sash to reduce air, water and dust penetration. |
| Balance | Sometimes called a balancer, it is a device that offers a counterbalance to the weight of the window's sash when opening and closing. |
| Bay Windows | A combination of two or more operating and/or stationary windows arranged to project from the exterior of the building. |
| Bead | Also known as a stop, it is a molding piece used to separate, hold or position the parts of a window or door. |
| BETEC | An acronym for the Building Enclosure Technology and Environment Council charged with encouraging optimum energy usage in buildings through a better understanding of how overall, complex building components interact with each other and with the environment. |
| Blindstop | A piece of molding nailed between the outside trim piece and the outside sashes, used to prevent air infiltration. |
| Block frame window | A replacement window that utilizes the existing wood perimeter frame. |
| BOCA | An acronym for Building Officials and Code Administrators International. An association tasked with the development and enforcement of building codes. |
| Boot Glazed | Glass surrounded by a vinyl gasket known as a boot. |
| Bottom Rail | The horizontal bottom piece of a window sash. |
| Bottom Sweep | A flexible piece secured to the bottom of a door to prevent the infiltration of air, water, insects or sound. |
| Bow Window | A combination of windows, typically four or more, arranged to project away from the home's exterior in a curved shape. |
| Box Bay | A configuration of windows that project away from the home's exterior at 90 degree angles. |
| Breather Tube | Typically used in areas of high altitude, it is a metal tube placed in the airspace of insulated replacement window units to accommodate for pressure changes. The tube is sealed upon installation. |
| Brickmould | A trim piece attached to the exterior of a replacement window or door frame to give it the look of a traditional wooden frame. |
| Butyl | A type of flashing tape used for sealing the rough openings around windows and doors. |
| Bypass | A type of sliding door in which one panel slides behind the other when opened. |
| C | |
| Cam Lock | A fastening mechanism that pulls the sash together when locked. |
| Caming | The metal used to create a decorative glass panel by holding smaller pieces of glass in place. |
| Capillary Tubes | Small stainless steel or aluminum tubes used in insulating glass units that help equalize the pressure between the panes of glass. Typically used when windows are to be installed in high altitude areas. |
| Casement Window | A window with a sash hinged on one side, which allows the window to open outward or inward using a crank mechanism. |
| Casing | The trim attached around a window or door to cover the space between the window or door frame and the rough opening in the wall. |
| Caulking | A material used to fill joints or seal cracks to prevent air and water leakage. |
| Cellular PVC | A synthetic wood-replacement material used in windows and doors and for trim. |
| Check Rail | Also called the meeting rail, it is the horizontal rails on the upper and lower sashes that meet when a double-hung window is closed. |
| Circle Top | Sometimes called a round top, arch top or circlehead, it is a term describing a window or group of windows having a curved top. |
| Cladding | A covering or coating attached to the exterior face of a door or window to prove a low-maintenance surface. |
| Clerestory | A window placed high up on an exterior wall to allow light to the center of the room. |
| Coil Stock | Aluminum used for trim on the exterior. |
| Combination Unit | A window or door that is made of a storm window or door combined with a screen and used in conjunction with the primary door or window. |
| Composite Frame | A window or door frame that consists of two or more materials. |
| Condensation | Water vapor that forms on the surface of the glass resulting from the temperature of the glass being below the dew point. |
| Condensation Resistance (CR) | A scale from 1 to 100 that measures how effectively a window resists the formation of condensation. The higher the CR number, the more efficient the window is at resisting condensation. |
| Conduction | The process by which heat is transferred through matter from an area of higher temperature to an area of lower temperature. |
| Convection | The tendency of hotter, less dense air to rise, and cooler, denser air to sink, causing the transfer of heat. |
| Conversion Kit | A kit that allows for retrofit windows that can tilt. |
| Cornice | A horizontal decorative molding that goes over a door or window. |
| Cottage Window | a double-hung window with an upper sash smaller than the lower. |
| CRF | An acronym for Condensation Resistance Factor. It is a way to measure a window's ability resist the formation of condensation. CRF numbers generally range from 30 to 80, with a higher number being better. |
| D | |
| Daylight Opening | A measurement of the width and height of a window or patio door. |
| Desiccant | A substance that is used in the sealed airspace of a window to absorb and remove moisture. |
| Design Pressure (DP) | A measurement that tests the structural soundness of a window or door, with regard to wind and weather conditions. |
| Dewpoint | The temperature, which varies with pressure and humidity, below which water droplets form. |
| Direct Glaze | A window unit in which the glass is glazed directly into the frame and no sash is needed. |
| Divided Lites | A window with multiple panes of glass divided and held by muntins. |
| Door Rollers | The wheels that allow sliding doors to move back and forth. |
| Dormer | A window that projects from a sloped roof of a house. |
| Double Glazing | Two panes of glass with an airspace in between that improves the energy efficient quality of a window. |
| Double-hung | A window having both an upper and lower sash that slide up and down. |
| Double-hung Tilt | A double-hung window with the added feature of being able to tilt toward the interior of the home for ease of cleaning. |
| Double Slider | A window with sashes that slide side to side. |
| Double-strength Glass | Glass that is approximately 1/8" in thickness. |
| Drip Cap | A piece of molding made of either aluminum or vinyl fitted above a window or door to divert water. |
| E | |
| Edge Effect | The transfer of heat at the edge of a unit of glass. |
| Egress Window | A window that can be used as a means of escape in an emergency, required by building codes. |
| Electric Operator | The device used to operate an awning window remotely. |
| Electrochromics | A type of glaze that allows a window to change from clear to dark electronically. |
| Electromagnetic Spectrum | The range of wavelengths of radiant energy |
| Emergency Exit Window | Also known as an egress window, it is a window required by building codes that can serve as an emergency escape route. |
| Emittance | The ratio of heat emitted by an object to that of a standard black body under the same conditions. |
| Energy Ratings | Performance ratings put out by the National Fenestration Rating Council measuring windows on their U-Factor, Solar Heat Gain Coefficient, Visible Transmittance, Air Leakage and Condensation Resistance. |
| ENERGY STAR® | A program of the Environmental Protection Agency (EPA) and Department of Energy (DOE) that certifies windows as energy efficient based on U-Factor and Solar Heat Gain Coefficient ratings. |
| Equal Lite | A window in which all sashes are equally spaced. |
| Escutcheon Plate | An ornamental plate that surrounds a door handle or keyhole. |
| Evacuated Glazing | A window unit in which the airspace between panes is not filled with a gas, but is instead a vacuum. The vacuum eliminates conduction and convection, giving the window a low U-factor. |
| Extension Jamb | Wooden trim that covers the space between the interior window frame and the wall. |
| Exterior Trim | Ornamental trim that is installed around an exterior window or door. |
| Extruded Aluminum | A thick, sturdy type of aluminum used to clad exterior wood windows. Preferable to roll-form aluminum, which is much thinner. |
| Extrusion | Any item made by forcing a heated material through a die. In window and door production, aluminum or vinyl is often formed using this process to manufacture components. |
| Eyebrow | A low window that is hinged at the bottom and rounded at the top, with no straight sides. Usually placed on a roof where a dormer would be. |
| F | |
| Fanlight | Sometimes called a circle top transom, a fanlight is a semi-circle window placed over another window or door with radiating bars, resembling the look of a fan. |
| Fenestration | An industry term that refers to windows, doors, and skylights and their related accessories. |
| Fiberglass | A material composed of glass fibers that have been embedded in a resin mix, often used in replacement windows. |
| Film | The clear material placed on glass to temporarily protect it during construction and installation. |
| Finger Lifts | The indentations on a window's bottom sash that allow a person to slide the window sash up and down with ease. |
| Fixed Lite | A pane of glass that is installed in a window frame that is non-operable. |
| Fixed Panel | A non-operational panel, usually paired with an operational panel, in a sliding glass door unit |
| Fixed Window | Sometimes called a picture window, it is a window that does not vent or have an operable sash. |
| Flanker | A window placed to the side of center window unit. |
| Flashing | A water resistant material, such as sheet metal, that diverts water away from the joints of a window or door. |
| Float Glass | Glass that is manufactured using a process of floating the material across molten metal, producing high-quality glass that doesn't need polishing. |
| Flush Door | A solid or hollow core door covered on both faces with a skin of wood veneer, sheet metal, fiberglass or vinyl. |
| Flush Fin | A replacement widow commonly used in California, where original windows are often aluminum, and exteriors are often stucco, that has a large exterior flange to hide the existing window frame. |
| Foam Spacer | Foam material used instead of a metal spacer to improve structure and insulation. |
| Fogging | A film on the inside of sealed insulating glass that appears as a result of being exposed to extreme temperatures or having a faulty seal. |
| Folding Door | A door with vertically hinged panels that can fold flat against each other. |
| Footbolt | A locking mechanism operated by using foot pressure to hold a door panel or screen in an open or closed position. |
| Frame | The outside structure that encloses the panel. |
| Frame Size | The size of the window unit, measured from outside to outside edges. |
| French Casement | A window with two operating sashes, each hinged on the outside edge, with no center post. When both sashes are opened, there is an unobstructed view to the outside. |
| French Door | Two hinged doors that open from the middle. Can swing either in or out. |
| French Sliding Door | A patio door with the look of a French door, but slides open instead of swinging open on hinges. |
| Full Divided Lite | Meant to replicate the look of a True Divided Lite (TDL), with a spacer between the sheets of glass as well as inside and outside grilles. |
| Full Round | A circular window unit. |
| Fusion Weld | Also called a welded corner, it is the process of fusing corner pieces of a window sash or frame together by softening the material on the ends of the two pieces to be attached together with heat. |
| G | |
| Gas Fill | A gas that is placed between window panels to reduce the U-factor rating by suppressing conduction and convection. The gases most often used for this purpose are argon and krypton. |
| Glass | A hard, brittle, often transparent substance made by fusing a mixture of sand, soda, lime and other ingredients and cooling it rapidly. |
| Glass Size | The measurement of the entire pane of glass, not just the visible part. |
| Glazing | Refers to the glass panes in a window or door. Can also refer to the process of fitting the glass into its frame or door panel. |
| Glazing Bead | A convex molding piece placed around the perimeter of the window frame that holds the glass in place. |
| Glider | Sometimes called a horizontal sliding window, a glider is a window with a sash that opens horizontally. |
| Gothic | A style of window commonly found in Gothic architecture that is typically long and narrow with a pointed arch at the top. |
| Greenhouse Window | A window built out from the exterior of a house that has glass on the sides and top, and a shelf on the bottom. |
| Grille | Vertical and/or horizontal bars that visually divide a pane of glass into sections. They can usually be detached for ease of cleaning. |
| Grilles Between Glass (GBGs) | Also called grilles in the airspace or airspace grilles, they are bars that visually divide the glass that are enclosed in the space between panes of glass. |
| H | |
| Half Insect Screen | A screen used on double hung windows to cover the operating sash. |
| Half Round | Also called half circle or round top, it is a window with a flat bottom and rounded top, whose height is half its width. |
| Hallmark | A certification program for products that meet a set of standards set by the Window and Door Manufacturer's Association (WDMA). |
| Handing | A term to describe the way a door or window opens. In a casement window, if the hinges are on the right side, when viewing the window from the exterior, the handing is right. In gliding windows or doors, the handing is determined by the side of the operating panel. If the operating panel is on the right side, when viewed from the exterior, the handing is right. |
| Handle Set | A door's hardware that can include the door handle or knob (inside and out), strike plate, turning mechanism, core and lock plate. |
| Hard-coat Glass | Often used for storm windows, hard-coat glass is a type of low-E glass that incorporates indium tin oxide into the glass to make it more durable. |
| Hardware | The mechanisms that allow doors and windows to operate and lock, including hinges, locks and handles. |
| Head | The horizontal frame piece at the top of a window or door. |
| Head Track | The track along the top of a sliding door or gliding window. |
| Head Bolt | A locking device that is installed vertically on a door or screen that, when activated, secures the panel or screen in a stationary position. |
| Header | A beam used in framing, placed over the top of a rough opening of a window or door to support the weight of the wall and roof above. |
| Heat Gain | When heat is transferred from the outside to the inside of a house through conduction, convection and radiation. |
| Heat Loss | When heat is transferred from the inside to the outside of a house by means of conduction, convection and radiation. |
| Heat-absorbing Glass | Also called tinted glass, it is window glass with a bluish, gray or bronze tint that absorbs heat and reduces brightness and glare. |
| Heat-strengthened Glass | A type of glass that is rapidly cooled after being heated to a temperature between 1100 and 1500 degrees F. It is typically about twice as strong as annealed glass. |
| Heating Degree Day (HDD) | The term that refers to the amount of energy needed to heat a specific building. |
| Hinged Patio Doors | A two-paneled patio door that has hinges on the outside, allowing the door panels to open from the center and swing either inward or outward. |
| Hinged Windows | A window with one or more sash that operates on a hinge, such as a casement, hopper or awning window. |
| Hinges | Movable mechanism by which a door or window is allowed to open and close. |
| Hopper | A window that swings open from the top, typically inward. |
| Horizontal Slider | Also called a gliding window, it is a window in which the operable sash slides horizontally. |
| I | |
| IBC | An acronym for International Building Code, which is a book of codes published by the International Code Council that covers all buildings except one and two story homes and townhomes up to three stories tall. |
| ICC | An acronym for the International Code Council, an association dedicated to establishing codes and standards used in the design and construction of structures. |
| IECC | An acronym for the International Energy Conservation Code, which is a publication of the ICC that establishes minimum regulations for energy-efficient structures. |
| Impact Resistant Glass | Windows using glass that is laminated to offer extra protection. Often used in areas prone to hurricanes. |
| Inactive | A window or door panel that will open only after an active panel is opened first. |
| Infiltration | A term that describes the air or water that moves between the inside and outside of a building. |
| Insect Screen | A mesh material attached to a frame that allows ventilation when a window is opened, while still keeping insects outside. |
| Insert Replacement | A replacement window that makes use of the original frame. |
| Inside Stop | Used on older wooden windows, it is a thin, vertical piece of wood that keeps the window from falling inward. |
| Insulated Shutters | Window coverings that help prevent heat loss. |
| Insulating Glass (IG) | Glass panes that are separated by a spacer and sealed with air or gas in between to increase energy efficient properties. |
| Insulation | Any material used to reduce or prevent the transfer of heat, cold, noise or fire. |
| Inswing | Doors or windows with panels that swing inward. |
| Interior Casing | Interior trim around a door or window. |
| Interlock | The engagement point where the mechanisms of two adjacent sliding doors or gliding windows connect. |
| IRC | An acronym for the International Residential Code, a publication of the ICC that outlines codes for single-family homes, and low-rise multi-family buildings. |
| J | |
| J-channel | A finishing piece used to cover the seam between exterior siding and a window for a finished appearance. |
| Jalousie | A window composed of multiple horizontal glass slats that fit together tightly when closed and are able to rotate open to allow airflow. |
| Jamb | The vertical pieces that make up the sides of a window or door frame, also known as the side jamb. When referring to the horizontal top piece of a window frame, it is called the head jamb. |
| Jamb Clips | Used in replacement window installation, they are the metal brackets that secure the window jamb to the stud next to the window opening. |
| Jamb Liner | A strip of material used to make a window fit snugly within a frame. In modern replacement windows, it contains the track on which a double-hung window sash slides. |
| Jamb Depth | The measurement of the window or door from the inside of the exterior trim to the inside of the interior trim. |
| Jamb Extension | A piece that is added to the window frame in order to match the wall's thickness. |
| K | |
| Knocked Down (KD) | A window or door unit that is unassembled. |
| Keeper | The piece of hardware on the sash that engages the lock. |
| Krypton | An inert gas sometimes used in the airspace of insulating glass to make the replacement window more energy efficient. |
| KWH | Stands for kilowatt-hour, which is a unit of energy that is equivalent to one kilowatt of power expended for one hour. |
| L | |
| Laminated Glass | Sheets of glass that are fused with an inner layer of clear plastic, so that if the window is broken, the pieces adhere to the plastic. Used as a type of safety glass. |
| Lift | A handle attached to the bottom of the lower sash in a double-hung window, used for raising and lowering the window. |
| Lite | An individual pane of glass in a window or door. |
| Light Shaft | A shaft that extends from a roof window, through the attic, to a skylight, in order to direct light into a room. |
| Light-to-solar-gain Ratio (LSG) | A measurement used to describe the ratio between visible transmittance (VT) and solar heat gain coefficient in a window. |
| Lineal | An uncut length of window material that is used to make components for replacement windows and doors. |
| Lintel | Also called a header, it is a beam above a window or door that supports the wall above. |
| Liquid Crystal Glazing | Laminated glass that can change from clear to diffused through the use of liquid crystals. |
| Lite Cut | The pattern in a window with divided lites. |
| Lock | A mechanism for keeping a door or window securely fastened. |
| Lockset | A system for securing a door that can include inside and outside door handles, keys, latchbolt, dead bolt, strike plate, and other parts. |
| Low-conductance Spacers | Material placed between panes of glass, typically made of aluminum, that helps create an insulating barrier and provide a barrier to moisture. |
| Low-E Glass | Short for low emissivity, it refers to a type of glass that is coated to offer better UV protection and energy efficiency. |
| Low-emittance (Low-E) Coating | A thin metal or metallic oxide layer that is applied to one or more surfaces of insulated glass. The coatings let visible light pass through the window, while reflecting radiant infrared energy, reducing the U-factor of the window. |
| M | |
| Masonry Clip | A clip that allows an installer to mount a replacement window to existing brick, concrete, wood or metal walls. |
| Masonry Opening | An open space in a wall of brick, stone or stucco in which a window or door can be installed. |
| MDF | An acronym for medium-density fiberboard. An engineered wood product used in doors and trim. |
| Measurement Guide | Helpful instructions, usually with diagrams, that allow you to do your own accurate measurements for replacement windows and doors. |
| Mechanical Window | A window with corners fastened together by screws, as opposed to a welded corner window, in which the corners are welded together. |
| Meeting Stile | Also called a meeting rail, it is the part of a sliding glass door, sliding window or double-hung window where the two panels or sashes meet in a closed position. |
| Metal-clad Windows | Windows with their wooden parts covered by metal, usually aluminum, for weatherproofing and maintenance purposes. |
| Miter | A joint made by beveling two pieces to be joined together, usually at a 45 degree angle. |
| Model Energy Code (MEC) | A publication of the International Code Council (ICC) containing energy efficiency criteria for residential and commercial buildings. |
| Monolithic Glass | A single lite of glass. |
| Mortise | A rectangular slot that is cut into a piece of wood to be fitted with a coordinating tenon. |
| Mortise-and-tenon | A type of woodworking joint that is formed when a rectangular slot (mortise) is cut in one piece of wood and is fitted with another piece of wood with a coordinating extension (tenon). |
| Mulling | When two or more windows are joined together, either vertically or horizontally. |
| Mull Cover | The connector joining two windows that provides a finished look and also helps prevent air and water infiltration. |
| Mullion | The structural piece joining two windows, which can run vertically or horizontally. |
| Multipoint Lock | A lock that is operated with one motion, but secures the window or door at multiple locations. |
| Muntin Bars | Also called grilles, muntins are bars that separate glass into a decorative pattern. |
| N | |
| Nail-on | Refers to the way that a frame is attached when a window is installed in new construction. |
| Nailing Fin | A piece that is either part of a replacement window, or added on as an accessory, through which a window is nailed in place to the studs of the building. |
| NFRC | An acronym for the National Fenestration Rating Council, an independent non-profit organization that certifies windows, doors and skylights based on their energy efficiency. |
| Non-keyed Cylinder | Typically used on inactive doors, it is a door handle that has no key and cannot be locked from the outside. |
| NWWDA | Stands for National Wood Window and Door Association, now called the Window and Door Manufacturers Association (WDMA). It is a trade organization for standards in wood window and door manufacturing. |
| O | |
| Obscure Glass | Any glass that is obscured for decorative or privacy purposes using frosting, etching, or other means. |
| One-step Distributor | A term for a company that buys products like replacement windows or doors from a manufacturer and then sells them directly to homeowners, contractors or builders. |
| Operable Window | Any window that is able to open and close. |
| Operator | The hardware piece that is usually crank-operated and used to open and close a casement, awning or jalousie window. |
| Oriel | A type of bay window that extrudes from a building, usually from an upper floor, that is supported by corbels or brackets. |
| OITC | An acronym that stands for Outdoor/Indoor Transmission Class, which is the standard that indicates the rate in which sound travels between the outside and inside of a structure. |
| Outside Stop | Also called a blind stop, it is the piece of wood trim that is attached to the side jambs on the exterior. |
| Outswing | Windows or door panels that swing outward from the structure. |
| OX / XO | Used on diagrams of windows and doors, the "X" indicates the operating panel or sash, and the "O" indicates the stationary panel or sash. |
| P | |
| Palladian | A window with an arch-top that has smaller windows on either side. |
| Pane | A single sheet of glass enclosed in a window or door frame. |
| Panel | Refers to the a lite of glass installed within a door frame that can be either sliding or stationary. |
| Panning | Aluminum trim used on the outside of a replacement window to cover old window components. |
| Particle Dispersed Glazing | An electrically controlled glazing in which microscopic particles are suspended randomly between panes of glass, but when powered on, align to change the transmission. |
| Parting Stop | A narrow strip of wood that holds a window sash or glass door panel in position in the frame |
| Passive House Windows | Extremely well-insulated windows that meet the rigorous and voluntary energy efficiency standards set by the passive house concept that originated in Germany. |
| Passive Solar Collector | A glazed area built into a structure that takes advantage of heat from the sun without the use of mechanics. |
| Patterned Glass | Translucent glass with a regular pattern or texture. |
| Performance Grade (PG) | A rating given by the North American Fenestration Standard/Specification (NAFS) for windows, doors and skylights that tests overall performance. |
| Perimeter Grille | Pane dividers that can be removed for cleaning or to change the look of windows and doors. |
| Photochromics | Glazing that darkens with added exposure to ultraviolet (UV) radiation. |
| Picture Window | A large, fixed window that usually hangs horizontally so as to offer a panoramic view of the exterior. |
| Pitch | A measurement of the steepness of a roof. |
| Pivot Window | A window sash that revolves within a window frame on pivots that are either on the side or at the top and bottom. |
| Plastic Film | A thin film that can be applied to windows to help provide insulation. |
| Plate Glass | Glass that is produced by grinding and polishing, offering excellent visibility. Most glass being made today no longer plate glass, but float glass. |
| Plinth Block | A decorative block of wood placed in the corners of the casing around windows and doors. |
| Plumb | A term that means a vertically installed piece is perpendicular to the ground. |
| Pocket Door | A door panel that slides into an opening in the wall. |
| Pole Crank | A pole used to open and close windows and awnings that are out of reach. |
| Polycarbonate | A plastic glazing material. |
| Polyvinyl Butyral (PVB) | Material used in laminated safety glass that causes shattered glass to be held in place. |
| Polyvinylchloride (PVC) | An extruded material commonly used in replacement window frames as a substitute for wood. |
| Pre-finished | Refers to a unit that is pre-painted or stained in the factory and is ready for immediate installation. |
| Pre-hanger | A company that purchases replacement window and door components and assembles the units for installation. |
| Primary Active Panel | The operating panel in a pair of bi-hinge doors. |
| Prime | Also called primer, it is the first coat in multiple applications of paint. |
| Primed Window | A window unit with a frame that already has a coat of primer applied and is ready to be painted. |
| Profile | The contour of a piece of lineal material. |
| Projected Window | Windows with sashes that move away, or project, from the exterior of a wall, as in casement windows, hoppers and awnings. |
| Pultrusion | Rigid, composite material that is cut and processed for window and door components needing to be especially strong and weather resistant. |
| Push-out Casement | A casement window unit opened by letting out the sash lock and pushing out the window, with no crank handle utilized. |
| Pyrolytic Low-E Glass | Glass with a hard coat deposited onto its surface that improves solar control. |
| Q | |
| Quarter Round | A window unit that is one fourth of a circle in shape. |
| R | |
| R-value | A measure of a unit's ability to resist the flow of heat. A window with a high R-value has better insulating properties. |
| Rabbet | A groove in a piece of wood that is typically joined to the coordinating tongue in another piece of wood. |
| Radiation | The emission of heat from one source to another in the form of electromagnetic waves. Low-E glass reduces the transfer of heat from the sun to the inside of a building by reflecting the electromagnetic waves. |
| Radius | The measurement from the center of a circle to the outside edge. |
| Rail | The horizontal parts that make up the top and bottom of a door panel or window sash. |
| Reflectance | The measure of the proportion light or energy striking a surface to that which is reflected off that surface. |
| Reflective Glass | Glass that is coated in such a way that it has improved capacity to reflect light. |
| Refraction | Light or other waves being bent from a straight path as they pass obliquely through an object, such as a window. |
| Reinforced Mullion | A connecting unit that goes between two windows, two doors, or between an adjacent window and door that is reinforced with a material such as steel or aluminum. |
| Relative Humidity | Sometimes abbreviated RH, it is the percentage of water vapor present in the air, in relation to the amount needed for saturation at the same temperature. |
| Relief Kerf | A kerf that is machined into the door or window frame that helps prevent warping. |
| Removable Interior Grille | Grilles that are attached to the inside of the window with latches that can be removed for cleaning. |
| RESFEN | A computer software program that calculates the heating and cooling use and the costs associated with specific window products. |
| Reverse Cottage Window | A type of double-hung window in which the lower sash is smaller than the upper sash. |
| Roll-form Aluminum | A thin sheet of aluminum used to clad the exterior of wood windows. Much thinner than windows clad with extruded aluminum. |
| Roof Window | A window unit placed on a sloped roof. |
| Rough Opening | The wall opening for a window or door that is to be installed. |
| Round Top | A semicircle window, usually placed on top of another window or a door. |
| S | |
| Safety Glass | Glass that has been toughened or laminated so that less splintering will occur if broken. |
| Sash | A portion of a window that includes the glass, rails and stiles, but does not include the frame into which it is fitted. |
| Sash Balance | A mechanism comprised of springs or counterweights that help a double-hung window remain open. |
| Sash Cord | The rope or chain that attaches to the sash and the sash balance in a double-hung window. |
| Sash Lift | A handle attached to or routed into the bottom rail of the lower sash in a single- or double-hung window. |
| Sash Limiter | A device that controls how far a window can open. |
| Sash Lock | A device that secures the window sash to the frame. |
| Sash Opening (SO) | The distance between the outside casings of a window. |
| Sash Pulls | The routed handle on the vertical stiles of a sliding window that allow the window to be easily opened. |
| Sash Retainer Plate | Hardware located on the top of the lower sash that secures the bottom sash in place. |
| Sash Weights | The counterweights in older double-hung windows that kept the sash from closing. |
| Screen | A framed, woven mesh material fitted on the exterior of a window or door that allows for ventilation, while keeping out insects. |
| Screen OM (Outside Measurement) | Different from the window measurement, the screen is measured from the outside corner to the outside corner of the frame for both it's width and height. |
| Sealant | A material used to close off any openings or junctions where two or more parts come together. |
| Secondary Active Panel | The panel in a set of bi-hinge doors that does not have the lockset. |
| Self-cleaning Glass | Glass coated with a thin clear layer of titanium dioxide that reacts with sunlight to break down dirt and grime. Water alone can then easily wash away the dirt. |
| Sequential Locking System | A locking system that secures at multiple locations on a casement window. |
| Set Up | A complete window unit that is ready to be installed, with all mulling and casings already applied. |
| Shade Screen | Also called a solar shade, solar screen or sun screen, it is a specially manufactured screen that helps reduce glare, block harmful UV rays and improve the energy efficiency of the home. |
| Shading Coefficient (SC) | The way to measure a window or skylight's ability to transmit solar heat, compared to a single, 1/8-inch clear, double-strength unit of glass. A lower SC number is preferable. |
| Sheet Glass | The clear, flat glass that is found in the windows of older homes. |
| Shim | A thin piece of material, often wood, that is used to level window and door frames during installation. |
| Side Jamb | The vertical side pieces of a window or door frame. |
| Sidelites | Narrow glass units installed adjacent to a door. |
| Sill | The bottom of a window or door frame. |
| Sill Angle | The pitch of the exterior window sill. |
| Sill Track | The track of a sliding glass door that is located on the sill. |
| Simulated Divided Lites (SDLs) | A window unit meant to look as if it is made up of smaller panes of glass separated by muntins, but is actually made of large panels of glass with grilles installed on the inside and outside surfaces of the glass. |
| Simulated True Divided Lite | A window unit with three sets of grilles: one on the interior, one on the exterior and one between the panes of glass. Meant to closely simulate true divided lites. |
| Single Glazing | A window or door unit with a single lite of glass. |
| Single-hung | A window with two sashes in which the top sash is inoperable. |
| Single-strength Glass | Glass that is 3/32" thick, as opposed to double-strength glass that is 1/8" thick. |
| Skin | A material that covers the face of a door. |
| Skylight | A window installed in the roof to give light and ventilation to the room below. |
| Slab | A door panel without the hinges or frame attached. |
| Sliding French Door | See French Sliding Door. |
| Sliding Glass Door | A multi-paneled door that slides horizontally on a track or in grooves. |
| Sliding Window | A single- or double-hung window that has sashes that open by sliding in grooves within the frame. Can slide either vertically or horizontally. |
| Sloped Sill Adapter | A piece that covers the gap left when a block frame replacement window is put where a slope sill window used to be. |
| Smart Window | A window that has glass that controls heat transmission by changing light transmission properties. |
| Snubber | Brackets that help prevent bowing in tall casement windows. |
| Soft-coat Glass | A coating used in an insulating glass unit that offers glass low-emissivity and better solar control with a process called sputter coating. Unlike hard-coat glass, soft-coat glass requires special care and handling. |
| Solar Control Glass | Glass that has a special coating for absorbing and reflecting solar energy. |
| Solar Heat Gain Coefficient (SHGC) | A rating that indicates a window or door's ability to prevent heat from passing through. A lower SHGC is preferable. |
| Solar Radiation | The radiant energy emitted by the sun. |
| Solar Screen | See shade screen. |
| Solid-core Door | A door that is solid underneath the door skins, as opposed to a hollow-core door. |
| Sound Transmission Class (STC) | A rating that measures a window's ability to reduce the transmission of sound. A high STC rating indicates less sound is transmitted. |
| Spacer | A piece separating two panes of glass in an insulating glass panel. |
| Spectrally-selective Glass | A type of coating or tinted glazing that allows visible light or daylight to pass through, but reflects UV radiation as well as short-wave and long-wave infrared radiation. |
| Sputter Coating | See Soft-coat glass. |
| Square Foot | The area of a unit measured in feet. |
| Stacked | Two or more windows arranged vertically. |
| Stat | Short for stationary. See below. |
| Stationary | A nonoperable panel or sash. |
| Stick Grille | A grille with no exterior frame. |
| Stile | The vertical frame pieces of a window sash or door. |
| Stile and Rail Door | A type of wood door with decorative raised panels surrounded by a frame. |
| Stool | An extension of the interior window sill that acts as a small shelf. |
| Stop | The molding against which the window sash closes, located on the inside of the window frame. Also called the bead. |
| Storm Door | An additional door placed in front of an exterior door for additional protection for weather elements. |
| Storm Window | A second window placed either inside our outside of a window to protect against bad weather and to offer increased insulation. |
| Structural Masonry Brackets | Brackets that help secure a window or door into a masonry opening. |
| Stud Pocket Mull | When two or more window units are joined vertically, but an amount of space is left in between for a supporting unit (stud). |
| Sub-sill | An additional part of a window frame under the sill that catches the rain water that travels through the window frame and releases it away from the wall of the building. |
| Sun Control Film | A reflective or tinted film that can be applied after installation to reduce solar heat gain. |
| Super Window | A term for a window with multiple glazings, gas fills and coatings that achieves a U-factor that is less than 0.15. |
| Surround | The accent trim around a window or door. |
| Sweep | The bottom vinyl piece on a door that offers a tight seal when the door is closed by making contact with the threshold. |
| Switchable Glazings | Glazing that offers different light transmissions, changing from clear to dark or reflective with the application of voltage, light or heat. |
| T | |
| Telescoping Patio Doors | A type of sliding patio doors with as many as six panels that slide on a track and either nest at the end of the track or disappear into a pocket in the wall. |
| Tempered Glass | A type of glass that is heated and then cooled rapidly, making it much stronger than annealed glass. When broken, it shatters into small pieces without sharp edges. |
| Tenon | A rectangular extension that is cut in a piece of wood to be joined with a piece of wood with a coordinating mortise. |
| Thermal Break | An insulating material placed between two conductive elements. |
| Thermal Conductivity | The property of a certain material to conduct heat. |
| Thermal Expansion | The change in size of a material resulting from exposure to high temperatures. |
| Thermochromics | A glazing material used in windows that automatically responds to changes in temperature to control the amount of heat, light and glare that passes through the glass. |
| Threshold | The wood, stone or other material that lies at the bottom of a door frame. |
| Tilt Window | A window, either single- or double-hung, with an operable sash that is able to tilt into a room for cleaning. |
| Tinted Glass | Glass that is coated with a colored mineral mixture to reduce radiant transmittance. |
| Top-hung Screen | An insect screen used with patio doors that hangs from the top of the frame and moves side to side with rollers or guides. |
| Transition Block | A wooden piece that covers the joint between new and existing casings. |
| Transmittance | Ratio of radiation falling on a glazing, to the amount that passes through the window. |
| Transom | A window installed above another window or door, to allow extra light into a room. |
| Triple Glazing | A unit with three panes of glass, separated by two airspaces. |
| Triple Slider | A window unit with three sashes, with the center sash being stationary and the two outside sashes able to slide sideways. |
| True Divided Lites (TDL) | A window composed of multiple smaller pieces of glass separated by muntins within a frame. |
| Two-step Distributor | A term for a company that buys products directly from a manufacturer, and then sells them to a retail store, which then sells to consumers, builders and contractors. |
| U | |
| U-factor (U-value) | A measure of how much heat is allowed through a window or door. A low U-factor indicates better insulating properties. |
| USGBC | An acronym for the U.S. Green Building Council, a non-profit organization dedicated to promoting cost-efficient and energy-saving ways to design, build, maintain and operate buildings and homes. |
| UBC | An acronym for the Uniform Building Code, published by the International Council of Building Officials until 1997, which promoted safety in construction. It was replaced in 2000 by the new International Building Code (IBC), published by the International Code Council (ICC) |
| Ultraviolet Light (UV) | The invisible rays found in sunlight that cause heat buildup and can also cause fading and the deterioration of certain materials. |
| Unison Lock | A system for locking a window that secures it a two separate points using only one handle. |
| Unit Dimension (UD) | The measurement of a complete window unit, including the frame, but not including brickmould. |
| United Inch | A term coined by the window industry to ensure accurate price estimating. To calculate the united inch of a window, you would add together the height and width of a window, measured in inches. |
| Unobstructed Glass Opening | The visible glass in a window unit. |
| V | |
| Vapor Barrier | An impermeable material that keeps moisture from entering a building. |
| Vent Limiter | A device that restricts the amount a window is able to open. |
| Venting Unit | A window unit or door that is operable (able to open and close). |
| Vinyl | The common term for polyvinylchloride or PVC, a material used in replacement window and door frames. |
| Vinyl-clad Window | Windows in which the wooden parts on the exterior are covered in extruded vinyl for strength and weather resistance. |
| Visible Light | Wavelengths on the electromagnetic spectrum that are able to be seen, ranging from 380 to 720 nanometers. |
| Visible Transmittance (VT) | A rating of the NFRC that indicates the amount of light that can come into a room through a window. VT will always be a number between 0 and 1, with a higher number meaning more natural light is coming through. |
| W | |
| Warm-edge | A type of insulating glass unit that uses spacers to separate the panes of glass made of a material other than traditional aluminum that conducts less heat or cold at the edge of the glass. |
| WDMA | An acronym for the Window and Door Manufacturers Association. It is a trade organization that defines standards for the window, door and skylight industry. |
| Weatherstripping | A strip of material or a device that seals window sashes and door frames to keep out moisture and air. |
| Weep Hole | A small venting hole located at the bottom of a window frame to allow for drainage. |
| Weld | A way to fuse two components together, using heat to soften or melt the material and then pushing the pieces together. |
| Wet Glazed | Glass that is installed using a sealant that attaches it to the frame. |
| Windload | The impact of the wind's force on a structure. |
| Window | Commonly refers to a glass opening in an exterior building wall. In the window industry, it refers to the entire unit, which consists of the glass, frame, and any other elements used its operation. |
| Window Hardware | Devices built in or attached to a window, such as those for locking or opening and closing. |
| Window Opening Control Device (WOCD) | A safety device that keeps a window from opening more than 4 inches, which can be disengaged in emergencies. |
