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Glossary of Window Terminology

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AAMA	American Architectural Manufacturers Association. A national trade association that establishes voluntary standards for the window, door, storefront, curtain wall, and skylight industries.
Absorptance	The ratio of radiant energy absorbed to total incident radiant energy in a glazing system.
Accessory Groove	A shape included on a fenestration product frame that is designed to mate with installation accessories.
Acid Etching	A process used in decorative glass where hydrofluoric acid is applied to the surface of the glass. Where the acid contacts the glass surface, the glass becomes frosted with a matte finish (similar to the effect caused by a sandblasting process). Patterns can be applied using special wax coatings on the glass. Where the glass is coated with wax, no corrosion of the surface will take place.
Acrylic	A thermoplastic with good weather resistance, shatter resistance, and optical clarity, used for glazing.
Adhesion	That property of a sealant/compound that measures its ability to bond to a surface on which it is applied
Adhesion Failure	The pulling away of a sealant/compound from the surface it is applied to, resulting in water penetration.
Aerogel	A microporous, transparent silicate foam used as a glazing cavity fill material, offering possible U-values below 0.10 BTU/(h-sq ft-?F) or 0.56 W/(sq m-?C).
Air Chambers	Small honeycomb spaces within the sash and frame which help to insulate and strengthen the window
Air Infiltration	The amount of air that passes between a window sash and frame. In windows it is measured in terms of cubic feet or air per minute, per square foot of area. The lower the number, the less air the window lets pass through.
Air Latch	Latch mechanism on the interior face of the sash that retains the window in a partially open position for ventilation.
Air leakage rating	A measure of the rate of infiltration around a window or skylight in the presence of a specific pressure difference. It is expressed in units of cubic feet per minute per square foot of window area (cfm/sq ft) or cubic feet per minute per foot of window perimeter length (cfm/ft). The lower a window's air leakage rating, the better its airtightness.
Air-leakage (air infiltration)	The amount of air leaking in and out of a building through cracks in walls, windows, and doors.
Aluminum Clad	A window or door made from wood with an exterior skin of aluminum.
Aluminum Window	A window whose frame and sashes are made from aluminum.
Angled Exterior	A sloped extension from the frame that adds an aesthetically-pleasing dimension to the exterior of the window.
Annealed glass	Standard sheet of float glass which has not been heat-treated.
Annealing	Heating above the critical or recrystallization temperature, then controlled cooling of metal, glass, or other materials to eliminate the effects of cold-working, relieve internal stresses, or improve strength, ductility, or other properties.
ANSI	American National Standards Institute - a clearing house for all types of standards and specifications.
Apron	The inside trim piece that lies flat against the wall beneath the stool (interior sill extension). This is a traditional treatment usually associated only with double hung windows.
Argon	An inert colorless gas which has good thermal resistance properties. Argon gas is commonly used to fill the air cavity between panes of glass in an IG unit, in order to improve the insulating properties of the unit.
Argon gas	Argon is a safe, odorless, colorless, non-toxic, non-flammable inert gas that is commonly used in place of air between the glass panes of an insulated Low-E glass unit.
ASHRAE	American Society of Heating, Refrigerating and Air Conditioning Engineers.
ASTM	American Society for Testing and Materials. Organization that sets standards for testing of materials.
Astragal	The center member of a double door, which is attached to the fixed or inactive door panel.
Awning Window	A window unit which projects outward toward the exterior of the building as it opens. Hinges at the top of the side frame members, permitting the sash to open up and out like an awning.
Azurelite Glass	An aquamarine-tinted solar glass designed for controlling heat exchange through the glass panel.
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Backer Rod	A material placed into a joint, primarily to control the depth of the sealant. Also serves as a bond breaker.
Balance	A mechanical device (normally spring-loaded) used in single- and double-hung windows as a means of counterbalancing the weight of the sash during opening and closing.
Balance (Sash Balance)	A system of cords and pulleys (block and tackle) or spring friction devices which help in raising double hung sash and keep it in any position by counter balancing the sash's weight. This mechanical device is mounted in the jamb. The two most common types are currently the coil and spiral balances.
Balance Shoe	Part attached to bottom of balance that attaches balance to sash. A bar or pin on the sash fits in a "slot" in the shoe.
Balance Spring	A device for counterbalancing a sliding sash, generally associated with a double-hung window, so that it can be held open at a position. See Sash Balance.
Balance System	Device for holding vertically sliding sash in any desired position through the use of a spring or weight to counterbalance the weight of the sash.
Basement Sash Unit	(cellar sash unit) - A sash unit, usually of the in swinging or hopper sash type, used for basement or cellar sash openings; usually consists of one, two or three glass lites (lights); may include screens and storm panels.
Basic Unit	This term is given to the fundamental "building block" units of each standard window product line. These units are members of a series of standard sizes. They lack exterior trim or installation flanges but are otherwise complete.
Bay Window	A composite of three or more windows, usually made up of a large center unit and two flanking units at 30?, 45? or 90? angles to the wall.
Bead	A sealant/compound after application in a joint. Also a molding or stop used to hold a glass product in position.
Bent Glass	Flat glass that has been shaped while hot into cylindrical or other curved shapes.
Bevel	A machine angle other than a right angle, i.e., a 3 bevel is equivalent to a 1/8 inch drop in a 2 inch span (1mm in 16mm).
Beveled Exterior	An angled extension from the frame that adds an aesthetically-pleasing dimension to the exterior of the window.
Beveling	The removal of material on a glass surface by abrasion, which causes the edge to slope. This is a common practice on mirror glass to finish the edge of the mirror.
Big Box	A term used to refer to large home center chains like Lowe's, Home Depot, and Menards.
Bite	The dimension by which the edge of a glass product is engaged into the glazing channel.
BIY	Buy-It-Yourself. Usually refers to home owners who purchase home improvement projects then hire a constractor to perform the installation.
Blackbody	The ideal, perfect emitter and absorber of thermal radiation. It emits radiant energy at each wavelength at the maximum rate possible as a consequence of its temperature, and absorbs all incident radiance.
Blind Stop	A sash or window frame member applied to the exterior vertical edge of the side and head jamb in order to serve as a stop for the top sash and to form with the brick moulding and/or casing a rabbet for the storm sash, screens, blinds and shutters.
Block	Rectangular, cured sections of neoprene or other approved material, used to position the glass product in the glazing channel.
Block Frame Window	Used when replacing the wood sash of an old double hung wood window.
BOCA	Building Officials and Code Administrators.
Bottom rail	The bottom horizontal member of a window sash.
Bow Window	An angled combination of windows in 3-, 4- or 5-lite configurations. The windows are attached at 10-degree angles to project a more circular, arced appearance. Butyl
Breather Tube	See Venturi Tube
Brick Molding	An exterior (milled) trim piece to cover the gap between the window frame and masonry in a masonry opening or in other siding.
Brick Mould	A form of exterior trim (casing) for windows and doors. In addition to serving as an anchor point for installation of the unit brick mould provides a boundary for brick or other siding material on the face of the building and attachment of hardware. (Sometimes called Shake mould).
Brickmold	A type of external casing which frames windows and doors.
Bronze-Tint Glass	Glass tinted with a light bronze coloring used to reduce the amount of light transmitted through the pane. This glass is predominantly used in southern locations where light intensity from the sun is stronger.
Btu (B.T.U.)	An abbreviation for British Thermal Unit, the heat required to increase the temperature of one pound of water one degree Fahrenheit.
Buck	A jamb stud or header; wood buck. Rough framework to which a window or door is installed.
Buck Opening	The opening in a wall formed by the rough framing members; also stud opening.
Bullet-Resistant Glass	A multiple lamination of glass with tough clear sheet plastic, usually at least 1 3/16 inches thick overall, which is designed to stop bullets from ordinary firearms other than high-powered rifles.
Butt Glazing	The installation of glass products where the vertical glass edges are without structural supporting mullions.(See also Channel Glazing).
Butt Joint	A joint formed by square edge surfaces (ends, edges, faces) coming together; end butt joint, edge butt joint.
Butyl	A sealant compound commonly used in the production of insulated glass units.
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Cam Lock and Keeper	The mechanisms which pull the sash together when placed in the locked position.
Caming	Grooved, usually H-shaped, rod of cast lead used, as in stained glass, to hold the panes or pieces of glass together.
Cap/Capping	Cosmetic covering, usually found on the exterior of the window or door to achieve aesthetic sight lines or to integrate the window or door system into the building surface or weatherproofing system. If panning is being used for weatherability, the panning is not considered cosmetic, but part of the window system.
Capillary Tubes	Small hollow tubes which penetrate the spacer system of an insulating glass unit. They allow pressure equalization between manufacturing locations, shipping, and installation locations. Since the insulating glass unit is not permanently sealed, the air space cannot be filled with Argon gas.
Casement	A window sash that swings open on side hinges; in-swinging are French in origin; out-swinging are from England.
Casement Window	A projecting window with a single sash hinged at the sides and usually opening outward like a door and operated by a (crank) handle which turns to open or close the unit.
Casing	(Trim): Exposed molding or framing around a window or door, on either the inside or outside, to cover the space between the window frame or jamb and the wall.
Caulk	To seal cracks and joints around window and door frames to prevent leakage of water and air.
Caulking	A mastic compound for filling joints and sealing cracks to prevent leakage of water and air, commonly made of silicone, bituminous, acrylic, or rubber-based material.
Center of Glass U- and R-values	The U- and R-values measured from the center of the glass to 2-1/2" from the frame.
Center Swinging Patio Door	A center swinging patio door attempts to project the feeling of an authentic French door but it differs in two major ways: A. Panel(s) is permanently fixed B. The operating panel is not hinged on the side jamb-instead the panel is hinged from a special structural mull in the center of the unit.
Certified IG Unit	An insulating glass unit constructed like a unit test model, that has successfully passed the ASTM E773 and E774 tests of insulating glass seal durability performance at specific levels.
CFM	Cubic Feet per Minute.
Channel Glazing	The installation and sealing of glass products into U-shaped glazing channels employing removable strips.
Check Rail	On a double-hung window, the bottom rail of the upper sash and the upper rail of the lower sash, where the lock is mounted.
Chemically-Strengthened Glass	Glass which has undergone ion-exchange to produce a comprehensive stress layer.
Chlorinated PVC	Produced by the post chlorination of polyvinyl chloride resins. Used extensively in pipe, fittings, and valves in water piping systems.
Circle Top Transom	A half-circle window over a door or window, with radiating bars.
Circle Top Window	A window having a curved (radius) top and a flat bottom. The shape of the window is an exact half-circle with the height being exactly one-half of the width. Also called circle head, half-circle and half-round.
Circlehead	A generic term referring to any of a variety of window units with one or more curved frame members, often used over another window or door opening.
Clad	A designation given to products whose exposed exterior surfaces are sheathed with specially formed aluminum.
Cladding	Any material locked to the outside faces of doors and windows to provide a durable, low-maintenance exterior surface.
Clerestory window	A venting or fixed window above other windows or doors on an upper outside wall of a room.
Co-Extrusion	The technique of extruding two or more materials through a single die being fed by separate extruders.
Cohesive Failure	The splitting and opening of a sealant/compound within its body, resulting in water penetration.
Combination Storm Sash and Screen	A frame assembly of stiles and rails containing a half screen and two glass storm panels; in summer the bottom storm panel is stored in the top of the combination frame and replaced by the screen panel; sometimes called "combination storm sash and screen unit" or simply "combination window unit".
Complete Window Replacement	The installation of a replacement window where the previously-installed window is completely removed and replaced with a new frame/sash unit.
Composite	Window and door members which are comprised of two or more materials, which are structurally combined or connected so as to perform structurally as a singular material; i.e., poured and debridged aluminum shapes, fiberglass and man-made wood products, etc.
Composite frame	A frame consisting of two or more materials for example, an interior wood element with an exterior fiberglass element.
Compound	A formulation of vehicle, fillers and polymer(s) producing an elastometric sealant.
Condensation	The deposit of water vapor from the air on any cold surface whose temperature is below the dew point, such as a cold window glass or frame that is exposed to humid indoor air.
Condensation Resistance Factor	A measure of the effectiveness of a window or glazing system to reduce the potential for condensation. The higher the condensation resistance factor, the more efficient the window and glazing system.
Conduction	Heat transfer through a solid material by contact of one molecule to the next. Heat flows from a higher-temperature area to a lower-temperature one.
Contractor	A business entity that is hired by a person or business to perform a specific job or function.
Convection	A heat transfer process involving motion in a fluid (such as air) caused by the difference in density of the fluid and the action of gravity. Convection affects heat transfer from the glass surface to room air, and between two panes of glass.
Core	Insulating or other center material used in the door.
Cottage Style Window	A window with the meeting rail located off-center of the frame.
Coved Exterior	An arced extension from the frame that adds an aesthetically-pleasing dimension to the exterior of the window.
Crack length	Total outside perimeter of window vent. Used in figuring air infiltration during AAMA certification testing.
Crackle Glass	To produce the crackle effect, the glass is submerged in water during the curing process to cause the surface to crack. A second layer of glass is then applied and the entire unit is re-heated in order to fuse the glass together.
CRF	Condensation Resistance Factor. An indication of a window's ability to resist condensation. The higher the CRF, the less likely condensation is to occur.
Cripple Stud	A short stud above or below a window or door opening.
Cripples	The short 2" x 4" members used to frame under the sill or above the header in a rough opening for a window in a frame wall.
Crystal Sheet Glass	Sheet glass with a thickness between 0.180" to 0.199" (4.50 to 5.50 mm) or approximately 3/16" thick. Used in very large window units.
Cullet	Broken glass, excess glass from a previous melt, or edges trimmed off when cutting glass to size. Cullet, in some regular proportion, is an essential ingredient in the raw batch charge in glassmaking - in that it facilitates melting.
Curb	A watertight wall or frame used to raise slope glazing above the surface of the roof as a preventive measure against water leakage from melting snow or rain run-off.
Curing Agent	One part of a two-part sealant that, when added to the base material, causes it to vulcanize by chemical reaction.
Curtainwall	An exterior building wall which carries no roof or floor loads and consists entirely or principally of metal or a combination of metal, glass, and other surfacing materials supported by a metal framework. There are two basic types: Custom: Walls designed specifically for one project and using parts and details specially made for this purpose Standard: Walls made up principally of parts and details standardized by their manufacturer and assembled in accordance with either the architect's design or the manufacturer's stock patterns.
Cylinder Lock	Lock in which keyhole and tumbler mechanism are contained in a cylinder separate from the lock case.
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DADO	Rectangular groove recessed into a wood door frame.
Daylight Opening	The portion of a window or door's glazing which is actually visible. A small percentage of a unit's glass will always be concealed as it is mounted in the wood parts.
Dead Bolt	Lock bolt having neither spring action nor bevel and is operated by a key or a turn piece.
Dead Lite	A non-operable lite which is fixed to the structure.
Dead Loads	Load force due to glass weight.
Dead-air space	The space between the panes of glass of an I.G. Unit.
Deadlite	A piece of glass or IGU with a sash profile around it; not set within the main frame of a window unit.
Dealer	A business entity that typically deals in a small range of products and sells to an end user.
Degree Day	A unit that represents a one-degree Fahrenheit deviation from some fixed reference point (usually 65? F) in the mean, daily outdoor temperature. See also heating degree day.
Desiccant	A drying agent usually in granular form (similar to silica gel) used by some manufacturers between the panes of insulating glass (in edge spacer) to prevent "fogging" between the panes.
Dewpoint	The temperature at which water vapor in air will condense at a given state of humidity and pressure.
Dimensional Windows	Custom units created by reducing the size of existing standard units. Dimensional units cannot be smaller in size than the smallest standard size nor larger than the largest standard size.
Direct Set	Refers to window units which do not have sash. The glass is mounted directly into the frame. Units of this type do not operate.
Divided Light	A window with a number of smaller panes of glass separated and held in place by muntins.
DIY	Do-It-Yourself. Usually referring to home owners to take on the task of home improvements.
DOE-2.1E.	A building-simulation computer program used to calculate total annual energy use.
Dome	the spherical shape associated with skylights.
Door Jamb	The part of a door frame which surrounds and contacts the edges of the stiles and top rail of a door; jambs may be classified as (1) "head or "side" jambs and (2) "plain" or "rabbeted".
Door Skin	Sheet of material (wood, steel, fiberglass, PVC, etc.) that forms the exterior faces of the door.
Door Slab	A door without lites or sweep installed.
Dormer	A space which protrudes from the roof of a house, usually including one or more windows.
Double Glazed Units	Units consisting of two lites of glass and one air space in between.
Double Glazing	In general, two thicknesses of glass separated by an air space within an opening to improve insulation against heat transfer and/or sound transmission. In factory-made double glazing units, the air between the glass sheets is thoroughly dried and the space is sealed airtight, eliminating possible condensation and providing superior insulating properties.
Double Hung Replacement System	A packaged system furnishing new sash and operating block and tackle mechanism powered by springs or weights (balance). For replacement of sash only in double hung windows found in older buildings.
Double Hung Window	Two sash which move vertically, by-passing each other in a single frame. Sash may be counter-balanced by weights or springs.
Double or Dual Glazing	Use of two panes of glass in a window to increase energy efficiency and provide other performance benefits.
Double Pitch Design	pertaining to two opposite roof slopes, e.g., sloping North and South; also referred to as a ridge connection.
Double Strength	A glass thickness designation. In float glass, approximately 1/8" thick.
Double Strength Glass	(DSB) 1/8" thickness.
Drip Cap	A piece of flashing which is contoured for application on top of windows and doors during installation. Its purpose is to prevent water from seeping down behind the casing and invading the interior of the wall. For Clad windows this item is often incorporated into the head nailing flange.
Dry Glazing	An alternative method of placing glass in a door or window. No glazing mastic is used. Dry glazing is recommended whenever reflective coatings are glazed to first surface.
Dual Durometer	A material that has two or more levels of flexibility. An example is the weatherstripping used between the frame and sash of a casement window.
Dual-Sealed Units	Sealed insulating glass units fabricated with an inner primary seal and an outer primary seal. Generally, each of the two seals has been selected for its special performance characteristic, i.e., adhesion and moisture vapor transmission properties.
Durometer	A gauge used to measure the hardness of an elastometric material.
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Edge Clearance	Nominal spacing between the edge surface of the glass product and the glazing channel base.
Edge Effects	Two-dimensional heat transfer at the edge of a glazing unit due to the thermal properties of spacers and sealants.
Edge Glued	A method of developing wood composites to provide wood parts with greater width. The width is achieved by gluing the smaller component wood pieces edge to edge.
Edging	The finishing or shaping of the edge surfaces of glass. This process is usually done with an abrasive wheel as a grinding process.
Egress	Literally, an exit (a means of exit). Actual open size determined by local building code.
Egress Code	The code that requires a minimum opening of a window for persons to exit or firefighters to enter a building.
Egress Window	a window with specific release hardware and minimum clear opening size to allow occupants to escape through the window in case of a fire.
Elastometric	Having the property of returning to its original shape and position.
Electrochromics	Glazing with optical properties that can be varied continuously from clear to dark with a low-voltage signal. Ions are reversibly injected or removed from an electrochromic material, causing the optical density to change.
Electromagnetic Spectrum	Radiant energy over a broad range of wavelengths.
Electrostatic	a painting process by which the aluminum is grounded and the paint carries a positive electric current. This creates a magnetic attraction between the paint and the aluminum allowing for uniform paint coverage on extrusion surfaces that are exposed when the assembled window is installed and closed.
Emergency Exit Window	Fire escape window (egress window) large enough for a person to climb out. In U.S. building codes, each bedroom must be provided with an exit window. The exact width, area, and height from the floor are specified in the building codes.
Emissivity	The ability of a material to emit radiant energy. Emittance is the ratio of the total radiant energy emitted by a given surface to that emitted by an ideal black body at the same temperature. To emit is to give out, to discharge - in the case of glass, essentially, to reradiate absorbed energy (heat).
Emittance	The ratio of the radiant flux emitted by a specimen to that emitted by a blackbody at the same temperature and under the same conditions.
Energy Panel	This device is a single piece of glass whose edges are protected by an aluminum surround. Its purpose is to increase thermal efficiency on single glazed, 15/16" bar true divided lite units.
ENERGY STAR?	ENERGY STAR? is an independent U.S. government program establishing a standard set of guidelines to recognize the energy efficiency of various products. ENERGY STAR? guidelines are used in conjunction with a variety of building materials, including windows and patio doors. Over the past ten years, ENERGY STAR? guidelines have helped double the efficiency of windows they endorse
Entrance Door	A door on the front entrance of a structure; also "front" or "main" entrance door; may be single or in pairs.
Equivalent Combined Glass Load	Combination of the instant applied load of wind and the factored long-term loading of glass weight and snow accumulation.
Escutcheon	Ornamental shield or plate mounted behind the knob, "surrounding" the lock base.
Evacuated Glazing	Insulating glazing composed of two glass layers, hermetically sealed at the edges, with a vacuum between to eliminate convection and conduction. A spacer system is needed to keep the panes from touching.
EWS	See Exact Window Size
Exact Window Size (EWS)	The dimensions of a window or door unit measured along the outside of the frame.
Extension Casement Hinge	A hinge for a casement window which provides clearance for cleaning the two sides of the sash from the inside.
Extension Jambs	Flat parts made of vinyl, wood or other materials which are attached to the inside edges of a window jamb to extend it in width to adapt to a thicker wall.
Exterior Glazed	Glass set from the exterior of the building
Exterior Stop	The removable glazing bead that holds the glass or panel in place when it is on the exterior side of the light or panel, in contrast to an interior stop located on the interior side of the glass.
Extrude	the process of shaping aluminum or vinyl by forcing it through a die.
Extruded Screen Frame	Different from a Roll formed frame, this frame is pressed through a form or die.
Extruder, Compounding	The basic functions of a compounding extruder are to melt the polymer and evenly disperse and distribute additives or fillers to obtain the specifications of the end product. Large-scale compounding is done on either single or twin-screw extruders. Single screws are used for basic operations where little variation in material formulation and viscosity is expected. Twin screw compounders offer better conveyance characteristics.
Extruder, Single Screw	Basic machine consists of a screw, barrel, drive mechanism, resin feed arrangement, and controls. The constantly turning screw augers the resin through the heated barrel where it is heated to proper temperature and blended into a homogeneous melt. Before the melt can leave the barrel, it must pass through a breaker plate and screen pack. This unit builds up back pressure in the barrel, filters out contaminants, and tends to convert turbulent melt flow into more laminar flow. The melt is then extruded through the die into the desired shape.
Extruder, Double Screw	Two screws, side by side, are placed within the extruder barrel, and they are either co-rotating or counter-rotating. Counter-rotating twin screw extruders are used primarily for processing PVC products such as pipe, siding, sheet, pellets, and film. The co-rotating units are used for compounding materials where thorough mixing and high output rates are important. The twin screw unit resembles a positive displacement screw pump. It conveys the material at low speeds with controlled shear. The positive action assures that all portions of the material experience a uniform residence time.
Extrusion	A process for the production of continuous strips of material formed to a specific shape or profile. The material is forced through a die which has been cut to match the desired profile. As the material is extruded through the die, it is cut to the desired length and allowed to cool. This process is very common in creating frame and sash materials, as well as glass insulating spacers and glazing sealers.
Eyebrow Window	Today, used to identify certain arch-topped or radius-topped windows that have a curved top like the shape of a human eyebrow. In older homes, low, inward-opening windows with a bottom-hinged sash. These attic windows built into the top molding of the house are sometimes called 'lie-on-your-stomach'
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Factory-Glazed Pyramid	pyramid-shaped skylights for commercial or residential use, offered in standard sizes ranging from 4'0" to 8'0", in a 7:12 roof pitch. Arrive assembled and factory glazed to the job site ready to set on a prepared curb eliminating on-site installation. Also known as the pre-glazed pyramid skylight.
Failed IG Units	An insulated glass unit failure exhibits permanent material obstruction of vision through the unit due to the accumulation of dust, moisture or film on the internal surface of the glass. Surface numbers 2&3 in double-glazed units, or surface numbers 2, 3, 4, & 5 in triple-glazed units are the affected surfaces.
Fanlight	A half-circle window over a door or window, with radiating bars. Also called circle top transom.
FCR	Fenestration Cooling Rating. A rating number developed by the National Fenestration Rating Council to indicate relative performance during the cooling season. A higher FCR indicates better cooling season performance.
Fenestration	An architectural term referring to the arrangement of windows in a wall. From the Latin word, "fenestra," meaning window.
Fenestration	An architectural term referring to the arrangement of windows in a wall. From the Latin word, "fenestra," meaning window.
Fenestration Product	Any transparent or translucent material plus any sash, frame, mullions, dividers, in the envelope of a building, including but not limited to: windows, sliding glass doors, french doors, skylights, curtain walls, and garden windows.
FHR	Fenestration Heating Rating. A rating number developed by the National Fenestration Rating Council to indicate relative performance during the heating season. A higher FHR indicates better heating season performance.
Fiberglass	A composite material made by embedding glass fibers in a polymer matrix that is pulled through a die to create a shape.. May be used as a diffusing material in sheet form, or as a standard sash and frame element.
Fiberglass Window	A window whose frame and sashes are made from Fiberglass.
Finger Joint	A method of joining wood parts end to end by machining a series of finger-like grooves in their ends. As they are interlocked, the fingers are bonded together with adhesive.
Finger-Jointing	A means of joining individual pieces of wood together to form longer lengths. The ends of the pieces are machined to form a set of interlocking fingers, which are then coated with adhesive and meshed together under pressure.
Fire Rated Doors	A door which has been constructed in such a manner that when installed in an assembly and tested it will pass ASTM E-152 "Fire Test Of Door Assemblies," and can be rated as resisting fire for 20 minutes, 30 minutes, 45 minutes (C), 1 hour (B), or 1-1/2 hours (B). The door must be tested and carry an identifying label from a qualified testing and inspection agency.
Fixed Light	(Fixed Sash): Window which is non-operative (does not open).
Fixed Lite	A pane of glass installed directly into non-operating framing members; also, the opening or space for a pane of glass in a non-operating frame.
Fixed Lite or Fixed Sash	Non-operable section of a window (example: the top sash of a single-hung window.)
Fixed Panel	An inoperable panel of a sliding glass door or slider window.
Fixed Window	Non-venting or non-operable window. Also known as picture window.
Flanker	The designation given to units that flank a center picture unit in a double or triple combination or bay window.
Flashing	Sheet material that protects and bridges the joint between the window or door frame members and the adjacent construction for the purpose of preventing water penetration by draining water away from the window or door to the exterior. See also Through-wall flashing.
Flat Casing	An exterior trim alternative to brick mould. This stock does not have a profile but is simply surfaced flat on four sides.
Flat Glass	All types of glass (rolled, float, plate, etc.) produced in a flat form, regardless of the method of production.
Float glass	Glass formed by a process of floating the material on a bed of molten metal. It produces a high-optical-quality glass with parallel surfaces, without polishing and grinding.
Flush Fin	A replacement window with flush fin is used when replacing an existing aluminum sliding window. This is the most commonly used replacement window type.
Foam Spacer	Foam material placed in the airspace of the insulating glass in a window to enhance the appearance and improve the performance of the window.
Fogging	A deposit of contamination left on the inside surface of a sealed insulating glass unit due to extremes of temperatures or failed seals.
Folding Glass Wall	a folding stackable glass wall system capable of opening up to 92% of the original rough opening. Commonly used to separate rooms or to install around pool enclosures.
Frame	The enclosure in which window sash or door panels are mounted. The outer components of a window unit-side jambs, head jamb and sill (bottom jamb). These parts Frame" the sash in an operating window and form an immediate boundary for the glass in a direct fixed unit.
Frame Dimension	Measurement from outside of side jamb to outside of side jamb or from outside of head jamb to outside of sill (bottom jamb).
French Door	An interior or exterior door consisting of stiles, top and bottom rail and divided glass panels or lights; often used in pairs; "casement" or "terrace" door.
French Hinged Door	Hinged door(s) which have wider panel members around the glass.
French Patio Door	A type of swinging patio door which features two operating panels. One panel is designated as the active panel and is equipped with the active handle and latch set. The secondary inactive panel is equipped with flush bolts at head and sill allowing it to be fixed in place or to swing freely. The unit which has just been described is a Traditional or authentic French door.
French Sliding Door	A sliding door which has wider panel members around the glass, giving the appearance of a French hinged door.
Friction Hinge	A window hinge, which remains open at any position by means of friction in the hinge.
Frit	A batch material which is melted with other materials and then ground into powder. This powder is applied to the glass and heated during the tempering process, which fuses the material into the glass surface. This process is commonly used to create logos and identification markings permanently imbedded on the glass surface.
Full Screen	A screen which covers the entire opening of a window.
Fully-Tempered Glass	Glass that has been tempered to a high degree. Specified by the ASTM C 1048 (Kind FT) as having a surface compression of not less than 10,000 pounds per square inch (PSI) or an edge compression of not less than 9,200 PSI. Fully-tempered glass, if broken, will disintegrate into many small pieces (dice) which are more or less cubical. Fully-tempered glass is four to five times stronger than annealed glass of the same thickness.
Fusion Welding	The process of heating mitered corners to 2008 F and bringing the heated corners into contact until they fuse together into a single piece of vinyl.
Fusion-Welded	The process of joining materials by melting them together with extreme heat (over 500?F), resulting in the materials uniting into a one-piece unit.
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Gas Fill	A gas other than air, usually argon or krypton, placed between window or skylight glazing panes to reduce the U-factor by suppressing conduction and convection.
Gas-Filled Units	Insulating glass units with a gas other than air (usually an inert gas such as argon or krypton) in the airspace between the panes. This is done to decrease the unit's thermal conductivity (U-value) and increase the unit's sound insulating value.
Gasket	A pliable, flexible continuous strip of material used to affect a watertight seal between sash and frame of roof windows much like the seal around a refrigerator door.
General Contractor	Usually the head contractor of a building project who coordinates sub-contractors and material suppliers in the completion of a construction project.
Geometric	Specially designed windows classified as either Straight line Geometrics such as rectangles, triangles, trapezoid, octagons, pentagons, etc., or Radius Geometrics which include half-rounds, quarter-rounds, full-rounds, sectors, ellipses, eyebrows, etc.
Geometric Windows	These are specialty windows classified as either of two types: A. Straight Line Geometrics, rectangles, triangles, trapezoid, octagons, pentagons, etc. B. Radius Geometrics-half rounds, quarter rounds, full rounds, sectors, ellipses, etc.
GIA	See Grids In the Airspace
Glass	An inorganic transparent material composed of sand (silica), soda (sodium bicarbonate), and lime (calcium carbonate) with small quantities of alumina, boric or magnesia oxides. Available Styles: Clear, Bronze, Grey and Tinted. ?
Glass (Insulating)	Two sheets of glass bonded together in a unit to enclose a captive air space. In the case of Xi welded glass, the edges are melted together and the air space is filled with an inert gas. Organic units have a hollow metal spacer around the perimeter and edges are sealed with an organic substance. These spacers must be filled with a desiccant, which is a chemical to absorb and hold any moisture trapped in the air space. The latest insulating units use Butyl, Silicone Foam and other non-conductive spacers at the edge for reduced thermal conduction. (Also called warm-edge.)
Glass Size	Actual Glass size, not merely that which is visible.
Glazed Sash	A sash in which the glass has been installed.
Glazing	Glass in a window or door; the act or process of fitting with glass.
Glazing (Double)	A single glazed sash with an additional glass panel installed on the sash to provide an air space between the two lites of glass. The second glass can either be removable (RDG) or fixed and can be installed on either the inside or outside of the sash. Double glazing differs from insulating glass in that there is no positive seal around the edges of the two lites of glass to provide a true dead air space and there's no desiccant within the unit to absorb and hold moisture.
Glazing (Single)	A single sheet of glass installed in a window sash.
Glazing bead	A plastic or wood strip applied to the window sash around the perimeter of the glass.
Glazing Block	A small, hard rubber block placed around the edges of the glass unit in a window sash to position the glass and prevent it from shifting.
Glazing Channel	A three-sided, U-shaped sash detail into which a glass product is installed and retained by a removable stop.
Glazing Channel Depth	The measurement from the bottom of the glazing channel to the top of its stops.
Glazing Channel Width	The measurement between the stationary stop and the removable stop.
Glazing Compound	A pliable substance applied between the window sash and the lites of glass to seal against the elements and sometimes to adhere the glass to the sash.
Glazing Stop	The part of the sash or door panel which holds the glass in place.
Glazing Tape	Double-sided tape used to adhere glass to sash and form an airtight, watertight seal.
Glazing (Triple)	A sash glazed with three lites of glass, enclosing two separate air spaces. This can be accomplished by applying a storm panel that is glazed with insulating glass or on some units by applying inside and outside storm panels to a single glazed sash.
Glazing	The glass or plastic panes in a window, door, or skylight.
Gliding Window or Door	Same construction as a sliding window. The moving sash generally travels on rollers.
Greenhouse Window	A three-dimensional window that projects from the exterior wall and usually has glazing on all sides except the bottom, which serves as a shelf.
Grids	Decorative horizontal or vertical bars installed between the glass panes to create the appearance of the sash being dividing into smaller lites of glass .
Grids in the Air Space	Grids mounted between the two panes of glass of an insulated glass unit.
Grille	A term referring to windowpane dividers or muntins, usually a type of assembly which may be detached for cleaning.
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Half Screen	A screen which does not cover the entire opening of a window. Used on the bottom half of single hung units and on the operating sash of single sliders.
Hard Coat	A term used for a type of Low-E glass that is usually less expensive and a lower performing type of Low-E glass. Sometimes referred to as 'Pyrolytic Low-E".
Head	The main horizontal member forming the top of the window or door frame.
Head Board	A flat board cut to fit the contour of a bow or bay window and installed between the head jambs and the flat wall surface to finish off that area which would normally be ceiling.
Head Expander	An inverted U-channel installation accessory that may be fitted to the head of a replacement window to accommodate differences between rough opening and window heights.
Head Jamb	Also called "header" or "head": Cross or horizontal jamb member forming the top of the frame.
Head Track	The track provided at the head of a sliding glass door. Also, the head member incorporating the track.
Header	A horizontal framing member placed over the rough opening of a window to prevent the weight of wall or roof from resting on the window frame.
Heat Fusion	(welding) method to join PVC frame and/or sash members by heating the cut ends, squeezing them together, and allowing the assembly to cool.
Heat Gain	The transfer of heat from outside to inside by means of conduction, convection, and radiation through all surfaces of a house.
Heat Loss	The transfer of heat from inside to outside by means of conduction, convection, and radiation through all surfaces of a house.
HEAT MIRROR?	A thin transparent insulating film that is inserted between double glazing which permits transmission of visible light but reflects far-infrared radiation. Heat Mirror? is a registered trademark of Southwall Technologies.
Heat Mirroring	The coating applied to a glass surface which has a reflective property which is effective in reducing the thermal transmission of heat through the glass.
Heat Mirror? Unit	a triple-ply insulating glass unit (IGU) utilizing a polyester internal film with a special coating to reflect heat, but allows light to pass through. Heat Mirror is a trademark of Southwall Technologies Inc.
Heat Transfer Coefficient (U-Value)
Heat Treating	the process where glass or aluminum extrusions are heated and cooled to make these materials harder and stronger.
Heat-Absorbing Glass	Glass for intercepting appreciable portions of radiant energy, especially solar energy, in specific transmittance values as defined in ASTM C 1036. It is obtainable as float or patterned glass.
Heating Degree Day	Term used by heating and cooling engineers to relate the typical climate conditions of different areas to the amount of energy needed to heat and cool a building. The base temperature is 65 degrees Fahrenheit. A heating degree day is counted for each degree below 65 degrees reached by the average daily outside temperatures in the winter. For example, if on a given winter day, the daily average temperature outdoors is 30 degrees, then there are 35 degrees below the base temperature of 65 degrees. Thus, there are 35 heating degree days for that day.
Heat-Resisting Glass	Glass able to withstand high thermal shock, generally because of low coefficient of expansion.
Heat-Strengthened Glass	Glass that has been heat-treated to a state less than that of fully-tempered glass. Specified by the ASTM 1048 (Kind HS) as having a surface compression of not less than 3,500 pounds per square inch (PSI) or greater than 10,000 PSI or an edge compression of not less than 5,500 PSI. Heat-strengthened glass is approximately two times as strong as annealed glass of the same thickness and has a much increased thermal endurance. Heat-strengthened glass is not considered a safety glass and will not completely dice as will a fully-tempered glass.
Heat-Treated	Term sometimes used for both fully-tempered glass and heat-strengthened glass.
Heavy Float Glass	Used in furniture, tabletops, storefronts.
Hermetically Sealed Unit	An insulating glass unit made up of two lites of glass, separated by a spacer, or equivalent product (at the full perimeter), which is filled with a moisture absorbing material. The unit is then completely sealed, creating a moisture-free, clean, dead-air space.
High Transmission Glass	Glass which transmits an exceptionally high percentage of visible light.
Hinge	A movable joint enabling a window or door to swing open.
Hinge Mortise	The area cut away to accept the hinge leaf for mounting on the door frame or door edge.
Hinge Stile	Stile to which the hinges are applied, as distinguished from the lock stile.
Hinged Door	An exterior or interior door hung by attached butts to the stile so that the door swings on a vertical axis; may be single (swinging thru 90 degrees) or double-acting (swinging thru 180 degrees); double-acting doors do not require a door stop; conventionally hinged.
Hinged Windows	Windows (casement, awning, and hopper) with an operating sash that has hinges on one side. See also Projected window.
Hollow Extrusion	a tubular extrusion having an enclosed cavity within it. It is usually stronger, although more costly, than a solid extrusion.
Home Center	A term used to refer to large home improvement chains like Lowe's, Home Depot, and Menards.
Hook Accessory	Accessories that snap to the hook frame and provide easy installation.
Hopper	Type of window hinged on the sides or bottom that opens at the top by swinging in or out.
Hopper Vent	Inward-opening sash hinged at the bottom (an upside-down awning window). Many basement windows are this type.
Horizontal Slider	A window with a movable panel that slides horizontally.
Hung Window	a window in which the operating sash move up and down within the master frame. The weight of each operating sash is counterbalanced with balances to permit easy operation.
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I.G. Unit (Insulating Glass Unit)	Two or more lites of glass separated by a spacer and hermetically sealed at the glass edges.
ICC	International Code Council. A national organization that publishes model codes for adoption by states and other agencies. Codes include the International Building Code (IBC) and the International Energy Conservation Code (IECC).
IECC	International Energy Conservation Code published by the ICC. The successor to the Model Energy Code, which is cited in the 1992 U.S. Energy Policy Act (EPAct) as the baseline for residential Energy Codes in the United States.
Inactive Door	A door that does not contain a lock, but is bolted when closed, and to which a strike is fastened to receive the latch or bolt of an active door.
Infiltration	Leakage of outdoor air into a house, such as through cracks around sash or window frame.
Infrared Radiation	Invisible, electromagnetic radiation beyond red light on the spectrum, with wavelengths greater than 0.7 microns.
Installation Accessories	Components supplied by the fenestration manufacturer that are specifically designed to mate or "trim out" the product with various surrounding constructions.
Installation Fin or Flange	A vinyl or metal flange inserted into or an integral part of the side and head jambs of a window unit which is used for installing it in an opening. It also affords a weather seal or flashing around the perimeter of the window frame.
Installation Holes	Holes in window or door frames that are fabricated by the manufacturer to locate and accommodate installation fasteners.
Installed Sales	A purchase of a product that includes installation.
Insulated Glass Unit (IG Unit)	A combination of two or more panes of glass with hermetically sealed space between the panes of glass. This space may or may not be filled with an inert gas, such as argon. The purpose of bonding the glass panes in this fashion is to increase the insulating properties of the unit.
Insulated Shutters	Insulating panels that cover a window opening to reduce heat loss.
Insulated Window	A window with multiple glazing that provides one or more air spaces between layers of glazing.
Insulating Glass	Two or more pieces of glass spaced apart and hermetically sealed to form a single glazed unit with one or more air spaces in between. Also called double glazing.
Insulating Glass (IG)	A combination of two or more panes of glass with a hermetically sealed air space between the panes of glass. This space may or may not be filled with an inert gas, such as argon.
Insulating Glass Unit (IGU)	two pieces of glass spaced apart and hermetically sealed to form a unit with an air space between. Heat transmission through this type of glass may be as low as half that without such an air space.
Insulating Value	See U-factor.
Insulation	Construction materials used for protection from noise, heat, cold or fire.
Interior Glazing	Glass set from the interior of the building.
Interlayer	A layer of standard or polycarbonate-compatible polyvinyl butyral or of urethane, used to bind two or more pieces of glass or glass and polycarbonate sheets into a laminated unit.
Interlock	a design feature which enables sash to engage one another when closed.
Interlocker	An upright frame member of a panel in a sliding glass door which engages with a corresponding member in an adjacent panel when the door is closed. Also called interlocking stile.
Internal Grids	Grids mounted between the two panes of glass of an insulated glass unit.
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Jack Stud	Framing members, generally 2" x 4"s, which form the inside of the window or door rough opening. They run from the sole plate to the header, which is supported by them.
Jalousie	Window made up of horizontally-mounted louvered glass slats that abut each other tightly when closed and rotate outward when cranked open.
Jalousie Windows	A window composed of overlapping narrow glass, metal or wood louvers, operated by means of a crank handle for adjusting the louver angles; introduced in the 1950's.
Jamb	The main vertical members forming the sides of a window or door frame.
Jamb Liner	In a modern double-hung window, the track installed inside the jambs on which the window sashes slide.
J-Channel	Integral extension on the outside of a new construction window that eases installation on siding applications.
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K Factor	The coefficient of thermal conductivity. The amount of heat that passes through a unit cube of material in a given time when difference in temperature of 2 faces is 1? .
KD	See Knocked-Down
Keeper	The part of a window lock, mounted on an opposing surface of the window, that the lock arm locks under or into to pull the sash into a locked position and fully releases it when opened.
Keeper Rail	Sash meeting rail on to which the keeper (see lock and keeper) is mounted.
Keeper Stile	The vertical section of the sash where the keeper is attached.
Kerf	A thin cut-out in the frame to accommodate the weatherstrip flange.
Kiln	Oven used in the process of heating or melting. In glass factories, a kiln is used for tempering the glass, applying frit, etc.
King Stud	The full length stud next to a door or window opening to which the trimmer and lintel are nailed.
Knocked Down (K.D.)	Not assembled; parts for a window (or door) frame pre-manufactured for assembly at a later date on the job-site.
Krypton	An inert, odorless, colorless, tasteless, nontoxic gas which is about 12 times denser than air. It is used to replace air between the glass panes to reduce temperature transfer and deter convection. Used when a higher performance is desired than that produced with
KWH	KiloWatt Hour. Unit of energy or work equal to one thousand watt-hours.
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Laminate	A composite unit of glass and interlayer material.
Laminated Glass	Two or more pieces of glass bonded together over a plastic interlayer.
Laminating	A method of bonding an overlay(wood acrylic etc.) to a window component.
Latch (Catch/Lock)	A device which holds a window shut, such as the latch at the meeting of a double-hung window or one mounted on the stile of casement windows, often referred to as Lock.
Leaded Glass	Small, usually irregular panes of glass, sometimes vari-colored, joined together by lead or zinc muntins and bars and used primarily for decorative purposes; zinc bar glazing.
LEXAN?	A trade name for a glazing material which is extremely resistant to breakage. LEXAN? is a registered trademark of G.E.
Lift	A handle or grip installed on the bottom rail of the lower sash of a double-hung window to make it easier to raise or lower the sash.
Lift Handle	A handhold for raising and lowering the sash. Handle implies that the handhold is not continuous across the sash.
Lift Rail	Sash rail component with a molded handgrip integrated into the profile. This makes raising and lowering the sash easier.
Light or Lite	Glazing framed by muntins and/or sash in a window or door.
Light Shaft	An insulated shaft built to direct the light from a roof window or skylight through the attic to the room below.
Light-to-Solar-Gain Ratio.	A measure of the ability of a glazing to provide light without excessive solar heat gain. It is the ratio between the visible transmittance of a glazing and its solar heat gain coefficient. Abbreviated LSG.
Lineal Footage	A dimension expressing length (in feet) only. For example, the width of a unit (in inches) plus the height (in inches) x 2 divided by 12 = the perimeter measurement of the unit in lineal feet.
Lintel	A horizontal member above a window or door opening that supports the structure above.
Liquid Crystal Glazing	Glass in which the optical properties of a thin layer of liquid crystals are controlled by an electrical current, changing from a clear to a diffusing state.
Lite	A unit of glass in a window or door; it is enclosed by the sash or by muntins and bars - also called a pane.
Live Load	Load force due to weight of non-permanent attachments; people, glazing rigs, washing rigs, etc.
Lock	Device mounted on a sash meeting rail which, when coupled with a keeper, prevents the sash from being opened. Some lock designs incorporate a cam design that pulls the sash rails together for a tighter fit as it is locked.
Lock Rail	Sash meeting rail on to which the lock (see lock and keeper) is mounted.
Lock Stile	The vertical section of the sash where the cam lock is attached.
Lockblock	A concealed block the same thickness as the door stile or core which is adjacent to the inside edge of the stile at the midpoint and into which a lock is fitted.
Long-Wave Infrared Radiation.	Invisible radiation, beyond red light on the electromagnetic spectrum (above 3.5 micro meters), emitted by warm surfaces such as a body at room temperature radiating to a cold window surface.
Louvered Window	A window having louvers or slats that fill all or part of the opening. See Jalousie Window.
Low E (Emissivity) Glass	Glass with a transparent metallic oxide coating applied onto or into a glass surface. The coating allows short-wave energy to pass through but reflects long-wave infrared energy which improves the U-value.
Low E Glass	a transparent coating applied to a glass surface to separate long wave (heat) energy and short wave (light) energy. The long wave is reflected back to the heat source. The short wave is allowed to pass through the coating.
Low-Conductance Spacers	An assembly of materials designed to reduce heat transfer at the edge of an insulating window. Spacers are placed between the panes of glass in a double- or triple-glazed window.
Low-E Squared Glass:	A trade name for a particular brand of Low-E glass.
Low-Emissivity (Low-E) Glass:	A special type of glass having a transparent material fused into its surface which acts as a thermal mirror. Increases the performance of windows and doors
Low-Emittance (Low-E) Coating.	Microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface primarily to reduce the U-factor by suppressing radiative heat flow. A typical type of low-E coating is transparent to the solar spectrum (visible light and short-wave infrared radiation) and reflective of long-wave infrared radiation.
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Main Frame	The head, sill and jambs sections of a window.
Manufacturer	A business entity that builds products.
Masonry Opening	The space in a masonry wall left open for windows or door.
Mechanical Frame Window	A window where all of the fastening has been accomplished mechanically (typically with screws) rather than with welding processes.
Mechanically Fastened Frame	Refers to window or door frames fastened with screws.
Meeting Rail	The horizontal sections of a pair of sash that meet when the sash are closed. Meeting Stile The vertical section of a pair of sash that meet when the sash are closed.
Meeting Rail (Lock Rail)	One of the two horizontal members of a double-hung sash which come together.
Meeting Stile	The vertical member in a pair of stiles, as in abutting casement windows.
Mesh	Fabric made of either fiberglass or aluminum, used in the making of screens.
Metal-Clad Windows	Exterior wood parts covered with extruded aluminum or other metal, with a factory-applied finish to deter the elements.
Micron	One millionth (10-6) of a metric meter.
Mil	One thousandth of an inch, or 0.0254 millimeter.
Miter	Moulding returned upon itself at right angles. In joinery, the ends of two pieces of wood that are cut at a 45E angle abutting upon one another so as to form a right angle.
Miter Joint	Two members joined at an angle, commonly 45 degrees.
Model Energy Code (MEC)	The Model Energy Code is cited in the 1992 U.S. Energy Policy Act (EPAct) as the baseline for residential Energy Codes in the United States. It has been succeeded by the International Energy Conservation Code (IECC) published by the International Code Council (ICC).
Modular Opening	Callout opening. "M.O.".
Modular Size	Callout size. "M.S.".
Modulus	Stress at a given strain. Also tensile strength as a given elongation.
Modulus of Elasticity	The ratio of stress to strain, being an indicator of a material?s bending resistance to a load.
Monolithic	A glazing assembly construction consisting of only one lite or pane of glass, polycarbonate, acrylic, or plastic.
Mortise	A slot or rectangular cavity cut into a piece of wood to receive another part.
Mortise-and-Tenon	A strong wood joint made by fitting together a mortise in one board and a matching projecting member (tenon) in the other.
Mullion	A major structural vertical or horizontal member between window units or sliding glass doors.
Multi-Point Locking	A term used for locking hardware that engages a window sash to the frame at multiple locations with a single throw of an operator.
Muntin	Applies to any short or light bar, either vertical or horizontal, used to separate glass in a sash into multiple lights. Also called a windowpane divider or a grille.
Muntin Bar	Any small bar that divides a windows glass. Also called a grille or windowpane divider.
Muntin Grilles	Wood, plastic, or metal grids designed for a single-light sash to give the appearance of muntins in a multilight sash, but removable for ease in cleaning the window.
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Nailing Fin	An 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.
Nailing Fin (Flange)	A strip of sheet material (vinyl, Aluminum, steel etc.) which is integral to or fastened to the frame of units. This creates a flange which is a common method for installation of new construction windows and doors.
Nailing Fin	An 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.
Nail-On	Windows with nail-on fins are for new construction.
Needle Glazing	Application of a small bead of sealant/compound at the sight line by a nozzle gun.
Neodymium	A rare earth element used in its oxide form as a coloring agent to produce a violet color.
New Construction	The building of a brand new structure.
NFRC	National Fenestration Rating Council.
Nite Latch	hardware which, when extended, restricts the sash opening to a predetermined dimension.
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Obscure Glass	Any textured glass (frosted, etched, fluted, ground, etc.) used for privacy, light diffusion, or decorative effects.
Offal	In glass and lineal cutting, this is the term for scrap pieces of material left over at the end of a cutting run that are large enough to be reused for cutting hand-cut or special schedules.
Opacification	The application of a Mylar film to a glass unit to block light transmission. This process is sometimes referred to as spandrel.
Opal Glass	A translucent glass with a pearlescent finish resembling an opal in pattern and tint.
Open Sash	A sash in which the glass has not been installed.
Operable window	Window that can be opened for ventilation.
Operating Panel	In a two - door or two - panel swing or sliding door, the panel that opens.
Operator	Crank-operated device for opening and closing casement or jalousie windows.
Oriel Window	A window with the meeting rail located off-center of the frame.
OSM	See Outside Measurement
Outer Frame Member	The exterior protruding portion of a window frame which has no exterior casing.
Outside Casing	Trim or molding around a window or door on the exterior of the house. Casing usually refers to a flat board trim, typically, 3" or 4" in width.
Outside Measurement (OSM)	The dimensions of the rough opening.
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Palladian Window	A large, arch-top window flanked by smaller windows on each side.
Pan/Panning	Cosmetic covering, usually found on the exterior of the window or door to achieve aesthetic sight lines or to integrate the window or door system into the building surface or weatherproofing system. If panning is being used for weatherability, the panning is not considered cosmetic, but part of the window system.
Pane	One of the compartments of a door or window consisting of a single sheet of glass in a frame; also, a sheet of glass.
Panel	A major component of a sliding glass door, consisting of a light of glass in a frame installed within the main (or outer) frame of the door. A panel may be sliding or fixed.
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. Panning can be installed in the opening before the window, or can be attached directly to the window before installation.
Partial Window Replacement	The installation of a replacement window where some component of the previously-installed window frame will remain.
Particle Dispersed Glazing.	Glazing in which the orientation of small particles between two sheets of glass is controlled electrically, thus changing its optical properties.
Parting Bead	A vertical strip on each jamb that separates the sashes of a double-hung window.
Parting Stop	In a double-hung window, a strip of wood applied to the jamb to separate the sash.
Passive Solar Collector	Any glazed area in the walls or roof of a building pointed to the south to take maximum advantage of the sun's heat without a mechanical (or active) method of storage or distribution of the heat.
Patio Door	A glass door that slides opens and close on adjustable tandem rollers. Available in 2- or 3-lite configurations with the operable panel available in any position.
Patio Room	a modular wall system designed with single pane glass.
Patterned Glass	(Also known as rolled or rough-rolled glass) One type of rolled glass having a pattern impressed on one or both sides. Used extensively for light control and decorative glazing.
Peak Load	The maximum thermal load to be provided by a heating or cooling system in a house.
Photochromics	Glazing with the optical properties that change in response to the amount of incident light.
Picture	Non-venting or non-operable window. Also known as a fixed window.
Picture Framing Casing	The use of trim casing on all four sides of the interior of a window, resembling a picture frame when installed.
Picture Frame Casing	The use of casing on all four sides of the interior of a window, replacing the stool and apron at the sill. Also know as full-bound casing.
Picture Window	A large, fixed window framed so that it is usually, but not always, longer horizontally than vertically to provide a panoramic view.
Pivot	A mode of operation for ventilating windows which generally means the sash pivots on a central axis and turns 90 or more degrees.
Pivot Alignment System	An exclusive hinge-type system used on hung windows. This system attaches the sash to the balance, creating perfect alignment between the sash and frame, while allowing the sash to tilt inward for cleaning.
Pivot Bar	A metal post attached to a moving sash and seated in a balance shoe that allows a window sash to tilt.
Pivot Pin (Pivot Bar)	Part mounted on or in the end of the sash that fits into balance shoe and from which the sash may be tilted or pivoted in.
Pivot Window	A window with a sash that swings open or shut by revolving on pivots at either side of the sash or at top and bottom.
Plastic	The word ?Plastic? means capable of being shaped or molded to some definite form or shape during the manufacturing process and possessing the property of permanently retaining the shape into which it was molded or extruded.
Plastic Film	A thin plastic substrate, sometimes used as the inner layers in a triple- or quadruple-glazed window.
Plastics	Artificial substances made of organic polymers that can be extruded or molded into various shapes including window frames and sashes.
Plate Glass	A rolled, ground, and polished product with true flat parallel plane surfaces affording excellent vision. It is now being replaced by float glass.
Plexiglass (Acrylic)	A trade name for a clear, durable sheet plastic made of acrylic; used for safety glazing and for inside storm panels. Plexiglass is a registered trademark of Rohm & Haas.
Plumb	Vertical; to make vertical.
Pocket Sill	A deep sill (frame) design that completely surrounds the bottom edge of the sash in the closed position.
Polished Wired Glass	Wired glass that has been ground and polished on both surfaces.
Polyvinylchloride (PVC)	An extruded or molded plastic material used for window framing and as a thermal barrier for aluminum windows.
Prairie Grid Pattern	Grid pattern which is typically approximately 4 inches from the rails and styles of each lite. The intersections at the corners of the lite create a 4 inch square box in each corner.
Prime Sash	The balanced or moving sash of a window unit.
Prime Window (Primary Window)	The first window completely installed in a rough opening, which is designed to function as the sole fenestration product (contrasted with a storm window, which serves as a secondary window in conjunction with a primary window).
Primer	Factory applied coating which is designed to promote better acceptance of a paint finish overcoat on the exterior surfaces of wood windows. All exterior wood parts should be primed. Primer is not a sealant and all primed products must have finish coats applied.
Priming	Sealing of a porous surface so that compound will not stain, lose elasticity, shrink excessively, etc., because of loss of oil or vehicle into the surround. A sealant primer or surface conditioner may be used to promote adhesion of a curing type sealant to certain surfaces.
Processed Glass	Glass in which the surface has been altered by etching, sandblasting, chipping, grinding, ceramic-enameling, etc., to change its light diffusion or to give decorative effects. Either or both surfaces may be so treated. Also glass which has been further treated (edge work, tempered, stained, etc.) after forming.
Projected Window	Casements and Awnings - project out when open
Psf	pounds per square foot - a measurement of air pressure used in window testing, e.g., 1.56 psf (25 mph) or 6.24 psf (50mph).
Pull	A handle for opening a window.
Pull Handle	A handhold for sliding the sash back and forth. Handle implies that the handhold is not continuous across the sash.
Pull Rail	A handhold for sliding the sash back and forth. Rail implies that the handhold is continuous across the sash.
Pull Stile	A handhold for sliding the sash back and forth. Stile implies that the handhold is continuous across the sash.
Pultruded	A term used to define the action of creating fiberglass window and door components. Glass fiber strands coated in plastic resin are pulled through a die to create a long board like component.
Purlins	Structural members, generally horizontal, in slope glazing frames.
Push Bar	Used on awning and other projecting sash windows for opening and closing instead of a crank (gear) operator.
PVC	Poly Vinyl Chloride - in rigid frame/sash members, and in flexible gaskets.
PVC (Polyvinyl chloride):	An extruded or molded plastic material used for window framing and as a thermal barrier for aluminum windows.
Pyramid	a square base design, typical to skylights, with all four slopes rising to form a point.
Pyrolytic Coating	A coating applied during the manufacturing of the glass itself. Because they are actually part of the glass sheet, pyrolytic or "hand coat" surfaces are very durable and require no special handling.
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Quarter Round Window	Stationary or operating window with glass shaped as a quarter circle; it is often divided into separate panes by a removable grille, installed on the interior or grille between the glass.
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R Value	a measurement of heat resistance (the higher, the better). R value = the number 1 divided by the U value.
Rabbet	A two-sided L-shaped recess in a sash frame to receive glass products. Addition of a removable stop will convert it to a glazing channel.
Radiation	Wave energy transmitted directly from one object to another through the atmosphere or through transparent or translucent materials. The energy radiated is transmitted, absorbed, reflected or a combination of all three.
Rafter	the structural main "rib" of a glazed structure available in straight and bent.
Rail	The top and bottom horizontal members of the framework of a window sash.
Raised Exterior	An angled extension from the frame that adds an aesthetically pleasing dimension to the exterior of the window
Reflectance	The ratio of reflected radiant energy to incident radiant energy.
Reflective Glass	Window glass coated to reflect radiation striking the surface of the glass.
Refraction	The deflection of a light ray from a straight path when it passes at an oblique angle from one medium (such as air) to another (such as glass).
Relative Humidity Condensation Point	The relative humidity level at which visible water vapor or other liquid vapor begins to form on the surface of the sash or frame, based on an inside temperature of 70E F and an outside temperature of 0E F. The higher the percentage, the more moisture the air can hold before condensation will occur.
Relative Humidity.	The percentage of moisture in the air in relationship to the amount of moisture the air could hold at that given temperature. At 100 percent relative humidity, moisture condenses and falls as rain.
Remodel	define, per Version 1.1 of Residential Widow and Door Guidelines of the Association of Window and Door Installers. Per ASTM E631, to replace or improve a building or its parts.
Remodeling	Changing and existing structure.
Replacment Installation	Installation of a fenestration product which is designed for replacement of existing like and type, by either destructive or non-destructive installation methods.
Replacement Window	A window that is designed for and subsequently installed after removal of all or part of a previously-installed window.
RESFEN	A computer program used to calculate energy use based on window selection in residential buildings.
Retail	Selling a product directly to the end user.
Retrofit	define, per Version 1.1 of Residential Window and Door Guidelines of the Association of Window and Door Installers. Per ASTM E631, to add new materials or equipment not provided at the time of original construction.
Retrofitting	Adding or replacing items on existing buildings. Typical retrofit products are replacement doors and windows, insulation, storm windows, caulking, weatherstripping, vents, landscaping.
Reveal	That part of the edge of a door or window jamb not covered by the casing.
Ridge	an extrusion at the top of the structure which all sloping rafters marry into.
RO	See Rough Opening
Roll Formed Screen	Frame A method of fabrication in which a flat (usually metal) material is placed on a machine where the material is formed into shape using differently shaped rollers and pressure.
Rolled Glass	Glass formed by rolling, including patterned and wired glass. As the glass is drawn horizontally from the tank, figured, engraved, etched, machine rolls impress a pattern on the surface of the glass, varying from almost smooth to deeply marked geometric, fluted, or random overall designs. It is made in 1/8- inch to 3/8- inch thicknesses.
Roof window	A fixed or operable window similar to a skylight placed in the sloping surface of a roof.
Roof Window	Sloped application of fenestration product, which allows for in-reach operation and rotation of sash to facilitate the cleaning of exterior surfaces.
Rough opening	The framed opening in a wall into which a window or door unit is to be installed.
Rough Sill	The horizontal rough framing member, usually a 2 x 4, which forms the bottom of the rough opening. It is toe-nailed into the jack studs and is supported by cripples.