AAMA (American Architectural Manufacturers Association) - a national trade association that establishes voluntary standards for the window, door and skylight industry.
Acrylic - a thermoplastic glazing material with good weather resistance, shatter resistance and optical clarity.
Aerogel - a micro-porous and transparent silicate foam used as a glazing cavity-fill material, offering very high thermal performance.
Air infiltration - the amount of air leaking in and out of a building through gaps in walls, windows and doors.
Air spacer - the component placed at the perimeter of an insulating glass (IG) unit to separate and hold the panes of glass.
ANSI (American National Standards Institute) - a clearinghouse organization for all types of standards and product specifications.
Annealed glass - a standard float glass that has not been heat-treated.
Apron - a flat trim piece placed horizontally just beneath the window stool or sill.
Arch-top (aka. circle-heads, circle-tops and round tops) - one of several terms used for a variety of window units with one or more curved frame members, often used over another window or door opening.
Argon - an inert, nontoxic gas used in insulating glass to reduce heat transfer.
ASHRAE (American Society of Heating, Refrigeration and Air Conditioning Engineers) - a national association that establishes standards for building energy performance.
Astragal - the center post between two swinging doors; also used to describe the inactive door panel of a French door that receives a flush bolt to keep it locked into position.
Awning - a window with a sash swinging outward from bottom and hinged on the top frame.
Backbedding - material or compound used to seal the glass to a window sash.
Balance - the mechanical device used in single-hung and double-hung windows as a means of counterbalancing the weight of the sash during opening and closing.
Bay - a combination of window units that projects out to the exterior of a building; usually features a large center unit with two flanking units at 30 or 45 degree angles to the adjacent wall.
BETEC (Building Environment and Thermal Envelope Council) - part of the National Institute of Building Sciences, an organization representing government and industry, BETEC is involved in communicating government policy and influencing standards development within the industry.
BIVP (Building Integrated Photovoltaics) - a term used for products, such as commercial glazing, with built-in solar-power collection cells.
BOCA (Building Officials and Code Administrators) - one of the three model code groups in the U.S. that has now merged into the International Code Council.
Bottom rail - the bottom horizontal member of a window sash or door panel.
Bow - a combination window that projects to the exterior of a building; usually features four or more window units in a radial or “bow” formation.
Box bay - a combination of window units that projects to the exterior of a building; usually features a large center unit with two flanking units at 90 degree angles to the wall.
Breather tube (aka. capillary tube) - a tube placed through the air spacer and seal of insulating glass that allows the unit to accommodate changes in pressure between manufacturing and installation; usually used to accommodate changes in altitude between the plant and the job site.
Brickmould - a type of external casing for windows and doors.
Caming - the metal used in the construction of decorative glass panels; usually zinc or brass, it is also applied to single glass lites to create a decorative glass look.
Capstock - a material co-extruded with PVC formulated to offer a specific color, finish and/or function, such as heat resistance.
Casement - a window with a sash cranking outward from a building, hinged on the left or right side of the frame.
Casing - exposed moulding or profile around a window or door, on either the inside or outside, to cover the space between the window frame or door jamb and the wall finish.
Caulking - a compound for filling joints and sealing cracks to prevent leakage of water and air.
Cellular PVC - an extruded polyvinyl chloride material used in window and door components and trim; unlike rigid (or hollow) vinyl, it features a foam or cell-structure inside and can often be nailed, sawn and fabricated like wood.
Cellulosic composite - generally, a material combining an organic material, such as wood fiber, extruded with a plastic.
Check rail (aka. meeting rail) - the bottom rail on the upper sash and the upper rail of the lower sash of a double-hung window unit; the sash lock is normally mounted here.
Circle-top (aka. arch-tops, circle-heads and round tops) - one of several terms used for a variety of window units with one or more curved frame members, often used over another window or door opening.
Cladding - the material placed on the exterior of wood frame and sash components to provide ease of maintenance; common cladding materials include vinyl and extruded or roll-formed aluminum.
Clerestory - a window in the upper part of a high-ceilinged room that admits light to the center of the room.
Combination door - a screen or storm door used in combination with a primary door; storm windows also are referred to as combination windows.
Composite - a term used for window or door components that consist of two or more materials, such as glass fibers or wood and plastic; also used for windows and doors that combine two or more materials in the frame or sash construction, such as a product with a wood interior and a vinyl or aluminum exterior.
Condensation - water vapor from the air deposited on any cold surface that has a temperature below the dew point; sometimes a problem on cold (and poorly insulated) window glass or framing that is exposed to humid indoor air.
Cottage double-hung - a double-hung window in which the top sash is shorter than the bottom sash.
CRF (Condensation Resistance Factor) - a rating of a window's ability to resist condensation; the higher the CRF, the less likely condensation is to occur.
Cylinder - a subassembly for a door lock containing a cylinder plug with keyway and a cylinder body with tumbler mechanisms.
Design Pressure (DP) - a measurement of the structural performance of a window or door; usually specified as one-and-a-half times greater than necessary based on expected building, wind and weather conditions.
Divided lites - separately framed pieces or panes of glass with separate glazing components.
Dormer - a wall and roof area that protrudes from the roof of a house, generally featuring one or more windows.
Double glazing - the use of two panes of glass in a window to increase energy efficiency and provide other performance benefits.
Double-hung window - a window featuring two operable sash that move vertically in the frame.
Double-strength glass - glass between 0.115 and 0.133 inches thick.
Drip cap - a moulding placed on top of the header brickmould or casing of a window frame.
Egress window - a window designed to be large enough for a person to climb out of in an emergency; generally required by the building code for each bedroom of a home; currently with an opening space of 5.7 cubic feet.
Electrochromic glazing - a glass or other glazing material that can be switched from clear to opaque electronically.
Energy Star - a program sponsored by the U.S. Department of Energy that establishes minimum performance standards for building products, appliances and fixtures to be recognized as energy efficient. (Windows and doors have four different sets of standards for U-value and solar heat gain for four different climate zones in the U.S.)
Extension jamb - a board or trim component that extends from the interior of the window frame to the interior wall finish; used to increase the depth of the jambs of a window to fit a wall of any given thickness.
Extrusion - the process in which a heated material is forced through a die to produce aluminum, vinyl (PVC) and other profiles or components used in the production of windows and doors.
Fanlight - a half-circle window over a door or window with radiating bars.
Fenestration - an architectural term for the arrangement of windows, doors and other glazed areas in a wall; use has evolved to become a standard industry term for windows, doors, skylights and other glazed building openings.
Fixed lite - a non-venting or non-operable window.
Fixed panel - a non-operable door usually combined with an operable door unit.
Flashing - a strip of material, usually metal, that diverts water away from any wall or roof opening including windows, doors or skylights.
Float glass - the most common method of producing glass using a process in which the ribbon is floated across a bath of molten tin; "plate" glass and "sheet" glass refer to older manufacturing methods still in limited use.
Flush door - a door produced using two skins or faces separated by a stile and rail frame construction at the perimeter either with a hollow core or solid core.
Fogging - a deposit or film left on an interior surface of a sealed insulating glass unit due to extreme conditions or failed seals.
French door - a general term for a pair of hinged doors that open from the middle and hinged on either side of the frame; usually includes a wider stile and rail.
Fusion-weld - a term used to describe the joining of two separate materials by melting a small amount of material to create one single piece of welded material.
Glazing - the glass and other materials in a window or door; also used to describe the act or process of fitting a door or window with glass.
Glazing stop - the component of the sash or door panel that holds the glass in place.
Glider (aka. horizontal sliding window) - a window with a movable sash that slides horizontally.
Grille - a term referring to window pane dividers or muntins either placed within the insulated glass unit or affixed to one or more sides of the glass in a door or window.
Head - the main horizontal frame member at the top of a window or door.
Header (aka. lintel) - the horizontal framing member placed over the rough opening of a window or door to divert the load or weight of a building’s structure to the foundation below.
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.
Hollow-core door - a door constructed with two skins or door faces separated by stiles and rails at the perimeter without the use of an inner fill material.
Hopper - a window with sash that swings inward from the top and hinged to the bottom frame.
Horizontal slider - a window with a movable sash that slides horizontally within its frame.
IECC (International Energy Conservation Code) - a set of compliance methodology published by the International Code Council for energy efficient construction of both residential and nonresidential construction.
Impact-resistant - a term used to describe window and door products that have passed established tests for resistance to windborne debris; typically used in coastal areas that are prone to hurricanes.
Insulating glass (IG) - two or more lites or panes of glass with a hermetically sealed airspace between them; the sealed space may contain air or be filled with an inert gas, such as argon.
Jalousie - a window made up of horizontally mounted glass louvers or slats that rest on top of each other tightly when closed and rotate outward when cranked open; normally used only in warm climates or for non-heated building spaces.
Jamb - the main vertical and horizontal members forming the sides of a window or door frame.
Jamb depth - the width of a window or door from the interior to the exterior of the frame.
Jambliner - the track cover installed inside the jambs of a double-hung window, on which the window sashes slide.
J-Channel - a j-shaped channel built into a window frame or applied separately to the exterior perimeter of a window or door that accepts siding or another building finish material.
KD (Knocked down) - a general term for any construction component, including windows or doors, that are unassembled in order to be installed and put together at the job site.
Laminated glass - two or more sheets of glass with an inner layer of transparent plastic to which the glass adheres if broken, for use as safety glass and for noise reduction.
Lintel (aka. header) - a structural component or beam above a window or door opening that supports the wall above.
Lite - a piece of glass; each separate piece or pane of glass in a window or door.
Low-emissivity (Low-E) glass - a coated glass product that reflects heat.
MDF (Medium Density Fiberboard) - a wood-fiber composite used in a variety of window, door and millwork applications.
Mechanical window - a term for a window that has been assembled using screws or other fastening mechanisms as opposed to a welded corner construction.
Mortise lock - a lock recessed into a cavity in the edge of a door, window or frame.
Mullion - a component used to structurally join two window or door units.
Multipoint lock - a locking system operated with one handle that secures a window or door at two or more locking points along one side for extra security and improved compression to the weather stripping.
Muntin - the profile or moulding used to separate glass in a sash into multiple lites.
Nailing fin - an accessory component or integral extension of a window or patio door frame that generally overlaps the conventional stud construction and through which nails are driven to secure the frame in place.
NFRC (National Fenestration Rating Council) – an independent body that has established methods for rating and certifying the energy performance of windows, doors, skylights and other fenestration products.
Panning - a term for the application of metal installed to cover exposed wood at the perimeter of windows and doors; often used in conjunction with replacement windows and doors.
Parting stop - a narrow moulding, either integral or applied, that holds a sash or panel in position in the frame.
Picture window - a non-operating window with fixed glass.
Pocket window - a unit designed for replacement applications that is installed into the existing window frame after removal of the sash, balance hardware and parting stops.
Polycarbonate - a plastic material used for glazing that is impact resistant.
Pultrusion - the process used to produce fiberglass composite profiles or components for the production of windows and doors.
PVC (Polyvinylchloride) - an extruded petroleum material used for window and door framing.
Rail - the horizontal member of the framework of a window sash or door.
Reflective glass - a window glass coated to reflect visible light and solar radiation striking the surface of the glass.
Roof window - an operable skylight installed into a roof’s surface for improved room ventilation.
Rough opening - the framed opening in a wall into which a window or door unit is to be installed.
Round-top (aka. arch-tops, circle-tops and circle heads) - one of several terms used for a variety of window units with one or more curved frame members, often used over another window or door opening.
R-value - a measure of the resistance to thermal transfer or heat flow; the R-value is the reciprocal of U-factor.
Safety glass - a strengthened or reinforced glass that is less subject to breakage or splintering and less likely to cause injury if broken; building codes require glass in and near doors to be some type of safety glazing product, such as tempered or laminated glass.
Sash - the assembly of stiles and rails (vertical and horizontal members) made into a frame for holding glass.
Sash cord - a rope or chain in double-hung windows that attaches the sash to the counter balance.
Sash lift - the protruding or recessed handle on the inside bottom rail of the lower sash on a double-hung or single-hung window.
Sash stiffener - the reinforcement inserted into a sash profile prior to assembly to increase the strength of the unit.
Sash weights - the concealed weights used to counterbalance the sash of older double-hung windows.
Self-cleaning glass - a glass treated with a special coating that uses the sun's UV rays to break down organic dirt through what is called a photocatalytic effect.
Sidelites - any narrow fixed glass units mulled or joined to operating door units to provide additional light.
Sill - the main horizontal member forming the bottom of the frame of a window or door.
Sill pan - a building material installed under a window or door that is designed for water drainage.
Simulated divided lites (SDLs) - a type of grille or grid design that creates the appearance of a number of smaller panes of glass separated by muntins, but actually uses larger lites of glass with the muntins placed between and/or on the surfaces of the glass layers.
Single-hung - a window resembling a double-hung window, but only the upper sash is operable.
Single-strength glass - glass with a thickness between 0.085 and 0.100 inches.
Solar heat gain coefficient (SHGC) - a measurement of a window's ability to transmit solar heat; the lower a unit's solar heat gain coefficient, the less solar heat it transmits, and the greater its shading ability; expressed as a number without units between 0 and 1.
Solid-core door - a door produced with a solid material placed within the door skins for safety, noise reduction, thermal resistance and fire control.
Sound Transmission Class (STC) - a rating measuring a window's acoustic properties or its ability to reduce sound transmission; the higher the number, the less sound transmitted.
Stile - the main vertical frame members of a sash or door.
Stool - the interior trim board sometimes used to extend a window sill and act as a narrow shelf.
Stop (aka. bead stop, side stop, window stop or parting stop) - the moulding used to hold, position or separate window or door parts; the moulding or component on the inside of a window frame against which the window sash rests or closes.
Tempered glass - glass that has been heat-treated to withstand greater than normal forces on its surface, allowing it to break into small pieces for safety purposes.
Tilt window - a single-hung or double-hung window whose operable sash can be tilted into a room to allow for cleaning of the exterior surface from the inside of a building.
Transom - a window used over the top of another door or window, primarily for additional light and aesthetic value.
Triple glazing - the use of three panes of glass within an insulated glass unit for improved thermal and solar heat gain characteristics.
True divided lites (TDLs) - the traditional window construction incorporating separate panes of glass divided by muntins.
U-factor - the rate of heat flow-values through a building component, from room air to outside air; the reciprocal of R-value.
Ultraviolet light (UV) - the invisible rays of solar radiation at the short-wavelength end of the spectrum; these rays can cause fading of paint finishes, carpets and fabrics, as well as deterioration of some materials.
Vinyl - the general term for polyvinylchloride or PVC, an extruded material used for window and door framing.
Warm-edge - a type of insulating glass construction using an air spacer offering lower thermal conductance than traditional aluminum spacer; typically offer higher resistance to condensation and an incremental improvement in window energy performance.
WDMA (Window and Door Manufacturers Association) - a trade organization that has established many standards related to wood window and door products.
Weather-stripping - a material or device used to seal the openings, gaps or cracks of operable window and door components to prevent water and air infiltration.
Weep hole - a small opening in a window or sill member through which water may drain to the building exterior.
Wind load - the force exerted on any surface by moving air.