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American Architectural Manufacturers Association, a national trade association that establishes voluntary standards for the window, door and skylight industry.
Thermoplastic glazing material.
This is an operating panel as viewed from exterior.
Air Infiltration
The amount of air leaking in and out of a building through cracks in walls, windows and doors.
Component placed at the perimeter of an insulating glass unit to separate the two lites of glass.
Annealed Glass
Standard float glass.
An inert, nontoxic gas used in insulating glass to reduce heat transfer.
Center post between two swinging doors.


The millwork around the outside edge of the window casing, usually used when the casing consists of flat boards.
Material or compound used to seal the glass to a window sash.
Ashworth's term for a two panel doors where both panels can open, hinged on the side, with one active panel and one passive panel.
Bottom rail
The bottom horizontal member of a window sash or door panel.
Breather tube
Tube placed through airspacer and seal of insulating glass which allows unit to accommodate changes in pressure between time and location of manufacture and time and location of installation, where it is sealed. Usually used to accommodate changes in altitude between plant and job site.
A type of external casing for windows and doors.


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.
A compound for filling joints and sealing cracks to prevent leakage of water and air.
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.
Clear IG
Two panes of glass sealed to form a dead air space between the two panes of glass.
A term used for window or door components, which consist of two or more materials, such as wood and plastic. The term also is used for windows and doors which combine two or more materials in the frame or sash construction, such as a product with a wood interior and a vinyl or aluminum exterior.
Water vapor from the air deposited on any cold surface, which has a temperature below the dew point. Sometimes a problem on cold (and poorly insulated) window glass or framing that is exposed to humid indoor air.


Daylight opening
The amount of visual area seen through a piece of glass.
Design pressure (DP)
A measurement of the structural performance of a window or door. Usually specified as one-and-half times greater than necessary based on expected building wind and weather conditions.
Direct set
A geometric shape that incorporates all straight legs.
Divided lites
Separately framed pieces or panes of glass. A double-hung window, for instance, often has several lites divided by muntins in each sash. These designs are often referred to as six-over-six, eight-over-one, etc., to indicate the number of lites in each sash. Designs simulating the appearance of separately-framed panes of glass are often referred to as SDLs or simulated divided lites. Designs using actual separate pieces of glass are sometimes referred to as TDLs or true divided lites.
Double glazing
Use of two panes of glass in a window to increase energy efficiency and provide other performance benefits. May or may not refer to an insulating glass unit.
Double-strength glass
Glass between 0.115 and 0.133 inches thick.
Drip cap
Moulding placed on top of the header brickmould or casing of a door frame.
Dual Low-E
A glazing option which combines Cardinal LoE 366 soft coat on the inside surface of the exterior pane with Pilkington Energy Advantage™ Low-E hard coat on the inside surface of the interior pane. The Pilkington Energy Advantage™ Low-E hard coat is a very thin pyrolytic coating that is integral to the interior glass surface. This hard, durable, low emissivity coating gives the product improved thermal insulation performance compared to clear insulated glass or standard Low-E insulated glass.


A double radius unit with tight radius on the end and a flowing/low arc radius on top with the height less than half the width.
Energy Star®
A program sponsored by the U.S. Department of Energy which establishes minimum performance standards for windows to be recognized as energy efficient. Three different sets of standards for U-value and solar heat gain have been established for three different climate zones in the U.S.
Extension jamb
A trim component which extends from the interior of the door frame to the interior wall.
Extruded aluminum
A heavier, thicker aluminum product used to clad the exterior of wood windows & doors.


Originally, an architectural term for the arrangement of windows, doors and other glazed areas in a wall. Has evolved to become a standard industry term for windows, doors, skylights and other glazed building openings. From the Latin word, "fenestra," meaning window.
A toothed joint used to combine two pieces of wood end-to-end.
Fixed panel
Non-operable door usually combined with operable door unit.
A thin strip of metal or other material that diverts water away from a window, door or skylight.
Float glass
Glass produced by a process in which the ribbon is floated across a bath of molten tin. The vast majority of flat glass is now produced using this method. The terms "plate" glass and "sheet" glass refer to older manufacturing methods still in limited use.
A deposit or film left on an interior surface of a sealed insulating glass unit due to extreme conditions or failed seals.
Frame size
The actual box size of the unit, outside to outside dimensions (not including brick mould). This is an important dimension used with special size Ashworth wood doors.
French door
Generally refers to a pair of hinged doors which open from the middle. Also incorporates wider stile and rail components around the glass than typical glazed doors.
French slider
Sliding patio door using wider stiles and rails to replicate a French door look.


Glass (and other materials) in a window or door. Also, the act or process of fitting a unit with glass.
Glazing stop
A component of the sash or door panel that holds the glass in place.
A term referring to window pane dividers or muntins. It may be a type of assembly fitted to the interior of the window or door unit which can be detached for cleaning. Also can be fitted inside the sealed insulating glass unit, when it also is referred to as a grid.


Half round
A stock or special ½ round unit. This unit height is half the width.
A window and door certification program sponsored by WDMA.
Handing and Hinging
Always viewed from exterior.
Main horizontal frame member at the top of a window or door.
Horizontal framing member placed over the rough opening of a window or door to prevent the weight of wall or roof from resting on the frame. Also known as a lintel.
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.


This is a fixed panel (O) as viewed from exterior.
Inner grille
Ashworth's term for GBG, or grille between the glass.
Insulating glass (IG)
Two or more lites of glass with a hermetically-sealed airspace between the lites. The sealed space may contain air or be filled with an inert gas, such as argon.
Panels swing to the interior as viewed from exterior.


Main vertical members forming the sides of a window or door frame, also refers to the horizontal member at the top of the window frame, as in head jamb and side jamb.
Jamb depth
Width of a window or door from the interior to the exterior of the frame to meet construction all thickness.


Laminated glass
Two or more sheets of glass with an inner layer of transparent plastic to which the glass adheres if broken. Used for enhanced safety and security, as well as sound reduction.
A standard length profile or shape which is cut and processed to make window and door components.
A piece of glass. In windows and doors, refers to separately framed panes of glass (as well as designs simulating the look of separately framed pieces of glass). Sometimes spelled "light."
Low-emissivity (LoE) glass
A coated glass product which reflects heat.


Masonry opening
Area in a masonry wall left open for windows or doors.
A component used to structurally join two window or door units.
Multipoint lock
A locking system, operated with one handle, which secures a window or door at two or more locking points.
Profile or moulding, either vertical or horizontal, used to separate glass in a sash into multiple lites. Generally refers to components used to construct divided lite grids or grilles simulating a divided lite look.


Nailing fin
An accessory component or integral extension of a window or patio door frame which generally laps over the conventional stud construction and through which nails are driven to secure the frame in place.
National Fenestration Rating Council. A body which has established methods for rating and certifying the energy performance of windows.


Component, usually wood, mounted within stile and rail members of doors. Also used to refer to the entire door.
Perimeter grille
Same as surround grille; a grille with a perimeter frame.
Primary active panel
This is the active panel of a bi-hinge door.
Pyrolytic glass
A glass product that is coated, usually to provide low-emissivity or solar control benefits, during the manufacturing process at the molten glass stage. Commonly referred to as a hard coat, this type of coating offers a surface that is generally as durable as an ordinary glass surface, and therefore requires no special handling and does not need to be used in an insulating glass unit. The other type of glass coating is a sputter-coat, which is applied in a secondary process. Sometimes referred to as a soft-coat, these types of coatings generally require some additional care in handling and fabrication and must be used within an insulating glass unit.


Resistance to thermal transfer or heat flow. Higher R-value numbers indicate greater insulating value. R-value is frequently used by the insulation industry and is the reciprocal of U-value, a value more generally used in the window industry.
Horizontal member of the framework of a window sash or door.
Rough opening
Framed opening in a wall into which a window or door unit is to be installed.


Secondary active panel
This is the passive panel of a bi-hinge door.
Shading coefficient (SC)
A measure of a window's ability to transmit solar heat, relative to that ability for lis-inch clear glass. The lower a unit's shading coefficient, the less solar heat it transmits, and the greater its shading ability. It is being phased out in favor of the solar heat gain coefficient (SHGC).
Narrow fixed units mulled or joined to operating door units to give a more open appearance.
The main horizontal member forming the bottom of the frame of a window or door.
Simulated divided lite (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-strength glass
Glass with thickness between 0.085 and 0.100 inches.
A single piece of material used as the face of a door.
Soft-coat glass
A glass product that is coated in a secondary process known as sputter coating, usually to offer low-emissivity or solar control benefits. The term refers to the fact that these types of coatings generally require some additional care in handling and fabrication and must be used within an insulating glass unit. A hard-coat or pyrolytic glass is coated during the manufacturing process at the molten glass stage. This type of coating offers a surface that is generally as durable as an ordinary glass surface, and therefore requires no special handling and does not need to be used in an insulating glass unit.
Solar control glass
Glass produced with a coating or tint that absorbs or reflects solar energy, thereby reducing solar gain.
Solar heat gain coefficient (SHGC)
A rating, which is now generally replacing shading coefficient, measuring a window's ability to transmit solar heat. It measures both the solar radiation which is directly transmitted, as well as the solar radiation absorbed by the glass and subsequently transmitted. The lower a unit's solar heat gain coefficient, the less solar heat it transmits, and the greater is its shading ability. It is approximately equal to the shading coefficient divided by 1.15. It is expressed as a number without units between 0 and 1.
Sound transmission class (STC)
A rating measuring a window's acoustic properties or its ability to reduce sound transmission. An STC rating is determined by measuring the sound transmission over a selected range of sound frequencies. The higher the number, the less sound transmitted.
Stationary, does not move.
The main vertical frame members of a sash or door.
Stile-and-rail door
Traditional type of wood door constructed with vertical stiles and rails with openings filled with raised wood panels or glass.
Stop glazed
A typical method using a stop with a glazing compound to make the seal.
Super window
A generic term for a window with a very low U-value. Typically, it incorporates multiple glazings, low-E coatings, gas fills, and an insulating spacer.
Swing door
Ashworth's version of all swing door options, including singles, bi-hinge, center hinge, including all 1, 2, and 3 panel options.


Tempered glass
Glass heat treated to withstand greater than normal forces on its surface. When it breaks, it shatters into small pieces to reduce hazard.
Thermal break
A thermally insulating or low-conductance material used between interior and exterior aluminum (or other conductive material) window and door components.
Gray and bronze available as standard options on Clear or LoE IG.
Window used over the top of a door or window, primarily for additional light and aesthetic value.


Rate of heat flow-value through a building component, from room air to outside air. Also referred to as U-value. The lower the U-factor, the better the insulating value. U-factor, a rating more generally used in the window industry, is the reciprocal of R-value, a rating commonly used in the insulation industry.
Ultraviolet light (UV)
Invisible rays of solar radiation at the short-wavelength violet end of the spectrum. Ultraviolet rays can cause fading of paint finishes, carpets, and fabrics, as well as deterioration of some materials.
Unit size
Overall dimensions of a door unit, including brick mould, subsill, etc., for primed units. Frame Size and Unit Size are same for Clad Ashworth products.


Visible Transmittance (VT)
A measurement of how much light comes through a product. VT is expressed as a number between 0 and 1. The higher the VT, the higher the potential for daylighting.


A type of insulating glass construction using an air spacer offering lower thermal conductance than traditional aluminum spacer. Warm-edge IG units typically offer higher resistance to condensation and an incremental improvement in window energy performance.
Window and Door Manufacturers Association. Formerly the National Wood Window and Door Association, this trade organization has established many standards related to wood window and door products.
A material or device used to seal the openings, gaps, or cracks of venting window and door units to prevent water and air infiltration.
Wet glazed
A typical method using a stop with a glazing compound to make the seal.
Force exerted on a surface by moving air.