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Use this windows and doors glossary to help you better understand the terms used to describe windows and doors.

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American Architectural Manufacturers Association.  A national trade association that establishes voluntary standards for the window, door, storefront, curtain wall and skylight industries.
(Plastic) A non-crystalline thermoplastic sometimes used for glazing.

A materials ability to stick or bond to the surface to which it is applied.

Adhesive failure
The inability of a material to remain adhered to the surface on which it was applied.

Air chambers
Small honeycomb spaces within the sash and frame which help to insulate and strengthen the window (also referred to as air cavities).
Air infiltration
The amount of air leakage through a door, window, or wall; the lower the number the better.  Standard for measurement is ASTM-E283.

Air latch
Latch mechanism on the interior face of the sash that retains the window in a partially open position for ventilation (aka night latch).

Air space
A cavity or space in walls, windows or other enclosed parts of a building between various structural members.  Usually used in reference to IG glass issues.
The method or type of fastening system used to install the product to its substrate.

Annealed glass
Standard sheet of float glass which has not been heat-treated.
To provide an extremely hard non-corrosive oxide film on the surface of aluminum, by electrolytic action.  The electrochemical process produces an anodic coating by conversion of aluminum into essentially aluminum oxide.  Appearance depends upon both the alloy involved and the surface preparation.  Anodic coatings may be transparent, of varying shades of silver, gray or brown, or colors may be incorporated by the use of dyes or pigments.

American National Standards Institute - an organization that generates standards and specifications for a multitude of products.

Arch top
A single hung window where the head is curved into a radius equal to 1/2 the window width.

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 to reduce temperature transfer.
American Society of Civil Engineers (national code)
American Society for testing and Materials - an organization that sets standards for testing of materials.

The vertical member of a multi-panel door, which is attached to the fixed or inactive door or panel and receives the active or operating door or panel.
Awning window
Window in which the sash(es) crank out from the bottom and are hinged at the top.
A mechanical device used in hung windows to offset the weight of the sash.
Balance shoe
Hardware that connects the balance to the sash.
A sealant or compound after application in a joint, irrespective of the method of application, such as caulking bead, glazing bead, etc.  Also molding or stop used to hold glass or panels in position.

Box frame window
Used when replacing the wood sash of an old double hung wood window.
Bottom rail
The bottom horizontal member of a sash or panel sometimes referred to as the sash, vent or panel sill.

Box screen
A heavy duty sliding glass door screen frame that simulates the actual glass panels.  It is typically similar in size and shape of the glass door panels.

Muntin configuration that frames a single centered large lite and intersects near corners.  Also known as Prairie Grid.
An abbreviation of British Thermal Units that defines the amount of head needed to raise the temperature of one pound of water to one degree Fahrenheit.
Material used to frame an opening for attachment of the window or door frame.
Buck dimension
Opening with buck strips installed and ready for window or door installation.  Also referred to as a finished opening.
Buck opening
Opening with buck strips installed and ready for window or door installation.  Also referred to as a finished opening.
Buck strips
See Buck
Bug sweep
A flexible rubber seal that is mounted to an extrusion and attaches to the bottom of the cabana door to keep out insects and air from passing underneath.
Cabana door
A swing type door with several window insert options and uses a z-bar extrusion outer frame.  Commonly used in sunrooms.
Cam lock and keeper
The mechanisms which pull the sash together when placed in the locked position.
Casement window
A window in which the sash(es) crank out from the side and are hinged from the other side.
A mastic compound for filling joints and sealing cracks to prevent leakage of water and air, commonly made of a silicone base, bituminous, acrylic, or rubber-based material.
A window in the upper part of a lofty room that admits light to the center of the room.
Colonial configuration
Window or door style in which vents or panels are divided into small sections (lites) by adding muntins.
Standard sizes developed for Florida Construction in accordance to block sizes.  Most commonly used in the masonry trade.
Composite frame
A frame consisting of two or more materials:  for example, an interior wood element with an exterior fiberglass element.
When water vapor, which is present in all but the driest air, comes in contact with a surface that is below what is called the "dew point temperature," the vapor becomes liquid and is called condensation.  An example is as follows, condensation forms on a glass of ice water since the surface of the glass is down to the dew point temperature of the inside air.
Describes the setup of panels or vents on windows and doors.  For example:  XO, OX, XOX or XXX.  PGT refers to "X" as operable and "O" as stationary.

Cottage window
On a hung window the sash lite (bottom) is larger than a fixed lite (top).

Removing the glass from the window frame.
A material used in insulating glass to prevent water vapor which causes fogging.
Design load
Wind load pressure, usually expressed in pounds per square foot (psf).  Equal to 2/3 of the Structural Test Load.
Design pressure
See Design load
An opening in a sloping roof, the framing of which projects out to form a vertical wall suitable for windows or other openings.
Double glazing
See IG
Double hung
A window consisting of two sashes of glass operating in a frame, both the upper and lower halves can be slid up and down and usually use a counter balance mechanism to hold the sash in place.
Double strength glass   
Sheet glass between 0.115" and 0.133" (3 - 3.38 mm) thick.
See Double Strength Glass
Electrostatic Paint - painting process used to paint aluminum extrusions - the metal is charged negatively and the paint positively to enable total coverage of the surface.
A fire code that requires entry and exit specifications.
Egress hinge
A hinge on the casement window that pivots closer to the corner and creates a greater clear opening.
Egress opening
See Egress
Egress window
A window that meets most egress codes.
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.
Exterior glazed
Glass set from the exterior of the building.
Exterior stop
The removable molding or bead that holds the lite or panel in place when it is on the exterior side of the lite or panel as contrasted to an interior stop located on the interior side of the lite or panel.
Eyebrow window  
An arch window that has vertical legs and a radius top.
The placement of window openings in a building wall, one of the important elements in controlling the exterior appearance of a building.  Also, a window, door or skylight and its associated interior or exterior elements, such as shades or blinds.
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 panel
An inoperable panel of a sliding glass door.
Fixed window
A window with no operating sashes.
Flange frame
A window frame profile where the exterior leg is longer than the interior.  Is commonly used to overlap the surrounding construction.
A thin strip of metal or synthetic material that diverts water away from a seam or joint in the construction.
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 the parallel surfaces, without polishing and grinding.
Foam backer rod
A filler to be used to support a sealant joint.
Fogged unit
An insulating glass unit with a permanent deposit of contaminates on an interior glass surface.
The enclosure in which window sashes, door panels or fixed glazing are mounted.
The process of joining materials by melting them together with extreme heat, resulting in the materials uniting into a one-piece unit.
Glass 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.
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.
Glass or other material that is placed into a window or door frame, or the process of installing this material.
Glazing bead
A molding or stop placed around a window to cover the glass edge.
Glazing tape
Two sided tape used to seal and attach glass to the glazing bed (dry glazing).
Decorative horizontal or vertical bars installed between the glass panes to create the appearance of the sash being divided into smaller lites of glass.  Also referred to as muntins.
A term referring to windowpane dividers or applied muntins.
Head or header
The horizontal top portion of the main frame.
Head expander
The u-shaped extrusion that closes the gap between the window head and the buck opening, used during installation.
Heat fusion
Welding method used to join two PVC members; consists of heating the PVC extrusions, squeezing together, and allowing assembly to cool.
Heat loss
Transfer of heat from inside to outside by way of conduction, radiation and convection through all surfaces of the house.
Heat transfer
Heat always moves from hot to cold.  It is mainly transferred by three methods:  convection, conduction and radiation.
Heat-strengthened glass
Glass that is reheated, after forming, to just below melting point and then cooled, forming a compressed surface that increases its strength beyond that of typical annealed glass.
Hermetically sealed unit
An insulating glass unit that is sealed, moisture free, clean dead air space made up of two lites of glass.
Hollow extrusion
An extrusion with a fully enclosed cavity within it.
An interlock that attaches to the wall to engage the end moving panel on a pocket door.
Hopper window
A window unit in which the top of the sash swings inward.
Horizontal slider
Window whose movable sash slides horizontally.
I.G. Unit
Insulating glass - Two or more lites of glass separated by a spacer and hermetically sealed at the glass edges.
Inside looking out.
Inside glaze
When the window is glazed from the inside of the house.
Insulating value
See U-factor or R-value
A term used on doors that swing into the interior of the home.  Is viewed from the inside for hinging.
Integral fin
Nailing fin protruding from the extrusion that is part of the extrusion (as opposed to an slip-on fin).
Interior casing
The interior trim that covers and overlaps the gap from the jamb to the sheet rock.
Design feature which enables sash, vent or panel to engage with another when closing.
A channel that receives siding
A window made up of horizontally mounted louvered slats that abut each other tightly when closed and extend outward when cranked open.
Jalousie door insert
A jalousie window (See Jalousie) mounted within a cabana door.
Jamb adjusters
Screws that extend outward from the jamb to take up gap in the buck opening.
Jamb liner
In some double-hung windows, the track installed inside the jambs on which the window sashes slide.
Device into which a window or patio door locking latch hooks for positive closure of sash or panel.
Krypton gas
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 Argon gas.
Laminated glass
Two or more pieces of glass bonded together with an interlayer between each lite.  Used for overhead, safety and sound reduction.
Lift handle
A handhold for raising and lowering the sash. Handle implies that the handhold is not continuous across the sash.
Lift rail
A handhold for raising and lowering the sash. Rail implies that the handhold is continuous across the sash.
An area of visible light, framed by either a window or door's primary extrusions or by muntins.
Lock rail
The horizontal section of the sash where the cam lock is attached.
Lock stile
The vertical section of the sash or panel where the lock is attached.
Low-E (Emissivity) Glass
Glass with a transparent metallic oxide coating applied onto or into a glass surface. The coating typically allows short-wave energy to pass through but reflects long-wave infrared energy which improves the U-value.
Main frame
The head, sill and jambs section of a window and or door.
Marine glazing
U-channel made of soft PVC used to cushion glass against aluminum or vinyl by wrapping it around the edge of the glass therefore allowing unrestricted expansion and contraction.
Masonry opening
Actual block opening – not including the buck strips.  Also referred to as the rough opening.
Mechanically fastened frame
Refers to frames that are not welded or molded, typically a screw assembly.
Fabric made of either fiberglass or aluminum, used in the making of screens.
Mill finish
Original finish produced on aluminum when it is extruded or cold rolled.
Standard window and door sizes given in feet and inches.
Mortise lock
A lock that is recessed in the edge of a stile and has a throw hook that engages with a keeper.
Mull clip
A clip designed to anchor a mullion into an opening.
Mullion / mull
A member that connects two or more windows or doors together in a single opening.
Multiple chambered frame
Frame member which has multiple core construction to provide strength and insulation.
A decorative lineal that an be applied to the exterior, interior, and in between panes of glass to simulate a true divided lite window or door.
Nailing fin / nail fin
An integral extension of a window or patio door frame which generally laps over the conventional stud construction and through which nails or screws are used to secure the frame in place.
National Fenestration Rating Counsel
Night latch
Hardware which restricts the sash opening to a predetermined dimension when extended.
Indicates a fixed section of a door or window. (O, OX, XO, XOX)
Outside Looking In
Obscure glass
Glass that has been made translucent instead of transparent.
Operable window
Window that can be opened for ventilation.
Operator W
Crank-operated device for opening and closing a window.
A window where the top portion is larger than the bottom porton.
Outside glaze
Glazed from the exterior side of the window or door.
A term used on doors that swing to the outside or exterior of the home.  Is viewed from the outside for hinging.
Parting stop
A narrow strip, either integral or applied, that holds a sash or panel in position in a frame.
Pass thru
Single Hung window without a main frame sill; has a cap piece with foam that fits onto the sash sill.
Patio door
A secondary door, not the primary door.
Picture window
A window that has no moveable sash.
Pivot bar
Attaches the sash to the balance shoe, creating alignment between the sash and frame, while allowing the sash to tilt inward for cleaning.
Pocket door
Sliding glass door that when opened slides clear of the opening.
Polyvinylchloride; an extruded or molded plastic material used for window framing and as a thermal barrier for aluminum windows.
Measurement of Resistance to heat gain or loss the higher the number the greater the resistance to heat flow.
Radius top window
A SH shaped like an architectural eyebrow, comes to a point where head and jambs meet.
Raised muntin
A decorative lineal that can be applied to the exterior, interior, and in between panes of glass to simulate a true divided lite on a window or door.
A steel or aluminum bar that is inserted into a hollow extrusion to add strength.
Window or door replacement, change out, or remodel.
Clearance or spacing between components in an assembly. 
Roll form bead
A glazing bead (or glass stop) that is made from roll formed sheet metal.
Roll formed screen frame
A screen frame that is made from a roll formed sheet metal.
Rough opening
An unfinished opening in a frame wall, sized to accept the frame of a door or window.
Safety glass
A strengthened or reinforced glass that is less subject to breakage or splintering.
A single assembly of stiles and rails made into a frame for holding glass. Sometimes referred to as vents.
Sash stop
A metal or plastic piece in the jamb track which limits the travel of the sash on windows.
Sash guides
A plastic piece that is placed in the top of the sash stile to prevent the sash head from rubbing against the balance.
Screen clip
A metal spring clip that holds a screen in place.
Screw boss
A channel or void in an extrusion which accepts a certain diameter sheet metal screw.
Screw channel
See screw boss
Screw-on bead or stop
Stop, bead, or molding attached by machine screws.
Setting blocks
Use of small blocks made of neoprene or plastic to distribute weight of glass. Also can be used as an aid in centering glass and prevents glass to metal contact.
Small pieces of material used to secure the window or door unit in the rough or masonry opening in a square, level and plumb position during and after installation.
Fixed units mulled or joined to the side of a door to give a more open appearance.
Side slider window
A window where the sash moves horizontally from side to side.  Also can be referred to as a horizontal roller.
The main horizontal member forming the bottom of the frame of a window or a sliding door.
Sill extender
An extrusion that is attached to the bottom of the window to cover the gap between the sill and the rough opening.
Sill pan
A type of flashing used to ensure that incidental water that penetrates the building envelope will be collected and allowed to drain.
Simulated divided lites
A window that has the appearance of a number of smaller panes of glass separated by muntins, but actually is a larger glazing unit with the muntins placed between or on the surfaces of the glass layers.
Single glazing
Single thickness of glass in a window or door.
Single hung window
Window in which the upper portion is fixed and the lower portion moves vertically.
Slide bolt
Hardware placed in the stiles of a French door to secure the inactive door to the header and threshold.  Also known as the throw bolt.
Side slider
Horizontal sliding window.
Sliding glass door
A door fitted with one or more panels that move horizontally.
Slip-on fin
Optional piece of nailing fin material that goes all the way around the parameter of the window.  Available in mill finish only.
Sloped sill
The sill of the window that has a downward slope to the outside. This sill has sufficient degree of slope to aid in water runoff.
Solar Heat Gain Coefficient
The fraction of solar radiation admitted through a window or skylight, both directly transmitted, and absorbed and subsequently released inward. The solar heat gain coefficient has replaced the shading coefficient as the standard indicator of a window's shading ability. It is expressed as a number between 0 and 1. The lower a window's solar heat gain coefficient, the less solar heat it transmits, and the greater it's shading ability. SHGC can be expressed in terms of the glass alone or can refer to the entire window assembly.

Solar spectrum
The intensity variation of sunlight across its spectral range.
Sound Transmission Class (STC)
The sound transmission loss rating of a material over a selected range of sound frequencies. The higher the number, the less sound is transmitted.
Spectrally selective glazing
A specially engineered Low-E coated or tinted glazing that blocks out much of the sun's heat while transmitting substantial daylight.
A vinyl or rubber material that is pressed into a groove in an extrusion to hold screening or vinyl glazing in place.
Vertical sash or panel extrusion sometimes referred to as the side rails or jambs.
Strike plate
Metal piece with a punched hole on the frame jamb or astragal, which accepts the lock plunger.
The term used with swing doors (French door) in regards to which way the door opens or swings. (Out or in)
Tandem rollers
Dual wheels inline and in the same mechanism.  Used in sliding glass doors.
Tempered glass
Treated glass that is strengthened by reheating it to just below the melting point and then suddenly cooling it. When shattered, it breaks into small pieces. Approximately four times stronger than standard annealed glass; is required as safety glazing in patio doors, entrance doors, side lights, and other hazardous locations. It cannot be re-cut after tempering.
Thermal break
An element of low conductance placed between elements of higher conductance to reduce the flow of heat. Often used in aluminum windows.
Three point lock
Deadbolts that protrude in three separate directions with the movement of a single lever or key.
The member that lies at the bottom of a sliding glass door or swinging door; the sill of a doorway.
Tilt latch
Mechanism that unlocks the sash and allows it to tilt in from the main frame.
Tilt-in/lift-out sash
A sash that can be tilted to the interior and removed for cleaning.
The percentage of radiation that can pass through glazing. Transmittance can be defined for different types of light or energy, e.g., visible light transmittance, UV transmittance, or total solar energy transmittance.
A window that fits over the top of a door or window, primarily for additional light and aesthetic value.
Triple glazing
Three panes of glass or plastic with two air spaces between.
True divided light
A term which refers to windows in which multiple individual panes of glass or lights are assembled in the sash using muntins.
U-factor (U-value)
A measurement of the insulating quality of the window or door.  U-factor is used to determine how well the window or door stops the flow of heat into an air-conditioned home or out of a heated home.  The U-factor is based on the temperature difference between the inside and outside, and does not include the energy passed by sunlight (see SHGC).  The lower the U-factor, the better.
United inch
Unit of measurement:  width plus height = United inch
The sliding or projecting portion of the window.

Ventilation latch
Latch mechanism on the interior face of the sash which retains the window in a partially open position for ventilation.
A rigid or flexible material made of poly vinyl chloride material used in window and door frames and glazing.
Vinyl-clad window
A window with exterior wood parts covered with extruded vinyl.
Visible Light Transmittance (VT)
The fraction of visible light from the outside that passes through the window or door into the home.  VT is used to determine how bright the inside room will be from natural daylight passing through the window or door:  the lower the VT, the darker the room.
Washable hinges
Track type hinges on casement windows that aside from normal operation has the ability to slide towards frame center and allow for easy sash cleaning.
Weather stripping
A material or device used to seal the openings, gaps or cracks of venting window and door units to prevent water and air infiltration.
Weep hole
A small opening in a wall, door or window sill member through which water may drain to the building exterior.
Weep hole cover
A plastic or metal piece that inserts into the weep hole to prevent air and bug infiltration.

Wet glazing
Method of sealing glass in a frame by using a gun-applied glazing material or sealant.
Wind load
Measurement of pressure (in psf) put forth by the wind.
Wire glass
Polished or clear glass, 1/4" thick. Wire mesh is embedded within the glass such that the glass will not shatter when broken. The wire pattern is available in many types. It is frequently used in skylights, overhead glazing, and locations where a fire-retardant glass is required.
Indicates a moveable panel or sash in a window or door.