Glossary of Window Terms

Acrylic (Plexiglas)
A durable sheet plastic used for safety glazing and for inside storm panels. Plexiglas is a registered trademark of Rohm and Haas.

Annealed Glass
Sheet glass used as a glazing product. Further heat processing is required to transform annealed glass into safety glass.

Argon Gas
A heavy gas that is used to fill the air space between panes of glass in an insulated glass unit. Argon is a non-toxic gas that is odorless, tasteless, and colorless. Argon improves the thermal efficiency of a window and its ability to act as a sound barrier.

Balance
The system in the side jambs of a single or double-hung window that helps open and support the weight of the vent and helps hold the vent in place while in an open position.

Buck Size
The exact window size, not including the nail fin.

By-Pass

GSDConfigsStacks1
Vents “stack,” or step back, in tracks proceeding from left to right when observed from the outside. A REVERSE by-pass is where the panels or vents step from right to left when observed from outside.

Center Meet (Center Open)
Panels or vents slide open from the center to stack on either side.

Circle Top
A generic term referring to any of a variety of window units having a curved top frame member. These are often used over another window or over a door.

Colonials

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A decorative grid on the interior or exterior surface of the glass, or found between sealed glass panes of an insulated unit. It divides the window opening into smaller openings to create a simulated divided lite or true divided lite. May or may not be removable.  Also known as grilles, grids or muntins.

Condensation
The formation of water vapor from the air on any cold surface whose temperature is below the dew point.

Cottage Window

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A single or double-hung window with a larger proportioned bottom vent as compared to the top vent.  This type of window is used when you want a larger unobstructed view at the bottom of the window.

Design Pressure (DP)
The pressure a product is designed to withstand. This value is a measure of a product’s capacity to withstand the forces of wind loading, in both positive and negative directions, while it is closed and locked. The higher the DP rating, the better performance under wind load. Coastal regions often require higher DP ratings per code to anticipate high wind velocities. Florida Building Code requires that the Design Pressure rating (expressed in pounds per square foot) be matched to the wind loads that a window or door can be expected to encounter.

Dew Point
The temperature where condensation occurs.

Double Glazing
Two panes of glass separated by a sealed air space, forming a glass panel that increases energy efficiency and provides other benefits such as improved noise reduction. Also called Insulated Glass.

Double Hung Window
A window unit that contains two vertically moving operable vents.

Egress Window
A window opening large enough, as defined by local building codes, for exit or entry in an emergency situation.

Extrusion
A particular cross-sectional shape produced by forcing the material through a die.

Fenestration
An industry term of Latin origin that refers to the broader category of windows, doors, and skylights.

Fixed
A window that is non-venting, non-operable, like a picture window.

Flange/Fin
A vinyl or metal collar inserted in or integrated into the side and head jambs of a window unit used to install the window in an opening. Flanges are typically 1” wide. A ½” flange is available for outside mounts. Lip frames have a ¾” flange to accommodate clips.

Flashing
A metal or plastic strip attached to the outside of the head or side jambs of windows and doors to provide a weather barrier, resisting leakage between the window or door frame and the wall.

Frame
The combination of head, jambs, and sill to form a precise opening in which a window vent or door panel fits.

Fusion Welded
Refers to vinyl frames and vents attached at corner joints, using a heat source to create a fused, weather-tight corner.

Geometric Window
Specialty windows of various shapes including: rectangles, triangles, trapezoids, octagons, pentagons, half-rounds, quarter-rounds, full-rounds, and ellipses.

Glazing
The glass panes or ‘lites’ in the vent of a window. Also the process of sealing glass to a vent or frame for a weather-tight seal.

Glazing Bead
A removable decorative trim around the glass perimeter covering the gap between the glass and frame, holding the glass in place.

Grille/Grid

Colonials1
A decorative grid on the interior or exterior surface of the glass, or found between sealed glass panes of an insulated unit. It divides the window opening into smaller openings to create a simulated divided lite or true divided lite. May or may not be removable. Also known as colonial or muntins.

Half Screen
A screen which does not cover the entire opening of a window. Used on the bottom half of a single hung unit or on the operating side of a single slider.

Head
The main horizontal member forming the top of the window or door frame.

Horizontal Sliding Window
One or more vents that slide horizontally past each other. Sliders utilize two, three, or four track frames. Optional removable screens occupy a separate channel of the frame. All of the vents are independently operable in both directions.

Impact Glass

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Two or more sheets of glass bonded together with a plastic inner-layer to produce a stronger, more break-resistant glass. Also known as Laminated Glass.

Infiltration
Outdoor air that is able to flow through the cracks and other spaces around a window or door.

Inside Mount
Window mounted with the frame flange facing inside the building. A REVERSE Inside Mount is the same set up as an Outside Mount except the flange is mounted on the inside wall around the perimeter of the window opening so that the tracks project back into the room rather than into the opening.

Insulated Glass
A combination of two or more panes of glass with a hermetically sealed air space between the glass panes. This space may or may not be filled with an inert gas, such as an argon gas.

J-Channel
“J” configuration designed into window frame exterior shape for the primary purpose of receiving siding to self-trim around window perimeter.

Jamb
The main vertical members forming the sides of a window or door frame.

Knock-Down (K.D.)
Not assembled; parts for a window (or door) frame pre-manufactured for assembly at a later date at a jobsite.

Laminated Glass

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Two or more sheets of glass bonded together with a plastic inner-layer to produce a stronger, more break-resistant glass.  Also known as Impact Glass.

LEXAN
A trade name for glazing material which is extremely resistant to breakage. LEXAN is a registered trademark of G.E.

Lite
A unit of flat glass. One glass panel is expressed as a ‘lite.’

Low-E (Emissivity) Glass
Microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window glazing surface to reduce the U-factor by suppressing radiative heat flow. Allows natural light and short-wave heat energy to freely penetrate glass during the winter, while reflecting long-wave heat energy back outside during the summer months. The principal mechanism of heat transfer in multilayer glazing is thermal radiation from a warm pane of glass to a cooler pane. Coating a glass surface with a low-emittance material and facing that coating to the airspace between the glass layers blocks a significant amount of this radiant heat transfer, thus lowering the total heat flow through the window. Low-E coatings are transparent to visible light, yet greatly reduce the ultra-violet light entering the home, minimizing fading of carpet and furnishings. Different types of Low-E coatings have been designed to allow for high solar gain, moderate solar gain, or low solar gain. More information about Low-E glass can be found at Cardinalcorp.com.

Main Frame
Consists of jambs on the sides, a head jamb or header on the top, and a sill on the bottom.

Masonry Opening
The opening in a masonry wall to accept a window or door unit, the same as a rough opening in a frame wall.

Mulled Unit
Two or more window units structurally joined together

Mull Bar/Mullion
Vertical or horizontal divisions or joints between single windows in multiple units. Can be either decorative or structural. Decorative only versions are also mull casings or covers.

Muntin

Colonials1
Pieces of decorative grid that divide a window opening into smaller sections. Also known as a grille, grid or colonial.

Nailing Fin
Used to secure the window into a rough opening.

Obscure/Translucent Glass
A frosted, textured, or etched glass that transmits light but obscures the view for privacy or decorative purposes.

Oriel Style Window

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A single or double-hung window with a larger proportioned top vent as compared to the bottom vent.  This type of window is used when you want a larger unobstructed view at the top of the window.

Outside Mount
Window mounted with the frame flange facing outside the building.

Pane/Panel
A framed sheet of glass within a window or door frame.  A pane may be operable or fixed.  Also known as a vent or sash.

Picture Window
A fixed window that contains no operable vent.

Plexiglas (Acrylic)
A trade name for durable sheet plastic made from acrylic. Used for safety glazing and for inside storm panels. Plexiglas is a registered trademark of Rohm and Haas.

Pocket Door
A variation of a Glass Sliding Door where the frames overshoot the actual door opening on one or both sides to allow the entire door opening to be exposed and conceal all of the panels.

Rail
The horizontal top and bottom members of a window vent or door panel.

R-Value
Resistance to thermal transfer or heat flow. Higher R-Value numbers indicate greater insulating value.

Rough Opening
The opening left in a framed wall to receive a window or door unit.

Safety Glass
Annealed glass that undergoes further processing to become safety glass. Safety Glass is designed to reduce severe injuries from accidental impact. The two types of Safety Glass are Tempered and Laminated. Tempered glass, through a heat strengthening process, becomes four times stronger than annealed glass and when broken, separates into dice-like cubes. Laminated glass is two lites of glass sandwiched together with an interlayer of polyvinyl butyral under heat and pressure. Laminated glass, when battered , tends to remain intact.

Sash
A single assembly of stiles and rails made into a frame, designed to hold the glass in a window.  May be operable or inoperable.  Also known as a vent or panel.

Screen Garage Enclosures
Four by-passing panels which hang from rollers captive in head-jamb tracks. A threshold extrusion on the floor guides the suspended panel bottoms.

Shims
Wood, plastic, or composite wedges used to secure the window or door unit in the rough or masonry opening in a square, level, and plumb position both during and after installation.

Sidelight
Tall, narrow, fixed or operating vent on either or both sides of a door to light an entryway or vestibule.

Sill
The main horizontal member forming the bottom frame portion of a window or door.

Single Glazing
Use of a single pane of glass in a window. Not as energy-efficient as insulated glass.

Single Hung Window
Window unit with a fixed top vent and a vertically operating bottom vent.

Sizes
Always described as WIDTH X HEIGHT. Can be expressed in three different ways:

Daylight Opening (DLO) – the size of the opening in a building into which a window or door unit will fit. Typically, Window Craftsmen will deduct and allowance to provide ample clearance for irregularities and out-of-square conditions.
Exact – the size to which the window or door will be built exclusive of the flange. Installers are responsible for any clearance allowances.
Tip-To-Tip (TTT) – size is the exact dimension of the window including the flange.

Slider Window
Window that slides horizontally to the left or right.

Sliding Glass Door
Consist of by-passing or center-meeting vents in two, three, or four track frames.

Solar Heat Gain Coefficient (SHGC)
A measure of how effective a window or door is at keeping out solar heat. It is calculated by taking the amount of solar heat that enters a room through a window or door, divided by the amount that is actually contacting the exterior of the unit. It is expressed in a number from zero to one. The lower the value, the better the unit keeps out the solar heat.

Stack

GSDConfigsStacks1
Vents “stack,” or step back, in tracks proceeding from left to right when observed from the outside. A REVERSE by-pass is where the panels or vents step from right to left when observed from outside.

Stile
The upright or vertical outside members of a window vent, door panel or screen.

Sweep
Door bottom weather-strip mounted to the door slab on swinging doors.

Swinging
Door are said to swing right or left when hinges are located on the right or left side, respectively, when observed from the outside. Doors may swing out or swing in.

Tempered Glass
A glass panel that is heated and subsequently rapidly cooled in its manufacturing process, creating a product that can withstand abnormal force or pressure on its surface, and which breaks into pebble-sized pieces. Also known as “safety glass.” Code requires tempered glass in all doors (including patio doors), and in windows that are located near doors, bathtubs, and showers.

Tilt Window

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A window designed in such a way that the vents tilt inward for easy cleaning of the outside glass surface.

Top Roller Guide
Hardware fastened to the top of a sliding door which contains a roller to guide the door in an overhead track.

Transom
A small window placed over the top of a door or window, primarily for additional light and aesthetic value.

U-Value (U-Factor)
Also known as Heat Transfer Coefficient. A calculation expressing the rate of heat transfer through a window or door. The lower the U-Value, the better the insulating properties of the window or door.

United Inches
The sum in inches of the width and height of a window unit.

Vent
A single assembly of stiles and rails made into a frame, designed to hold the glass in a window.  May be operable or inoperable.  Also known as a panel or sash.

Vent balance
A system of cords and/or springs that assist in raising a vent while keeping the vent in any placed position by counter-balancing the weight of the vent.

Vent Lock
Generally, a cam-action or other latch-type lock applied to the vents of a sliding window to both pull the vents tightly together and to seal the vent tightly to the frame, both for security and to create a weather-tight seal.

Vent Stop
An extrusion molding piece, generally about 2” long that covers the joint between the window vent and the jamb, stopping the operable vent at its maximum opening.

Vertical Four Tracks
Windbreaks consisting of four vents that move in a vertical direction. Optional removable or fixed screens are available.

Vertical Two Tracks
Window consisting of two tracks that move in a vertical direction used as a door insert.

Weather Strip
Various shaped metal, vinyl, plastic, or fiber strips that fit tightly against the window or door frame to resist air and water infiltration through gaps and cracks.

Weep Hole
A small hole (or holes) found along the bottom sill frame edge of a window or door unit that allows any trapped water to escape to the exterior.

Windbreaks
Arrangements of easily removable panels to enclose lanais, porches and balconies. Florida Building Code requires that they carry a label instructing the homeowner to remove the panels when the winds reach 75 miles per hour.

Wind Load
Force extended on a surface by moving air. Florida Building Code requires that the Design Pressure rating (expressed in pounds per square foot) be matched to the wind loads that a window or door can be expected to encounter. Your local building department can help determine the required Design Pressure for your building.