Welcome to Our Glossary

The following is a list of terms related to the window and door industry. (Click on + for detailed information)

Air Chambers
Small honeycomb spaces within the sash and frame extrusions that help to insulate and strengthen the window

A gas that is heavier than air used to fill the airspace of an insulated glass unit. Argon is a safe, colorless, odorless, tasteless, non-toxic gas, which is six times denser than air. Argon provides a significant increase in the insulating value of a glass unit as well as sound insulation.

Awning Window
A window that is hinged at the top, and cranks from the bottom, to open out on a horizontal (outward and upward) 45 Degree swing.

Balance (block & tackle, spiral type, coil type)
The system in the side jambs of a single or double-hung window that controls the tension and balance for smooth operation of the sash. See sash balance.

Balance Winding Tool
Used to adjust the tension of the spiral balance.

Bay Window
A bay window is made up of three or more windows. The side or flanker units project out from the building at 30, 45, or 90 degree angles. The center is parallel with the building wall and is made up of one or more windows. All of the units can be stationary, operating, or any combination of the two. Typically the center section is stationary, while the side units are operating.

Beveled Exterior
An extension of the vinyl frame that adds an aesthetically pleasing dimension to the exterior of the window.

Bow Window
A series of four or more adjoining window units, commonly five in number, projecting 10-20 degrees from the wall of a building, forming a circular arch appearance.

Brick Mould
Exterior casing around a window or door through which nails are driven to install the unit. Covers the gap between the frame and masonry opening. In some cases, siding is installed up to the edge of the brick mould.

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

Window –A window unit in which the single sash is either fixed or opens outward to the left or right.

Inside casing is a flat, decorative moulding that covers the inside edge of the jambs and the rough openings between the window unit and the wall. Outside casing (or brickmould), serves the same purpose, while it also is an installation device through which nails are driven to install the window unit into the wall.

A compound for filing joints to prevent leakage of water and air. Weather-proof caulking is made of a silicone base. Caulking is used where leakage and/or movement may occur.

A compound for filing joints to prevent leakage of water and air. Weather-proof caulking is made of a silicone base. Caulking is used where leakage and/or movement may occur.

Circle Top
A generic term referring to any of a variety of window units with one ore more curved frame members, often used over another window or door opening.

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

Cottage Window
A double hung or single hung window with a larger proportioned bottom sash.

Design Pressure
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.

Dew Point
The temperature at which condensation occurs.

Divided Lite
A window opening divided into smaller sections by a grid system on the interior or exterior of the glass, between the glass panes, or any combination of these three.

Double Glazing
Two panes of glass separated by an air space to form a glass panel that increases energy efficiency and provides other performance benefits.

Double Hung Window
A window unit that has two operable sashes which move vertically in the frame.

Drip Cap
A molding to divert water from the top of a window unit so that water drips beyond the outside of the frame.

Egress Window
A window large enough, as defined by local building codes, for exit or entry in case of an emergency. Typically required in bedrooms.

Update 12/18

A government-backed program helping businesses and individuals protect the environment through the use of high-efficiency products. ENERGY STAR® qualifying products, such as windows and doors, mean these items use less energy, save money and help protect the environment.

A form produced by forcing material through a die.

Refers to a window that is non-venting or non-operable.

An architectural term referring to the arrangement of windows and doors in a wall.

A metal or plastic strip attached to the outside of the head or side jambs to provide a weather barrier, preventing leakage between the frame and the wall.

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

Fusion Welded
Refers to frames and sash fused together with intense heat.

Garden Window
A window that projects out from the side of the structure and can be used as a greenhouse for plants. It has a slanted glass roof that allows heat and light from the sun to enter.

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

Glazing Bead
A removable trim that holds glass in place within the frame.

The process of sealing the glass to the sash.

A decorative grid on the interior or exterior of the glass, between the glass panes, or in any combination of these locations that divides a window opening into smaller openings to create simulated divided lite or true divided lite. Grilles may or may not be removable.

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

Hopper Window
The sash is hinged at the bottom so that the window opens into the house. Mainly used in basements.

Horizontal Sliding Window
Two or more sash that slide horizontally past each other; one or more of the sash may be fixed or inoperative or each sash may operate.

Air that is able to flow through cracks and other spaces around the window and at the meeting rail.

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

A series of small horizontal overlapping glass slats held together by a metal end frame attached to the faces of the window frame side jambs or door stiles and rails.

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

“J” Configuration designed into window frame exterior for the primary purpose of receiving siding.

Lift Rail Handle
handle or grip installed on the sash of a window to make it easier to raise or lower the sash.

A unit of glass.

Low E (Emissivity) Glass
Glass treated with a thin transparent coating of metal oxide and silver. 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. Keeps your home cool in the summer and warm in the winter. It reduces the penetration of ultraviolet rays to minimize fading of carpet and draperies.

Meeting Rail
The point at which the horizontal sections of the top and bottom sash meet. On sliders, the meeting rail is vertical.

A strip of wood, usually shaped to a curved profile, used to accent and emphasize the ornamentation of a structure and to conceal surface or angle joints.

Mounting Flange
Used to secure the window into a rough opening. Also called a nail fin.

Mulled Unit
Two or more window units structurally joined together.

A metal or vinyl extrusion used to structurally join two or more windows.

The pieces of decorative grid that help divide a window opening into smaller sections. Also called a grid or grille.

Muntin Bar
See muntin.

Obscure/Translucent Glass
A frosted glass that you cannot see through.

A framed sheet of glass within a window or door frame.

Usually refers to the separate panel or panels in a door frame. A panel may be operable or stationary.

Picture Window
A fixed window that has no moveable sash.

The pitch of a roof is the degree of the inclination upward from horizontal or flat. It may be expressed in degrees or as the ratio of the number of inches it rises in each 12 inches of horizontal span: 4/12 means the roof rises four inches for every foot of horizontal span.

A group of windows mulled in combination of fours.

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

Rough Opening
The framed opening in a wall into which a window or door unit is to be installed.

Replacement Window
A window designed to fit into an existing window opening.

Resistance to thermal transfer or heat flow. Higher R-value numbers indicate greater insulating value. It is the inverse of the U-Value (R=1/U).

Sash Stop
An extrusion molding generally about 2” long that covers the joint between window sash and the jamb that stops the operable sash at its maximum opening.

A single assembly of stiles and rails made into a frame for holding the glass in a window.

Sash Balance
A system of weights, cords, and/or coiled springs that assist in raising a sash and keep the sash in any placed position by counterbalancing the weight of the sash. See balance.

Sash Lock
Generally, a cam-action type lock applied to the rails of the sliding window to pull the check rails tightly together or to seal the sash tightly to the frame, both for security and weathertightness.

Wood wedges 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.

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

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

Simulated Divided Light
A method of constructing windows in which muntins are affixed to the inside and outside of a panel of insulating glass to simulate the look of true divided light.

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

Single Hung Window
Window with a fixed top sash and an operating bottom sash.

Slider Window
Window that slides to the left or right.

Sliding Patio Door
Patio door in which a vent panel moves horizontally on a track system past a fixed panel.

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 (center glass), divided by the amount that is actually contacting the exterior of the unit. The lower the value, the better the unit keeps out solar heat.

Sound Transmission Class (STC) Rating
Measures the amount of noise reduction that can be achieved with a given product. A noise reduction of 10 decibels represents cutting the noise level in half, as interpreted by the human ear. So a rating of 25 means that the product reduces the outside noise by approximately 25 decibels, cutting the noise in half 2-1/2 times, or cutting it by over 80 percent.

Vertical member of a window sash or door panel.

Tempered Glass
Glass that is treated with heat in its manufacturing, creating a product that can withstand abnormal force or pressure on its surface, and which does not break into sharp pieces; code requires tempered glass in all doors (including patio doors) and in windows that are located near doors, bathtubs, or showers.

Thermal Break
An element of low conductance placed between elements of higher conductance to reduce the flow of heat (or cold).

Tilt Window
A window designed in such a way that the sashes tilt inward for easy cleaning of the outside of the glass.

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

A group of windows mulled in combination of threes.

A group of windows mulled in combinations of twos.

U-Value (U-Factor)
The rate of heat transfer through a window or door (center glass). The lower the U-value, the better the insulating properties of the unit or glazing system.

Variously shaped metal, vinyl, plastic or molded fiber strips that fit tightly against the window or door frame parts to prevent air infiltration through cracks.

Small holes along the bottom edge of a window or door unit that allows any trapped water to escape outdoors.

Force extended on a surface by moving air.

Sound Control
From highway and railway noise, to airports and general noise pollution, SilentGuard® Windows are the superior choice for new construction and renovation projects in single family and multifamily/light commercial applications. Through extensive research and development, SilentGuard® Windows can help mitigate against a broad spectrum of noise ordinances and code compliance including STC (Sound Transmission Class), EWR/EWNR (Exterior Wall Noise Reduction), OITC (Outdoor-Indoor Transmission Class).

STC (Sound Transmission Class)
This rating was first published in 1970 in accordance with ASTM E413, and was designed to provide a performance rating for interior wall partitions against noises from speech, television, radio and office equipment. It is important to note that ASTM E413 specifically states that the STC calculation should not be used to evaluate partitions exposed to transportation noise such as motor vehicles, aircraft and trains.

EWR/EWNR (Exterior Wall Noise Reduction)
This rating was developed in 1977 by Wyle Laboratories for the U. S. Department of Transportation, Federal Highway Administration. It is similar to the STC rating, but, unlike the STC rating, it is designed to provide a performance rating for building facades that are exposed to transportation (traffic) noise.

OITC (Outdoor-Indoor Transmission Class)
This rating was first published in 1990 in accordance with ASTM E1332, and was designed to provide a performance rating for exterior facades and facade elements (windows and doors) that are subjected to transportation noise such as motor vehicles, aircraft and trains. The OITC rating can be assigned to specimens tested in the field and in the laboratory.