A
Air Chambers	Small honeycomb spaces within the sash and frame which help to insulate and strengthen the window
Air Infiltration	The amount of air that passes between a window sash and frame. In windows it is measured in terms of cubic feet or air per minute, per square foot of area. The lower the number, the less air the window lets pass through.
Air Latch	Latch mechanism on the interior face of the sash that retains the window in a partially open position for ventilation.
Angled Exterior	A sloped extension from the frame that adds an aesthetically-pleasing dimension to the exterior of the window.
Argon Gas	An odorless, colorless, tasteless, nontoxic gas which is six times denser than air. It is used to replace air between the glass panes to reduce temperature transfer.
Awning	Window A hinged window that swings outward for ventilation.
B
Balance	The system in the side jambs of a single or double-hung window that helps open and support the weight of the sash, and helps hold the sash in place while in an open position.
Bay Window	An angled combination of three windows that project out from the wall of the home. The windows are commonly joined at 30- or 45-degree angles.
Beveled Exterior	An angled extension from the frame that adds an aesthetically-pleasing dimension to the exterior of the window.
Bow Window	An angled combination of windows in 3-, 4- or 5-lite configurations. The windows are attached at 10- degree angles to project a more circular, arced appearance.
Butyl	A rubber material that seals the glass to the spacer, creating an airtight and watertight IG unit. Butyl has the lowest gas permeability of all rubbers.
Brick Mould	Exterior casing trim around a window or door. Brick mould 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 (net) window size, not including the nail fin.
C
Casement Window	A window with a side-hinged sash that opens outward for ventilation.
Casing	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.
Center of Glass U- and R-values	The U- and R-values measured from the center of the glass to 2-1/2" from the frame.
Condensation Resistance Factor	A measure of the effectiveness of a window or glazing system to reduce the potential for condensation. The higher the condensation resistance factor, the more efficient the window and glazing system.
Conduction	Energy transfer from one material to another by direct contact.
Cottage Window	A double hung or single hung window with a larger proportioned bottom sash, as compared to the top sash.
Convection	Heat transfer by currents that flow from a warm surface to a colder one.
Capping	An extension from the frame that adds an aesthetically-pleasing dimension to the exterior of the window.
D
Dead-air space	The space between the panes of glass of an I.G. Unit.
Double Hung Window	A window that has two operable sash which slide vertically.
Double-strength	Glass Glass with a thickness of approximately 1/8".
E
Egress Code	The code that requires a minimum opening of a window for persons to exit or firefighters to enter a building.
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. Over the past ten years, ENERGY STAR? guidelines have helped double the efficiency of windows they endorse
F
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 or non-operable, such as a picture window.
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 sash or door panel fits.
Fusion Welded	Refers to vinyl frames and sash attached together at corner joints, using a heat source to create a fused, weather tight corner joinery.
G
Glass	An inorganic transparent material composed of sand (silica), soda (sodium bicarbonate), and lime (calcium carbonate) with small quantities of alumina, boric or magnesia oxides. Available Styles: Clear, Bronze, Grey and Tinted. ? Glazing - The process of sealing the glass to the sash.
Glazing Bead	A strip of vinyl which surrounds the edge of the glass and holds it in place in conjunction with other sealants.
Grids	Decorative horizontal or vertical bars installed between the glass panes to create the appearance of the sash being dividing into smaller lites of glass
H
Header	The horizontal top portion of the main frame.
Haze	Haze is the percentage of transmitted light which in passing through the speci­men deviates from the incident beam by forward scattering. In essence, the higher the haze value, the poorer the product is for clarity. The haze % for Low E2 is 0.14 as compared to any­where from 0.74 up to 1 .40 for pyrolytic Mid-E coatings.
Hopper Window	The sash is hinged at the bottom so that the window opens into the house. Primarily used in basement applications.
Horizontal Sliding Window	One or more sash that slide horizontally past each other. One or more sash may be fixed (inoperable), or each sash may operate to open and close.
I
I.G. Unit	(Insulating Glass Unit) Two or more lites of glass separated by a spacer and hermetically sealed at the glass edges.
Interlocking Channel	The horizontal sections of a pair of sash that meet when the sash are closed.
J
Jamb	Vertical sections of the main frame.
J-Channel	“J” configuration designed into window frame exterior shape for the primary purpose of receiving siding to self-trim around a window perimeter.
Jalousie	A series of rectangular, horizontal overlapping glass slats held together by metal end-frames attached to a side-jamb mechanical unit that simultaneously opens or closes the slats in unison.
K
Keeper Rail	The horizontal section of the sash where the keeper is attached.
Keeper Stile	The vertical section of the sash where the keeper is attached.
L
Laminated Glass	Two or more pieces of glass bonded together over a plastic interlayer.
Lift Rail	A handhold for raising and lowering the sash. Rail implies that the handhold is continuous across the sash.
Lite	A unit of glass in a window.
Lock Rail	The horizontal section of the sash where the cam lock is attached.
Lock Stile	The vertical section of the sash where the cam lock is attached.
Lock and Keeper	The mechanisms which pull the sash together when placed in the locked position.
Low E Glass	Low E glass stands for Low Emissivity Glass. This type of glass coating was developed to provide improved solar heat gain coefficient performance.
Low E2	Glass Low E squared was developed to provide better summer daytime per­formance with only a slight reduction in visible light transmittance. Because of the excellent win­ter nighttime and summer daytime performance of Low E2, it is becoming the popular choice for many residential window applications.
M
Main Frame	The head, sill and jambs sections of a window.
Mechanically Fastened Frame	Refers to frames fastened with screws.
Meeting Stile	The vertical section of a pair of sash that meet when the sash are closed.
Mesh	Fabric made of either fiberglass or aluminum, used in the making of screens.
Mullion	A vertical or horizontal connecting unit between two or more windows.
N
Nailing Fin	An extrusion attached to the main frame of a window used to secure the unit to the rough opening.
O
Obscure Glass	Glass that has been made translucent instead of transparent.
Overlapping and Interlocking Meeting Rail	A patented meeting rail which overlaps and interlocks both sash.
Oriel Window	A double hung or single hung window with a larger proportioned top sash, as compared to the bottom sash.
P
Pane	A framed sheet of glass within a window or door frame.
Panel	Usually refers to the separate panel or panels in a door frame. A panel may be operable or stationary (fixed).
Patio door	A glass door that slides opens and close on adjustable brass rollers. Available in 2-3 or 4 lite configurations with the operable panel available in any position.
Picture Window	A window that has no moveable sash.
Pivot Alignment System	An exclusive hinge-type system used on hung windows. This system attaches the sash to the balance, creating perfect alignment between the sash and frame, while allowing the sash to tilt inward for cleaning.
Pull Handle	A handhold for sliding the sash back and forth. Handle implies that the handhold is not continuous across the sash.
Pull rail	A handhold for sliding the sash back and forth. Rail implies that the handhold is continuous across the sash.
Pyrolytic Coatings (Hard Coat)	As the name implies, these coatings are applied to hot glass. This type of coating gives a “Mid-E” performance far from that of Low E2. It pro­vides rather poor optical quality (color) and consistency of coating. Another disadvantage of pyrolytic coatings is that they exhibit high haze levels compared to that of Low E2. Most Low E glass available today on the market is made this way.
Q
Quad	A group of windows mulled in combination of fours
R
R-value	Resistance a material has to heat flow. The higher the R-value, the greater the resistance.
Radiation Wave	energy transmitted directly from one object to another through the atmosphere or through transparent or translucent materials. The energy radiated is transmitted, absorbed, reflected or a combination of all three.
Rail	The horizontal sections of the sash.
Raised Exterior	An angled extension from the frame that adds an aesthetically pleasing dimension to the exterior of the window
Relative Humidity Condensation Point	The relative humidity level at which visible water vapor or other liquid vapor begins to form on the surface of the sash or frame, based on an inside temperature of 70E F and an outside temperature of 0E F. The higher the percentage, the more moisture the air can hold before condensation will occur.
Rough Opening	The framed opening in a wall into which a window or door unit is to be installed.
S
Sash Balance	A system of cords, and/or springs that assist in raising a sash, while keeping the sash in any placed position by counter-balancing the weight of the sash.
Sash	The part of the window which contains the glass.
Sash Lock	Generally, a cam-action or other latch-type lock applied to the sashes of a sliding window to both pull the sashes tightly together and to seal the sash tightly to the frame, both for security and to create a weather tight seal.
Sash Stop	An extrusion molding piece, generally about 2” long that covers the joint between window sash and the jamb, stopping the operable sash at its maximum opening.
Sash Alignment System	An exclusive hinge-type system used on hung windows. This system attaches the sash to the balance, creating perfect alignment between the sash and frame, while allowing the sash to tilt inward for cleaning.
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 sash on either or both sides of a door to light an entryway or vestibule.
Simulated Divided Light (SDL)	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 panes.
Sill	The horizontal, bottom section of the main frame.
Sill Extender	An extrusion that is attached to the bottom of the window to cover the gap between the sill and the rough opening.
Single Glazing	Use of a single pane of glass in a window. Not as energy-efficient as insulated glass.
Single Hung	A window in which one sash slides vertically and the other sash is fixed.
Single-strength Glass	Glass with thickness between 0.085 and 0.100 inches.
Slider Window	A window in which the sash move horizontally. Sliders are available in a 2- or 3-lite configuration, with the 3-lite having operable end vents.
Solar Heat Gain Coefficient (SHGC)	The fraction of incident solar radiation which enters a building as heat. It is based on the sum of the solar energy transmittance plus inwardly flowing fraction of absorbed solar energy on all lites of the glazing. It can be expressed in terms of a window or the glazing alone.
Solar Energy Transmittance	In the solar spectrum, the percentage of ultraviolet, visible and near infrared energy from the sun that is transmitted through the glazing.
Spacer	Material placed between two or more pieces of glass in order to maintain a uniform width between the glass, and prevent sealant distortion.
Spiral Balance	Device for holding vertically sliding sash in any desired position through the use of a spring or weight to counterbalance the weight of the sash.
Sputtered Coatings (Soft Coat)	This is how Low E2 is made. The advantage of this coating is that it provides overall qualities of high visible light transmission, neutral color, coating uniformity and low emissivily. This combination provides a nearly invisible coating with the highest level of performance possible.
Solar Energy Reflectance	In the solar spectrum (300 to 2500 nanometers), the percentage of ultraviolet, visible and near infrared energy from the sun that is reflected from the glazing surface(s).
Sliding Patio Door	A patio door in which a vent panel moves horizontally on a sill track system past a fixed or operable panel.
Sound Transmission Class (STC) Rating	Measures the amount of noise reduction that can be achieved with a given product.  The higher the number, the better the product is at suppressing sound transmission.
Stile	The vertical member of a window sash or frame, or of a door panel.
T
Tape Glazing	Two-sided tape used to secure and seal the glass to the sash.
Tempered Glass	Glass with a surface compression of not less than 10,000 psi, or an edge compression of not less than 9,700 psi. When broken, the glass breaks into pebbles instead of shards.
Thermal Break	An element of low conductance placed between elements of higher conductance to reduce the flow of heat (or cold).  In thermal break window frames, a non-metallic polyurethane material separates the transmission of cold between the frame’s exterior and the frame’s interior.
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 and is manufactured by welding.
Total Unit U- and R- values	The U- and R-values of the window calculated from the average of the center of glass, edge of glass and frame U- and R-values. It is the reciprocal of the R-value.
Trapezoid	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
Transom	A small window placed over the top of a door or window, primarily for additional light and aesthetic value.
Triple	A group of windows mulled (joined) in combination of threes.
Twin	A group of windows mulled (joined) in combinations of twos.
U
U-value	Amount of heat transferred through a material. The lower the U-value, the slower the rate of heat flow and the better the insulating quality.
UV Block	The percent of ultraviolet rays blocked from being transmitted through the glass. The higher the number the lower the percentage of ultraviolet rays transmitted through the window.
V
Vent-lock	Latch mechanism on the interior face of the sash which retains the window in a partially open position for ventilation.
Vinyl	Generic term for Polyvinylchloride or PVC, an extruded material used for window and door framing.
Visible Light Transmittance	The percentage of light that is transmitted through glass in the visible light spectrum (380 to 720 nanometers). The higher the number the higher the percentage of visible light transmitted through the window.
W
Weather-stripping	Weather-stripping Material used to form a weather-resistant seal around operable sash.
Weep Flaps	A weep hole that is covered with vinyl flap that allows water to escape, while keeping insects out.
Weep Holes	Small openings designed to allow water to escape that might otherwise accumulate in a window's sill.
Weep Slots	Slots or holes in the sill (bottom) member of the sash frame that provides an outdoor release of infiltrated rainwater.
Wet Glazing	A silicone-based substance used to secure and seal the glass to the sash.
Wind Load	Force extended on a surface by moving air.