Glossary of Window Terminology

AAMA - American Architectural Manufacturers Association. A national trade association that establishes voluntary standards for the window, door, storefront, curtain wall and skylight industries.

Absorbtance - The ratio of radiant energy absorbed to total incident radiant energy in a glazing system.

Accessory Groove - A shape included on a fenestration product frame that is designed to mate with installation accessories.

Acid Etching - A process used in decorative glass where hydrofluoric acid is applied to the surface of the glass. Where the acid contacts the glass surface, the glass becomes frosted with a matte finish (similar to the effect caused by a sandblasting process). Patterns can be applied using special wax coatings on the glass. Where the glass is coated with wax, no corrosion of the surface will take place.

Acrylic - A thermoplastic with good weather resistance, shatter resistance and optical clarity, used for glazing.

Actual Dimension - The outside horizontal and vertical measurements of a window or door excluding the nailing fins. Also referred to as overall dimension.

Adhesion - The property of a sealant/compound that measures its ability to bond to a surface on which it is applied.

Adhesion Failure - The pulling away of a sealant/compound from the surface it is applied to, resulting in water penetration.

Aerogel - A micro porous, transparent silicate foam used as a glazing cavity fill material, offering possible U-values below 0.10 BTU/(h-sq ft-°F) or 0.56 W/(sq m-°C).

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.

Air Leakage (AL) - Heat loss and gain occur by infiltration through cracks in the window assembly. Air leakage is expressed in cubic feet of air passing through a square foot of window area. The lower the AL, the less air will pass through cracks in the assembly. While many think that air leakage is extremely important, it is not as important as U-factor and the Solar Heat Gain Coefficient. (See Air Infiltration.)

Airspace - The measured distance between the inner surfaces of the two pieces of glass in an insulated unit. Also used in reference to the thickness of the spacer bar.

Aluminum Clad - A window or door made from wood with an exterior skin of aluminum.

Aluminum Window - A window whose frame and sashes are made from aluminum.

Angled Exterior - A sloped extension from the frame that adds an aesthetically-pleasing dimension to the exterior of the window.

Angle Top - Any window with a horizontal sill, vertical jambs, and a straight sloping head (See TRAPEZOID.)

Annealed Glass - Non-tempered glass. The most common glass used in window products.

Annealing - Heating above the critical or re crystallization temperature, then controlled cooling of metal, glass or other materials to eliminate the effects of cold-working, relieve internal stresses or improved strength, ductility or other properties.

Anodize - An electrochemical process that increases the natural oxide coating of aluminum. Clear anodizing gives aluminum a smooth consistent surface that reduces corrosion, especially in salt air. Color anodizing can be effected by the use of dyes or special alloys. Anodizing is not normally used in residential applications, except in some coastal areas.

ANSI - American National Standards Institute - a clearing house for all types of standards and specifications.

Applied Muntin - A muntin in a glazed window that does not actually separate individual lights of glass. This muntin may be of a material different than the main frame- work of the window. The applied muntin may be attached to the glass with an adhesive or placed over the glass and held in place by the glazing bead.

Apron - The inside trim piece that lies flat against the wall beneath the stool (interior sill extension). This is a traditional treatment usually associated only with double hung windows.

Arch Top - Any window with a horizontal sill, vertical jambs, and a head that is curved upward. (See CIRCLE TOP and EYEBROW.)

Architectural Modular - An early method of sizing Awning windows for frame construction.

Argon - An inert colorless gas which has good thermal resistance properties. Argon gas is commonly used to fill the air cavity between panes of glass in an IG unit, in order to improve the insulating properties of the unit.

Argon Gas - Argon is a safe, odorless, 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.

ASHRAE - American Society of Heating, Refrigerating and Air Conditioning Engineers.

Assembled - A condition of a sliding glass door when all of the parts are in place, as opposed to Knocked Down (KD).

ASTM - American Society for Testing and Materials. Organization that sets standards for testing of materials.

Astragal - A channel on a sliding glass door panel, which allows another panel to slide into it. May also be used on screen doors.

Awning Window - A window with the sash hinged at the top that can be opened outward. Awning windows can have more than one sash and allows for a maximum venting area. Though once common in Florida and more tropical areas, it is less popular today.

Azurite Glass - An aquamarine-tinted solar glass designed for controlling heat exchange through the glass panel.

Back Bedding - The same as Glazing Compound.

Backer - A strip of aluminum glued to the interior side of a raised grid unit. When applied with a raised grid, the look simulates a true divided light.

Backer Rod - A material placed into a joint, primarily to control the depth of the sealant. Also serves as a bond breaker.

Balance - A device in a hung window that allows the sash to be adjusted to any position between fully open and fully closed. Originally, balances were weights attached to the top corners of the sash and draped over a pulley on either jamb. The weights and the friction of the pulleys "balanced" the weight of the sash. Balances normally are placed in pairs for each sash, one at each jamb. A heavier window may use two balances on each jamb. (See BLOCK AND FRICTION BALANCE, SPIRAL BALANCE, or TACKLE BALANCE.)

Balance Rod - Same as Spiral Balance.

Balance Shoe - Part attached to bottom of balance that attaches balance to sash. A bar or pin on the sash fits in a "slot" in the shoe.

Balance Spring - A device for counterbalancing a sliding sash, generally associated with a double-hung window, so that it can be held open at a position. (See Sash Balance.)

Balance System - 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.

Balance Tool - A hook-like tool used for adjusting spiral balances.

Basement Sash Unit - (cellar sash unit) - A sash unit, usually of the in swinging or hopper sash type, used for basement or cellar sash openings; usually consists of one, two or three glass lites (lights); may include screens and storm panels.

Basic Unit - This term is given to the fundamental "building block" units of each standard window product line. These units are members of a series of standard sizes. They lack exterior trim or installation flanges but are otherwise complete.

Bay Window - A composite of three or more windows, usually made up of a large center unit and two flanking units at 30°, 45° or 90° angles to the wall.

Bead - A sealant/compound after application in a joint. Also a molding or stop used to hold a glass product in position.

Bent Glass - Flat glass that has been shaped while hot into cylindrical or other curved shapes.

Bevel - A machine angle other than a right angle, i.e., a 3 bevel is equivalent to a 1/8 inch drop in a 2 inch span (1mm in 16mm).

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

Beveling - The removal of material on a glass surface by abrasion, which causes the edge to slope. This is a common practice on mirror glass to finish the edge of the mirror.

Big Box - A term used to refer to large home center chains like Lowe's, Home Depot and Menards.

Bite - The dimension by which the edge of a glass product is engaged into the glazing channel.

Blackbody - The ideal, perfect emitter and absorber of thermal radiation. It emits radiant energy at each wavelength at the maximum rate possible as a consequence of its temperature, and absorbs all incident radiance.

Blind Stop - A sash or window frame member applied to the exterior vertical edge of the side and head jamb in order to serve as a stop for the top sash and to form with the brick moulding and/or casing a rabbet for the storm sash, screens, blinds and shutters.

Block - Rectangular, cured sections of neoprene or other approved material, used to position the glass product in the glazing channel.

Block and Tackle Balance - A type of balance that employs a block and tackle apparatus and coiled spring. This type balance allows the sash to be easily removed from the window frame. A block and tackle balance can normally carry a heavier load than a spiral or friction balance. (See BALANCE.)

Block Frame Window - Used when replacing the wood sash of an old double hung wood window.

Block Modular - A method of sizing Awning windows for concrete block construction. Dimensions are based on full or half block sizes.

BOCA - Building Officials and Code Administrators.

Bottom Rail - The bottom horizontal member of a window sash.

Bow - A combination of two or more windows mulled together with each window offset at a small angle (usually between 10 and 20 degrees). A horizontal cross section would resemble an archer's bow. Bow window units normally consist of four to six individual hung windows or picture windows or a combination of both types.

Breather Tube - See Venturi Tube

Brick Molding - An exterior (milled) trim piece to cover the gap between the window frame and masonry in a masonry opening or in other siding.

Brick Mould - A form of exterior trim (casing) for windows and doors. In addition to serving as an anchor point for installation of the unit brick mould provides a boundary for brick or other siding material on the face of the building and attachment of hardware. (Sometimes called Shake mould.)

Brickmold - A type of external casing which frames windows and doors.

Bronze-Tint Glass - Glass tinted with a light bronze coloring used to reduce the amount of light transmitted through the pane. This glass is predominantly used in southern locations where light intensity from the sun is stronger.

BTU - An abbreviation for British Thermal Unit, the heat required to increase the temperature of one pound of water one degree Fahrenheit.

Buck - A jamb stud or header; wood buck. Rough framework to which a window or door is installed.

Buck Dimension - The height or width a window will finish to on the inside of the structure.

Buck Opening - The opening in a wall formed by the rough framing members; also, stud opening.

Bullet-Resistant Glass - A multiple lamination of glass with tough clear sheet plastic, usually at least 1 3/16 inches thick overall, which is designed to stop bullets from ordinary firearms other than high-powered rifles.

Bumper - A soft vinyl or rubber cushion that prevents the moving panel of a sliding glass door from striking the jamb on the fixed panel side of the door.

Butt Glazing - The installation of glass products where the vertical glass edges are without structural supporting mullions. (See also Channel Glazing.)

Butt Joint - A joint formed by square edge surfaces (ends, edges, faces) coming together; end butt joint, edge butt joint.

Butyl - A sealant compound commonly used in the production of insulated glass units.

Bypass Door - A sliding glass door style whereby the door panels pass around each other on separate tracks.

Call Out Size (C.O.S.) - The nominal size of a window or door. In other words the "name" of the size. For instance, a window that is 3 feet wide and 4 feet high would have a call out size of 3040.

Cam Lock and Keeper - The mechanisms which pull the sash together when placed in the locked position.

Caming - Grooved, usually H-shaped, rod of cast lead used, as in stained glass, to hold the panes or pieces of glass together.

Cap/Capping - Cosmetic covering, usually found on the exterior of the window or door to achieve aesthetic sight lines or to integrate the window or door system into the building surface or weatherproofing system. If panning is being used for weatherability, the panning is not considered cosmetic, but part of the window system.

Capillary Tubes - Small hollow tubes which penetrate the spacer system of an insulating glass unit. They allow pressure equalization between manufacturing locations, shipping and installation locations. Since the insulating glass unit is not permanently sealed, the air space cannot be filled with Argon gas.

Casement - A window sash that swings open on side hinges; in-swinging are French in origin; out-swinging are from England.

Casement Window - A projecting window with a single sash hinged at the sides and usually opening outward like a door and operated by a (crank) handle which turns to open or close the unit.

Casing - (Trim): Exposed molding or framing around a window or door, on either the inside or outside, to cover the space between the window frame or jamb and the wall.

Caulk - To seal cracks and joints around window and door frames to prevent leakage of water and air.

Caulking - A mastic compound for filling joints and sealing cracks to prevent leakage of water and air, commonly made of silicone, bituminous, acrylic or rubber-based material.

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.

Center Jamb - The same as Lockstile.

Center Swinging Patio Door - A center swinging patio door attempts to project the feeling of an authentic French door but it differs in two major ways:

A. Panel(s) is permanently fixed
B. The operating panel is not hinged on the side jamb - instead the panel is hinged from a special structural mull in the center of the unit.

Certification - A document that certifies a window or door has been tested and has met certain requirements of strength, safety, air and water infiltration, and resistance to forced entry. Qualified testing labs issue certifications after testing or witnessing the test of a manufacturers product.

Certified IG Unit - An insulating glass unit constructed like a unit test model, that has successfully passed the ASTM E773 and E774 tests of insulating glass seal durability performance at specific levels.

Channel Glazing - A method of glazing that entails a soft vinyl or rubber gasket-like material folded over the edges of the glass and then fitted inside a channel opening in the sash frame members. It is most commonly used in sliding glass doors. Also known as marine or wrap around glazing.

Check Rail - On a double-hung window, the bottom rail of the upper sash and the upper rail of the lower sash, where the lock is mounted.

Chemically-Strengthened Glass - Glass which has undergone ion-exchange to produce a comprehensive stress layer.

Chlorinated PVC - Produced by the post chlorination of polyvinyl chloride resins. Used extensively in pipe, fittings and valves in water piping systems.

Circle - A fixed lite window in the shape of a whole circle.

Circle Top Transom - A half-circle window over a door or window, with radiating bars.

Circle Top Window - A fixed lite window whereby the head of the window is formed into a full radius half circle. This curved head is either attached to the jambs of a window or to a sill section that can then be attached to a horizontal head of a standard window. Circle top units are occasionally used alone.

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

Clad - A designation given to products whose exposed exterior surfaces are sheathed with specially formed aluminum.

Cladding - Any material locked to the outside faces of doors and windows to provide a durable, low-maintenance exterior surface.

Clerestory Window - A window in the upper part of a lofty room, usually out of reach from the floor. These windows can be fixed or operating and an extension device is used for operating clerestory windows.

Closed Pocket Door - A sliding glass door style whereby the door panels stack up inside a wall.

Co-Extrusion - The technique of extruding two or more materials through a single die being fed by separate extruders.

Cohesive Failure - The splitting and opening of a sealant/compound within its body, resulting in water penetration.

Colonial Lite - Windows with small rectangular panes or divided lites and designated as a 12-lite, 16-lite, and so on.

Combination Storm Sash and Screen - A frame assembly of stiles and rails containing a half screen and two glass storm panels: in summer the bottom storm panel is stored in the top of the combination frame and replaced by the screen panel; sometimes called "combination storm sash and screen unit" or simply "combination window unit".

Commercial Window - A window used in commercial buildings, which are normally heavier than residential windows and often anodized.

Commodity - A Florida window industry method of determining standard window opening sizes.

Complete Window Replacement - The installation of a replacement window where the previously-installed window is completely removed and replaced with a new frame/sash unit.

Composite - Window and door members which are comprised of two or more materials, which are structurally combined or connected so as to perform structurally as a singular material; i.e., poured and debridged aluminum shapes, fiberglass and man-made wood products, etc.

Composite Frame - A frame consisting of two or more materials for example, an interior wood element with an exterior fiberglass element.

Compound - A formulation of vehicle, fillers and polymer(s) producing an elastometric sealant.

Condensation - A condition caused by warm moist air coming into contact with a colder object with moisture appearing on the colder surface. A large difference in the temperature of either side of a window and humid air present on the warmer side will cause condensation to appear.

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 - Heat transfer through a solid material by contact of one molecule to the next. Heat flows from a higher-temperature area to a lower-temperature one.

Contractor - A business entity that is hired by a person or business to perform a specific job or function.

Convection - A heat transfer process involving motion in a fluid (such as air) caused by the difference in density of the fluid and the action of gravity. Convection affects heat transfer from the glass surface to room air, and between two panes of glass.

Core - Insulating or other center material used in the door.

Corner Key - A metal or plastic device used to secure the corners of a sash, frame, spacer bar, or screen section. The device is generally an "L" shaped part that fits inside mitered ends of the perimeter parts. The corner key can be crimped (staked) in place or screws can be inserted. The corner key makes a rigid joint possible. (See CORNER LOCK)

Corner Lock - The same as Corner Key.

C.O.S. - Same as Call Out Size and Nominal Size.

Cottage Style Window - Hung Window (Single or Double) that has a larger bottom sash (lite) than the top sash (lite).

Coved Exterior - An arced extension from the frame that adds an aesthetically-pleasing dimension to the exterior of the window.

Crack length - Total outside perimeter of window vent. Used in figuring air infiltration during AAMA certification testing.

Crackle Glass - To produce the crackle effect, the glass is submerged in water during the curing process to cause the surface to crack. A second layer of glass is then applied and the entire unit is re-heated in order to fuse the glass together.

CRF (Condensation Resistance Factor) - An indication of a window's ability to resist condensation. The higher the CRF, the less likely condensation is to occur.

Cripple Stud - A short stud above or below a window or door opening.

Cripples - A short stud above or below a window or door opening.

Crystal Sheet Glass - Sheet glass with a thickness between 0.180" to 0.199" (4.50 to 5.50 mm) or approximately 3/16" thick. Used in very large window units.

Cullet - Broken glass, excess glass from a previous melt, or edges trimmed off when cutting glass to size. Cullet, in some regular proportion, is an essential ingredient in the raw batch charge in glass making - in that it facilitates melting.

Curb - A watertight wall or frame used to raise slope glazing above the surface of the roof as a preventive measure against water leakage from melting snow or rain run-off.

Curing Agent - One part of a two-part sealant that, when added to the base material, causes it to vulcanize by chemical reaction.

Curtainwall - An exterior building wall which carries no roof or floor loads and consists entirely or principally of metal or combination of metal, glass and other surfacing materials supported by a metal framework. There are two basic types:

Custom: Walls designed specifically for one project and using parts and details specially made for this purpose.
Standard: Walls made up principally of parts and details standardized by their manufacturer and assembled in accordance with either the architect's design or the manufacturer's stock patterns.

Cylinder Lock - A type of adjustable pin lock, cylindrical in shape, used in sliding glass doors and storm doors for security.

DADO - Rectangular groove recessed into a wood door or frame.

Daylight Opening - The portion of a window or door's glazing which is actually visible. A small percentage of a unit's glass will always be concealed as it is mounted in the wood parts.

Dead Bolt - Lock bolt having neither spring action nor bevel and is operated by a key or a turn piece.

Dead Lite - A non-operable lite which is fixed to the structure.

Dead Loads - Load force due to glass weight.

Dead-Air Space - The space between the panes of glass of an I.G. Unit.

Deadlite - A piece of glass or IGU with a sash profile around it; not set within the main frame of a window unit.

Dealer - A business entity that typically deals in a small range of products and sells to an end user.

Degree Day - A unit that represents a one-degree Fahrenheit deviation from some fixed reference point (usually 65° F) in the mean, daily outdoor temperature. (See also, heating degree day.)

Desiccant - A drying agent usually in granular form (similar to silica gel) used by some manufacturers between the panes of insulating glass (in edge spacer) to prevent "fogging" between the panes.

Dew Point - The temperature at which water vapor in the air will condense at a given state of humidity and pressure.

Dimensional Windows - Customer units created by reducing the size of existing standard units. Dimensional units cannot be smaller in size than the smallest standard size nor larger than the largest standard size.

Direct Set - Refers to window units which do not have sash. The glass is mounted directly into the frame. Units of this type do not operate.

Divided Light - A window with a number of smaller panes of glass separated and held in place by muntins.

DIY - Do-It-Yourself. Usually referring to Homeowners who take on the task of home improvements.

Doghouse Window - A fixed-lite window with a horizontal sill, vertical jambs and a peaked head that resembles the front view of a common doghouse. Also known as a pentagon or a double rake head.

Dome - The spherical shape associated with skylights.

Door Jamb - The part of a door frame which surrounds and contacts the edges of the stiles and top rail of a door; jambs may be classified as (1) "head" or "side" jambs and (2) "plain" or "rabbeted".

Door Skin - Sheet of material (wood, steel, fiberglass, PVC, etc.) that forms the exterior faces of the door.

Door Slab - A door without lites or sweep installed.

Dormer - A space which protrudes from the roof of a house, usually including one or more windows.

Double - Two windows mulled side by side to form one unit. Also known as a twin window.

Double Glazed Units - Units consisting of two lites of glass and one air space in between.

Double Glazing - In general, two thicknesses of glass separated by an air space within an opening to improve insulation against heat transfer and/or sound transmission. In factory-made double glazing units, the air between the glass sheets is thoroughly dried and the space is sealed airtight, eliminating possible condensation and providing superior insulating properties.

Double Hung Replacement System - A packaged system furnishing new sash and operating block and tackle mechanism powered by springs or weights (balance). For replacement of sash only in double hung windows found in older buildings.

Double Hung Window- A type of window with two vertically moving sashes, with each sash employing balances. (See BALANCE and HUNG.)

Double Pitch Design - Pertaining to two opposite roof slopes, e.g., sloping North and South; also referred to as a ridge connection.

Double Strength - A glass thickness designation. In float glass, approximately 1/8" thick.

Double Strength Glass - (DSB) 1/8" thickness.

Drip Cap - A piece of flashing which is contoured for application on top of windows and doors during installation. Its purpose is to prevent water from seeping down behind the casing and invading the interior of the wall. For Clad windows, this item is often incorporated into the head nailing flange.

Drop In Glazing - A type of glazing that attaches directly to the glazing leg in the sash and frame members using glazing compounds or tape and glazing bead.

Dry Glazing - An alternative method of placing glass in a door or window. No glazing mastic is used. Dry glazing is recommended whenever reflective coatings are glazed to first surface.

DSB - This symbol represents Double Strength sheet glass, which is 1/8" (3mm) in thickness. The B specifies “B quality” glass that at one time was a lesser grade than “A quality”. Improvements in glass manufacturing are now such that B quality is of very good strength and clarity. The term “A quality” is not used today.

Dual Durometer - A material that has two or more levels of flexibility. An example is the weather stripping used between the frame and sash of a casement window.

Durometer - A gauge used to measure the hardness of an elastometric material.

Edge Clearance - Nominal spacing between the edge surface of the glass product and the glazing channel base.

Edge Effects - Two-dimensional heat transfer at the edge of a glazing unit due to the thermal properties of spacers and sealants.

Edge Glued - A method of developing wood composites to provide wood parts with greater width. The width is achieved by gluing the smaller component wood pieces edge to edge.

Egress - Literally, an exit (a means of exit). Actual open size determined by local building code.

Egress Code - The code that requires a minimum opening of a window for persons to exit or firefighters to enter a building.

Egress Window - A window with specific release hardware and minimum clear opening size to allow occupants to escape through the window in case of a fire.

Elastometric - Having the property of returning to its original shape and position.

Electrochromics - Glazing with optical properties that can be varied continuously from clear to dark with a low-voltage signal. Ions are reversibly injected or removed from an eletrochromic material, causing the optical density to change.

Electromagnetic Spectrum - Radiant energy over a broad range of wavelengths.

Electrostatic - A painting process by which the aluminum is grounded and the paint carries a positive electric current. This creates a magnetic attraction between the paint and the aluminum, allowing for uniform paint coverage on extrusion surfaces that are exposed when the assembled window is installed and closed.

Elevation - The front view or views from the street as shown in the blueprint plans of a home.

Elongated Octagon - A fixed lite window shaped in the form of an extended octagon.

Emergency Exit Window - Fire escape window (egress window) large enough for a person to climb out. In U.S. building codes, each bedroom must be provided with an exit window. The exact width, area and height from the floor are specified in the building codes.

Emissivity - The ability of a material to emit radiant energy. Emittance is the ratio of the total radiant energy emitted by a given surface to that emitted by an ideal black body at the same temperature. To emit is to give out, to discharge - in the case of glass, essentially, to reradiate absorbed energy (heat).

Emittance - The ratio of the radiant flux emitted by a specimen to that emitted by a blackbody at the same temperature and under the same conditions.

Energy Panel - This device is a single piece of glass whose edges are protected by an aluminum surround. Its purpose is to increase thermal efficiency on single glazed, 15/16" bar true divided lite units.

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.

Entrance Door - A door on the front entrance of a structure; also "front" or "main" entrance door; may be single or in pairs.

Equivalent Combined Glass Load - Combination of the instant applied load of wind and the factored long-term loading of glass weight and snow accumulation.

Escutcheon - Ornamental shield or plate mounted behind the knob, "surrounding" the lock base.

Evacuated Glazing - Insulating glazing composed of two glass layers, hermetically sealed at the edges, with a vacuum between to eliminate convection and conduction. A spacer system is needed to keep the panes from touching.

EWA - See Exact Window Size.

Exact Window Size - The dimensions of a window or door unit measured along the outside of the frame.

Exfiltration - The escape of air from a structure. The opposite of infiltration.

Exposed Pocket Door - A sliding glass door style whereby the door panels stack up onto the exterior of a wall.

Extension Casement Hinge - A hinge for a casement window which provides clearance for cleaning the two sides of the sash from the inside.

Extension Jambs - Flat parts made of vinyl, wood or other materials which are attached to the inside edges of a window jamb to extend it in width to adapt to a thicker wall.

Exterior Glazed - Glass set from the exterior of the building

Exterior Stop - The removable glazing bead that holds the glass or panel in place when it is on the exterior side of the light or panel, in contrast to an interior stop located on the interior side of the glass.

Exterior Track Sliding Glass Door - A sliding glass track style that is used for exterior applications and is available in various riser heights to protect against water infiltration.

Extrude - the process of shaping aluminum or vinyl by forcing it through a die.

Extrusion - The act of forcing a material through a die to form a part that has a cross section similar to the opening in the die. In the window industry, the resulting part obtained from the extrusion process makes up the structural members of a window or door. This part is usually aluminum or a vinyl. Vinyl parts are sometimes called "Profiles" and aluminum parts are sometimes called "Shapes" or "Extruded Shapes". As an example, when toothpaste is squeezed from a tube, the portion of paste squeezed out is an extrusion that has a cross section similar to the opening of the tube. If the tube has a round opening then the paste is cylindrical, but if the tube were to have a square opening, the paste would have a cross section with four straight sides.

Eyebrow Window - A fixed lite window with a gently arched head similar in appearance to one's eyebrow and has jambs of equal height. In older homes, low, inward-opening windows with a bottom-hinged sash.

Eyelid - A fixed lite window with a gently arched head similar in appearance to one's eyelid. Similar to an eyebrow but the eyelid has no jambs.

Factory-Glazed Pyramid - Pyramid-shaped skylights for commercial or residential use, offered in standard sizes ranging from 4'0" to 8'0", in a 7 : 12 roof pitch. Arrive assembled and factory glazed to the job site ready to set on a prepared curb eliminating on-site installation. Also known as the pre-glazed pyramid skylight.

Failed IG Units- An insulated glass unit failure exhibits permanent material obstruction of vision through the unit due to the accumulation of dust, moisture or film on the internal surface of the glass. Surface numbers 2 & 3 in double-glazed units, or surface numbers 2, 3, 4 & 5 in triple-glazed units are the affected surfaces.

Fanlight - A half-circle window over a door or window, with radiating bars. Also called circle top transom.

FCR - Fenestration Cooling Rating. A rating number developed by the National Fenestration Rating Council to indicate relative performance during the cooling season. A higher FCR indicates better cooling season performance.

Fenestration - An architectural term referring to the arrangement of windows in a wall. From the Latin word, "fenestra,", meaning window.

Fenestration Product - Any transparent or translucent material plus any sash, frame, mullions, dividers, in the envelope of a building, including but not limited to: windows, sliding glass doors, french doors, skylights, curtain walls and garden windows.

FER (Forced Entry Resistant) - A requirement of some codes that a locked window or door meet certified tests that determine if the product is resistant to entry from the outside using normal hand tools. Also, that any attempt to enter the locked door or window will show definite signs of the attempt. FER does not mean "burglar proof". Any structure can be entered with enough time, privacy and effort.

FHR - Fenestration Heating Rating. A rating number developed by the National Fenestration Rating Council to indicate relative performance during the heating season. A higher FHR indicates better heating season performance.

Fiberglass - A composite material made by embedding glass fibers in a polymer matrix that is pulled through a die to create a shape. May be used as a diffusing material in sheet form or as a standard sash and frame element.

Fiberglass Window - A window whose frame and sashes are made from Fiberglass.

Field Glaze - The glazing of a window after the frame has been installed in the structure. (See OPEN.)

Fin Seal - A trade name for a type of wool pile weather strip employing a strip of rigid plastic material running lengthwise, greatly reducing air infiltration.

Finger Joint - A method of joining wood parts end to end by machining a series of finger-like grooves in their ends. As they are interlocked, the fingers are bonded together with adhesive.

Finger-Jointing - A means of joining individual pieces of wood together to form longer lengths. The ends of the pieces are machined to form a set of interlocking fingers, which are then coated with adhesive and meshed together under pressure.

Finish - The preparation of the surface of an aluminum window that adds color or protection to the aluminum. Mill finish is the unfinished surface of aluminum just as it comes from the mill. Painted finishes are factory applied to the aluminum extrusions before the assembly of the final product. Painted finishes come in many colors most commonly bronze (or brown), white, or beige. In rare instances and by special order, gray, blue, red or any color can been used. Anodized finishes are sometimes used, but mainly in architectural applications because of the expense. Clear lacquer finishes are called for on mill finish surfaces for protection during construction. (See ANODIZE.)

Fire Rated Doors - A door which has been constructed in such a manner that when installed in an assembly and tested it will pass ASTM E-152 "Fire Test Of Door Assemblies," and can be rated as resisting fire for 20 minutes, 30 minutes, 45 minutes (C), 1 hour (B), or 1 - 1 1/2 hours (B). The door must be tested and carry an identifying label from a qualified testing and inspection agency.

Fixed Frame - A type of window with no operating parts, just simply, a frame and glass. Also, referred to as a Picture Window.

Fixed Light - (Fixed Sash): Window which is non-operative (does not open).

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 Lite or Fixed Sash - Non-operable section of a window (example: the top sash of a single-hung window.)

Fixed Panel - An inoperable panel of a sliding glass door or slider window.

Fixed Vent - The non-operating sash, lite, or panel of a sliding window or door.

Fixed Window - Non-venting or non-operable window. Also known as a picture window.

Flanker - The designation given to units that flank a center picture unit in a double or triple combination or bay window.

Flashing - Sheet material that protects and bridges the joint between the window or door frame members and the adjacent construction for the purpose of preventing water penetration by draining water away from the window or door to the exterior. (See also Through-Wall Flashing.)

Flat Casing - An exterior trim alternative to brick mould. This stock does not have a profile but is simply surfaced flat on four sides.

Flat Glass - All types of glass (rolled, float, plate, etc.) produced in a flat form, regardless of the method of production.

Flat Grid - A rectangular shaped grid applied to the exterior side of a light.

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 parallel surfaces, without polishing and grinding.

Floating Muntin - A type of muntin that actually separates lights of glass in a window but is not attached to the frame itself. (See MUNTIN and DIVIDED LIGHT.)

Flush Fin - A replacement window with flush fin is used when replacing an existing aluminum sliding window. This is the most commonly used replacement window type.

Foam Spacer - Foam material placed in the airspace of the insulating glass in a window to enhance the appearance and improve the performance of the window.

Fogging - A deposit of contamination left on the inside surface of a sealed insulating glass unit due to extremes of temperatures or failed seals.

Folding Glass Wall - A folding stackable glass wall system capable of opening up to 92% of the original rough opening. Commonly used to separate rooms or to install around pool enclosures.

Frame - The outer members of a window or door. The frame includes the head, sill or threshold, the two jambs and the meeting rail of a window.

Frame Dimension - Measurement from outside of side jamb to outside of side jamb or from outside of head jamb to outside of sill (bottom jamb).

French Door - An interior or exterior door consisting of stiles, top and bottom rail and divided glass panels or lights; often used in pairs; "casement" or "terrace" door.

French Hinged Door - Hinged door(s) which have wider panel members around the glass.

French Patio Door - A type of swinging patio door which features two operating panels. One panel is designated as the active panel and is equipped with the active handle and latch set. The secondary inactive panel is equipped with flush bolts at head and sill allowing it to be fixed in place or to swing freely. The unit which has just been described is a Traditional or authentic French door.

Friction Balance - A type of balance that holds a sash in position by friction. The friction balance usually has an adjustment device. This is a low cost substitute for other types of balances and is often not accepted by many building codes.

Friction Hinge - A window hinge which remains open at any position by means of friction in the hinge.

Frit - A batch material which is melted with other materials and then ground into powder. This powder is applied to the glass and heated during the tempering process, which fuses the material into the glass surface. This process is commonly used to create logos and identification markings permanently imbedded on the glass surface.

Full Screen - A screen which covers the entire opening of a window.

Fully-Tempered Glass - Glass that has been tempered to a high degree. Specified by the ASTM C 1048 (Kind FT) as having a surface compression of not less than 10,000 pounds per square inch (PSI) or an edge compression of not less than 9,200 PSI. Fully-tempered glass, if broken, will disintegrate into many small pieces (dice) which are more or less cubical. Fully-tempered glass is four to five times stronger than annealed glass of the same thickness.

Fusion Welding - The process of heating mitered corners to 2008° F and bringing the heated corners into contact until they fuse together into a single piece of vinyl.

Fusion-Welded - The process of joining materials by melting them together with extreme heat (over 500° F), resulting in the materials uniting into a one-piece unit.

Gas 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.

Gas-Filled Units - Insulating glass units with a gas other than air (usually an inert gas such as argon or krypton) in the airspace between the panes. This is done to decrease the unit's thermal conductivity (U-value) and increase the unit's sound insulating value.

Gasket - A pliable, flexible continuous strip of material used to affect a watertight seal between sash and frame of roof windows much like the seal around a refrigerator door.

General Contractor - Usually the head contractor of a building project who coordinates sub-contractors and material suppliers in the completion of a construction project.

Geometric Windows - 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-round, full-round, sectors, ellipses, eyebrows, etc.

GIA - See Grids In the Airspace.

Glass - Any of a large class of materials with highly variable mechanical and optical properties that solidify from the molten state without crystallization. They are typically based on silicon dioxide (sand), boric oxide, aluminum oxide, or phosphorus pentoxide, generally transparent or translucent, and are regarded physically as super cooled liquids rather than true solids. (From The American Heritage Dictionary)

Glass (Insulating) - Two sheets of glass bonded together in a unit to enclose a captive air space. In the case of Xi welded glass, the edges are melted together and the air space is filled with an inert gas. Organic units have a hollow metal spacer around the perimeter and edges are sealed with an organic substance. These spacers must be filled with a desiccant, which is a chemical to absorb and hold any moisture trapped in the air space. The latest insulating units use Butyl, Silicone Foam and other non-conductive spacers at the edge for reduced thermal conduction. (Also called warm-edge.)

Glass Size - Actual Glass size, not merely that which is visible.

Glazed Sash - A sash in which the glass has been installed.

Glazing - Glass in a window or door; the act or process of fitting with glass.

Glazing (Double) - A single glazed sash with an additional glass panel installed on the sash to provide an air space between the two lites of glass. The second glass can either be removable (RDG) or fixed and can be installed on either the inside or outside of the sash. Double glazing differs from insulating glass in that there is no positive seal around the edges of the two lites of glass to provide a true dead air space and there's no desiccant within the unit to absorb and hold moisture.

Glazing (Single) - A single sheet of glass installed in a window sash.

Glaze - The act of installing glass or other glazing materials, such as plastic, into a window or door. (See REGLAZE.)

Glazing Bead - A part used to trim around the edge of the glass after it has been installed in a window. Glazing bead can be made from vinyl, aluminum extrusion, or aluminum formed sheet. The glazing bead either is screwed in place or snapped into grooves in the sash member.

Glazing Block - A small, hard rubber block placed around the edges of the glass unit in a window sash to position the glass and prevent it from shifting.

Glazing Channel - A three-sided, U-shaped sash detail into which a glass product is installed and retained by a removable stop.

Glazing Channel Depth - The measurement from the bottom of the glazing channel to the top of its stops.

Glazing Channel Width - The measurement between the stationary stop and the removable stop.

Glazing Compound - A pliable substance applied between the window sash and the lites of glass to seal against the elements and sometimes to adhere the glass to the sash.

Glazing Stop - The part of the sash or door panel which holds the glass in place.

Glazing Tape - Double-sided tape used to adhere glass to sash and form an airtight, watertight seal.

Glazing (Triple) - A sash glazed with three lites of glass, enclosing two separate air spaces. This can be accomplished by applying a storm panel that is glazed with insulating glass or on some units by applying inside and outside storm panels to a single glazed sash.

Glazing - The glass or plastic panes in a window, door, or skylight.

Gliding Window or Door - Same construction as a sliding window. The moving sash generally travels on rollers.

Greenhouse Window - A three-dimensional window that projects from the exterior wall and usually has glazing on all sides except the bottom, which serves as a shelf.

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 .

Grids in the Air Space - Grids mounted between the two panes of glass of an insulated glass unit.

Grille - A term referring to windowpane dividers or muntins, usually a type of assembly which may be detached for cleaning.

Half Screen - A screen which does not cover the entire opening of a window. Used on the bottom half of single hung units and on the operating sash of single sliders.

Hard Coat - A term used for a type of Low-E glass that is usually less expensive and a lower performing type of Low-E glass. Sometimes referred to as "Pyrolytic Low-E".

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

Head Board - A flat board cut to fit the contour of a bow or bay window and installed between the head jambs and the flat wall surface to finish off that area which would normally be ceiling.

Head Expander - An inverted U-channel installation accessory that may be fitted to the head of a replacement window to accommodate differences between rough opening and window heights.

Head Jamb - Also called "header" or "head": Cross or horizontal jamb member forming the top of the frame.

Head Track - The track provided at the head of a sliding glass door. Also, the head member incorporating the track.

Header - A horizontal framing member placed over the rough opening of a window to prevent the weight of wall or roof from resting on the window frame.

Heat Fusion - (Welding) method to join PVC frame and/or sash members by heating the cut ends, squeezing them together, and allowing the assembly to cool.

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.

Heat-Absorbing Glass - Glass for intercepting appreciable portions of radiant energy, especially solar energy, in specific transmittance values as defined in ASTM C 1036. It is obtainable as float or patterned glass.

Heating Degree Day - Term used by heating and cooling engineers to relate the typical climate conditions of different areas to the amount of energy needed to heat and cool a building. The base temperature is 65 degrees Fahrenheit. A heating degree day is counted for each degree below 65 degrees reached by the average daily outside temperatures in the winter. For example, if on a given winter day, the daily average temperature outdoors is 30 degrees, then there are 35 degrees below the base temperature of 65 degrees. Thus, there are 35 heating degree days for that day.

Heat-Resisting Glass - Glass able to withstand high thermal shock, generally because of low coefficient of expansion.

Heat-Strengthened Glass - Glass that has been heat-treated to a state less than that of fully-tempered glass. Specified by the ASTM 1048 (Kind HS) as having a surface compression of not less than 3,500 pounds per square inch (PSI) or greater than 10,000 PSI or an edge compression of not less than 5,500 PSI. Heat-strengthened glass is approximately two times as strong as annealed glass of the same thickness and has a much increased thermal endurance. Heat-strengthened glass is not considered a safety glass and will not completely dice as will a fully-tempered glass.

Heat-Treated - Term sometimes used for both fully-tempered glass and heat-strengthened glass.

Heavy Float Glass - Used in furniture, tabletops, storefronts.

Hermetically Sealed Unit - An insulating glass unit made up of two lites of glass, separated by a spacer, or equivalent product (at the full perimeter), which is filled with a moisture absorbing material. The unit is then completely sealed, creating a moisture-free, clean, dead-air space.

High Transmission Glass - Glass which transmits an exceptionally high percentage of visible light.

Hinge - A movable joint enabling a window or door to swing open.

Hinge Mortise - The area cut away to accept the hinge leaf for mounting on the door frame or door edge.

Hinge Stile - Stile to which the hinges are applied, as distinguished from the lock stile.

Hinged Door - An exterior or interior door hung by attached butts to the stile so that the door swings on a vertical axis; may be single (swinging thru 90 degrees) or double-acting (swinging thru 180 degrees); double-acting doors do not require a door stop; conventionally hinged.

Hinged Windows - Windows (casement, awning, and hopper) with an operating sash that has hinges on one side. (See also Projected Window.)

Hollow Extrusion - A tubular extrusion having an enclosed cavity within it. It is usually stronger, although more costly, than a solid extrusion.

Home Center - A term used to refer to large home improvement chains like Lowe's, Home Depot, and Menards.

Hook Accessory - Accessories that snap to the hook frame and provide easy installation.

Hopper - Type of window hinged on the sides or bottom that opens at the top by swinging in or out.

Hopper Vent - Inward-opening sash hinged at the bottom (an upside-down awning window). Many basement windows are this type.

Horizontal Slider - A window with a movable panel that slides horizontally.

Hung Window - A window in which the operating sash move up and down within the master frame. The weight of each operating sash is counterbalanced with balances to permit easy operation.

I.G. Unit (Insulating Glass Unit) - Two or more lites of glass separated by a spacer and hermetically sealed at the glass edges.

ICC - International Code Council - A national organization that publishes model codes for adoption by states and other agencies. Codes include the International Building Code (IBC) and the International Energy Conservation Code (IECC).

IECC - International Energy Conservation Code - Published by the ICC. The successor to the Model Energy Code, which is cited in the 1992 U.S. Energy Policy Act (EP Act) as the baseline for residential Energy Codes in the United States.

Inactive Door - A door that does not contain a lock, but is bolted when closed, and to which a strike is fastened to receive the latch or bolt of an active door.

Infiltration - Leakage of outdoor air into a house, such as through cracks around sash or window frame.

Infrared Radiation - Invisible, electromagnetic radiation beyond red light on the spectrum, with wavelengths greater than 0.7 microns.

Installation Accessories - Components supplied by the fenestration manufacturer that are specifically designed to mate or "trim out" the product with various surrounding constructions.

Installation Fin or Flange - A vinyl or metal flange inserted into or an integral part of the side and head jambs of a window unit which is used for installing it in an opening. It also affords a weather seal or flashing around the perimeter of the window frame.

Installation Holes - Holes in window or door frames that are fabricated by the manufacturer to locate and accommodate installation fasteners.

Installed Sales - A purchase of a product that includes installation.

Insulated Glass Unit (IG Unit) - A combination of two or more panes of glass with hermetically sealed space between the panes of glass. This space may or may not be filled with an inert gas, such as argon. The purpose of bonding the glass panes in this fashion is to increase the insulating properties of the unit.

Insulated Shutters - Insulating panels that cover a window opening to reduce heat loss.

Insulated Window - A window with multiple glazing that provides one or more air spaces between layers of glazing.

Insulating Glass - Two or more pieces of glass spaced apart and hermetically sealed to form a single glazed unit with one or more air spaces in between. Also called double glazing.

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

Insulating Glass Unit (IGU) - Two pieces of glass spaced apart and hermetically sealed to form a unit with an air space between. Heat transmission through this type of glass may be as low as half that without such an air space.

Insulating Value - See U-factor.

Insulation - Construction materials used for protection from noise, heat, cold or fire. Interior Glazing Glass set from the interior of the building.

Interlayer - A layer of standard or poly carbonate-compatible polyvinyl butyral or of urethane, used to bind two or more pieces of glass or glass and poly carbonate sheets into a laminated unit.

Interlock - A design feature which enables sash to engage one another when closed.

Interlocker - An upright frame member of a panel in a sliding glass door which engages with a corresponding member in an adjacent panel when the door is closed. Also called interlocking stile.

Internal Grids - Grids mounted between the two panes of glass of an insulated glass unit.

Jack Stud - Framing members, generally 2" x 4"s, which form the inside of the window or door rough opening. They run from the sole plate to the header, which is supported by them.

Jalousie - Window made up of horizontally-mounted louvered glass slats that abut each other tightly when closed and rotate outward when cranked open.

Jalousie Windows - A window composed of overlapping narrow glass, metal or wood louvers, operated by means of a crank handle for adjusting the louver angles; introduced in the 1950's.

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

Jamb Liner - In a modern double-hung window, the track installed inside the jambs on which the window sashes slide.

J-Channel - Integral extension on the outside of a new construction window that eases installation on siding applications.

K Factor - The coefficient of thermal conductivity. The amount of heat that passes through a unit cube of material in a given time when difference in temperature of 2 faces is 1° .

KD - See Knocked-Down

Keeper - The part of a window lock, mounted on an opposing surface of the window, that the lock arm locks under or into to pull the sash into a locked position and fully releases it when opened.

Keeper Rail - Sash meeting rail on to which the keeper (see lock and keeper) is mounted.

Keeper Stile - The vertical section of the sash where the keeper is attached.

Kerf - A thin cut-out in the frame to accommodate the weather strip flange.

Kiln - Oven used in the process of heating or melting. In glass factories, a kiln is used for tempering the glass, applying frit, etc.

King Stud - The full length stud next to a door or window opening to which the trimmer and lintel are nailed.

Knocked Down (K.D.) - Not assembled; parts for a window (or door) frame pre-manufactured for assembly at a later date on the job-site.

Krypton - 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.

KWH - KiloWatt Hour - Unit of energy or work equal to one thousand watt-hours.

Laminate - A composite unit of glass and interlayer material.

Laminated Glass - Two or more pieces of glass bonded together over a plastic interlayer.

Laminating - A method of bonding an overlay(wood acrylic etc.) to a window component.

Latch (Catch/Lock) - A device which holds a window shut, such as the latch at the meeting of a double-hung window or one mounted on the stile of casement windows, often referred to as Lock.

Leaded Glass - Small, usually irregular panes of glass, sometimes vari-colored, joined together by lead or zinc muntins and bars and used primarily for decorative purposes; zinc bar glazing.

Lift - A handle or grip installed on the bottom rail of the lower sash of a double-hung window to make it easier to raise or lower the sash.

Lift Handle - A handhold for raising and lowering the sash. Handle implies that the handhold is not continuous across the sash.

Lift Rail - Sash rail component with a molded handgrip integrated into the profile. This makes raising and lowering the sash easier.

Light or Lite - Glazing framed by muntins and/or sash in a window or door.

Light Shaft - An insulated shaft built to direct the light from a roof window or skylight through the attic to the room below.

Light-to-Solar-Gain Ratio - A measure of the ability of a glazing to provide light without excessive solar heat gain. It is the ratio between the visible transmittance of a glazing and its solar heat gain coefficient. Abbreviated LSG.

Lineal Footage - A dimension expressing length (in feet) only. For example, the width of a unit (in inches) plus the height (in inches) x 2 divided by 12 = the perimeter measurement of the unit in lineal feet.

Lintel - A horizontal member above a window or door opening that supports the structure above.

Liquid Crystal Glazing - Glass in which the optical properties of a thin layer of liquid crystals are controlled by an electrical current, changing from a clear to a diffusing state.

Lite - A unit of glass in a window or door; it is enclosed by the sash or by muntins and bars - also called a pane.

Live Load - Load force due to weight of non-permanent attachments; people, glazing rigs, washing rigs, etc.

Lock - Device mounted on a sash meeting rail which, when coupled with a keeper, prevents the sash from being opened. Some lock designs incorporate a cam design that pulls the sash rails together for a tighter fit as it is locked.

Lock Rail - Sash meeting rail on to which the lock (see lock and keeper) is mounted.

Lock Stile - The vertical section of the sash where the cam lock is attached.

Lockblock - A concealed block the same thickness as the door stile or core which is adjacent to the inside edge of the stile at the midpoint and into which a lock is fitted.

Long-Wave Infrared Radiation - Invisible radiation, beyond red light on the electromagnetic spectrum (above 3.5 micro meters), emitted by warm surfaces such as a body at room temperature radiating to a cold window surface.

Louvered Window - A window having louvers or slats that fill all or part of the opening. See Jalousie Window.

Low E (Emissivity) Glass - Glass with a transparent metallic oxide coating applied onto or into a glass surface. The coating allows short-wave energy to pass through but reflects long-wave infrared energy which improves the U-value.

Low E Glass - a transparent coating applied to a glass surface to separate long wave (heat) energy and short wave (light) energy. The long wave is reflected back to the heat source. The short wave is allowed to pass through the coating.

Low-Conductance Spacers - An assembly of materials designed to reduce heat transfer at the edge of an insulating window. Spacers are placed between the panes of glass in a double- or triple-glazed window.

Low-Emissivity (Low-E) Glass - A special type of glass having a transparent material fused into its surface which acts as a thermal mirror. Increases the performance of windows and doors.

Low-Emittance (Low-E) Coating - Microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a window or skylight glazing surface primarily to reduce the U-factor by suppressing radiative heat flow. A typical type of low-E coating is transparent to the solar spectrum (visible light and short-wave infrared radiation) and reflective of long-wave infrared radiation.

Main Frame - The head, sill and jambs sections of a window.

Manufacturer - A business entity that builds products.

Masonry Opening - The space in a masonry wall left open for windows or door.

Mechanical Frame Window - A window where all of the fastening has been accomplished mechanically (typically with screws) rather than with welding processes.

Mechanically Fastened Frame - Refers to window or door frames fastened with screws.

Meeting Rail - The horizontal sections of a pair of sash that meet when the sash are closed.

Meeting Stile - The vertical section of a pair of sash that meet when the sash are closed.

Meeting Rail (Lock Rail) - One of the two horizontal members of a double-hung sash which come together.

Meeting Stile - The vertical member in a pair of stiles, as in abutting casement windows.

Mesh - Fabric made of either fiberglass or aluminum, used in the making of screens.

Metal-Clad Windows - Exterior wood parts covered with extruded aluminum or other metal, with a factory-applied finish to deter the elements.

Micron - One millionth (10-6) of a metric meter.

Mil - One thousandth of an inch, or 0.0254 millimeter.

Miter - Moulding returned upon itself at right angles. In joinery, the ends of two pieces of wood that are cut at a 45E angle abutting upon one another so as to form a right angle.

Miter Joint - Two members joined at an angle, commonly 45 degrees.

Model Energy Code (MEC) - The Model Energy Code is cited in the 1992 U.S. Energy Policy Act (EP Act) as the baseline for residential Energy Codes in the United States. It has been succeeded by the International Energy Conservation Code (IECC) published by the International Code Council (ICC).

Modular Opening - Callout opening. "M.O."

Modular Size - Callout size. "M.S."

Modulus - Stress at a given strain. Also tensile strength as a given elongation.

Modulus of Elasticity - The ratio of stress to strain, being an indicator of a material?s bending resistance to a load.

Monolithic - A glazing assembly construction consisting of only one lite or pane of glass, poly carbonate, acrylic, or plastic.

Mortise - A slot or rectangular cavity cut into a piece of wood to receive another part.

Mortise-and-Tenon - A strong wood joint made by fitting together a mortise in one board and a matching projecting member (tenon) in the other.

Mullion - A major structural vertical or horizontal member between window units or sliding glass doors.

Multi-Point Locking - A term used for locking hardware that engages a window sash to the frame at multiple locations with a single throw of an operator.

Muntin - Applies to any short or light bar, either vertical or horizontal, used to separate glass in a sash into multiple lights. Also called a windowpane divider or a grille.

Muntin Bar - Any small bar that divides a windows glass. Also called a grille or windowpane divider.

Muntin Grilles - Wood, plastic, or metal grids designed for a single-light sash to give the appearance of muntins in a multilight sash, but removable for ease in cleaning the window.

Nailing Fin - An 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.

Nailing Fin (Flange) - A strip of sheet material (vinyl, Aluminum, steel etc.) which is integral to or fastened to the frame of units. This creates a flange which is a common method for installation of new construction windows and doors.

Nailing Fin - An 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.

Nail-On - Windows with nail-on fins are for new construction.

Needle Glazing - Application of a small bead of sealant/compound at the sight line by a nozzle gun.

Neodymium - A rare earth element used in its oxide form as a coloring agent to produce a violet color.

New Construction - The building of a brand new structure.

NFRC - National Fenestration Rating Council.

Nite Latch - Hardware which, when extended, restricts the sash opening to a predetermined dimension.

Obscure Glass - Any textured glass (frosted, etched, fluted, ground, etc.) used for privacy, light diffusion, or decorative effects.

Offal - In glass and lineal cutting, this is the term for scrap pieces of material left over at the end of a cutting run that are large enough to be reused for cutting hand-cut or special schedules.

Opacification - The application of a Mylar film to a glass unit to block light transmission. This process is sometimes referred to as spandrel.

Opal Glass - A translucent glass with a pearlescent finish resembling an opal in pattern and tint.

Open Sash - A sash in which the glass has not been installed.

Operable Window - Window that can be opened for ventilation.

Operating Panel - In a two - door or two - panel swing or sliding door, the panel that opens.

Operator - Crank-operated device for opening and closing casement or jalousie windows.

Oriel - A window with the meeting rail located off-center of the frame. Most Oriels have a 60/40 configuration.

Oriel Window - The name of every traditional style of Double Hung window which has an upper sash which is larger than its lower sash counterpart.

OSM - See Outside Measurement.

Outer Frame Member - The exterior protruding portion of a window frame which has no exterior casing.

Outside Casing - Trim or molding around a window or door on the exterior of the house. Casing usually refers to a flat board trim, typically, 3" or 4" in width.

Outside Measurement (OSM) - The dimensions of the rough opening.

Palladian Window - A large, arch-top window flanked by smaller windows on each side.

Pan/Panning - Cosmetic covering, usually found on the exterior of the window or door to achieve aesthetic sight lines or to integrate the window or door system into the building surface or weatherproofing system. If panning is being used for weatherability, the panning is not considered cosmetic, but part of the window system.

Pane - One of the compartments of a door or window consisting of a single sheet of glass in a frame; also, a sheet of glass.

Panel - A major component of a sliding glass door, consisting of a light of glass in a frame installed within the main (or outer) frame of the door. A panel may be sliding or fixed.

Panning - In replacement window work, the outside aluminum trim that can extend around the perimeter of the window opening; used to cover up the old window material. Panning can be installed in the opening before the window, or can be attached directly to the window before installation.

Partial Window Replacement - The installation of a replacement window where some component of the previously-installed window frame will remain.

Particle Dispersed Glazing - Glazing in which the orientation of small particles between two sheets of glass is controlled electrically, thus changing its optical properties.

Parting Bead - A vertical strip on each jamb that separates the sashes of a double-hung window.

Parting Stop - In a double-hung window, a strip of wood applied to the jamb to separate the sash.

Passive Solar Collector - Any glazed area in the walls or roof of a building pointed to the south to take maximum advantage of the sun's heat without a mechanical (or active) method of storage or distribution of the heat.

Patio Door - A glass door that slides opens and close on adjustable tandem rollers. Available in 2- or 3-lite configurations with the operable panel available in any position.

Patio Room - A modular wall system designed with single pane glass.

Patterned Glass - Also known as rolled or rough-rolled glass. One type of rolled glass having a pattern impressed on one or both sides. Used extensively for light control and decorative glazing.

Peak Load - The maximum thermal load to be provided by a heating or cooling system in a house.

Photochromics - Glazing with the optical properties that change in response to the amount of incident light.

Picture - Non-venting or non-operable window. Also known as a fixed window.

Picture Framing Casing - The use of trim casing on all four sides of the interior of a window, resembling a picture frame when installed.

Picture Frame Casing - The use of casing on all four sides of the interior of a window, replacing the stool and apron at the sill. Also know as full-bound casing.

Picture Window - A large, fixed window framed so that it is usually, but not always, longer horizontally than vertically to provide a panoramic view.

Pivot - A mode of operation for ventilating windows which generally means the sash pivots on a central axis and turns 90 or more degrees.

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.

Pivot Bar - A metal post attached to a moving sash and seated in a balance shoe that allows a window sash to tilt.

Pivot Pin (Pivot Bar) - Part mounted on or in the end of the sash that fits into balance shoe and from which the sash may be tilted or pivoted in.

Pivot Window - A window with a sash that swings open or shut by revolving on pivots at either side of the sash or at top and bottom.

Plastic - The word "Plastic" means capable of being shaped or molded to some definite form or shape during the manufacturing process and possessing the property of permanently retaining the shape into which it was molded or extruded.

Plastic Film - A thin plastic substrate, sometimes used as the inner layers in a triple- or quadruple-glazed window.

Plastics - Artificial substances made of organic polymers that can be extruded or molded into various shapes including window frames and sashes.

Plate Glass - A rolled, ground, and polished product with true flat parallel plane surfaces affording excellent vision. It is now being replaced by float glass.

Plexiglass (Acrylic) - A trade name for a clear, durable sheet plastic made of acrylic; used for safety glazing and for inside storm panels. Plexiglass is a registered trademark of Rohm & Haas.

Plumb - Vertical; to make vertical.

Pocket Sill - A deep sill (frame) design that completely surrounds the bottom edge of the sash in the closed position.

Polished Wired Glass - Wired glass that has been ground and polished on both surfaces.

Polyvinyl chloride (PVC) - An extruded or molded plastic material used for window framing and as a thermal barrier for aluminum windows.

Prairie Grid Pattern - Grid pattern which is typically approximately 4 inches from the rails and styles of each lite. The intersections at the corners of the lite create a 4 inch square box in each corner.

Prime Sash - The balanced or moving sash of a window unit.

Prime Window (Primary Window) - The first window completely installed in a rough opening, which is designed to function as the sole fenestration product (contrasted with a storm window, which serves as a secondary window in conjunction with a primary window).

Primer - Factory applied coating which is designed to promote better acceptance of a paint finish overcoat on the exterior surfaces of wood windows. All exterior wood parts should be primed. Primer is not a sealant and all primed products must have finish coats applied.

Priming - Sealing of a porous surface so that compound will not stain, lose elasticity, shrink excessively, etc., because of loss of oil or vehicle into the surround. A sealant primer or surface conditioner may be used to promote adhesion of a curing type sealant to certain surfaces.

Processed Glass - Glass in which the surface has been altered by etching, sandblasting, chipping, grinding, ceramic-enameling, etc., to change its light diffusion or to give decorative effects. Either or both surfaces may be so treated. Also glass which has been further treated (edge work, tempered, stained, etc.) after forming.

Projected Window - Casements and Awnings - project out when open.

Psf - pounds per square foot - a measurement of air pressure used in window testing, e.g., 1.56 psf (25 mph) or 6.24 psf (50mph).

Pull - A handle for opening a window.

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.

Pull Stile - A handhold for sliding the sash back and forth. Stile implies that the handhold is continuous across the sash.

Pultruded - A term used to define the action of creating fiberglass window and door components. Glass fiber strands coated in plastic resin are pulled through a die to create a long board like component.

Purlins - Structural members, generally horizontal, in slope glazing frames.

Push Bar - Used on awning and other projecting sash windows for opening and closing instead of a crank (gear) operator.

PVC - Poly Vinyl Chloride - in rigid frame/sash members, and in flexible gaskets.

PVC (Polyvinyl chloride) - An extruded or molded plastic material used for window framing and as a thermal barrier for aluminum windows.

Pyramid - A square base design, typical to skylights, with all four slopes rising to form a point.

Pyrolytic Coating - A coating applied during the manufacturing of the glass itself. Because they are actually part of the glass sheet, pyrolytic or "hand coat" surfaces are very durable and require no special handling.

Quarter Round Window - Stationary or operating window with glass shaped as a quarter circle; it is often divided into separate panes by a removable grille, installed on the interior or grille between the glass.

R Value - A measurement of heat resistance (the higher, the better). R value = the number 1 divided by the U value.

Rabbet - A two-sided L-shaped recess in a sash frame to receive glass products. Addition of a removable stop will convert it to a glazing channel.

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.

Rafter - the structural main "rib" of a glazed structure available in straight and bent.

Rail - The top and bottom horizontal members of the framework of a window sash.

Raised Exterior - An angled extension from the frame that adds an aesthetically pleasing dimension to the exterior of the window.

Reflectance - The ratio of reflected radiant energy to incident radiant energy.

Reflective Glass - Window glass coated to reflect radiation striking the surface of the glass.

Refraction - The deflection of a light ray from a straight path when it passes at an oblique angle from one medium (such as air) to another (such as glass).

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.

Relative Humidity - The percentage of moisture in the air in relationship to the amount of moisture the air could hold at that given temperature. At 100 percent relative humidity, moisture condenses and falls as rain.

Remodel - define, per Version 1.1 of Residential Widow and Door Guidelines of the Association of Window and Door Installers. Per ASTM E631, to replace or improve a building or its parts.

Remodeling - Changing and existing structure.

Replacement Installation - Installation of a fenestration product which is designed for replacement of existing like and type, by either destructive or non-destructive installation methods.

Replacement Window - A window that is designed for and subsequently installed after removal of all or part of a previously-installed window.

RESFEN - A computer program used to calculate energy use based on window selection in residential buildings.

Retail - Selling a product directly to the end user.

Retrofit - define, per Version 1.1 of Residential Window and Door Guidelines of the Association of Window and Door Installers. Per ASTM E631, to add new materials or equipment not provided at the time of original construction.

Retrofitting - Adding or replacing items on existing buildings. Typical retrofit products are replacement doors and windows, insulation, storm windows, caulking, weather stripping, vents, landscaping.

Reveal - That part of the edge of a door or window jamb not covered by the casing.

Ridge - An extrusion at the top of the structure which all sloping rafters marry into.

RO - See Rough Opening.

Roll Formed Screen - Frame A method of fabrication in which a flat (usually metal) material is placed on a machine where the material is formed into shape using differently shaped rollers and pressure.

Rolled Glass - Glass formed by rolling, including patterned and wired glass. As the glass is drawn horizontally from the tank, figured, engraved, etched, machine rolls impress a pattern on the surface of the glass, varying from almost smooth to deeply marked geometric, fluted, or random overall designs. It is made in 1/8- inch to 3/8- inch thicknesses.

Roof Window - A fixed or operable window similar to a skylight placed in the sloping surface of a roof.

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

Rough Sill - The horizontal rough framing member, usually a 2 x 4, which forms the bottom of the rough opening. It is toe-nailed into the jack studs and is supported by cripples.

R-Value - A measure of the resistance of a glazing material or fenestration assembly to heat flow. It is the inverse of the U-factor (R = 1/U) and is expressed in units of hr-sq ft-?F/Btu. A high-R-value window has a greater resistance to heat flow and a higher insulating value than one with a low R-value.

Safety Glass - A strengthened or reinforced glass that is less subject to breakage or splintering.

Sand Blasting - Compressed air forces an abrasive material (resembling sand) through a nozzle on to the surface of the glass. This process removes the surface of the glass, which gives the sandblasted area a frosted look.

Sash - The part of the window which contains the glass.

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.

Sash and Frame - A window and its cased framing.

Sash Balance - A system of weights, cords and/or coiled springs which assist in raising double-hung sash and tend to keep the sash in any placed position by counterbalancing the weight of the sash.

Sash Cord - In double-hung windows, the rope or chain which attaches the sash to the counter balance.

Sash Crack - The opening between the operating sash and the frame of the window. Its thickness or measurement is equal to 2 the difference between the inside window frame dimension and the outside sash width. Crack foot length is used in calculating total air infiltration on a window unit.

Sash Lift - A handle for raising the lower sash.

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

Sash Opening - The space described by the interior of a window frame. It is bounded by the interior surface of the frames. Jamb liners or hardware adapters must be disregarded. (Primary use of this dimension is for the Replacement Double Hung System).

Sash Stop - A molding that covers the joint between window sash and the jamb.

Sash Weights - In older double-hung windows, the concealed cast-iron weights which are used to counterbalance the sash.

Screen - Woven mesh of metal, plastic, or fiberglass stretched over a window opening to permit air to pass through, but not insects.

Screen Wire Cloth - A close-mesh woven screening material of metal, plastic or fiberglass for a window screen, to block the entry of insects but permit light, air and vision through the screen.

SDL - See Simulated Divided Light.

Sealant - A compressible plastic material used to seal any opening or junction of two parts, such as between the glass and its sash, commonly made of silicone, butyl tape or polysulfide.

Sealed Double Glass - Two panes separated by a sealed space.

Sealed Insulating Glass Units - Units constructed of two or more lites of glass separated and hermetically sealed in spacer frames at the glass edges with the enclosed air chamber(s) dehydrated at the plant's atmospheric pressure.

Seat Board - A flat board cut to fit the contour of a bow or bay window and installed between the sills and the flat wall surface, providing a seat or shelf space.

Setting Block - A small piece of neoprene or other suitable material used to position a piece of glass in its frame.

Shade Screen - A specially fabricated screen of sheet material with small narrow louvers formed in place to intercept solar radiation striking a window; the louvers are so small that only extremely small insects can pass through. Also called sun screen. Also, an awning with fixed louvers of metal or wood.

Shading Coefficient (SC) - A measure of the ability of a window or skylight to transmit solar heat, relative to that ability for 1/8-inch clear, double- strength, single glass. It is being phased out in favor of the solar heat gain coefficient, and is approximately equal to the SHGC multiplied by 1.15. It is expressed as a number without units between 0 and 1. The lower a window's solar heat gain coefficient or shading coefficient, the less solar heat it transmits, and the greater is its shading ability.

Sheet Glass - A transparent, flat glass found in older windows, now largely replaced by float glass.

Shelf Life - Used in the glazing and sealant business as referring to the length of time a product may be stored before beginning to lose its effectiveness. Manufacturers usually state the shelf life and the necessary storage conditions on the package.

Shims - Wood wedges (often wood shingles) 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.

Shore Hardness - Measure of firmness of a compound by means of a Durometer Hardness Gauge (A range of 20-25 is about the firmness of an art gum eraser. 90 is about the firmness of a rubber heel). Shore Hardness Measurement of the hardness of a cured elastometric material by means of a durometer hardness gauge.

Short-Wave Infrared Radiation - Invisible radiation, just beyond red light on the electromagnetic spectrum (between 0.7 and 2.5 microns), emitted by hot surfaces and included in solar radiation.

Side Jamb - The upright vertical member forming the sides of the frame of a window or door unit.

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

Side Lite (Light) - A fixed, often narrow, glass window next to a door opening (or window).

Sight Line - Imaginary line around the perimeter of a glazed glass product, defined by the top edge of stationary and removable stops or the line where the glazing sealant or gasket contacts the glass.

Sill - The horizontal member which forms the bottom of a window or door frame.

SILL ANGLE - An L-shaped installation accessory that may be employed at the sill of a replacement window to accommodate the slope of the existing sill construction.

Sill Course (Soldier Course) - The row of bricks, cement blocks or stones laid across the bottom of a masonry opening which lie under the outside edges of the window sill.

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 Horn - An extension of a window's sill or sub sill beyond the outer surface of the frame side jambs. This extension provides a bottom contact point for the exterior trim.

Sill Track - The track provided at the sill of a sliding glass door. Also, the sill member incorporating such a track.

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.

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

Single Hung - A window in which one sash slides vertically and the other sash is fixed

Single Pitch - Design pertaining to a single slope of a roof on a skylight, solarium or sunroom, also known as a lean-to design.

Single Strength Glass - (SSB) 3/32" thickness.

Single Hung Window - A window consisting of two sashes of glass, the top one stationary and the bottom movable.

Skylight (operable or pivot) - A roof window that gives light and ventilation.

Slider - A window where the moveable sash "slides" horizontally on rollers to open rather than vertically (like a double-hung).

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.

Sliding Door - A door consisting of two or more panels, one of which is fixed and one that operates by sliding in a track to open and close. Also called a gliding door.

Sliding Glass Door - A door fitted with one or more panels that move horizontally on a track and/or in grooves. Moving action is usually of rolling type (rather than sliding type). Also called gliding door, rolling glass door, and patio sliding door.

Sliding Sash - A window which moves horizontally in grooves or tracks.

Sliding Window - A window fitted with one or more sashes opening by sliding horizontally or vertically in grooves provided by frame members. Vertical sliders may be single- or double-hung.

Sloped Glazing - Any installation of glass that is at a slope of 15 degrees or more from vertical.

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.

Sloped Sill Adapter - Used to cover the gap between the old sloped sill window and the new block frame window. It adapts a new window to the existing sloping sill.

Smart Window - Generic term for windows with switchable coatings to control solar gain.

Snap on Grids - Removable wood or plastic grids mounted on the surface of the glass.

Snap in Grid - Removable wood or plastic grids mounted on the surface of the glass.

Soft Coat - Term used for a multi layered Low-E glass that typically performs better and costs more than hard coat Low-E. Sometimes referred to a "Sputter Coated" Low-E.

Solar Control Coatings - Thin film coatings on glass or plastic that absorb or reflect solar energy, thereby reducing solar gain.

Solar Gain - The process of providing a net heat gain within a structure, over and above the normal heat loss, by passive collection of the sun's heat through windows and other glazed areas.

Solar Heat Gain - The percentage of heat gained from both direct sunlight and absorbed heat. The smaller the number, the greater the ability to reduce solar heat gain.

Solar Heat Gain Coefficient (SHGC) - 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 its shading ability. SHGC can be expressed in terms of the glass alone or can refer to the entire window assembly.

Solar Radiation - The total radiant energy from the sun, including ultraviolet and infrared wave lengths as well as visible light.

Solar Screen - A sun shading device, such as screens, panels, louvers, or blinds, installed to intercept solar radiation.

Solar Spectrum - The intensity variation of sunlight across its spectral range.

Solarium - A thermally broken frame and insulated glass unit which makes a room addition to a home or business. Offers energy savings in the moderate price range.

Sole Plate - The bottom horizontal member in a frame wall. Usually either single or doubled 2 X 4's. It is nailed to the deck or rough floor and the studs are nailed to it.

Solid Extrusion - An extruded shape other than a hollow or a semi-hollow extruded shape. Less costly to produce compared to semi or hollow shapes.

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 transmitted.

Spacer - Material placed between two or more pieces of glass in order to maintain a uniform width between the glass, and prevent sealant distortion.

Spacer Block - See Glazing Block.

Spacer - The material used around the edges of an insulated glass unit to separate the panes of glass. They may be hollow metal tubes of aluminum or steel, or non-conductive materials such as silicone, butyl, etc. or a combination of materials.

Spacers (Shims) - Small blocks of neoprene or other approved material, placed on each side of the glass product to provide glass centering, maintain a uniform width of sealant bead and prevent excessive sealant distortion.

Spandrel - That portion of the exterior wall of a multi-story commercial building that covers the area below the sill of the vision glass installation and the area above the head of the glass installation below. This glass area is usually opacified.

Spandrel Glass - Heat-strengthened float glass with a colored-ceramic coating adhered to the back by a heat-fusing process. It has double the strength of annealed glass of the same size and thickness, enabling it to withstand greater uniform loads and thermal stresses. Spandrel glass cannot be re-cut after heat strengthening. It is used as fixed opaque colored glass on buildings in front of floor slabs and columns. It is available in a wide array of colors.

Specialty or Special Shaped Window - A window of a "non-standard" shape or construction such as a triangle-shaped window, round or curved window or with unusual lite (light) arrangements, etc.

Spectrally Selective Coating - A coated or tinted glazing with optical properties that are transparent to some wavelengths of energy and reflective to others. Typical spectrally selective coatings are transparent to visible light and reflect short-wave and long-wave infrared radiation.

Spline - For screening, a small strip of metal or flexible tubing or gasket material that fits into a groove in the screen frame to secure the screen cloth.

Sputter Coating - A micro-thin metallic oxide coating vacuum-deposited on the surface of glass after manufacturing. Sputter coatings are vulnerable to moisture and abrasion and must be enclosed in sealed insulating window units.

Square Foot - A unit of measure for designating area One foot by one foot. Derived from width (in inches) x height (in inches) divided by 144 = area in square feet.

Stacked Window Units - A vertical (combined) grouping of awning, hopper, casement or non-operating windows to form a large, multiple unit.

Stain - Attack of a glass surface by water or other solutions involving: a. Leaching of sodium ions to the surface of the glass b. An increase in the pH on the glass surface c. The breaking of silica bonds in the glass structure. If this process advances to c, the glass will have a blotched, streaked, cloudy appearance and cannot be restored to pristine condition short of grinding and polishing the damage away, a process that is generally more expensive than simply replacing the glass.

Stationary Sash - A fixed sash; also referred to as a picture, studio, vista or view sash.

Step Glazing - The creation of an IG unit that has one pane larger than the other (also known as an offset IG unit). This method is mostly used in commercial building applications.

Stepped Sill - A sloped sill design that utilizes a step configuration to improve water control and insulating values.

Stile - The upright or vertical edges of a door, window, or screen.

Stile - The main vertical members of the framework of a sash.

Stones - Crystalline contaminations in the glass, usually pieces of undissolved or crystallized silica, bits of refractory, or crystals due to devitrification. Stones are detrimental to appearance and may seriously weaken the glass, particularly if present in highly stressed areas.

Stool - An interior sill extension used almost exclusively with double hung windows.

Stop - A trim member attached to the window frame to stop the sash of a projecting window when closed to prevent it from swinging through the opening. It also covers the perimeter crack between the sash and the window frame in double hung and sliding windows and prevents the sash from coming out of the frame. Stops used at the top or bottom of the balance channel prevent the sash in hung windows from hitting when opened.

Storm Windows - A second set of windows installed on the outside or inside of the primary windows to provide additional insulation and wind protection.

Straight Eave Lean-To - Describing the angular connection or transition between the vertical front wall and sloping roof of a solarium, sunroom, or skylight.

Strike -Metal plate or box, mounted in the doorframe that is pierced or recessed to receive the bolt or latch when projected.

Structural Glazing - Based on the use of a sealant not only as a weather seal, but also for the structural transfer of loads from the glazing panel to its perimeter support system. Only certain specific sealant formulations are suitable for this purpose.

Structural Glazing Gaskets - Cured elastometric channel-shaped extrusions used in place of a conventional sash to install glass products onto structurally supporting sub-frames, with the pressure of sealing exerted by the insertion of separate lockstrip wedging splines.

Stucco Brick Mould - Standard exterior trim which has been modified by having a groove cut in the top rear edge permitting exterior stucco to flow behind the trim.

Stucco Fin - An extrusion used in stucco home installations that is attached to the main frame to create a smooth, finished look for both the window and the stucco.

Stud - Vertical wood framing members which form a frame wall. In normal construction these are eight foot-long 2" x 4"s.

Subcontractor - A small business that is hired by a larger contractor to perform a specific task or job.

Subsill - A trim piece for windows. Subsill application (underneath the bottom jamb) simulates the appearance of a true sloped sill and also provides a drainage surface.

Substrate - Material that supports and reinforces.

Sun Control Film - A tinted or reflective film applied to the glazing surface to reduce visible, ultra-violet, or total transmission of solar radiation. Reduces solar heat gain in summer and glare. Some can be removed and reapplied with changing seasons.

Sunroom - A thermally broken modular vertical panel wall system with double insulated performance glass, topped off with a 4"-6" thick insulated foam panel roof. Offers maximum ventilation in the moderate price range.

Superwindow - A window with a very low U-factor, typically less than 0.15, achieved through the use of multiple glazings, low-E coatings, and gas fills.

Supplier - A term used for any business unit that supplies goods or services.

Surface Hinge - Hinge having both leaves surface applied as opposed to mortised in.

Suspended Film Insulating Glass - An IG unit manufactured with a light- and energy-controlling film suspended within the air space.

Swinging Door - A door of one or more panels that opens and closes by swinging on hinges mounted along one edge of the door. The door may swing either in or out.

Switchable Glazings - Glazings with optical properties that can be reversibly switched from clear to dark or reflective.

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.

Tempering - The process of hardening a piece of glass by heating and cooling it.

Tenon - A rectangular projection cut out of a piece of wood for insertion into a mortise.

Thermal Barrier - A strip of non-conducting material, such as wood, vinyl or foam rubber, which is used to separate the inside and outside surfaces of a metal window sash or frame, or a metal door or sill to stop the conduction of heat to the outside (which results in a cold inside surface). Vinyl windows, because of their thermal efficiency, do not require a thermal barrier.

Thermal Break - The addition of a thermal insulating material between two thermally conductive materials.

Thermal Expansion - Change in dimension of a material as a result of temperature change.

Thermal Mass - Mass in a building (furnishings or structure) that is used to absorb solar gain during the day and release the heat as the space cools in the evening.

Thermochromics - Glazing with optical properties that can change in response to temperature changes.

Thermogram - An image of an object taken with an infrared camera that shows surface temperature variations.

Thin Float Glass - Used in homes, apartments, schools, hospitals, malls.

Threshold - The member that lies at the bottom of a sliding glass door or swinging door; the sill of a doorway.

Through Wall Flashing - Flashing that extends completely underneath the sill or over the head of a window, and has an upturned leg on the interior side.

Tilt Latch - Mechanism that unlocks the sash and allows it to tilt in from the main frame.

Tilt Pin - A metal or hard plastic nail-like pin fastened to the sash to allow it to engage the balance shoe and from which the sash may tilt or pivot in. See Pivot Pin.

Tilt Window - A single- or double-hung window whose operable sash can be tilted into the room for interior washability.

Tilt-In/Lift-Out Sash - A sash that can be tilted to the interior and removed for cleaning and is manufactured by welding.

Tinted Glass - Glass with a material added to give the glass a light and/or heat reducing capability and color.

Top Roller Guide - Hardware fastened to the top of a sliding door and which contains a roller which glides in the door's overhead track.

Total Solar Absorption - The percent of incident solar radiation that is absorbed by a glazing system.

Total Solar Reflectance - The percent of solar radiation that is reflected by a glazing system.

Total Solar Transmittance - The percent of incident solar radiation that directly passes through a glazing system.

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.

Transmittance - The ability of the glass to transmit solar energy in the visible light, the ultraviolet, and the infrared ranges, centrally measured in percentages of each.

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

Transom Window - A large horizontally-oriented window (typically semi-circular or an artistic variation of that shape) mounted above a door or group of windows.

Tri-Durometer - An elastomeric material with three different degrees of hardness.

Triple Glazing - Windows that are made of three panes of glass with air space between the lites, and may be filled with argon or other gasses for increased energy efficiency.

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 Value - A measurement of heat transmission. The U value of a window is measured by the number of BTU's that will pass through each square foot of area per degree of temperature difference from one side of the window to the other (the lower, the better). U value = the number 1 divided by the R value.

UBC - Uniform Building Code.

U-Factor (U-Value) - A measure of the rate of non-solar heat loss or gain through a material or assembly. It is expressed in units of Btu/hr-sq ft-°F (W/sq m-°C). Values are normally given for NFRC/ASHRAE winter conditions of 0° F (18° C) outdoor temperature, 70° F (21° C) indoor temperature, 15 mph wind, and no solar load. The U-factor may be expressed for the glass alone or the entire window, which includes the effect of the frame and the spacer materials. The lower the U-factor, the greater a window's resistance to heat flow and the better its insulating value.

UI - See United Inches.

Ultraviolet - Type of radiation with wavelengths shorter than those of visible light and longer than those of X-rays. Causes sunburn, fading and breakdown of fabric, wood, furniture and other exposed surfaces.

Ultraviolet Light (UV) - The invisible rays of the spectrum that are outside of the visible spectrum at its short-wavelength violet end. Ultraviolet rays are found in everyday sunlight and can cause fading of paint finishes, carpets, and fabrics.

Unison Lock - A casement locking system which secures the window at two locking points by operation of one handle.

Unit Dimensions - The dimensions of a window or door unit which are defined in a primed wood unit from outside of exterior trim to outside of exterior trim in both width and height. Unit dimensions for clad units are from outside of frame to outside of frame in width and height.

Unit Size (US) - The dimensions of a window or door unit which are defined in a primed wood unit from outside of exterior trim to outside of exterior trim in both width and height. Unit dimensions for clad units are from outside of frame to outside of frame in width and h

United Inches - The dimension found by adding the total of one width and one length of a window unit, expressed in inches. (example: a window that is 30" wide by 50" high is 80 United Inches).

US - See Unit Size.

UV Absorption - Normal glass absorbs ultraviolet rays. If ultraviolet transmission is desired, quartz-based glass is used.

U-Value - Rate of heat flow U-value through the complete heat barrier, from room air to outside air. The lower the U-value, the better the insulating value. (See U-factor.)

Vapor Barrier - A watertight material used to prevent the passage of moisture into or through floors, walls and ceilings.

Vapor Retarder - A material that reduces the diffusion of water vapor across a building assembly.

Vent - The operating portion of a window that swings or projects in or out.

Vent Unit - A window or door unit that opens or operates.

Venting Unit - A window or door unit that opens or operates.

Venting Window - Operating window, such as a venting awning, etc. One that opens for ventilation.

Vent-Lok - Latch mechanism on the interior face of the sash which retains the window in a partially open position for ventilation.

Venturi Tubes - Ventilating tubes placed in an IG unit to allow the shipment of sealed IG units to areas of differing altitudes. This prevents the IG unit from building up too much pressure when shipped to high altitudes When the IG unit reaches the final destination, the tube is normally removed and the IG unit re-sealed.

Vertical Sliding Window - One or more sashes that move in a vertical direction.

V-Groove - A V-shaped groove cut into the surface of a glass pane for decorative purposes.

Vinyl - A plastic material used for cladding or entire window units. Vinyl is a generic term for modified PVC (Polyvinyl Chloride).

Vinyl Window - A window whose frame and sashes are made from vinyl.

Vinyl-Clad Window - A window with exterior wood parts covered with extruded vinyl.

Visible Light Reflectance - The percent of total visible light that is reflected by a glazing system.

Visible Light Transmission - The percent of total visible light that passes through a glazing system.

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. Visible Light The portion of the electromagnetic spectrum that produces light that can be seen. Wavelengths range from 380 to 720 nanometers. Visible Transmittance (VT) The percentage or fraction of the visible spectrum (380 to 720 nanometers) weighted by the sensitivity of the eye, that is transmitted through the glazing.

Warm Edge Spacer - Use of a non-conductive edge spacer in insulating glass units instead of the conventional metal (conductive) edge spacer. "Warm Edge" spacers may be made of butyl, silicone foam or other non-metallic materials and sealants.

Warm-Edge Technology - The use of low-conductance spacers to reduce heat transfer near the edge of insulated glazing.

Weather strip - A strip of resilient material for covering the joint between the window sash and frame in order to reduce air leaks and prevent water from entering the structure. Many types - woolpile, bulb, fin, leaf, etc. Older types include metal, foil and felt strips (used primarily on doors).

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 Flaps - A weep hole that is covered with vinyl flap that allows water to escape, while keeping insects out.

Weep Hole - A small opening in a wall or window sill member through which water may drain to the building exterior.

Weep Slots - Slots or holes in the sill (bottom) member of the sash frame that provides an outdoor release of infiltrated rainwater.

Welding (Fusion) - Joining thermoplastic pieces by one of several heat-softening processes. A properly welded corner is as strong, or stronger, than the extrusion itself.

Wet Glazing - The practice of using a silicone-type adhesive and sealer to fasten the lites into a sash.

Wholesale - Selling a product from a business to a distributor or dealer who in turn sells it to the end user.

Wholesaler - A business entity that buys from a manufacturer then resells a product to another business or end user.

Wind Load - The force exerted by winds on building panels and completed structures. May be inward (positive) or outward (negative). Outward forces generally occur on the leeward sides of buildings.

Window - A glazed opening in an external wall of a building; an entire unit consisting of a frame sash and glazing, and any operable elements.

Window/Wall Assembly - The building envelope and the fenestration products incorporated into it.

Window Frame - The fixed frame of a window which holds the sash as well as the operating hardware for the window.

Window Hardware - Various devices and mechanisms for the window including: catches, cords and chains, fasteners and locks, hinges and pivots, lifts and pulls, pulleys and sash weights, sash balances and stays.

Window Schedule - A listing of windows required in a given house, stating types, sizes, number of lites (lights), manufacturer, and any special needs, etc.

Window Screen - Woven mesh of metal, plastic, or fiberglass stretched over a window opening to permit air to pass through, but not insects.

Window Size - Always expressed as width first, then height.

Window Style - the description of the way a window operates, e.g., hung, sliding, casement, etc.

Windowpane Divider - A short bar used to separate glass in a sash into multiple lights. Also called a muntin or a grille.

Wire Glass - 1/4" clear or obscure glass having a layer of diamond or square pattern wire mesh embedded in the glass lite. It cannot be tempered and is not an approved safety glazing material.

Wire-Reinforced Glass - Glass sheets laminated with wire mesh between the surfaces. This glass is commonly used in glass doors where there is a high risk of glass breakage from objects striking the glass.

Wood Blocks - Pieces of plywood that come in different thickness, depending on the depth of the hook of the frame. They are used to make the window flush with the opening it is filling. They are also used to assist in pre-mulling windows together and give the screw more to bite into when joining the windows.

Wood Window - A window whose frame and sashes are made from wood

Work Life - The time during which a curing sealant (usually two compounds) remains suitable for use after being mixed with a catalyst.

XO Sliding Window - Since "O" indicates the fixed sash, this is a window in which the left sash slides and right sash is fixed, looking from the outside in.

XX Sliding Window - Since "X" indicates the moving sash, this is a window in which both sash operate.

XXX - The designation for three-panel sliding window or door in which all three panels are operable.

Zinc Oxide - A chemical added to certain types of laboratory and studio glass. The chemical makes the glass more elastic, which aids in the forming of glass using glass-blowing techniques.

About Us | Affiliates | Acrylic Block Windows | Glass Block Windows | Garden Windows

Copyright © 1999-2007 Crystal View™ Acrylic Block and Glass Block Windows - Builders Accessories, Inc.