Glossary of Terms



At Solar Innovations®, we know taking on a new project can be a bit intimidating. We’ve provided a glossary of commonly used terms in the glazing and construction industry that you may come across throughout the duration of your project or while browsing our website.


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

Adjustment Clip – Hardware on hung window jambs to align jamb after window installation.

Air Infiltration – The amount of air leaking in and out of a building through cracks in walls, windows, and doors.

Ambient Temperature – The outdoor temperature.

Annealed Glass – A glass which is created in molten form. The process occurs in a long oven, where the glass is heated and then slowly cooled under controlled conditions, emerging as a flat and “fire polished” glass product. When annealed glass is broken, long, jagged, razor-sharp shards are produced, which can be dangerous. Because of this, building codes in many parts of the world restrict the use of annealed glass. Solar Innovations® does not incorporate annealed glass in any of our products because of the danger if the glass breaks.

Anodize – The process that provides a hard, durable oxide film on the surface of aluminum by electrolytic action.

[ANSI (American National Standards Institute)] – A clearinghouse organization for all types of standards and product specifications.

Apron – Interior flat trim piece, used under the stool at the bottom of the window.

Argon – An inert, nontoxic gas used to increase insulation by injecting between two panes of glass.

[ASHRAE] – American Society of Heating, Air-conditioning, and Refrigeration Engineers

[ASTM International]– (American Society for Testing and Material) – an organization that establishes material standards (including glass) and test methods. It has also produced a window installation standard.

Astragal – The center member of a double door that is attached to the fixed or inactive door panel.

Awning Window – A window with the sash swinging outward from the bottom.

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Back Bedding – The process of adhering and sealing.

Balance – A mechanical device, normally spring loaded, used in hung windows to counterbalance the weight of the sash during operation.

Balance Shoe – Nylon hardware in a hung window jamb that connects the balance with the sash.

Bay – The section of a structure from one post to the next, extending from the sill to the ridge.

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

Bay Width – The distance from one centerline of a rafter or post to the center of another.

Base Wall – A short wall below the glazing on exterior walls. Also see Knee Wall. (Base wall is typically completed by another contractor.)

Bead – A molding or stop placed around a window frame to hold the glass in place by pressure.

Billet – The cylindrical form of aluminum just prior to the extruding process.

Bite – A glazing term referring to the dimension of the glazing leg overlapping the edge of the glass.

Bow Window – A composite of four or more window units in a radial or bow formation and a gently curved contour. Bow windows project from the walls of the structure.

Brickmold – A type of external casing which frames windows and doors. The brickmold covers jambs and provides means for nailing during installation.

BTU – The heat required to increase the temperature of one pound of water one degree Fahrenheit.

Butyl – A synthetic rubber that can be used as a sealant and architectural glazing tape. Butyl is prepared by co-polymerization of isobutylene with a small amount of isoprene.

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Casement Window – A projecting window hinged at the sides and usually opening outward like a door.

Casing – Molding of various widths, shapes, and thicknesses applied to the framework of window and door units. Interior casing is a flat, decorative molding which covers the inside edge of the jambs and the rough opening between the window unit and the wall. Exterior casing (or brick mold) serves the same purpose, while it also is an installation device through which nails are driven to install the window unit into the wall.

Caulking – A compound for filling joints and sealing cracks to prevent leakage of water and air.

Center of Glass – All glass area of window except that within 2.5” (10 cm) from the edge of the glass; used in measuring and calculating glazing performance, such as R-values and U-values.

CFM (Cubic Feet per Minute) – A unit of measurement used in air infiltration testing.  (E.g., “maximum 0.10 cfm per foot of sash perimeter”)

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. The top rail of the lower sash and the bottom rail of the upper sash meet when a double-hung window is closed. Both pieces should be weather stripped for maximum weather ability.

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.

Cladding – Material placed on the exterior of a frame and sash components.

Clerestory – A glazed section located near the top of a high wall, often found in churches and cathedrals.

CMR (Centerline of Meeting Rail) – A reference line used to locate integral mullions and/or size oriel (unequal) sash, e.g., “the height of the lower sash should be 22 inches from the frame sill to CMR.”

Collection – The act of trapping solar radiation and converting it to heat.

Comfort Engineering – Optimizing glazing selections on a window-by-window basis to fulfill a prioritized set of objectives; e.g., comfort, energy efficiency (both summer and winter), UV protection, natural lighting, desired aesthetics, views, and budget.

Condensation – The conversion of water from vapor to liquid when warm, moisture-laden air comes in contact with a cold surface.

Conduction – A process of heat transfer, whereby heat moves directly through a material by molecular agitation. The handle of a cast-iron frying pan becomes hot due to conduction.

Conductivity – The transfer of heat through a given material; see U-value,

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 the air within the structure and between two panes of glass.

Cottage Double-Hung – A double-hung window in which the upper sash is shorter than the lower sash.

Countersink – When the top of a screw or nail is flush with or below the surrounding material

Crack Length – Total outside perimeter of window sash/vent; used when defining the AAMA air infiltration rate.

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. Based on AAMA standard.

Curb – Watertight wall or frame used to raise slope glazing above the surface of the roof as a preventative measure against water leakage from melting snow or rain runoff.

Curb Appeal – The visual attractiveness of a home as seen from the street; often the first impression. Realtors see curb appeal as an influential factor in evaluating and selling homes.

Custodial Lock – Window hardware only operable with a tool or key.

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Dade County – Florida county, including Miami, that has set numerous standards and requirements for hurricane-resistant windows and doors.

Daylight Transmittance – The percentage of visible light that glazing transmits through a window; a standard clear dual pane has a daylight transmittance of 82%.

Debridge – The process of cutting away the metal on the bottom of an aluminum thermal break cavity once the two-part polyurethane has reached full strength, thus creating a thermally-broken extrusion.

Desiccant – A porous, crystalline substance used to absorb moisture and/or sealant solvents from within the sealed air space of an insulating glass unit.

Design Pressure – The project wind load to be determined by the architect and expressed in psf, e.g., “the project design load shall be 38.7 psf, both positive and negative.”

Designation Number – Prescribed by AAMA; one for each window style. It provides a code for architectural selection, e.g., TR-5000=DH-C45=Double Hung-Commercial Grade-45 psf Design Pressure.

Dew Point – The temperature at which water vapor will condense as warm, moist air is cooled.

Die – A perforated steel block through which aluminum or vinyl is extruded.

Direct Gain – A direct gain passive solar system utilizes south-facing windows to give a structure the most sun exposure; a large window area accepts direct sunlight while thermal mass serves as storage.

Dormer – An area that protrudes from the roof of a structure.

Double Glazing – Use of two panes of glass in a window to increase energy efficiency and provide other performance benefits.

Double Glazing Panel (DGP) – A removable interior glass panel which creates an air space between the exterior glazing and itself. It provides improved insulation and condensation control and allows for between-glass shading options, such as muntins, blinds, and pleated shades.

Double Strength Glass (DSG) –  1/8” thickness.

Double-Hung Window – A window unit with two operable sashes that vertically bypass each other in a single frame. Sashes typically fit within vinyl balances and tilt outward.  They can be removed for safe, easy cleaning.

Drip Cap – A molding placed on the top of the head brickmold or casing of a window frame.

Dry Glazing – A method of securing glass in a window frame with a dry, preformed, resilient gasket, without the use of a glazing compound.

Dual Durometer – A material that has two or more levels of flexibility.

Dual Durometer Bead – A vinyl bead with a softer flap against the glass and a harder section inserted into a sash member.

Dual Glazed – Two single lites glazed into a split sash with an airspace, not hermetically sealed, between the two single lites.

Dual Window – Two windows joined together, one in front of the other, to provide superior sound control.

Dual Pane – Two panes of glass with a single airspace, held together by an edge spacer; the most economical Insulated glazing unit (IGU).

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Eave – The area of a structure where the front wall meets the roof.

Eave Height – The vertical dimension that spans from finished floor to the eave.

Edge of Glass – The glass area within 2 ½ inches (10 cm) of the edge of a window.

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.

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 all exposed extrusion surfaces.

Emissivity – Emission or the ability to radiate heat in the form of long-wave radiation.

End Dam – Used to close the ends of a subsill and prevent water leakage. It makes the subsill a complete water trough, allowing it to collect excess water and drain it to the exterior.

EPDM (Ethylene Propylene Diene Monomer) – A weather-resistant synthetic rubber used to make flexible gaskets for windows.

ER Rating – Energy Rating number developed by CSA (Canadian Standards Association) to compare the thermal performance of windows. Measured in watts per square meter (W/m2).

Escutcheon Plate – Hardware for handles, etc.

Etch – To alter the surface of glass with hydrofluoric acid or other caustic agents. Unintentional permanent etching of glass may occur from alkali and other runoff from surrounding building materials.

Expansion Mullion – Self-mulling window frame jambs that, when slipped together, permit expansion/contraction while preserving strength and water tightness.

Extension Jambs – Flat wood parts which are nailed to the interior edges of the window jamb to extend it in width and adapt to a thicker wall. The inside edge of extension jambs should be flush with the finished wall surface. Interior casing is then nailed into it.

Exterior Glazed – Glass glazed from the exterior of the building.

Extrude – The process of shaping aluminum or vinyl by forcing it through a die.

Extrusion – The process, in which a heated material is forced through a die, used to produce aluminum, vinyl (PVC) and other profiles or components.

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Fenestration – The arrangement and design of openings in a building for the admission of light.

Fin Seal – A form of pile weatherstrip with a plastic mylar fin centered in the pile. This fin reduces air infiltration and ensures weatherstrip contact throughout the window’s life.

Finger-Jointing – A means of forming a single longer piece of wood by joining smaller individual pieces together. 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.

Fixed Lite – Non-venting or non-operable window.

Fixed Panel – Non-operable door, usually combined with operable door units.

Fixed Window – Non-operable window.

Flange Frame – A window frame with the head, jamb, and sill exterior perimeter leg longer than the interior perimeter leg.

Flanges – Aluminum edges used  to attach fenestrations to a structure.

Flashing – Metal used to prevent water penetration and/or provide water drainage, especially between a roof and wall, and over exterior door openings and windows.

Float Glass – Transparent glass with flat, parallel surfaces formed on the surface of a pool of molten tin.

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

Foundation – The wall that supports the structure of a building. Can consist of poured concrete, block, stone, or break.

Frame – Outside members of a window unit which enclose the sashes; composed of side jambs, head jamb, and sill.

French Door – Generally refers to a pair of hinged doors that open from the middle.

French Sliding Door – A sliding door which has wider panel members around the glass, giving the appearance of a French hinged door.

Front Wall – Wall of a structure running the length of a building between the two gable ends.

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Gable – A vertical surface commonly situated at the end of a building, usually adjoining a pitched roof.

Gable End – A wall of a structure with a gable at its end.

Gas-filled Glass – A gas, other than air, placed between insulated glass to reduce the U-factor by suppressing conduction and convection. (Usually Argon, Krypton, or Carbon Dioxide.)

Gasket – A rubber or plastic pliable material used to separate glazed glass and aluminum or vinyl.

Glazing – The glass or polycarbonate panes in a structure. Also the act of installing panels of glass in a structure.

Glazing Bead – A molding or stop around a window frame that applies pressure to the glass to hold it in place.  A vinyl or wood strip, applied around the perimeter of the glass on the exterior of the window sash, for holding the glass in place.

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

Green Building – A movement in architectural and building circles aimed at creating occupant and environmentally friendly structures. Criteria such as sustainability, energy efficiency, and healthfulness are considered.

Greenhouse Effect – The property of glass that permits the transmission of short-wave solar radiation, but is opaque to long-wave thermal radiation. The interior of a car heating up from direct sun illustrates the greenhouse effect.

Grille – A term referring to windowpane dividers or muntins; typically detachable for cleaning

Gusset – A concealed, strong, right-angled shape used to reinforce mitered corners in tubular aluminum extrusions.

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Heat-Strengthened Glass – Produced by heating the glass to temperatures approaching 1300º F, then rapidly cooling it with air, similar to tempered glazing. The process results in a thermally-strengthened glass that is approximately two times stronger than a piece of annealed glass. Heat-strengthened glass benefits from reduced breakage from thermal and bending stress, which allows the use of larger pieces that do not require increased thickness.

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

Head Expander – A u-shaped extrusion slipped over the frame head that closes the gap above the window when pushed up after window installation.

Header – A heavy beam extended across the top of the rough opening to prevent the weight of a wall or roof from resting on the 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 Treating – The process where glass or aluminum extrusions are heated and cooled to become harder and stronger.

Hermetically Sealed Unit – An insulating glass unit that is sealed against moisture. The unit is comprised of two lites of glass that are separated by a roll-formed metal spacer tube (at the full perimeter), which contains a moisture and/or solvent absorbing material. The unit is then completely sealed, creating a moisture free air space.

Hollow Extrusion – An extrusion having an enclosed cavity within it.

Hopper – A window unit in which the top of the sash swings inward.

Hurricane Impact Resistant Glazing – Used in coastal regions that are subjected to hurricane winds and flying debris. Specially designed, laminated glass products can fulfill these requirements – the multiple layers of glass may break from an impact, but the plastic interlayer and the structural bonding of the glass to the window frame allows the panel to remain in place, protecting the interior of the building. The test method for compliance involves impacting the window in multiple locations and then subjecting the assembly to cycles of positive and negative pressures to replicate the exposure seen during a hurricane.

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[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).

[IGCC (Insulating Glass Certification Council)] – Directs a certifications program of periodic, accelerated laboratory testing and unannounced plant inspections to ensure sealed, insulating glass performance is in conformance with ASTM E 774-88.

Impact-resistant – Term used to describe window and door products that have passed established tests for resistance to wind-borne debris. Such products are typically used in coastal areas that are prone to hurricanes.

Infiltration – The seepage or flow of air into a room or space through cracks around windows, under doors, etc.

Inside Snap Trim – Used in retrofit work to cover the inside gap between the new window and the existing opening.

Insolation – Incident solar radiation; the total radiation striking an exposed surface.

Insulated Glass (IG) – IG glass is made up of two discrete pieces of glass with an airspace interlayer. The added insulation will isolate the room from the outdoor temperatures. Insulating values can be improved by adding a Low-E coating or inert gas fills, such as argon. Variations, such as heat-treated and laminated glass, can be incorporated where additional strength and security may be desired. The thickness of the glass used will depend on window size and building design requirements (e.g. windload). Solar Innovations® standard glazing thickness for insulated glass is 1”.

Insulation – A material with high resistance (high R-value or low U-value) that is used to retard heat flow. Air, Argon, or Krypton gas spaces between panes of glass provide insulation in IGUs.

Insulating Value – See U-factor.

Integral Mullion – A frame member trapped within the master frame to separate vents or fixed glass.

Interior Glazed – Glass glazed from the interior of the building.

Interlock – A design feature which enables sashes to engage with one another when closed.

Internal Gain – The heat produced in the interior of a dwelling from the operation of lights, appliances, etc.

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Jack Stud – Vertical framing members, generally 2×4’s, which form the inside of the window or door rough opening. They support the header and run down to the sole plate.

Jamb – A vertical member at the side of a window frame, or the horizontal member at the top of the window frame, as in head jamb.

Jamb Liner – The tracker installed inside the jambs of a modern double hung window, on which the window sashes slide. Vinyl or metal covering applied to the side jambs of double hung and single hung windows. They are generally formed to include an integral balance system and stops for the exterior and interior surfaces of the sash.

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K.D. (Knocked Down) – Product components that are shipped unassembled, e.g., the frame for a sliding glass door.

Keeper – A hardware device into which a window locking latch engages for security, also known as the receiving portion of a lock that interlocks with the lock arm. It’s mounted to the upper sash check rail on a double hung or single hung window and the inside surface of the sash stile on a casement window.

Kitchen Bay Window – A small bay window used above counter-height in kitchens; allows for a wider view and an inside sill for herbs and flowers.

Knee Wall – A short wall below the glazing on all or some of the exterior walls. Also see Base Wall. (A Knee wall is typically completed by another contractor.)

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Laminated Glass – Consists of a plastic interlayer material, polyvinyl butyral, that keeps the glass in place should it break. The pieces are retained within the frame, even after suffering an impact. Laminated glass can qualify as a safety glazing with any combination of annealed, heat strengthened, or tempered glass as layers.

Left or Right – Location information, always outside looking in, that can be used to specify direction, e.g., “the operating sash slides to the right.”

Lift – A handle or grip installed or routed into the bottom rail of the lower sash of a double hung or single hung window.

Lite – A pane of glass, a window, or a compartment of a window. Sometimes spelled “light.”

Louver – A slatted opening to provide ventilation but prevent rain from entering the room

Low-Emittance (LowE) Coating – Microscopically thin, virtually invisible, metal or metallic oxide layers deposited on a glazing surface primarily to reduce the U-factor by suppressing radioactive heat flow through the glass. Solar Innovations® utilizes LoE 272 as our standard Low-emittance glass.

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Marine Glazing – A u-channel of soft PVC, which is wrapped around the edge of the glass, and cushions it against the aluminum or vinyl. This process allows for unrestricted expansion and contraction while providing water tightness.

Masonry Opening – The space in a masonry wall that is left open for windows or a door; the same as a rough opening in a frame wall. The header (or lintel) in a masonry opening is usually a steel beam.

Meeting Rail – The part of a hung window where the two sashes meet and create a weather barrier.

Mill – Unfinished and unpainted aluminum material.

Miter Joint – A joint formed by fitting together two pieces cut at an angle to form a corner.

Monolithic Glazing – Consists of a single sheet of glass that is formed using the float glass manufacturing process. From this development, the monolithic glass is modified for increased strength, improved insulating capability, and safety glazing requirements. The glass can be annealed, heat-treated, or bonded to another piece of glass with a plastic interlayer to form laminated glass and it is installed as a single pane. Monolithic glass allows the heat and cold from the outside to penetrate the structure and greatly affect the inside temperature.

Monomer – A substance or simple chemical compound that can be polymerized to yield a much larger polymer molecule.

Mortise Lock – A lock fitting a rectangular-shaped cavity in the edge of a door.

Mullion – A horizontal or vertical member that supports and holds panels, glass, sash, or sections of a curtain wall.

Muntin – Horizontal or vertical bars that divide the sash frame into smaller lites of glass. Muntins are smaller in dimensions and weight than mullions.

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Nailing Fin – A vinyl or metal flange integrated into (or attached to) the perimeter of a window frame for installation on the rough opening’s header, jack studs, and rough sill. A continuous nailing fin may surround the frame as with an all-vinyl window, or a nailing fin may be affixed to the head and side jambs as with a vinyl ultraviolet stability.

Neoprene – A synthetic rubber with physical properties that closely resemble those of natural rubber. Neoprene has extremely good weather and temperature resistance, for both heat and cold, with ultraviolet stability.

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

Non-Tempered Glass – See annealed glass.

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Obscure Glass – See patterned glass.

Operator – A metal arm and gear device which allows for easy opening and closing of projecting windows; e.g. casement and awning windows.

Orientation – The compass direction that a structure faces. To optimize heat-gain in the northern hemisphere, the major facade of a building should face south. (A variation as much as 30 degrees east or west of south should not seriously affect performance.)

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Patterned Glass – Glass that has a pattern impressed on one or both sides. Used extensively for light control, bath enclosures, and decorative glazing.  This is sometimes called “rolled”, “figured,” or “obscure” glass.

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

Pane – A framed sheet of glass.

Panel – Framework holding the glass option in an operable door or fixed window frame.

Panning – A set of extrusions which are fastened to a new window to cover the exterior perimeter of an existing opening in a retrofit application.

Parting Stop – A strip of wood applied to the jamb to separate the sash in a double-hung window.

Passive Solar – A solar heating system which operates on natural thermal processes and does not use external mechanical power to move the collected heat. Generally, the building’s structure itself forms the solar system.

Patio Doors – Sliding glass doors, often used for access to a deck or terrace.

Picture Frame Casing – The use of casing on all four sides of the interior of a window. The stool and apron at the sill are replaced with casing.

Picture Window – A large stationary (non-ventilating) window which is designed for a maximum view without obstruction.

Pitch – The degree of the inclination upward from horizontal or flat. It may be expressed in degrees or as the ratio of the number of inches it rises in each 12″ of horizontal span (e.g. 3/12 means the roof rises 3″ in every foot of horizontal span).

Pleated Shade – A shade of folded fabric which can be installed like regular shades or between the panes of glass of a window.

Polycarbonate – Strong, semi-transparent plastic used in place of glass that is available in varying thicknesses. Polycarbonate is a less expensive infill selection when compared to glass.

Polymerization – A reaction occurring when two or more molecules of a compound are united to form a larger, more complex compound.

Prime Frame – A window frame which has an extended perimeter leg 1” back from the window exterior plane, which becomes a nailing fin for new construction installation.

Projected Window – A window in which the sash opens on hinges or pivots. Refers to casement and awning windows.

Projection – The distance from a structure’s point of attachment to an existing structure to the farthest point outward of the structure.

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 (50 mph).

Purlins – The horizontal components of a roof structure that are used to support and attach roof panels.

PVC (Polyvinylchloride) – An extruded material used for window and door framing.

Pyrolytic Coating – A special coating “sprayed” directly onto glass while it is still in a molten state, resulting in a permanently embedded surface coating.

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Radiation – The transmission of heat through space by means of electromagnetic waves or particles from one surface to another.

Rafter – Structural members of a roof that support the roof load and run from the ridge to the eaves.

Rail – The top and bottom horizontal members of the framework of a window sash or door panel; a horizontal sash member.

Receptor – Framing system consisting of two snap-together extrusions that are used to contain a window frame head and jambs in a masonry-type opening. It allows for deflection and inconsistencies in the openings.

Reflectance Back – A measurement in percentage of the visible light reflected back into a room.  A lower rating equals better external visibility.

Reflected Radiation – Solar radiation that strikes an exposed surface (like a window) after being reflected from the ground, trees, buildings, snow, etc. Reflected radiation can provide a significant amount of heat when vertical windows are used.

Reflective Glass – Glass with a metallic coating to reduce solar heat gain.

Relative Heat Gain – A measurement of the total heat gain through glazing for a specific set of conditions.

Relative Humidity – Humidity expressed as a percentage of the maximum possible humidity at a given temperature.

Removable Grilles – Ornamental or simulated muntins and bars designed to provide a divided light appearance. Generally made of wood, they are applied to the inside of the sash against the glass surface for easy removal.

Ridge Height – The vertical dimension from finished floor to the ridge.

Rough Opening – An opening in a wall or the frame work of a building where a door frame, window frame, or sub frame is fitted.

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

R-value – The measure of resistance to heat gain or loss (insulated ability). R-values, rather than thickness, can be compared for different materials. The higher the R-value, the greater the glass’s resistance to heat flow and the higher the insulating value. The R-value is the inverse of the U-value.

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Safety Glass – A strengthened or reinforced glass that is less prone to breakage or splintering.

Sash – Framework holding the glass in a window unit. Composed of stiles (sides) and rails (top and bottom).

Sash Balance – A coiled spring or spiral system integrated into the jamb liners to allow double-hung or single-hung sashes to open and close. They also allow the sashes to remain open in varied positions.

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

Sash Lift – A protruding handle screwed to the inside bottom rail of the lower sash on a double-hung window.

Screw Channel – The threaded channel centered in the glazing track.

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

Seismic Load – The force produced on a structural system due to the action of an earthquake.

Self-cleaning Glass – Glass treated with a special coating that uses the sun’s UV rays to break down organic dirt through what is called a photocatalytic effect. The coating also provides a hydrophilic effect, which reduces the surface tension of water, causing it to sheet down the surface easily and wash away dirt.

Setting Block – A piece of rubber on which a piece of glazing is set.

Shading Coefficient (SC) – The total amount of solar energy that passes through a glass relative to a 1/8″ (3 mm) thick clear glass under the same design conditions; includes solar energy transmitted directly plus any absorbed solar energy subsequently re-radiated or convected into a room; lower values indicate better performance in reducing summer heat gain and therefore air-conditioning loads.

Sidelites – A fixed frame of glass beside a window or door.

Sill – The lowest horizontal member in a door, window, or sash frame; generally slanted down and to the outside to shed standing water.

Simulated Divided Lites (SDLs) – Glass that has the appearance of a number of smaller panes of glass separated by muntins, but is actually a larger glazing unit with the muntins placed between or on the surfaces of the glass layers.

Single Glazing – A single layer of glazing used to enclose a structure, usually glass or plastic.

Single Hung – A type of window in which the bottom sash is operable, but the top sash is fixed or inoperable.

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

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

Span – The distance between any two consecutive structural supports.

Solarcool Bronze Glass – In extremely hot regions, Solarcool bronze can help keep your area cooler with a special light and heat reflective coating. The coating is permanently fused to the outside surface of the glass. This coating reduces the amount of sunlight entering your structure by 75% and reflects much of the infrared heat waves radiating from the ground or nearby buildings.

Solar Heat Gain Coefficient (SHGC) – The solar heat gain coefficient, also called a shading coefficient, is a measure of how well a window absorbs or reflects heat from the sun. The lower the coefficient, the better the window is at blocking the sun’s heat. Windows in hot or temperate climates should have a low SHGC; south-facing windows in cold climates should have a high SHGC.

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

Stile – The vertical members of a window sash or door panel.

Stool – An interior trim piece on a window which extends the sill and acts as a narrow shelf.

Stop – A molding used to hold, position, or separate window parts.

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Tempered Glass – Glass that is manufactured by heating annealed float glass to its softening point (1300º F), then rapidly cooling it with air. The resulting compression layer increases the glass strength to four times that of common annealed glass. Tempered glass will break into small particles. The pieces of broken glass are sufficiently smaller in size, allowing it to be classified as a “break safe” glass.

Note: For skylight applications in commercial situations, laminated glass may be required. Please review the local and state building codes in your area.

Thermal Barrier – A stop of non-conducting material, such as wood, vinyl, or foam rubber, that is used to separate the inside and outside surfaces of a metal frame. The thermal barrier minimizes the conduction of heat to the outside which results in a cold inside surface.

Thermal Break – An element of low conductance placed between elements of higher conductance to reduce the flow of heat. Often used in aluminum windows.

Tinted Glass – Glass with colorants added to the basic glass batch that gives the glass color, as well as light and heat-reducing capabilities.

Transmittance – The ability of the glass to pass light and/or heat, usually expressed in percentages (visible transmittance, thermal transmittance, etc.).

Transom – A horizontal transverse beam or bar in a frame; a crosspiece separating a door or the like from a window or fanlight above it. Also, a window above a door or other window built on and commonly hinged to a transom.

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uPVC – Unplasticized polyvinyl chloride, a rigid, chemically resistant form of PVC used for piping, window frames, and other structures.

U-value (U-Factor) – The measure of different structural components’ ability to conduct heat. The U-value of glass is measured by the number of BTUs that will pass through each square foot area, per degree of temperature difference, from one side of the glass to the other. U-values indicate how well the glass will hold the heated or cooled air. The lower the U-value, the greater the glass’s resistance to heat flow, and the higher the insulating value. The U-value is the inverse of the R-Value.

Ultraviolet Light (UV) – Invisible rays of solar radiation at the short-wavelength violet end of the spectrum. Ultraviolet rays can cause fading of paint finishes, carpets, and fabrics, as well as deterioration of some materials.

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Vent Panel – The panel that moves horizontally on a sliding door.

Vent Unit – A window unit that opens and closes.

Visible Transmittance (VT) – The percentage of visible light striking the glass that penetrates to the interior, expressed as a number between 0 and 1.

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Weatherstrip – A material used to seal the openings, gaps, or cracks of venting windows and doors to minimize water and air infiltration.

Weep Hole – Holes in the sill of the glazing system that prevent accumulation of condensation and water.

Windload – The force of wind against the exposed surfaces of the structure. Expressed in pounds per square foot (psf).

Wire Glass – Rolled glass with a layer of meshed or stranded wire completely imbedded. Available as polished glass and patterned glass. Approved polished wired glass is used as a transparent or translucent fire protection-rated glazing option. The wire keeps the fragments from falling out of the frame when broken.

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