Soffit - The exposed undersurface of any overhead component of a building, such as an arch, balcony, beam, cornice, lintel, or vault.

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

Solar Transmittance - The percentage of total solar energy that glazing transmits through a window – a standard clear dual pane has a solar transmittance of 71%.

Solar-Tempered House - A dwelling that obtains a large part of its heat from the sun.

Sole Plate - The bottom horizontal piece in a frame wall, usually single or double 2x4's. The wall is nailed into the deck or rough floor through the sole plate.

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 - The sound transmission loss rating of a material over a selected range of sound frequencies. The higher the number, the less sound transmitted.

Span - Distance between centers of supports.

Spandrel - Opaque glazing material most often used to conceal building elements between floors of a building, so they cannot be seen from the exterior.

Spectrally Selective Coat - 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.

Speed Control - The mechanism that controls the rate of speed at which a door will operate.

Splice - A longitudinal or latitudinal connection between the parts of a continuous member.

Sputtered Coating - A coating deposited on glass or film atom-by-atom in a precise process inside a vacuum chamber. Softcoat low-E uses sputtered coatings.

STC (Sound Transmission Class) - Describes acoustical control for interior panels, and, even though inadequate, sometimes exterior windows. The higher the number, the better the product is at resisting typical sound frequencies excluding airplane and train noises.

Steel Reinforcing - A steel component placed within a vertical mullion to add stiffness and increase the windload capability of the system. Steel reinforcing may also be used to limit deadload deflection in intermediate horizontals.

Stiffener - A reinforcing member which serves to limit the deflection of the member to which it is attached.

Stile - A vertical member of a window or door, exclusive of applied glazing beads. Stiles are usually designated by function, such as lock stile, hinge stile or meeting stile.

Stool - The narrow shelf fitted on the inside of a window which butts against the sill.

Stop - The molding on the inside of a window frame against which the window sash closes; in the case of a double-hung window, the sash slides against the stop. Also used to describe a glazing bead.

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

Strike - Typically the portion of the lock that engages the keeper in the jamb or mullion.

Subframe - A supporting frame installed prior to installing a finished door frame.

Subsill - An aluminum extruded profile installed beneath the primary sill of a framing system specifically designed to function as a secondary defense for collecting infiltrated water which is then weeped to the exterior.

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.

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.

Sweep Strip or Door Sweep - A weatherstrip mounted at the top or bottom edge of a swing door.

Swing - The direction a swing door opens. Also see Hand of Door.

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

Temper (Aluminum) - Process used to bring a proper degree of hardness or elasticity by heat treatment. T5 - Artificially aged to improve mechanical properties and stability. T6 - Solution treated and artificially aged to improve the allowable stresses and consequently the capacity to resist greater movements.

Tempered Glass - Strong, break-resistant glass created in a secondary process via controlled air cooling of the heated glass. Tempered glass is four times stronger than annealed glass; a form of safety glazing. When shattered, it breaks into small pieces.

Tempering - Strengthening glass with heat and controlled air cooling.

Template (For Hardware) - A master pattern or scaled drawing showing all dimensions and hole spacing for hardware application.

Template Hardware - Hardware manufactured within template tolerances.

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

Thermal Break - An insulating material of low-thermal conductivity placed between materials of high conductivity within the system itself to inhibit the flow of cold or heat.

Thermal Cavity - The hollow, channel or void provided in the extruded framing member into which the liquid-thermal-break material is poured.

Thermal Expansion and Contraction - An increase in the dimensions of a material in direct proportion to the rise in its temperature and conversely a dimensional shrinking as a result of a drop in temperature.

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.

Thermal Resistance - The ability of a material to impede the flow of heat. See R-Value.

Thermal Stress - Strain on the edges of a glass pane caused by the faster expansion rate of the center of the light when exposed to heat.

Thermal Transmittance (U-Value) - The time rate of heat flow per unit area under steady state conditions through a body for a unit-air temperature difference on the two sides of the body.

Thermally Improved - Framing systems which for the most part have a continuous thermal isolator between the exterior and interior aluminum framing members, but which have intermittent contact between the exterior and interior by a highly conductive material such as aluminum or a steel fastener.

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

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

Throw - The distance which a lock bolt or latch bolt projects when in the locked position.

Thumbturn - A permanently attached small lever which, when turned, operates the bolt on a dead lock in the same manner as a key.

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

Tinted glass - Glass colored by incorporation of a mineral admixture. Any tinting reduces both visual and radiant transmittance.

Translucent - A glazing such as frosted glass, which transmits electromagnetic radiation (light) but causes scattering so that a clear image cannot be seen.

Transmittance - The percentage of radiation that can pass through glazing. Transmittance can be defined for different types of light or energy, e.g., visible light transmittance, UV transmittance, or total solar energy transmittance.

Transom Bar - The horizontal frame member (header) which separates the door opening from the transom.

Transom Window - The window sash located above a door. Also called transom light.

Transparent - Clear glazing that transmits light without diffusion for a clear view.

Trim Hardware - Decorative finish hardware used to operate functional hardware or the door itself.

Triple Glazing - Three panes of glass or plastic with two air spaces between.

True Divided Light (TDL) - A term which refers to windows in which multiple individual panes of glass or lights are assembled in the sash using muntins.

U-Factor - NFRC simulated overall coefficient of heat, transmittance of heat flow measured in BTU/hr-ft2-F. Lower U-factors indicate better performance.

U-Value - Measures the heat transfer through a material due to the difference in air temperatures on the two sides. (Lower U-values indicate better performance.) Also see Thermal Transmittance.

U.L. - Underwriters' Laboratories, Inc.

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 cause paint finishes, carpets, and fabrics to fade.

Uniform Building Code (UBC) - The building code generally used in the western United States, developed by the International Conference of Building Officials (ICBO) in Whittier, CA. Area of influence: Regions in the United States west of the Mississippi River. Replaced by ICC.

Uniform Construction Index - CSI format system to standardize classification of construction-related products; united inches the sum total of one window width and one window height expressed in inches.

Valley - The trough or gutter formed by the intersection of two inclined planes on a roof. The inclined planes are perpendicular to each other.

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

Vault - An arched structure forming the supporting structure of a ceiling or roof.

Veneer - A thin surface layer glued to a base of inferior material. To overlay (a surface) with a thin layer of a fine or decorative material.

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

Vent Unit - A window or door that opens to provide ventilation.

Vestibule - A small entrance hall or passage between the outer door and the interior of a building.

Vinyl - Polyvinyl chloride material, which can be both rigid or flexible, used for window frames.

Visible Light - The portion of the electromagnetic spectrum that produces light that can be seen. Wavelengths range from 380 to 720 nanometers.

Visible Light Transmittance - Visible Light Transmittance (VT) measures how much light comes through a product. The visible transmittance is an optical property that indicates the amount of visible light transmitted.

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

Wave-Length Selective - "Intelligent" coatings such as Low-E allow for glazing combinations to permit selective gain or shielding of the sun's heat, while letting in visible light.

Weatherstripping - 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.

Wedge Glazing - A flexible, continuous gasket that ensures a high-compression seal between the glass and glazing bead by applying pressure.

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

Windload - Force exerted on a surface by moving air.

Windload Formula - Formula used to relate wind speed to wind loads. MPH = Sqrt (PSF/.00256).

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 Hardware - Various devices and mechanisms for the window including catches, fasteners and locks, hinges, pivots, lifts and pulls, pulleys and sash weights, sash balances, and stays. Always expressed as width first, then height.

Windowpane Divider - See Muntin.

Wire Glass - 1/4" clear or obscure glass having a layer of diamond or square pattern wire mesh embedded in the glass lite.