Testing and Rating Associations
AAMA: American Architectural Manufactures Association – a certification program that provides consumers with a way to compare window performance.
Energy Star: A government-backed program helping businesses and individuals protect the environment through the use of high-efficiency products. ENERGY STAR qualifying products, such as windows and doors, means these items use less energy, save money and help protect the environment.
LEED Green Bldg Rating System: The Leadership in Energy and Environmental Design (LEED) Green Building Rating System is the nationally accepted benchmark for the design, construction, and operation of high performance green buildings.
NFRC: National Fenestration Rating Council – a nonprofit organization that provides fair, accurate and credible energy performance ratings for windows and doors.
Argon: An inert, nontoxic gas used in insulating glass units to reduce heat transfer.
Condensation: The deposit of water vapor from the air on any cold surface whose temperature is below the dew point, such as cold window glass or frame that is exposed to humid indoor air.
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.
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.
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.
Dewpoint: The temperature at which water vapor in air will condense at a given rate of humidity and pressure.
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 or krypton.
Krypton: An inert, nontoxic gas used in insulating windows to reduce heat transfer.
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.
R-Value: Resistance to the thermal transfer or heat flow. Higher R-value numbers indicate a greater
insulating value. It is the inverse of the U-Value (R=1U).
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 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.
Thermal Break: A material of low thermal conductivity that is inserted between members of high
conductivity in order to reduce the heat transfer.
Triple glazing: A sash glazed with three lights of glass, enclosing two separate air spaces.
U-value: The rate of heat transfer through a window or door. The lower the U-value, the better the
insulating properties of the unit or glazing system.
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.
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.
Window Glossary Terms
Awning: Window similar to a casement except the sash is hinged at the top and always swings out.
Bay Window: A combination assembly which is composed of two or more individual windows joined side by side and which projects away from the wall on which it is installed.
Bow window: A round bay window that projects from a wall in the shape of an arc.
Casement window: A window containing one or more sash hinged to open from the side, that project outward.
Double-strength glass: Sheet glass between 0.115” and 0.133” (3-3.38 mm.) thick.
Double-hung window: A window unit that has two operable sashes which move vertically in the frame.
Egress window: A window large enough, as defined by local building codes, for exit or entry in case of emergency with little or no effort required. Typically required in bedrooms.
Fixed window: A window designed to be non-operable. Also called a picture window.
Grid (Grids): Wood, plastic or metal dividers (grilles, grids, bars) designed for a single light sash to give the appearance of a divided light sash. These can be removable or fixed.
Grids-Between-Glass: Grids are permanently installed between the panes of the insulating glass.
Hopper window: A typical basement window usually with one sash that projects inward, it is often used below grade.
Impact Resistant Glass: Single or double pane construction made up of laminated glass containing a .090 interlayer.
Obscure Glass: Glass having an image, pattern or texture that distorts the vision through the glass.
Sash: A single assembly of stiles and rails made into a frame for holding glass.
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 lock: Generally, a cam-action type lock applied to the check rails of a sliding window to pull the check rails tightly together, both for security and weather tightness.
Simulated Divided Light: Grilles permanently bonded to the interior and exterior of the insulating glass simulating a divided light appearance.
Single-hung: A double-hung type of window in which the top sash is fixed or inoperable.
Tempered Glass: Glass manufactured to withstand greater than normal forces on it surface. It is approximately five times stronger than annealed glass. When it breaks, it shatters into small pieces to reduce hazard. Tempered glass can not be cut after tempering.
Tilt Latch: Used to release the sash and tilt forward for cleaning.
Transom: A small window that fits over the top of a door or window, primarily for additional light and aesthetic value.