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

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

Argon gas
An inert, nontoxic gas used in insulating glass units to reduce heat transfer.

American Society for Testing and Materials. Organization that develops methods for testing of materials.

Awning window
A window that is hinged at the top and swings outward for ventilation.

A rubber material that seals the glass to the spacer, creating an air-tight and water-tight insulated glass unit.

Cam-action lock and keeper
The mechanisms, which pull and secure the sashes together when placed in the locked position.

Casement window
A window with a side-hinged sash that opens and closes outward by a crank handle mechanism. Available in continuous mainframe, with multi-lite configurations.

The deposit of water vapor from the air on any cold surface whose temperature is below the dew point, such as a cold window glass or frame that is exposed to humid indoor air.

Egress code
The minimum opening of a window for people to exit or firefighters to enter a building/dwelling. Different states or regions have different code requirements.

The ENERGY STAR® program is a joint venture between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Energy (DOE) designed to encourage homeowners to purchase energy-efficient products. Using less energy in our homes reduces the amount of CO2 emissions released into the atmosphere from burning fossil fuels such as coal, oil and natural gas. The advanced components and design used in each and every Alpine Window utilizing the Low-E insulated glass package exceed all performance criteria required by the ENERGY STAR® program.

The placement of window openings in a building wall, one of the important elements in controlling the exterior appearance of a building. Also, a window, door or skylight and its associated interior or exterior elements, such as shades or blinds.

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 panel
An inoperable panel of a sliding glass door or sliding window.

Fixed window
A window with no operating sashes.

French patio doors
A two panel glass door where both panels operate — available as either in-swinging or out-swinging.

The process of joining materials by melting them together with extreme heat (in most cases over 500¼F), resulting in the materials combining into a one-piece unit.

Garden window
Designed much like a bay or bow window, a garden also extends from the wall to the exterior of the home. It is built in a square or rectangular shape at right angles. The two sidelights often operate for added ventilation.

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.

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

Glazing bead
A molding or stop around the insulating glass of a window frame to hold the glass in place.

Optional horizontal or vertical lineals installed between the glass panes help to create the appearance of a divided window design.

Hinged patio doors
A two panel glass door where one panel is stationary or fixed, while the other operates and swings either inward or outward.

Insulating air chambers
Various chambers within the sash and mainframe, which help to insulate and strengthen the window.

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.

Handle for raising the lower sash in a single-hung window. Also called sash lift.

A unit of glass in a window.

Low-E (Emissivity) glass
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 longwave infrared radiation.

The combination of the head, sill and jamb sections of a window.

Meeting rail
The part of a sliding glass door, a sliding window or a hung window where two panels meet and create a weather barrier.

A weatherstripping material that is present where the sash frame meets the mainframe. Adds increased resistance to air infiltration.

National Fenestration Rating Council.

Obscure glass
Glass that has been made translucent instead of transparent.

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.

Picture window
A picture window that does not move or operate.

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-¼F/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.

The transfer of heat in the form of electromagnetic waves from one separate surface to another. Energy from the sun reaches the earth by radiation and a person's body can lose heat to a cold window or skylight surface in a similar way.

Separate from the mainframe, the portion of the window that contains the glass.

Sash vent stops
A feature that allows a window to be safely raised to a certain height.

The horizontal, bottom section of the mainframe.

Single-Hung window
A window that has two vertical sashes the lower sash being an operating sash.

Sliding patio doors
A combination of fixed and sliding glass door panels that operate on solid brass roller trucks. Available in 2-, 3- or 4-panel configurations with the operable panel available in any position.

Sliding window
A window in which the sash moves horizontally.

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.

An object placed between two or more pieces of glass to maintain a uniform width between the glass, and prevent sealant distortion.

U-value (U-factor)
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-¼F (W/sq. m-¼C). Values are normally given for NFRC/ASHRAE winter conditions of 0¼F (18¼ C) outdoor temperature, 70¼ F (21¼ 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.

UV reflection
The percentage of ultraviolet rays being blocked rather than being transmitted through the window's glass unit. The higher the number, the lower the percentage of ultraviolet rays being transmitted through the window.

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.

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

Material used to form a weather-resistant seal around the operable sash.