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

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

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.

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.

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

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.

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.

Krypton. An inert, nontoxic gas used in insulating windows to reduce heat transfer.

Laminated glass. Two or more sheets of glass with an inner layer of transparent plastic to which the glass adheres if broken. Used for safety glazing and sound reduction.

Lite. A window; a pane of glass within a window. Double-hung windows are designated by the number of lights in upper and lower sash, as in six-over-six. Also spelled informally light.

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.

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.

NFRC. National Fenestration Rating Council.

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.

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.

Sash. The portion of a window that includes the glass and the framing sections directly attached to the glass, not to be confused with the complete frame into which the sash sections are fitted.

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

Sill. The lowest horizontal member in a door, window, or sash frame.

Single glazing. Single thickness of glass in a window or 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.

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

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

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

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.