AAMA
American Architectural Manufacturers Association. A national trade association that
establishes voluntary standards for the window, door, storefront, curtain wall,
and skylight industries.
Absorptance
The ration of radiant energy absorbed to total incident radiant energy in a glazing
system.
Acrylic
A thermoplastic with good weather resistance, shatter resistance, and optical clarity,
used for glazing.
Aerogel
A microporous, transparent silicate foam as a glazing cavity fill material, offering
possible U-values below 0.10 BTU/(h-sq ft-oF) or 0.56 W/sq m-oC).
Air-leakage
(air infiltration). The amount of air leaking in and out of a building through cracks
in walls, windows, and doors.
Air-leakage rating
A measure of the rate of air-leakage around a window, door, or skylight in the presence
of a specific pressure difference. It is expressed in units of cubic feet per minute
per square foot of frame area (cfm/sq ft). Formerly expressed as cubic feet per
minute per foot of window perimeter length (cfm/ft) but not now in use. The lower
a window’s air-leakage rating, the better its airtightness.
Annealed glass
Standard sheet of float glass which has not been heat-treated.
Annealing
Heating above the critical or recrystallization temperature, then controlled cooling
of metal, glass, or other materials to eliminate the effects of cold-working, relieve
internal stresses, or improve strength, ductility, or other properties.
ANSI
American National Standards Institute. Clearing house for all types of standards
and specifications.
Argon
An inert, nontoxic gas used in insulating glass units to reduce heat transfer.
ASHRAE
American Society of Heating. Refrigerating and Air Conditioning Engineers.
ASTM
American Society for Testing and Materials. Organization that develops methods for
testing of materials.
Awning
Window similar to a casement except the sash is hinged at the top and always swings
out.
Balance
A mechanical device (normally spring-loaded) used in single-and double-hung windows
as a means of counterbalancing the weight of the sash during opening and closing.
Bay window
An arrangement of three or more individual window units, attached so as to project
form the building at various angles. In a three-unit bay, the center section is
normally fixed, with the end panels operable as single-hung or casement windows.
Bead
A wood strip against which a swinging sash closes, as in a casement window. Also,
a finishing trim at the sides and top of the frame to hold the sash, as in a fixed
sash or a double-hung window. Also referred to as bead stop.
Blackbody
The ideal, perfect emitter and absorber of thermal radiation. It emits radiant energy
at each wavelength at the maximum rate possible as a consequence of its temperature,
and absorbs all incident radiance.
BOCA
Building Officials and Code Administrators.
Bottom rail
The bottom horizontal member of a window sash.
Bow window. A rounded bay window that projects from the wall in an arc shape,
commonly consisting of five sashes.
Brick molding
A standard milled wood trim piece that covers the gap between the window frame and
masonry.
Btu (B.T.U.)
An abbreviation for British Thermal Unit-the heat required to increase the temperature
of one pound of water one degree Fahrenheit.