Glossary

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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 ratio 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 used as a glazing cavity fill material, offering possible U-values below 0.10 BTU/(h-sq ft-F) or 0.56 W/(sq m-C).
Air infiltration
The amount of air leaking in and out of a building through cracks in walls, windows and doors.
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.
Airspace
The space in the cavity between two panes of glass in an insulated glass unit.
Aluminum-clad window
Window with wood construction covered with aluminum sheet. Has a factory-applied finish to deter the elements.
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 sets standards for testing of materials.
Awning
Window similar to a casement except the sash is hinged at the top and always swings out.