glossary
Click on a glossary term to read the definition.
AAMA:
American Architectural Manufacturers Association. A national trade association that establishes voluntary standards for the aluminum window, door and skylight industry.
ANSI:
American National Standards Institute. A clearing house for all types of standards and specifications.
ASTM:
American Society for Testing and Materials. A society of engineers which sets standards for testing of materials.
Condensation:
The accumulation of water vapor or droplets as the result of warm, moist air coming in contact with a cold surface and cooling to its dew point temperature. Condensation may occur when a cold window glass or frame is exposed to humid indoor air. Low-conductivity, insulated glass and warm-edge spacers reduce condensation.
Curtain Wall:
An exterior building wall which carries no roof or floor loads and consists entirely or principally of metal, or a combination of metal, glass and other surfacing materials supported by a metal framework. There are two basic types:
- Custom - Walls designed specifically for one project, and using parts and details specially made for this purpose;
- Standard - Walls made up principally of parts and details standardized by their manufacturer and assembled in accord with either the architect's design or the manufacturer's stock patterns.
Double Glazing:
In general, any use of two thicknesses of glass, separated by an air space, within an opening, to improve insulation against heat transfer and/or sound transmission. In factory-made double glazed window units the air between the glass sheets is thoroughly dried and the space is sealed airtight, eliminating possible condensation and providing superior insulating properties.
Heat Soak:
The heat soak test or heat soak process is used to minimize the risk of spontaneous breakages of heat-treated glass caused by NiS inclusions. In this process, glass channels are placed inside a chamber and subjected to an oven temperature of 290 degrees Celsius to accelerate nickel sulphide expansion. This causes glasses containing nickel sulphide inclusions to break in the heat soak chamber, thus reducing the risk of potential field breakages. The full heat soak process involves testing all glass in the order, virtually eliminating any chance of NiS breakage.
Low-emissivity (low-e) Coating:
Microscopically thin metal or metallic oxide layers are deposited on glass to reflect invisible long-wave infrared or heat. They reduce heat gain or loss in a building by redirecting the heat. In addition, they typically provide greater light transmission, low reflection and reduce heat transfer.
OITC Rating:
An abbreviation for Outside-Inside Transmission Class Rating. This rating is used to classify the performance of glazing in exterior applications. It is based on ASTM E-1332 Standard Classification for the Determination of Outdoor-Indoor Transmission Class. While STC rating is based on a "White' noise spectrum, this standard utilizes a source noise spectrum that combines Aircraft/Rail/Truck traffic and is weighted more to lower frequencies.
Nickel Sulfide:
An inclusion in float glass that can cause spontaneous breakage in fully tempered glass.
R-Value:
A measure of resistance to heat gain or loss (insulative ability). R-Values rather than thicknesses can be compared for different materials, since 6" of fiberglass (R-19) might compare with 12" of wood or 18" of stone.
Shading Coefficient:
This is a ratio of the solar energy entering through a window/wall compared to that which enters through a window/wall of clear 1/8" (3mm) double strength sheet glass. The solar energy which enters includes both that which is transmitted directly through the window/wall and that portion of the energy absorbed in the window that is transferred to the interior. This measurement is being phased out in favor of solar heat gain coefficient, and is approximately equal to the SHGC multiplied by 1.15. As the shading coefficient number decreases, heat gain is reduced, which means a better performing product.
Solar Heat Gain Coefficient (SHGC):
The fraction of solar radiation transmitted through a window or skylight, expressed as a percentage. The lower a window's SHGC, the less solar heat it transmits and the greater it's shading ability. SHGC can be expressed in terms of the glass alone or can refer to the entire window assembly. Generally, a lower SHGC is desirable in warm climates, and a higher SHGC is desirable in cold ones. SHGC has replaced shading coefficient (SC) as the standard indicator of a window's shading ability.
Sound Transmission Class (STC):
The sound transmission loss rating of a material over a selected range of sound frequencies. The higher the number, the better. Its original intent was to quantify interior building partitions, not exterior wall components. As a result, it is not recommended for glass selection of exterior wall applications, since the single-number rating was achieved under a specific set of laboratory conditions.
STC Rating:
Abbreviation for Sound Transmission Class Rating. When glass is used on the building interior, the sound transmission classification (STC) value can be used to categorize the glass performance. The STC rating is a single-number rating system for interior building partitions and viewing windows. The STC rating is derived by testing in accordance with ASTM E90, 'Laboratory Measurement of Airborne Sound Transmission of Building Partitions". The STC value is achieved by applying the Transmission loss (TL) values to the STC reference contour of ASTM E413, "Determination of Sound Transmission Class". The STC rating is a basis for glass selection. Its original intent was to quantify interior building partitions, not exterior wall components. As a result, it is not recommended for glass selection of exterior wall applications, since the single-number rating was achieved under a specific set of laboratory conditions.
Tempered Glass:
The glass is heated in a special furnace to just below the melting point, then suddenly cooled in the "quench" process. Tempered glass is approximately four times stronger than standard annealed glass. When broken, it shatters into small, relatively harmless, pieces. Tempered glass must have either a minimum surface compression of 10,000 psi or an edge compression not less than 9,700 psi in accordance with the requirements of ASTM C 1048, kind FT or meet the requirements of ANSI Z97.1 or CPSC 16 CFR 1201 safety glazing standards. It must be used as safety glazing in floor to ceiling partition walls, entrance doors, side lites, and other hazardous locations. Glass cannot be further processed (cut, drilled,etc.) after tempering.
Trombe Wall:
A glass covered concrete wall that collects and stores heat passively. Heat radiates back into the outdoors or into internal air or heating.
U-Value:
This is a measure of the ability of the window/wall to transfer heat from one side to the other due to the difference in temperature of the air and surroundings on each side of the window/wall. A low "U" value results in a low transfer of heat across the window/wall. A window/wall with a low emissivity or high reflectivity of room radiant energy will have a lower "U" value than a window with a high emissivity. The U-value of a wall/window is measured by the number of BTU's that will pass through each square foot of area per degree of temperature difference from one side of the window to the other. U-values calculate how well walls/windows will hold in heated or cooled air. The lower the number, the better.
Wired Glass:
Channel glass having a wire strands completely imbedded as nearly as possible to the center of thickness of the lite and approximately 1" apart. This glass is available as patterned and unpatterned glass. Wired glass is sometimes used as decorative glass. It breaks more easily than unwired glass of the same thickness, therefore wired glass is not a safety glass. Wired glass may have a safety film applied to it (film does not add strength) but it cannot be tempered.
