glass term

Argon - A relatively inexpensive, colorless, odorless, inert gas with 30 percent less thermal conductivity than air. Argon is 1,000 times more abundant than krypton and comprises .94 percent of the Earth's atmosphere.

Condensation - The process by which water vapor, which is present in all but the dries air, comes in contact with a surface that is below the "dew point" temperature and becomes liquid. As an example, condensation occurs on the sides of a glass of ice water since the temperature of the surface of the glass has reached the dew point of the surrounding air.

Decibel - A unit for expressing the relative intensity of sounds on a scale of zero to 130, zero being the average least perceptible sound, and 130 being the average pain level.

Heat Gain - The transfer of heat from outside to inside by means of conduction, convection, and radiation through all surfaces of the house.

Heat Loss - The transfer of heat from inside to outside by means of conduction, convection, and radiation through all surfaces of the house.

Infrared Energy - Invisible solar energy, measured in nanometers, ranging on the solar energy spectrum from 760 nm to 2100 nm, about 59 percent of the spectrum. IR waves are what we feel as heat.

Krypton - A very expensive, colorless, odorless, inert gas that is twice as dense as argon. It comprises .0001 percent of the Earth's atmosphere.

Newton Rings - Or Interference Fringes, are observed when insulated glass units are fabricated using two lites of glass of exactly the same thickness and viewed under certain lighting conditions. if the difference in thickness of the two lites is less than .0001, these rings may appear to be an oil stain. Then can be seen in either daylight or artificial light from both inside and outside the window. These fringes are visible at 90 degrees, but they become more apparent at angles less than 45 degrees.

Pyrolytic Coated Glass - Glass with a coating, either visually reflective or non-reflective, applied at high temperatures and fired onto the glass surface during float-glass production.

R-value - A measure of resistance to heat gain or loss, or insulative ability. R-values, rather than thickness, are used to compare different materials. For example, 6" of R-19 fiberglass might compare to 12" of wood or 18" of stone. A product's R-value is the inverse of its U-value, that is, U=1/R or R=1/U.

Solar Heat Gain (or Shading Coefficient) - Indicates the total amount of solar energy that passes through glass relative to a 1/8" (3mm) thick clear glass under the same design conditions. It includes both solar energy transmitted directly plus any absorbed solar energy subsequently re-radiated or convected in the room. Lower values indicate better performance in reducing summer heat gain and, in turn, air conditioning loads.

Sound Transmission Class (STC) - The sound transmission loss rating of a material over a selected range of frequencies. The higher the number, the better the rating.

Thermal Conductivity - A measure of how quickly heat passes through a material such as glass.

Ultraviolet Radiation - The portion of the electromagnetic spectrum with a shorter wavelength than visible light. UV radiation is what produces fading in different materials.

Ultraviolet Transmittance - The percentage of UV rays that are transmitted through a piece of glass (about 3 percent).

U-Value - The measure of heat flow in BTU's/hour/square foot/degrees F conducted through glass. Lower U-values indicate better insulating performance against conducted heat gain and loss. Winter nighttime U-values are calculated using an outdoor air temperature of 0 degrees F and outdoor air velocity of 15 mph, indoor air temperature of 70 degrees F, and air velocity of 0 mph.

Vacuum Coated Glass (Magnetic Sputtered Vacuum Deposition, MSVD) - Glass with a coating applied in a secondary process at ambient temperature with a vacuum chamber.

Visible Light Transmittance - The percentage of the visible light spectrum that is transmitted through glass (about 38 percent).