SAGE Electrochromics, Inc. SAGE Electrochromics, Inc. - Glossary

Glossary of Terms

cycle: See switching cycle.

dynamic range: The range of variation between its darkest state and its clearest state that a switchable glazing is capable of. So, for example, one type of SageGlass® IGU has a dynamic range of 3.5-64%. This means that on the low (dark) end, it blocks all but 3.5 percent of incoming visible light and almost all the heat, and on the high (clear) end, it blocks only 36 percent incoming light, and allows in more solar heat.

insulating glass unit (IGU): Typical configuration of glass in a window or skylight frame, consisting of two (or more) pieces of glass held apart with a spacer and hermetically sealed to form a single glazed unit with one or more air spaces in between. Also called double glazing or dual pane.

Krochmann Damage Function (KDF): Used to rate a window’s ability to limit fabric-fading potential. It expresses the percentage of both UV and of that portion of the visible spectrum that passes through the window and causes fading. Lower numbers are better.

light to solar gain ratio (LSG) The ratio is equal to the Visible Light Transmittance divided by the Solar Heat Gain Coefficient. The Department of Energy's Federal Technology Alert publication of the Federal Energy Management Program (FEMP) views any LSG of 1.25 or greater to be Green Glazing/Spectrally Selective Glazing.

light transmission (also, visible light transmission): The percentage of the visible spectrum transmitted through a glazing and perceived by the human eye.

low-emissivity (low-e): Coatings applied to glass which allow transmission of light through glass but reflect thermal energy. Emissivity varies from 0 to 1; the lower the emissivity, the lower the resultant U-value. Low-e coatings help keep heat in when it’s cold outside, and help keep it out when it’s hot.

organic: In this context, materials that contain polymers which are susceptible to the deleterioius effects of the sun such as UV radiation and high temperatures.

polyvinyl butyral (PVB): Resin or polymer interlayer that bonds together two or more lites of glass to create a single, solid construction.

solar heat gain (SHG): The solar energy transmitted through a glazing plus the portion of solar radiation that is absorbed and either convected or reradiated toward the interior.

solar heat gain coefficient (SHGC): The fraction of solar radiation admitted through a window or skylight, both directly transmitted as well as absorbed and released inward. It is expressed as a number between 0 and 1. The lower a window’s solar heat gain coefficient, the less solar heat it transmits, and the greater its shading ability.

spectrally selective (SS): The U.S. Department of Energy defines spectrally selective glass as any glass with a Light to Solar Gain (LSG) ratio of 1.25 or better. LSG is a derivative of Solar Heat Gain Coefficient (SHGC) and Visible Light Transmission (VLT).

static glazing: Glass that has fixed performance with respect to visible, near-infrared, and UV transmission.

switching cycle: One cycle of a SageGlass window is from its clear state to its fully tinted state and then back to clear.

switching speed: The speed at which SageGlass glazing changes from its clear state to its tinted state (and vice versa).

treated glass: Glass that has been coated or tinted to help improve its solar control properties.
Tvis: Abbreviation for visible light transmission.

Ultraviolet radiation (UV):
The portion of the sun’s spectrum that causes fading (along with visible light).

U-value: The heat flow rate through a given glass construction due to the difference between indoor and outdoor temperatures, expressed in Btu/hr/sq.ft. The lower the U-value, the less heat transmitted through the glazing material and the more efficient the window is at reducing winter heating costs and summer cooling costs. There are different U-values for a product used during the winter and summer.

VIS: Visible.

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