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Glass Definitions > Low-e glass |
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Low-e glass |
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Low-emissivity glass (Low-E) is a tinted or clear glass, which has a microscopically-thin coating of metal oxide. This allows the sun's heat and light to pass through the glass into the building. At the same time it blocks heat from leaving the room, reducing heat loss considerably.ProductionOn-line coated (pyrolitic process)This is a clear or tinted glass which has been coated with a metal oxide through pyrolysis when the glass leaves the tin bath (at 650°C). The coating is therefore very resistant to mechanical damage, and this Low-E glass can be cut, tempered or laminated just as normal uncoated glass. Off-line coated (magnetron process) This is a clear or tinted glass which has been coated on one of its faces, with a metal coating produced of either Titanium, Silver , or Copper applied by magnetically-enhanced cathodic sputtering. The process is somewhat similar to the electroplating process. The coatings are softer than the Pyrolitic coatings but may with some care be used as monolithic (single) panels in glazing with Titanium or Silver coatings, but are required to be produced as insulating glass, with the coating on an internal face of two panels held together as a sealed unit. This type of product can be supplied as toughened or laminated, and insulating double glazed panels The glass panels produced by the Magnetron sputtering process usually have higher performance characteristics than those produced by the pyrolitic process. Winter TimeThe sun's energy is "short wave radiation" that passes through the window and is absorbed by carpet, furniture, etc. The energy is then transformed into long wave radiation. The long wave radiation wants to flow from warm to cool. Naturally it will try to escape from the glass. At night the radiant heat produced from fireplaces, radiant heaters, wood stoves, etc. will also want to escape out through the glazing to the outside cold air. The above coatings prevent this when the radiant room side heat is reflected back in to the home. This results in a lower winter U-value. For winter comfort, the higher the indoor glass temperature, the better the product is for comfort.Summer TimeThe coatings manage the sun's heat in the summer by reducing the amount of heat transferred through the window. The coatings filter the sun's short wave radiation which cuts down on the amount of solar heat gain into the home. For summer comfort, the lower the indoor glass temperature, the better the product is for comfort. Throughout the year, these coatings reduce the impact of Ultraviolet rays which can damage curtains, flooring, furniture, etc.How Low-E works
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Hard Coat vs. Soft Coat Low-ELow-E glass is available in two basic classes, hard coat or soft coat.Hard Coat Low-EHard coat Low-E, or pyrolitic coating, is a coating applied at high temperatures and sprayed onto the glass surface during the float glass process.Advantages
Disadvantages
Soft Coat Low-ESoft coat Low-E, or sputter coating, is applied in multiple layers of optically transparent silver sandwiched between layers of metal oxide in a vacuum chamber. This process provides the highest level of performance and a nearly invisible coating.Advantages
Disadvantages
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