Low-emissivity (or low-e) glass is thermally reinforced double glazing to which is added a thin transparent layer on one of the panes so that, as well as its double glazing functions, it prevents the energy (cold or heat) generated inside “escaping” to the outside, achieving a financial saving on electricity bills.
Advantages of low-emissivity glass
● Low emissivity cancels out the “cold wall” effect (in winter) and the “hot wall” (in summer): windows and balcony doors can be made bigger and the room can be used closer to them as they cease to become “freezers” or “ovens”, increasing comfort near to them.
● Low emissivity reduces thermal transmission by more than 60% compared with single glazing and more than 30% compared with double glazing. The U value of thermal transmission with single glazing is 5.8 W/m2K, with normal double glazing (12 mm air chamber) it is 2.8 W/m2K and with low-emissivity glass the U value falls to 1.8 W/m2K. Its appearance is almost the same as colourless glass.
Low-emissivity causes a high level of heat (long wave energy) reflectance but not visible light (short wave energy) reflectance: it prevents the heat generated in the room from “escaping” outside. And it does all this without losing brightness because it allows sunlight through the glass.
Low-e glass is highly recommended in countries with long, cold winters where it is necessary to make maximum use of the warmth generated by central heating
The layer of low-emissivity glass can also be combined with the solar control layer to achieve the benefits deriving from heat retention in the building (in winter) at the same time as the benefits of reinforced reflection of the sun (in summer). Low-emissivity glass can also be combined with other functions: sound insulation, personal anti-accident safety, self-cleaning and anti-burglary or vandalism security.