Our company uses low E glass: low E is low emissivity, to be precise, low heat emissivity. What is it for and how it works?
In short, it’s all about energy efficiency. Glass, as any other materials, absorbs, reflects and emits radiant energy. We are talking about a special wavelength interval of radiant energy – ultraviolet and infrared light that can pass through glass. Window glass is highly heat emissive.
To improve insulation properties of the glass used for windows, special low-e coatings have been developed. There are two major types of low-e coating: pyrolytic and magnetron sputtering. As it is stated in Wikipedia, “The first involves deposition of fluorinated tin oxide at high temperatures. Pyrolytic coatings are usually applied at the float glass plant when the glass is manufactured. The second involves depositing thin silver layers with antireflection layers. Magnetron sputtering uses large vacuum chambers with multiple deposition chambers depositing 5 to 10 or more layers in succession.”
Applied to the glass surfaces, these low-e coatings reflect infrared light, keeping radiant heat on the side of the glass where it originated, while letting visible light pass. So, in summer low E window glass reflects radiant heat away, keeping it cooler inside. Energy-efficient windows reflect much more sunlight than normal glass windows. In winter is vice versa – it reflects indoor heat back inside. Using low-e glass results in more energy efficient windows.