Low-E Glass Explained

Glass is naturally considered to have a high-emissivity characteristic. To better understand this think of your morning coffee cup, when you poor hot coffee into a glass cup you can easily feel the heat transfer from the coffee to the coffee mug. This example applies to the glazing in your home’s windows as well. In the winter your home’s interior heat is transferred outdoors due to the high-emissivity of your window’s glass. A similar effect happens in the summer but in reverse, the glass transfer heat from the warm outdoors into your cool home.

What are Low-E Coatings?

Low-emissivity (low-E) coatings were created to counteract the naturally high-emissivity of characteristics of glass. In essence, low-e coatings act as a thermos would for your coffee cup; it helps control where to keep the heat, either indoors in the winter or outdoors in the summer.
Low-E coatings are thin, invisible layers applied to the glass or suspended films of an energy efficient window. The coating works by reflecting back heat to its source. In the winter, the heat is reflected back into the house. In the summer, the sun’s excess heat is reflected back outside. Low-E coatings are unique in that they block long-wave infrared heat and UV rays without preventing visible light from passing.