What is Low-E glass?

Low-emissivity, or Low-E, glass features a microscopically thin metallic coating applied to one or more panes. This coating works by reflecting thermal radiation (infrared energy) while permitting visible light to pass through the glass. In winter, the coating bounces heat radiating from interior rooms back inside. In summer, it reflects solar heat away from the building. The result is reduced reliance on heating and air conditioning systems.

The metallic layer is typically composed of silver, tin oxide, or other oxides applied in layers only a fraction of a micron thick. This invisible coating is what distinguishes Low-E glass from standard uncoated glass, which radiates heat energy away more readily.

Two main types exist. Hard-coat Low-E, also called pyrolytic coating, bonds directly to glass during the manufacturing process at high temperature. It is durable and tolerates handling but offers slightly lower solar control. Soft-coat Low-E, also called sputtered coating, is applied in a vacuum chamber after manufacturing and offers superior thermal performance and better light transmission, though it requires careful handling and cannot be exposed to moisture before installation.

Connecticut contractors installing replacement windows typically specify Low-E glass to meet energy codes and improve home comfort. The coating is most effective when paired with multiple panes and insulating gas fills between them.