What is coated glass and how does it work?

Coated glass is ordinary float glass with an ultra-thin, transparent coating applied to one surface to give it a specific performance benefit — most commonly improved thermal insulation, but also solar control, self-cleaning or other functions. The coating is typically a microscopically thin layer (often metal oxides, measured in nanometres) that you can’t see in normal use but which changes how the glass handles heat, light and — in some cases — dirt and water.

The most common type in modern windows is low-emissivity (low-E) glass. Its coating reflects heat back into the room rather than letting it escape through the glass, which is what allows a sealed unit to meet today’s energy-efficiency and Building Regulations requirements. In a double-glazed unit the coating sits on a surface inside the sealed cavity, where it’s protected from wear and weather while still doing its job.