An energy-efficient double-glazed unit is a type of window or glass panel composed of energy-efficient glass panes separated by air or gas-filled spaces with the purpose of reducing heat transfer and minimizing heat loss through the window. Energy-efficient glass is a special type of glass that has a thin, nearly invisible coating of silver atoms. This heat-reflective coating helps retain warmth inside a room, much like the way a thermos keeps its contents at a consistent temperature and prevents it from escaping.

Energy-efficient double-glazed units help reduce energy consumption in a building by decreasing heat loss during the winter and blocking the intrusion of heat during the summer. This contributes to lowering heating and air conditioning costs and reducing carbon emissions, which is a significant consideration in modern construction practices, given the changing climate and the growing interest in sustainable building methods.