Low E, or low emissive (also low emissivity) glass is a much more efficient glass than clear glass. Low E is a special coating placed on the inside of a dual paned glass section. It is designed to make the glass almost twice as efficient as clear glass. It is designed to reduce radiant heat direct sunlight heat and greatly reduces the harmful UV’s that damage floorings and furnishings. Low E glass is required in all new construction in Northern California and we highly recommend Low E for your new windows and doors.