Solar glass is the combination of solar and glass technologies. Glass windows coated with a low-emittance (low-E) coating block radiant heat transfer. This lowers the amount of heat that passes through a window. Depending on energy needs, different types of low-E coatings allow for high, moderate, or low solar gains. Solar glass is often used to lower energy costs. Low-E coatings are nearly invisible, and made up of layers of metal or metallic oxide on a glass surface. The coating is transparent to visible light. In layered glazing, heat can be transferred between panes of glass, from warmer to cooler. Putting a low-E coated pane in the space.