Ordinary glass absorbs and radiates heat on the cooler surface. In cold weather this surface is the external face of the glass or the outer pane in the case of a double-glazed unit. To prevent heat from being lost in this way, low E-glass is coated with a microscopic layer of metallic oxide that reflects heat back into the interior. The basic principle is the same as that low-tech strategy of placing sheets of foil behind radiators to reflect heat back into the room.
Low-E glass is designed to be used in double- or triple-glazed units, not as single glazing. It is installed as the inner pane, with the coating facing into the gap between the glass layers. Different types of coatings are available to provide high solar gain, moderate solar gain, or low solar gain, with the high-solar gain glass being suitable for climates where most energy is consumed in heating and low-solar gain glass for climates where most energy is consumed in cooling. Another important factor is siting. In a cold or temperate climate, for example, using low-E glass in double-glazed south facing units reduces the U-value to virtually nil, with the amount of heat lost being balanced by the amount of heat gained from the sun.
- Coated with glass with a low U-value. A double-glazed unit that incorporates low-E glass has a similar U-value to a triple-glazed unit
- Virtually the same in appearance as clear float glass
- Available in a range of dimensions
- Any glazing aplication where there is the potential for unwelcome heat loss or gain
- Conservatories, glazed extensions and toplighting