(2) Tongue licking: Even in the dog days of hot summer, licking the natural crystal surface with the tongue also has a cold and cool feeling. Fake crystal, there is no cool feeling.
In addition to the multiple panes of glass, insulated window units also feature low-emissivity (low-E) coatings on the glass surfaces. These coatings help to reflect heat back into the room, further reducing heat transfer through the windows. Low-E coatings also help to block harmful ultraviolet (UV) rays, which can fade furniture and flooring over time.