Conductive heat loss around the perimeter of insulated glass units (dark areas in the thermographic image, left) caused by metal edge spacers has led to recent innovations in “warm-edge” nonmetal spacers, such as the PPG Intercept (right).
Although blocking UV light is important for preventing fading, some damage is also caused by portions of the visible light spectrum. To determine the actual fading potential of light passing through a glazing system, use the total damage weighted (Tdw) values. The lower the Tdw, the less fading will occur.
This infrared photo was taken on a cool (30°F) winter day. Notice how hot the high-solar-gain glass (at center) is relative to the other windows.