Question

A double-pane insulated window has four surfaces of glass. These surfaces are numbered in the following order: the exterior face is called surface 1; the internal face of the exterior glass is surface 2; surface 3 is the internal face of the interior glass; and the interior glass face exposed to the room is surface 4. For which surface would you specify the low-E coating and why?

Answer

In order to protect the low-E coating, it is placed on one of the internal surfaces. The best location is on surface 2. If the coating is placed on surface 3, you are more likely to have heat gain in the trapped air space, which could lead to seal failure.