Glazing
Much of the building's thermal performance is due to its advanced windows (often called "superwindows"), which were used here commercially for the first time. Virtually all are krypton-filled Heat Mirror® windows. Heat Mirror® is a 0.003-inch-thick (76-µm) clear polyester film with special, almost atomically thin, coatings that are transparent to visible light but reflect infrared (heat) rays. The film is suspended between glass panes in a double-paned window unit and performs the way a third pane would perform—only better, because it keeps in more heat and lets in more light than a third piece of glass would. In fact, the type of Heat Mirror® film originally used in RMI's windows (Heat Mirror® 88, designed to maximize solar heating in cold climates) loses only about one-tenth as much heat as a single pane of glass, and lets in three-quarters of the visible light and half of the total solar energy.
During the 1990s, most of our building's original argon-filled, single-Heat Mirror® units were replaced with krypton-filled units having a double-sided film (Heat Mirror® coated on each side of a single suspended polyester film), and in some units supplemented by a low-emissivity (heat-reflecting) coating inside the outer lite of glass. The building's window configurations vary, but their light-reflecting and insulating capacities are keys to its efficiency.
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