Window Materials & Assemblies: Glazing Materials
Insulated | Tinted | Reflective Coatings | Low-E Coatings | Surface Treatments | Laminated Glass
Reflective Coatings
As the SHGC falls in single-pane tinted glazings, the daylight transmission (VT) drops even faster, and there are practical limits on how low the SHGC can be made using tints. If larger reductions are desired, a reflective coating can be used to lower the solar heat gain coefficient by increasing the surface reflectivity of the material. These coatings usually consist of thin metallic or metal oxide layers. The reflective coatings come in various metallic colors-silver, gold, bronze-and they can be applied to clear or tinted glazing. The solar heat gain coefficient can be reduced by varying degrees, depending on the thickness and reflectivity of the coating, and its location in the glazing system. Some reflective coatings are durable and can be applied to exposed surfaces; others must be protected in sealed insulating glass units.
Figure 3-17 illustrates a highly reflective coating placed over a bronze-tinted, double-glazed unit. The emittance of the coating creates modest changes in the U-factor.
As with tinted glazing, the visible transmittance of a reflective glazing usually declines more than the solar heat gain coefficient. Reflective glazings are usually used in commercial buildings for large windows, for hot climates, or for windows with substantial solar heat gains. Reflective glazing is also used by many architects because of its glare control and uniform, exterior appearance.