Glass window or crystal can consist of a solid sheet or several panels supported by a mullion or a secondary frame. These forms can include laminated glass, created by a vinyl layer joint and two or more pieces of glass, to provide minimal injury following breakage. Tempered glass, another safety design, undergoes a process of thermal heating and cooling to give strength and resist breakage.
The improvement of the energy efficiency of window panes can include one or more approaches: the change of physical or chemical characteristics; the application of coatings; and assembly of glazing layers. For example, technology includes tinting, low emissivity coatings, and low conductance gas between the layers. Double glazed windows include two layers with a spacer. The trapped air provides some insulation. Triple-glazed windows include three layers of glass or two layers of low-emissivity film (Low-E). These energy-efficient windows reduce heat transfer and condensation. Although triple-glazed windows insulate better than double-glazed windows, some disadvantages include weight gain and cost.
Between two or more sheets of glass in a sealed unit, inert, dense gases such as argon or krypton provide less thermal conductivity and insulation higher than air. Low-E (Low-E) coatings consist of a thin layer of metal oxide to allow sunlight to transmit, however, block heat from escaping. These coatings reduce radiant heat transfer or total heat flow. Low E coatings help Sun’s ultraviolet (UV) filter that can disappear or dull carpets and upholstery. The different types of low E coatings can achieve low solar gain, moderate solar gain or high solar gain.