Columbus Roofing: Article About Low E Coatings For Windows
Energy efficient windows are quickly becoming standard equipment on new homes. Since windows are one of the main sources of heat loss in homes, this is no surprise. One technology that Columbus roofing contractors and window installers alike are familiar with on this front is low emissivity glass. Also known as low E glass, window panes with this rating are specially coated to restrict the amount of radiant energy that passes through them. Low E windows can significantly reduce energy loss. In most cases, they are 30 to 50 percent more efficient than untreated window glass at stopping energy transfer through the pane.
Low E glass is made by applying metallic compounds in a microscopic layer that reflects more light energy than regular glass while still appearing clear. Some low E coatings are spectrally selective. This means they allow visible light to pass through while reflecting the heat energy of infrared and the damaging ultraviolet rays. These coated panes are typically used in multipane windows, in conjunction with inert gas pockets, to increase the insulation value of the window.
The low E coating is applied differently for different climates. For example, in colder climates, the coating is applied to the interior facing side of the glass to help keep heat energy from the sun trapped inside. While in hotter climates, the metallic coating is applied to the outward facing surface to reflect more of the daytime heat away from the home.
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There are also middle of the road models for use in areas with roughly equal heating and cooling needs. This attribute of low E windows is known as the solar heat gain coefficient (SHGC) and rates the window from low to high numbers based on the amount of heat the window allows to pass through from the sun to the interior. Hot climates would use low SHGC windows, and colder climates would use high SHGC windows.
The coating is applied to the glass in one of two ways. The first is known as pyrolytic, or hard coating, and involves spraying the metallic compound onto the glass while it is still hot during the manufacturing process. Method two is known as sputtered or soft coating. This involves using multiple layers to apply the coating either directly to the glass or onto a film, which is then applied to the glass. Soft coating is more susceptible to moisture damage, so it is generally found inside the inert gas pockets in multiple pane windows. One benefit of soft coating over hard coating is that it can be applied to older windows to retrofit them.