he window glazing.
             U-Value – The amount of heat transmitted by the window.
             Center Of Glass R-Value/U-Value – Performance of a window measured through the center of the glass only; not the entire unit.
             Unit R-Value/U-Value – A measure of thermal resistance/ heat transmittance for an entire window, including the frame.
             Visible Light Transmittance – A measure of the amount of that portion of the total solar radiation visible to the human eye.
             Understanding How Is Energy Moves Through Windows
             Understanding how windows work and how energy travels through them is the first step necessary to comprehend this concept of windows and energy. Windows start with the glass, or glazing. According to Krahn glazings do three basic things: "They light in, they let you look out, and they isolate indoor environment from outdoors."(Wilson, p.94). Glass is transparent to sunlight, in other words short wavelength radiation. Glass absorbs radiant heat, or long wavelength infrared radiation, warming up in the process. (Wilson, p.94). The glass radiates this heat bot
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