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visible transmittance

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Energy performance ratings for windows and doors tell you the potential for gaining and losing heat as well as for transmitting light into your home. Ratings are typically broken down into measurements that include R-Value, U-value, solar heat gain coefficient and visible transmittance. R-Value R-value (or R-factor) is a measure of conductance and resistance. R-value measures heat flow resistance through a given material. Higher numbers signify greater insulation. A double-pane window with Low-E filled with Argon Gas generally has an R-value of R-4.00. R-values measure only conduction and not heat transfer.U-Value U-Value U-value (or U-factor) measures heat transfer through a material, establishing the rate of that heat transfer or loss. Lower numbers mean less heat transfer and therefore more insulation. A double-pane window with Low-E filled with Argon Gas  typically has a U-value of 1.53. U-values determine heat gain through a window in summer and heat loss in winter. Solar…