Post reviews of replacement windows
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It's either a .27 or a .24. That number indicates either the U-factor or the Solar Heat Gain Coefficient. Whether higher or lower is better depends on where you live. There would not be much of a difference in heating and cooling costs between the 2.
That number is the Emissivity Value of the glass. How much heat it absorbs and emits. The number in () is the surface or surfaces the coating is located. A lower number indicates the glass will have more reflective properties. I would still put more weight on the overall U-vale of the entire window when making a buying decision.