The NFRC rating sticker should be on every window you purchase whether it is a replacement window or new construction. This sticker will show you how well a window performs. It evaluates the performance of the window's frame, the glass, and the spacers that keep the glass apart.National Fenestration Rating CouncilU-Factor - The U-factor is resistance to heat flow. It measures the performance of the entire window. The lower the u-factor, the better.Solar Heat Gain Co-Efficient - The SHGC measures how much infrared light (or heat in the light) gets thru the glass. The lower the number, the better.Visible Light Transmission - This measures the amount of visible light that comes thru the glass. Here, the higher the %, the more visible light will pass thru the glass.Read the full article from Exterior Contractors July 2011 issue. Contact Renewal for a free consultation to learn more about window options.Jay L. Bachman, Managing Partner