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Understanding the U-Value and SHGC Ratings of Windows

Energy performance ratings are an important consideration when comparing replacement windows. As you peruse through window options, you may have come across the terms “U-value” and “SHGC.” Renewal by Andersen® of Montana explains the differences between the two and why they’re important when investing in energy-efficient replacement windows.

U-Value and SHGC Ratings of Windows


The U-value, which is also known as the U-factor, measures the amount of heat transfer through a window. The rating ranges between 0.20 to 1.20. Generally, you would want to choose a window with a lower U-value as it can help retain heat inside your home during the winter and keep the heat out during the summer. It is also worth noting that some window labels may indicate R-value instead of U-value. R-value also tells you about a window’s insulating properties, but it is a measure of thermal resistance. Thus, a window with a low U-value should have a high R-value.


Solar heat gain coefficient (SHGC) is a measurement of how well a window can resist unwanted heat gain from the sun. Its ratings range from 0 to 1. The lower your window’s SHGC rating, the less solar heat can enter your home, making it an ideal choice for areas of your home that receive direct sunlight.

What to Consider When Choosing Replacement Windows

Energy performance ratings such as U-value and SHGC are important indicators in determining the best replacement windows for your home. However, these aren’t the only factors you have to consider when making such a significant investment.

Take the local climate, for instance. Montana’s year-round weather means your choice of window should have low U-value and SHGC ratings, so you remain comfortable during hot summers and cold winters. Window orientations should also be taken into account. Walls that receive direct sunlight during the day must have windows with low SHGC.

To learn more about our energy-efficient replacement windows, get in touch with Renewal by Andersen of Montana. Call us now at (406) 259-3944 or fill out our contact form for a free quote.


"I highly recommend Renewal by Andersen. We were treated well and everything went smoothly from start to finish. The company kept in contact with me before, during, and after the installation and let me know what to expect. I'm in love with my new windows! I will be using this company again when we refinish our basement. "

July, 21

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