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Understanding Your Windows | Beginner’s Guide to Window Values Pt. 2

January 3, 2019

We care about our customers and want to help people make the most informed purchase possible. In our previous blog, we covered two values important to windows, R-value and U-value. While these values are necessary to understand in their own aspect, there are other factors that tie in. These factors are called the Solar Heat Gain Coefficient, and low-e glass. Understanding all of these values, as a cohesive unit, is the key to purchasing the best windows.

Solar Heat Gain Coefficient

SHGC, based on a value scale between 0 and 1, is the amount of heat that is absorbed by a window which can then be emitted inward.

Typically there are two ways of rating a windows SHGC. One method includes the entire window and frame, whereas the second method includes only the glass portion. Because of this, SHGC values including the frame are generally lower than glass-only values.

In a warmer climate, you’ll want to find windows that have a score closer to 0, as this signifies that there is less heat being transmitted. The opposite applied to cooler climates, in which you’ll need a higher SHGC score to help keep your home warm.

Low-e Glass

Low emissivity glass is specially crafted to allow visible light to pass through while mitigating the effects of heat transfer. There is a special coating that is placed on the surface of the window, usually an invisible metal or metallic oxide.

Along with the benefit of being more energy efficient, these windows are proven to help reduce fabrics such as drapes from fading as quick.

It is important to mention that this coating should be applied depending on the climate. For warmer climates, the coating should be applied to the outside of the window pane which prevents radiant heat from entering. For cooler climates, the coating is the opposite, being applied to the inside of the window pane to trap in radiant heat.

Example glazing options for replacement windows with their U-factor and SHGC values

Considering All Factors

Between these two blog posts we’ve covered; low-e glass, SHGC, U-value, and R-value. The picture above shows an example of various scores offered by Marvin Windows, our supplier of beautiful Infinity windows.

By understanding what all of these values mean, and knowing your homes climate/conditions, you can make the right choice for your next window purchase.

For example, we serve the Wisconsin area which is a mixed-climate region. Because of this, you would want to purchase windows with the following values:

  • Window U-value – low.
  • Frame – low conductive foam-filled fiberglass and vinyl (low U-value).
  • SHGC – between those of windows for cold and hot climates; it varies according to the side of the house; high SHGC glazed should be used with caution on the sun’s facing windows (to avoid summer overheating).

Not only will your home look fantastic, but you’ll see savings in heating and cooling costs as well. Of course, it is always a good idea to contact the professionals to be positive you’re getting the best windows for your hard earned money.


Windows of Wisconsin | (920) 429-9119 |
2300 Tower Dr. | Kaukauna, WI 54130