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There are a lot of elements to consider when choosing windows for a project. In fact, we previously wrote about companies who advertise low-priced windows, as well as why you shouldn’t pick the cheapest window, so we’ll avoid those topics for now. (You’re more than welcome to read those articles for refreshers on each subject.)

Two aspects about window selection that don’t always get the attention they deserve are geography and climate. It’s not unusual for people to ask which windows offer the most energy efficiency. But a window that is most energy-efficient in one area of the country may not perform as efficiently in another.

What Are U-Factor and SHGC?

As many contractors know, products that meet certain specifications can receive Energy Star accreditation. Energy Star products have been tested by EPA-recognized laboratories and meet or exceed certain performance standards. For a window to be receive Energy Star status, it must demonstrate acceptable performance related to its U-Factor and Solar Heat Gain Coefficient (SHGC).

• U-factor is a measure of a door or window’s insulating qualities, and are based on a score between zero and one (the lower the number, the better the efficiency.) A window’s U-factor doesn’t focus exclusively on the insulating properties of the glass; rather, it reflects the performance of the window unit as a whole. Lower U-factor scores indicate superior insulating characteristics and are most desirable when the window is needed in areas with extreme differences in indoor and outdoor temperatures, such as cold-weather climates encountered in the northern hemisphere.

• SHGC is a measurement for how well a window can decrease heat gain inside a structure, and is also based on a score between zero and one. Higher SHGC scores indicate that a window will allow in more light – and thus more heat – into the structure. Windows with low SHGC ratings are preferable in hotter climates, as they help preserve cool interior air by deflecting warm energy from the sun’s rays from entering the structure.

Why It Matters For Your Windows

Although there’s a baseline score for achieving Energy Star accreditation, the ideal U-factor and SHGC scores for a window depend on the climate zone in which it will be installed. In the US, there are four distinct climate zones: Northern, North-Central, South-Central, and Southern. The St. Louis metropolitan area is located in the North-Central climate zone. As such, windows in this climate zone should have a U-Factor greater than or equal to .20 and an SHGC score less than or equal to .40.

For some people, this may just seem like it’s all numbers. However, the consequences for picking the wrong windows will inevitably come back to hit your pocketbook at some point. Choosing the wrong windows could end up hitting your wallet – either in the form of higher utility bills or as inflated maintenance costs for your overworked heating or A/C system.

Wholesale Siding Depot not only carries an extensive selection of energy-efficient windows, we also have experienced representatives on hand to answer your questions and help pick out the perfect units, whether they’re for new construction or as replacements for your remodel. Call, email or stop by today with any questions you may have – because when it comes to finding the perfect windows for your project, we’ll help get you into your comfort zone.