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So you’ve decided to go for it and invest in those new windows you’ve been thinking so much about. Replacing your home’s windows is a huge investment, and there are so many factors to consider. If the environment is one of your most important considerations, you aren’t alone.

With more knowledge than ever about the impact of our lifestyles on the environment, many consumers are wondering how to decrease their carbon footprint and make eco-friendly investments when planning home improvements. The good news is, greening your window replacement plans can be a boon for the environment, your home’s energy efficiency, and your budget! For the next two weeks, we’ll take you through the process of selecting the best windows to meet your green needs.

Greening Your Windows: The Basics

When just starting out in the process of selecting new windows, you should be aware of two industry terms that will guide your understanding of any given product’s energy efficiency.

  • U-factor: A U-factor describes how quickly or slowly a windowpane conducts non-solar The lower the U-factor, the more energy-efficient the product. Most manufacturers will list their U-factor, but to get a true sense of the entire window structure’s energy efficiency, follow the advice of the US Department of Energy (USDOE) and look for the NFRC U-factor ratings which “represent the entire window performance, including frame and spacer material.” The U-factor that you’ll need to make sure your windows perform best will depend on your geographical location. Use this chart as a guide.
  • Solar Heat Gain Coefficient (SHGC): This term refers to the amount of solar radiation–heat from the sun–that a window lets in. Once again, the lower the SHGC rating, the more energy-efficient the product. And like the U-factor, the SHGC that’s right for your home will be dependent upon your climate and your home’s orientation.
Greening Your Windows: Glass

When choosing glass for your new windows, rest assured that the environmental impact of using this material is slim, as glass is made from sand. That said, the type of glass you choose will impact the energy efficiency of your window.


Glazing refers to the actual window panes you choose for your window. A double-pane window style–the most popular choice, also referred to as insulated window glazing–protects your home with additional insulation from the elements. As the USDOE explains, “Insulated window glazing refers to windows with two or more panes of glass. To insulate the window, the glass panes are spaced apart and hermetically sealed, leaving an insulating air space.” More insulation means a more energy-efficient product.

Gas Fills

You can choose to further increase your windows’ insulating power by selecting double- or triple-paned models that come filled with one of two non-toxic, clear, odorless gases: argon or krypton. These gasses slow the transfer of heat, thereby keeping your home cooler in the summer and warmer in colder months.


Another option available to consumers: windows treated with low-emissivity (low-e) coatings. These coatings are undetectable and made of metal or metallic oxides. They provide yet another line of defense to protect your home from gaining (or losing) heat. And they’re one of the most cost-effective measures for greening your window replacement project; the USDOE notes that “Windows manufactured with low-e coatings typically cost about 10% to 15% more than regular windows, but they reduce energy loss by as much as 30% to 50%.”

Check back next week, when we’ll explore the environmental friendliness of several window frame options!

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