energy efficient replacement windows

In part one, we covered the importance of window frame design, construction and materials in energy efficient windows. We also introduced who the National Fenestration Rating Council (NFRC) is and why understanding what they do is important. If you missed that, click here. In today’s blog we’re going to talk about the window glass and fill options. We’ll also briefly touch on style of window. Surprising to many, installation and how that may impact the energy efficiency of windows.

Glass & Glass Fills

One of the first questions we’re often asked is if it’s necessary to upgrade to Argon or Krypton gas filled windows. Although gas fills do improve a window’s energy efficiency, most windows made today meet minimum ENERGY STAR® requirements without a gas fill. Some manufacturers include one of the two gases standard and others offer as an upgrade. You’ll have to decide if the increased energy efficiency is worth the increased cost.

However, more important than what’s between the glass is what’s on the glass. All energy efficient windows today have a Low-E coating on the glass. Often called Low-E glass, the glass itself isn’t anything different than what is in your old windows. Low-E is actually a coating on each pane of glass. The easiest explanation as to how the Low-E coating makes a window more energy efficient is that Low-E glass helps prevent the summer’s heat from getting into your home and the winter heat in your home from escaping.

Window Styles

Let’s pretend there’s a brand and line of windows called Perfect Indianapolis Windows. They come in single and double hung, sliding, casement, and picture windows. If you were to look at the NFRC ratings on those windows, from the same manufacturer in the same line, you would notice slight differences in their energy efficiency. That’s because due to their difference in operation and design, they have different points where air can escape. In most window lines, the most energy efficient windows are picture windows. After that comes casement windows. Sliding and single or double hung windows tend to be about the same as they all operate in a similar manner.


Installation of your windows can contribute to its energy efficiency. However, that isn’t calculated in the NFRC’s ratings. They assume the window is properly installed. Some reasons a window isn’t installed properly can be because it’s not perfectly sized for the window opening. This is one reason a custom window is always a better choice than a stock or builder grade window.

Another reason is inexperience on the part of the installer. This often happens when a handyman or even a roofing company installs windows. Also, a properly installed window requires caulk both inside and outside. One benefit of choosing an experienced window company for your new windows is that they’ll do the installation as the manufacturer intended it be done.

Call Blair Windows for Your Energy Efficient Windows

We offer both new construction and replacement windows that are energy efficient. You can count on our nearly 70 years’ experience as an Indianapolis based window company to ensure that you get energy efficient windows that look great and are properly installed. Call us today for your free quote for new or replacement windows – (317) 356-4666 or fill out our contact form.

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