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How Do Energy-Efficient Windows Work?

Aug 20, 2021

If you’ve been researching the wide world of replacement windows with intent to buy some, there’s a good chance you’ve seen the term “energy efficient” fairly often. But many dealers and manufacturers will either stop there or fire off a list of features without explaining their benefits. How are you supposed to be confident that these energy-efficient windows really do perform as advertised if the details are so vague?

Fortunately, understanding how energy-efficient windows work is simple! These windows are meticulously designed with a bunch of parts that play small roles on their own, and that all adds up to achieve the ultimate goal of reducing heat transfer. Once you know about heat transfer, everything else about these replacement windows makes more sense.

What is Heat Transfer?

Think of your refrigerator for a minute. You know how it beeps annoyingly when you leave the door open for too long? That’s because its ability to produce cold air isn’t enough to keep your food and drinks at the desired temperature when warm air is able to get inside. Warm air has a natural tendency to move into colder areas as a way to equalize the temperature difference. This, in a nutshell, is heat transfer.

In your fridge, that means your items are going to be lukewarm before long. With your windows, that means your home will be forced to be much closer to the outside temperature than the indoor one you want. That may be fine for a few months out of the year, but it can also have nasty implications for your energy bills at other times. Here’s how:

  • In the summer, when it’s hot outside, that warm air will try to work its way into your home however it can. If successful, your air conditioner will work overtime to keep you cool.
  • In the winter, when you’re heating your home to escape the cold, that warm air will want to go outside to balance the temperature difference between your home and the area just outside of it. If successful, that puts a lot of strain on your heater.

While there are a number of parts of your home that may somehow contribute to energy loss through heat transfer, windows are one of the leading causes of energy loss in a home. That’s why it’s great to have energy-efficient windows that are engineered to keep outdoor summer heat out of your home and indoor winter heat in it.

You may also see related terms called U-Factor (or U-Value) and solar heat gain coefficient (SHGC). Here’s what you need to know: U-Factor is the rate at which heat escapes your home, while SHGC is the rate at which outside heat enters your home. Both are expressed with decimals and lower ratings are better.

What Do Those Window Parts Do?

The glass system in energy-efficient windows does much of the work. They’re equipped with low emissivity (Low-E) glass, which has a coating that filters out harmful ultraviolet (UV) and infrared (IR) rays while letting visible light through. That controls temperature and limits sun damage to things like furniture. These windows also contain several panes of glass which are spaced apart from each other, and these gaps are filled with a gas too dense for warm air to pass through. The glass panes are sealed tightly to trap that gas, and the windows’ frames are also insulated for even further protection from heat transfer.

If you’d like to learn more about energy-efficient windows—and perhaps have some of the best replacement windows in Arizona installed on your home—contact the Energy Pros at FOR Energy today.

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