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Low-E Windows: Helping Your Home’s Energy Efficiency

Posted on October 15, 2021 by Miller and Smith Blog Team

Windows let in light.

They let in sunshine and star light, street lamps and moonbeams.

They let us look out into the world, see what the weather is like, and wave to our neighbors—all from the comfort of our own home.

But they are also a key player in keeping your home comfortable by affecting your home’s energy efficiency. Care must be taken when selecting windows to make sure they keep out as much as they keep in.

Miller & Smith build our homes exclusively with low-E window, ensuring your new home’s windows aren’t a pane in the neck (see what we did there?). Keep reading to learn more about how our energy efficient windows help your entire home.

Why energy efficient windows are needed

The Department of Energy reports that 25–30% of all heat gain and heat loss occurs through windows. This means when it’s hot outside, the heat transfers into your home through your windows, while the coolness of your air-conditioned air transfers out. In the winter, the same exchange happens only in reverse.

This continual heat transfer forces your HVAC system to work harder to maintain the temperature you’ve set your thermostat to. You end up using more energy to maintain your desired home temperature—energy which you pay for on your electric bill.

But heat exchange isn’t the only thing happening with windows. That lovely light from the sun brings with it various wavelengths of light you can’t see, including UV light. UV rays are the parts of the light spectrum that give you sunburns. They also cause your furniture, carpet, and art to fade. In fact, according to the National Fenestration Rating Council, 40–60% of all fading damage is caused by UV rays.

To summarize, windows that aren’t efficient fail a home due to excessive heat transfer, increased energy bills, and fading damage. This is due to increased UV light transmission. As previously stated, Miller & Smith homes use only low-E windows to protect against all these issues. Here’s how our low-E windows improve your entire home.

How low-E windows help whole-home efficiency

Before we begin discussing the benefits of low-E windows, we need to describe what “low-E” actually means. Low-E is short for low emittance. Without getting too deep into Planck’s Law, just know that every substance absorbs, reflects, and emits radiant energy (e.g., light and heat) to varying degrees. That is to say, everything keeps radiant energy inside itself (absorbs), bounces it back where it came from (reflects), and passes some through to the other side (emits).

With low-E windows, we’re focusing on how much heat the windows emit, or pass through to the other side. This is how the heat transfer mentioned above occurs. The windows emit heat/cold from the outside of your home to the inside, and vice versa. And wouldn’t you know it, you can measure a window’s emittance with its emittance rating.

Regular glass windows have an emittance of 0.84, meaning 84% of heat is and passed through to the other side. That’s not good at all! Low-E windows have a special coating or film composed of thin layers of metal oxides. With this special layer in place, low-E windows can have an emittance as low as 0.04, meaning only 4% of heat gets through. That’s a 95% decrease in heat transfer by using low-E windows!

Though that’s the main reason Miller & Smith uses low-E windows—to preserve your home’s temperature and comfort levels—there’s an added bonus. Remember the extra energy mentioned in the previous section your HVAC would use to maintain your preferred temperature—energy you’d have to pay for? Well, by hugely decreasing the transfer of heat by using low-E windows, homeowners have saved over 24% (on average) per month on electricity bills vs. homes without low-E windows. That adds up to quite a lot of money.

How Low-E windows block UV Rays

Though we’re discussing energy efficient windows, we did mention in the heading of this section that low-E windows help whole-home efficiency, which is extremely important. We’ve shown how they keep your home more comfortable and affordable, and preserve the health of your HVAC system. But the low-E windows that Miller & Smith uses in our homes has one more trick up their metaphorical sleeves: UV blockage.

Low-E windows block about 75% of the sun’s harmful UV rays (those invisible wavelengths that cause sunburns and make the colors of your interior fabrics, furnishings, and artwork fade). By stopping such a high percentage of those often-destructive photons, low-E windows preserve the beauty and long life of everything inside your Miller & Smith home. And a happy home is always more efficient.

Low-E windows are just one of the many aspects that make Miller & Smith homes energy efficient. They are an important part in our overall plan to make your new home feel just as fantastic in 2 years, 5 years, and 10 years as the first day you move in.