Low-E Glass Windows Guide: Does Low-E Coating Improve Energy Efficiency?

Low-E Glass Windows Guide: Does Low-E Coating Improve Energy Efficiency?

Updated: 05.24.2023

By Nina Tsoy

Yes, it does! Low-E glass is an ideal solution for those looking for energy-efficient windows and ways to reduce home heat loss. This modern invention can help homeowners stay comfortable while saving energy costs throughout the year.

Heat loss through windows and doors accounts for about a third of the total heat loss in a house. By changing the way the window transfers heat, low-emissivity coatings help to reduce heat loss in the winter and prevent heat entry in the summer.

Here is everything you need to know about this smart window and door solution.

What Is Low-E Glass and How Does It Work?

Low-E glass, also called low-emissivity glass, is an energy-efficient option for windows and doors. The glass has a thin, non-toxic coating that helps minimize the amount of ultraviolet light that passes through while still allowing natural lighting in.

This type of glass was initially designed for colder climates to retain infrared light but is now an economical choice for buildings in all regions. This microscopically thin coating offers a great return on investment.

Is Low-E glass clear? No, completely clear Low-E glass doesn’t exist, although the tint is barely noticeable. 

How to Measure the Effectiveness of Low-E Glass Windows

Several factors are used to measure the effectiveness of Low-E coatings.

  • Solar heat gain coefficient: The fraction of incident solar radiation emitted through the window. It can either be directly transmitted and absorbed or radiated inward.
  • U-value: The rating given to a window based on how much heat loss it allows.
  • Visible light transmittance: The measure of how much visible light passes through the glass.
  • Light solar gain: The ratio between the window’s visible light transmittance and its solar gain coefficient rating.

Good Low-E glass will have an Energy Star label, indicating that it is energy efficient. Your window installer should also be able to tell you your window’s U-value and Solar Heat Gain Coefficient. Both of these Low-E ratings should be low.

Pros & Cons of Low-E Glass Windows

low e glass windows

The Advantages of Low-E glass:

  • Reduced heat loss (up to as much as 50%!);
  • Lower energy bills;
  • Scratch and damage-resistant;
  • Prevents ultraviolet and infrared light rays from damaging flooring, furniture, and upholstery;
  • Available in many options, such as Low-E vinyl windows and Low-E tempered glass windows.

The Disadvantages of Low-E glass:

  • More expensive than standard glass;
  • Has a tint that some homeowners dislike;
  • May cause cheap vinyl siding to melt, as it reflects heat like a magnifying glass.

Yet, despite these minor cons, Low-E glass can reduce heating and cooling costs over time and even improve property values, which appeals to many homeowners.

Low-E Coating Types

There are two types of low-emissivity coatings:

  • Passive Low-E (hard coat):  A pyrolytic coating is applied to the glass ribbon while it is being produced on the float line to create a robust bond, known as a passive Low-E coating. This fusion creates a strong bond (hard coat) that’s very durable.
  • Solar Low-E (soft coat): The Magnetron Sputtering Vapor Disposition (MSVD) process is used to manufacture solar control Low-E coatings applied to pre-cut glass in a vacuum chamber at room temperature. This type of coating has a lower emissivity and offers superior solar control performance compared to other coatings. The soft coat must be sealed in an insulated glass or laminated unit for the highest-performing solar control.

Which Type of Low-E Coating Is Best for My Climate?

low e tempered glass

In cold environments, hard coat Low-E glass is best due to its ability to let shortwave infrared energy from the sun penetrate the glass. This helps warm up your home in the winter and prevents interior longwave heat energy from escaping.

However, if your area experiences cold and hot weather, soft coat low-E glass is the optimal choice, as it offers better UV protection and a higher U-value. The soft coat also reflects warm and cool air into your home, preventing it from escaping.

Low-E coatings save money on energy costs. Furthermore, they help to protect your furniture and decor from fading by blocking UV rays. Therefore, choosing the right type of Low-E coating for your windows is important.

Low-E window vs. double-pane: Low-e glass is generally more energy efficient, while double-pane windows offer better sound reduction. Your choice will depend on your needs and budget. You can also have Low-E double-pane windows, which perform better than single-pane Low-E glass.

How Can I Tell If I Have Low-E Glass?

To determine whether you have Low-E energy-efficient windows, conduct a simple experiment by holding a flame up to the window and observing the reflection in the glass.

  • Four flames will be visible in a double-paned window.
  • One reflection will be a different color from the others.

You can also look for a manufacturer’s etching (label), usually in one of the corners, that stipulates the type of Low-E coating used. Lastly, if the glass has a blue-green hue, it’s likely to be Low-E.

Are Low-E Glass Windows Expensive?

Low-E windows are nominally more expensive than regular glass windows because they are designed with a special coating that helps reduce the heat loss from your home. This coating helps to keep warm air inside during the winter and cool air inside during the summer.

The cost of installing Low-E glass windows may seem high initially, but the extra cost is only a few dollars more than regular glass windows. The special coating also helps protect your windows from scratches and damage, and the energy savings you experience in the long run will compensate for the initial cost.

Conclusion: Get Customized Low-E Glass from Apex

With its many benefits, Low-E glass is a valuable investment that can help make buildings more energy efficient, comfortable, and environmentally friendly. Apex Window Werks is a proud manufacturer and supplier of Low-E glass.

We repair and install custom glass doors and windows. Our team of low-emissivity glass installers delivers excellent craftsmanship and customer service. Contact us today for a free consultation to learn more about Low-E glass ratings and how we can help you save money while adding flair to your property.

Nina Tsoy

Nina Tsoy

With over 15 years of experience in the window repair, replacement, and manufacturing business, Nina is in charge for strategic solutions and exceptional operational performance at Apex Window Werks. This allows her to offer innovative techniques and solutions to address any window-related problem, all while adhering to industry standards and best practices.

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