What Is Low-E Glass?

Not all windows and glass products are created equal, but by understanding how heat and light interact with different materials, and with the latest technologies available today, glass manufacturers have been able to develop better and more efficient windows for your home. While you can select a basic pane of glass for your home’s windows that will adequately act as a barrier between yourself and the outdoors, why not choose materials, coatings and features that enhance your home’s functionality and make your daily living more comfortable and convenient?

When shopping for new windows for your home, you may have come across the term low-e glass, or low-emissivity glass, but what exactly does it mean, and how does it affect the overall quality of your windows?

What Is Low-Emissivity Glass?

To understand the features of low-e glass, you must first understand the basics — the “e” in low-e stands for emissivity. Emissivity is the ability of a material to radiate and transmit heat. Depending on the type of material, heat is either absorbed or reflected away. For example, a reflective, light-colored surface like aluminum foil has very low emissivity, while darkly colored surfaces such as asphalt have high emissivity and will get hot.

If you’ve ever stood near a window with a standard pane of glass, you may have been able to feel heat coming through the surface. To reduce the effects of heat transference through the glass — as well as other harmful effects of the sun, like ultraviolet (UV) light — low-e glass coatings were developed.

These coatings are extremely thin layers applied to glass that allow the material to reflect that radiant energy. The low-e coating works two different ways — it can either keep precious heating inside your home during cold months, preventing escape through the glass, or prevent heat from entering your home on a hot day.


low e glass energy efficiency

Different Types of Low-E Glass Available

During research about low-emissivity glass, it’s important to note that there are two different types of low-e glass available — passive and solar coatings. A passive coating is intended to maximize the amount of solar heat entering the space to trap heat. The benefit of a passive low-e glass coating is that it reduces the dependence on a heating system to keep your home warm. Solar coatings work in an opposite manner, minimizing the amount of solar heat entry and keeping buildings cooler.

Solar and passive coatings are manufactured with two different methods, either with a hard or soft coating. A hard coating technique is often used for manufacturing passive coatings, while soft coating is typically applied for making solar coats. However, these methods vary depending on the manufacturer.

Hard coatings are created by pouring a thin ribbon of hot tin onto the glass sheet, forming a strong bond between the metal and glass that makes it difficult to scratch or damage. Soft coating involves adding silver, zinc or tin into a vacuum chamber that’s filled with electrically charged inert gas. The vacuum then sputters the metal onto the glass, creating a soft layer.


Benefits of Windows Featuring Low-Emissivity Glass

Low-e glass sounds like it could be a useful tool for your home, but why should you spend the extra money? When your windows have low-e glass installed, you’ll gain the following benefits:

  • Furnishing protection: One use of low-e glass is filtering out harmful UV light. Not only is UV damaging for your health, but it also harms your furniture, causing fabrics to fade and deteriorating the quality of materials and flooring.
  • Improved window durability: The added layer in your window, although thin, will allow for extra durability, reducing chances of scratching or breakage.
  • Increased energy efficiency: With low-e glass, your home will have added insulation, which will result in less heat transference from your interior to the outside. The reduction of heat loss will improve energy efficiency throughout your home. These low-emissivity windows can reduce energy losses by 30 to 50 percent.
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Glass.com attempts to provide accurate information but cannot be held liable for any information provided or omitted.  You should always work with a licensed, insured and reputable glass shop that can assess your specific needs and local building codes and offer professional services. Never attempt to cut, install, or otherwise work with glass yourself. All content is provided on an informational basis only.


By Daniel Snow

Daniel Snow serves as the operations manager for Glass.com and is also a contributing editor. He earned a Bachelor’s Degree in Business Management from George Mason University and has a background in the real estate industry. After high school, Daniel even worked at a family-owned glass shop for a short period of time and is an Auto Glass Safety Council certified installer.

In his free time, Daniel enjoys being outdoors, especially around the water where he can be found surfing, fishing, and boating. He has a passion for bringing old vehicles back to life and loves working with his hands to restore cars, boats, and motorcycles.

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