What is Low-E Glass & Does it Make Windows Energy Efficient?

Low-E, which stands for low-emissivity, is glazing with a microscopically thin, translucent layer that reflects. Infinity from Marvin Windows provides an energy-efficient solution to your home's climate control needs. Featuring Low E Coatings on glass surfaces that reduce heat and light transmittance, our products meet ENERGY STAR® guidelines for climates across the nation -- ensuring a dependable reduction in dependence on costly AC units or furnaces all year round.

Low E1 Glass

Low E 1 glass has been the window of choice for architects and builders seeking energy-efficient solutions for decades. Its advanced glazing technology dramatically reduces heat transfer between indoors and outdoors, helping to deliver long-term cost savings on cooling and heating bills. In addition to its highly efficient properties, this reliable option boasts a nonhazardous coating that offers added protection without relying on hazardous substances like arsenic or lead.

This product is the perfect balance of maximum solar heat gain and insulation in northern climates. By placing it on sun-exposed elevations in your home or business, you'll get optimal performance from its Low E coating that provides radiant heating during cold months.

Low E2 Glass

With low-emissivity windows, you can reduce your home's heat intake from the outside and enjoy a more comfortable interior. These modern coatings consist of ultra-thin layers of tin dioxide, silver, or other metals precisely applied to each glass pane for greater efficiency and protection. Now you don't have to worry about too much sunshine coming in - let Low-E2 take care of it.

Low-E2 coatings provide the perfect equilibrium for climates across multiple geographies. The two metallic layers offer superior insulation from solar heat while still providing excellent warmth retention and transfer properties compared to single-coated Low E1.

Low E3 Glass

Used in applications where solar heat gain may be a concern with multiple metallic layers offering radiant heating properties similar to Low E2. Most commonly used in Western, sunny climates where cooling is prioritized overheating. When selecting the right window for your home, understanding how much natural light can pass through each option can be a deciding factor. Low-E2 and low-E3 windows allow varying levels of natural light into your living space - so it's essential to consider their reflective properties and the amount of transmitted sunlight before you buy. For those in Southern climates where cooling takes precedence over overheating, low E2, with its multiple layers of metalized coating, often delivers the best results when seeking radiant benefits similar to Low E2 glass applications.

Low ERS Glass

A higher performing Low E glass with significantly improved U Factors. This coating resides on the interior surface of the glass and can be touched. It is used in conjunction with Low E2 or Low E3. This coating is effective at reflecting radiant heat back into the room. This means a slightly cooler interior glass surface since the heat is not absorbed by the glass. The cooler surface may see a bit more condensation in cold climates versus traditional Low E glass make-ups. Also, abrasive products must be avoided when cleaning the glass.

Learn more about energy performance ratings.


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This table compares the room-side center of glass temperatures of different glass types against two different winter conditions.


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LowE³-366® glass is the ultimate performance glass. It just might make all other Low-E glass obsolete.

We recommend Cardinal LoĒ³-366® Glass

When the temperature soars, ordinary window glass can’t handle the heat. And tinted glass spoils the view. Cardinal LowE³-366, however, has been specially formulated to reject the sun’s heat without affecting the view. It lets more light in and keeps more heat out. So your home stays cool and comfortable. Our patented LoE-366 coating provides the ultimate in performance of all our LoE products.

It’s also the one glass you can use to be compliant in every ENERGY STAR zone – in a double-pane window. Couple it with LoĒ-i89®, and you’re compliant in the North. Its low SHGC makes it compliant throughout the rest of the country as well. It’s the perfect glass wherever you live.

Beats the heat and Keeps the view

For years, Cardinal has been setting the standard for energy efficient glass. Top-of-the-line residential window and door manufacturers all rely on our high quality. Our patented state-of-the-art sputter coating processes are unmatched by any other glass manufacturer.

What’s more, LoĒ³-366 provides exceptional fading protection as well. It blocks 95% of the sun’s damaging ultraviolet rays (a leading cause of fading), so it will help your furniture, carpets, curtains and wall coverings stay beautiful for years to come.

It’s the perfect cold remedy, too.

During cold weather, the insulating effect of your windows has a direct impact on how your rooms feel. Typically, 75% of the exposed surface of a window is glass, and the temperature of the room-side of the glass directly affects the air temperature in the room. The better insulated the window glass, the warmer your room will be.

The Efficient Windows Collaborative (www.efficientwindows.org) suggests that when glass surface temperatures fall below 52°F, there is a risk of thermal discomfort. To maintain the best comfort during the winter, select a glass product that produces surface temperatures that will stay above this point during the coldest outdoor conditions.

The superior insulating capability of Cardinal LoĒ³-366 is a crucial factor in the construction of comfortable windows for cold climates. The dramatic comfort improvement from windows with warm glass surfaces also means the relative humidity of the indoor air can be controlled and maintained correctly. Proper humidity levels (not too much, not too little) will improve comfort and promote a healthier living environment.

Three layers of silver make a clear difference.

For years, Cardinal has been setting the standard for energy efficient glass. Top-of-the-line residential window and door manufacturers all rely on our high quality. Our patented state-of-the-art sputter coating processes are unmatched by any other glass manufacturer.

Now we’ve raised the bar.  LoĒ³-366 adds a third layer of silver coating. Result: a clear coating that blocks, even more, solar gain, reflects heat, and lets the light stream in. LoĒ³-366 outperforms the tinted glass often used in warm climates.

You’re always in season with LoĒ³-366 glass.

LoĒ³-366is the ultimate performance glass, with energy savings throughout the year, in every part of the country. All with exceptional visibility. It’s the perfect glass wherever you live.

LoĒ³-366 can be purchased with any Infinity from Marvin window, at Gravina's Window Center of Littleton,  in a variety of shapes and sizes.  Call us now for more info!

Read more at Cardinal Glass

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