Do Your New Windows Need Low-E Glass?

Low-e glass, also known as low-emissivity glass, is a microscopic glass coating that improves a window’s energy efficiency. It helps regulate temperatures by preventing heat from escaping and reflecting the sun’s rays away from the window.

There are two types of low-E glass. While both drastically improve energy efficiency, one type is better for cold climates and the other for warm and sunny areas. You can choose the best glass for your windows by looking at U-Value and SHGC.

If you’re in the market for new windows, here’s what you need to know about e-glass and the type best for your location.


What is Low-E Glass?

Low-e glassView in gallery

Low-e stands for low emissivity and is a microscopic coating that reflects heat. In the winter, Low-E glass stops heat from escaping and reflects it back inside your home. In the summer, when UV rays hit your windows, a Low-E coating reflects the heat off the window, blocking it from entering the house.

Low emissivity glass keeps a home cool in the summer and warm in the winter.

Types of Low-E Glass

There are two types of Low-E glass: passive and solar control. Here’s what you should know about each.

  1. Passive Low-e glass is a hard coat, best for cold climates. It allows some of the sun’s rays to penetrate the window, heating the home. It also prevents heat from escaping the glass, keeping warm air inside.
  2. Solar Control Low-E is a soft coat placed in insulated glass. Solar Control Low-E provides lower emissivity and is ideal for homes in hot or mild climates that use air conditioning. It reflects solar heat away from the glass, so the house stays cool.

How is Low-E Glass Measured?

There are a few ways you can measure the efficiency of Low-E glass, with the U-Factor and Solar Heat Gain Coefficient (SHGC) being the two most important.

Most windows have a U-Factor of .20 to 1.20. The lower the U-Factor, the better a window insulates.

SHGC measures how much solar heat comes through the window. A typical SHGC range is 0 to 1, with 0 being the lowest. If you live in a cold climate, you’ll want a higher SHGC, depending on your window’s direction. If you live in a warm environment, you’ll want a low SHGC.


Low E-Glass vs. Double Pane/Double Glazing

Even though double-glazing and double-pane sound different, manufacturers use them interchangeably. In general, when a manufacturer refers to a window as double-glazed, it means it has two panes or sheets of glass.

Double pane glass is more energy efficient than single pane glass and can receive a dense argon gas treatment that increases energy efficiency. Double-paned windows can also contain Low-E glass.

A Low-E, argon-treated double-paned window will have excellent energy efficiency.


Low-E Glass vs. Tempered Glass

Tempered glass is a type of safety glass. It’s heated to extreme temperatures and quickly cooled to increase tensile strength. It’s important in areas where windows are more likely to break – like around doors. When broken, tempered glass crumbles rather than shatters.

Low-E stands for low-emissivity and is a coating applied to glass to increase insulative benefits. It helps prevent air leaks in homes, increasing energy efficiency.

Whether you need Low-E or tempered glass depends on where you’re putting the window and what you wish to accomplish. You can find tempered glass with a Low-E coating if you need energy-efficient safety glass.


How Do You Clean Low-E Glass

You can clean Low-E glass the same as any other window. But avoid using cleaners with ammonia or alcohol and never use a scraper or sharp object.

One of the most commonly recommended cleaners for Low-E is diluted vinegar. To clean your window with vinegar, use one part white distilled vinegar to ten parts water. Clean with a lint-free cloth. You can also clean Low-E glass with commercial cleaners like Windex.


Are There Any Disadvantages to Low-E Glass?

While Low-E glass is advantageous in many ways, it has a few drawbacks. First, and most obvious, it’s more expensive than standard glass. Secondly, some Low-E glass has a bit of a tint that homeowners don’t like. (In most cases, low-E coatings look like ordinary glass – clear.)

The most significant disadvantage to Low-E coatings is that if too close to vinyl siding, it can cause it to melt. Since Low-E glass reflects heat, it can work like a magnifying glass, concentrating heat in one area. If close to vinyl, the intense heat can cause the siding to burn.


Do All Windows Need Low-E Glass?

While not a requirement in all areas, Low-E coatings are usually worth the investment. A Low-E coating can help prevent energy leaks and regulate the temperature within your home.


What Else Makes a Window Energy Efficient?

While Low-E glass increases energy efficiency, it’s not the only thing that matters. For your windows to be efficient, they must fit tight in their opening with no air leaks or drafts. You’ll also need to choose an energy-efficient frame material.

The most energy-efficient frames are fiberglass, insulated vinyl, wood, and clad.

Frequently Asked Questions (FAQ)FAQ

Does Low-E glass have a tint?

Low-E glass might look slightly darker than regular glass, but not noticeably. It’s standard glass with a microscopic coating that reflects heat.

Does Low-E glass block UV rays?

Low-E glass blocks most UV rays and keeps heat from escaping. Solar Control Low-E glass will prevent heat from the sun from entering the home.

What is Low-E glass with argon?

Argon is an insulating gas placed between the panes of double and triple-paned windows. Low-e is a coating that helps the window reflect heat and helps insulate a home or building. Low-e glass with argon is a combination of the two.

Does Low-E glass keep heat in?

Yes, Low-E glass will keep heat in the house. The low-emissivity coating reflects heat trying to escape the home.

Final Thoughts

Low-e glass is a microscopic coating on windows that increases energy efficiency. There are two types: passive and solar. Passive Low-E glass allows some solar heat to enter the house, which is excellent for cold climates. Solar control prohibits solar heat from entering the home, which is ideal for warm climates.

When shopping for new windows, you can see how effective a window’s Low-E coating is by looking at its U-Factor. The U-factor will range from .20 – 1.20. The lower the number, the more efficient the window.