Among building materials, glass is probably the only one that can both insulate, protecting people and items from temperature and weather extremes, and control the passage of heat and light. As glass makes up a huge part of a window, it plays a big role in window performance, making it highly important that you choose the right type.
By choosing the right glass type, you can enjoy both views and natural light while controlling heat and UV absorption, which can compromise comfort and energy efficiency in the home. In this post, we’ll take a look at low-emissivity (low-E) glass and why it’s the best choice for your new windows.
What is Low-E Glass?
Low-E glass is a type of glass fitted with a microscopically thin, invisible metallic oxide coating. Depending on window design, the coating may be applied on the inner, outer, or both sides of the glass. It was first introduced to the market in 1983 and has since then been popular among building professionals and property owners.
The “E” in low-e refers to emissivity, which pertains to a surface’s ability to emit or radiate heat. Standard, clear glass has an emittance level of 0.84, meaning it emits 84% and reflects just 16% of the heat that goes through it. Meanwhile, low-E glass has an emittance level of 0.04, allowing it to radiate just 4% of heat and reflect back 96% of it.
Types of Low-E Glass
Low-E glass comes in two basic types: hard coat and soft coat.
In hard coat low-E glass, the metallic oxide coating is poured onto the glass during production, “welding” it onto the glass to make it hard to scratch. Soft coat low-E glass, on the other hand, has the metallic oxide coating applied to glass after it has been manufactured by combining vacuum and electricity. This results in a coating that is soft and delicate. However, even though soft coat low-E glass has a more delicate coating, it generally has the highest R-values among glass options, making it highly energy-efficient.
R-value measures a material’s thermal resistance, and the higher the value, the better. Different types of glass have different R-values. For instance, single pane, regular glass has an R-value of 0.85. On the other hand, hard coat low-E insulated glass is rated at 2.45 and hard coat low-E insulated glass with argon has an R-value of 2.75. Soft coat low-E glass have the highest values: insulated glass is rated at 3.50, while insulated glass with argon has an R-value of 4.35. Even though these values can vary, you can expect soft coat low-E glass to always have higher R-values than its hard coat counterparts. Thus, when shopping for windows, ask the window company if the units they are offering have soft coat low-e glass. Renewal by Andersen, for one, uses soft coat low-E glass on their windows.
Benefits of Low-E Glass
Low-E glass offers a number of benefits making it a good choice if you want to get the best glass for your windows. These benefits are also practically the reason why many manufacturers, such as Renewal by Andersen, equip their products with low-E glass that offers varying degrees of reflectivity.
Among the benefits of low-E glass are:
● Low-E glass has the ability to reflect back outdoor heat while letting in as much light as possible. This is because the metallic oxide coating is spectrally selective, which means it only allows visible light through and filters out infrared light. As a bonus, it also blocks UV rays to prevent interior fading.
● When window glass is coated with low-E on both sides, this helps keep indoor heat in and outdoor heat out to keep you warm during the colder months and cool when the warmer months set in. Aside from ensuring indoor comfort, stabilizing indoor temperature increases energy efficiency in the home, reducing strain on your HVAC system to result in savings on your energy bill down the line.
● Low-E glass is highly functional but it doesn’t have specialized cleaning and maintenance requirements, making it convenient to care for. Just make sure your windows are cleaned and inspected regularly and you’re set!
Replacing your windows can be a significant investment but opting for low-E glass can bring great value to your home given its benefits. To ensure you make the most of your investment, make it a point that you only work with a reputable window professional in your area. New windows can do a lot for you and your home and a trusted contractor can guarantee that you get what you paid for and more.
Joe Ranzino is the president of Renewal by Andersen of Long Island. A lifelong Long Islander, Joe has vast experience in the replacement window and home remodeling industries. With roots in the home improvement business going back to the mid-70s, Joe understands what it takes to make Long Island, NY customers happy with their new windows. For updates from Joe, check out the company blog!