It’s not uncommon for some windows to have a green tint to the glass, with homeowners asking about the color after installation. Is it a defect? A film or coating? We approached several manufacturers to get their take on why it was more noticeable on some windows than others.
“The simple answer is that the low-e material itself is green in its natural state,” says Peter Cathey, an independent manufacturer’s representative for Anlin Windows & Doors. It’s very specific to low-e (low emission) glass, an energy efficient upgrade that blocks summer heat from entering the home through the glass.
“If you had low-e material in a white 5-gallon bucket, it’s translucent with a light green hue. Since that material is spatter-coated on insulated glass when an energy efficient window is being manufactured, more splatter creates more of that green hue. The more coats of low-e, the better the thermal performance of that window. Most have three coats.”
The green tint isn’t common to all low-e windows, only some of them. “Low-e glass with two coats will lose about 10% of its energy efficiency, but will have a noticeably less green hue,” says Sal Sucato, owner of DunRite Windows & Doors.
“What’s behind the glass can add or subtract from the green hue, too. For example, white blinds or shutters on the home’s interior will reflect color, making the green more noticeable from the curb,” adds Sucato. “Even the paint color surrounding the window can have an influence. Paint colors with red undertones can help offset the green, but blue or green undertones may enhance it.”
There’s a second reason glass may have a green tint, too – it’s the iron oxide in most glass. You don’t notice it when you’re looking straight through the glass because it’s so thin, but the edge of the glass will have an obvious green tint to it. Combining this glass with low-e treatment can result in a more pronounced green hue. If it’s something that might bother a homeowner, they should be sure to ask the salesperson about the best options.
Pella Windows added that their Sun Defense glass has a slight hue, but it’s the silver oxide coating causing the color to appear. They also offer bronze, gray and green tinted glass in many of their products, but it’s purely aesthetic and can decrease energy efficiency of the glass.
Does this green hue mean the window is energy efficient? It’s not enough to just have low-e glass. Effective window seals, insulating gas between the panes of glass, and the type of materials used in the window frame and sashes all play an important role in overall energy efficiency. However, if the window isn’t as efficient as it could be, it’s important that homeowners not add an aftermarket film to the glass to “cover up” the green, as it may reduce energy efficiency and void the manufacturer’s warranty. According to one builder on Houzz, “The manufacturer will not warranty windows to which additional tint has been applied because improperly applied tint on a dual- or triple-pane window causes the gas insulation between the panes of glass to expand, resulting in seal failure with visible moisture collecting between the 2 panes of glass. It completely voids the warranty.”
(Article last updated 6/10/22, originally published 6/28/21)