Innovative coating makes for ‘feel-good’ windows

Picture yourself sitting at work and looking out through a closed window. Now imagine opening that window to let in fresh air and direct sunlight. We all know how much more refreshing the second option is than the first.

Why? Part of the reason is that standard glass windows don’t let in the optimum amount of the blue light part of the spectrum. And blue light, particularly at wavelengths between 450 and 500 nanometers, contributes to our overall sense of well-being.

With that in mind, researchers at Germany’s Fraunhofer-Gesellschaft have developed a new kind of glass that’s especially good at transmitting blue light.

“Nobody’s ever made glass like this before,” said Walther Glaubitt, a graduate engineer at the Fraunhofer Institute for Silicate Research. “It makes you feel as if the window is permanently open.”

Blue light makes us feel better because it helps us regulate our bodies’ melatonin levels. The nerve connection between our retinas and our hypothalamus has receptors that are sensitive to blue light. These send signals to the “biological clock” part of our brain, which controls melatonin production. When we don’t get enough blue light — which can be a special problem during the dark days of winter — we can develop unusually high levels of melatonin and depression from seasonal affective disorder.

The new window glass from Fraunhofer features a barely perceptible inorganic coating just 0.1 micrometer thick that helps let more blue light pass through.

“The coating we’ve developed helps people to feel they can perform better and makes it less likely they will fall ill,” said Fraunhofer researcher Jörn Probst.

The company UNIGLAS is about to launch a new triple-glazed window that features the blue-light-friendly coating under the name UNIGLAS | VITAL® feel-good glass. The window lets through about 79 percent of light in the 460 nanometer wavelength range without affecting heat-insulating properties.

Meanwhile, the Fraunhofer research team is working to make a window that’s even more blue-light-friendly.

“Up to now we’ve only applied our special coating to the side of the glass facing into the cavity between panes,” said Glaubitt. “In future we will also be coating the glazing’s exposed surfaces — in other words, the outside and the inside of the window. That will allow us to achieve around 95 percent light transmissivity at 460 nanometers.”


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