Feel-good glass coating could increase your quality of life

As we previously mentioned in many of our articles about architecture, abundance of daylight  is very important since it influences our mood and efficiency since it stimulates the brain. Researchers from the Fraunhofer Institute have worked with industry partners to develop a coating for panes of glass that lets through more light at wavelengths which govern our hormonal balance.

You probably noted that persons with mood or even appetite disorders wear glasses which promote different wavelengths of light (or even glasses in some color). Another thing you might have noted is that well lit and airy environments increase your productivity. That’s no surprise, since daylight gives us energy and has a major impact on our sense of well-being.

Unfortunately, not everyone is lucky enough to live in a generously glazed home or bright and breezy working space. Modern heat-insulating, sun-protection glazing for glass doesn’t make things any better, since it isn’t optimized to allow the light that governs our hormonal balance to pass through. Those coating only reflect a part of the spectrum and lets a percentage of incident sunlight to pass through.

Anti-reflective glass that is more transmissive overall to daylight is reserved for certain special applications, such as in glass covers for photovoltaic modules or in glazing for shop windows. The aim with this kind of glass is to avoid nuisance reflections and to achieve maximum light transmission at the peak emission wavelength of sunlight. This is the wavelength at which the human retina is also most sensitive to light.

“However, our biorhythms are not affected by the wavelengths that brighten a room the most, but rather by blue light”, said graduate engineer Walther Glaubitt, a researcher at the Fraunhofer Institute for Silicate Research (Fraunhofer ISC) in Würzburg. That is why he and his team have developed glass that is designed to be particularly transmissive to light in the blue part of the spectrum. The secret is a special, long-lasting and barely perceptible inorganic coating that is only 0.1 micrometers thick.

According to its developers, the coating makes you feel as if the window is permanently open. One reason the glass gives this impression is that it exhibits maximum transmission at wavelengths between 450 and 500 nanometers – which is exactly where the effects of blue light are at their strongest.

“There is a nerve connecting the human retina to the hypothalamus, which is the control center for the autonomic nervous system”, said Dr. Jörn Probst, who is Glaubitt’s team colleague. “The coating we’ve developed helps people to feel they can perform better and makes it less likely they will fall ill.”

This is how it works: Special receptors sit at the ends of the nerve connections which are sensitive to blue light, converting it into light-and-dark signals and sending these to the area of the brain that functions as our biological clock. One of the things these nerve impulses do is regulate the levels of melatonin – a naturally occurring compound which regulates our daily cycle.

Lack of light leads to high levels of melatonin, which can lead to sleeping disorder and lack of concentration, as well as depression and other psychological impairments. Another example of disorders during unusually high levels of melatonin occur as a seasonal affective disorder, also known as winter depression.

Industrial partner Centrosolar Glas GmbH & Co. KG coats the glass, and UNIGLAS GmbH & Co. KG, handles the remaining finishing work as well as sales of UNIGLAS | VITAL feel-good glass. Its transmissivity to light is increased across the entire range from 380 to 580 nanometers, which is to say in the portion of the spectrum that is responsible for promoting well-being. At 460 nanometers, the light transmissivity of UNIGLAS | VITAL® is 79 percent.

Comparable triple glazing only lets through 66 percent of light at this wavelength. Meanwhile, the coating has no impact on the window’s heat-insulating properties. But the Fraunhofer ISC researchers plan to make more improvements to their coating.

“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.”