Not many people prefer spending their time in dark, dank rooms. The reasons for that are clear – it benefits us to receive sunlight. But many people, in the United States and other western countries, spend the majority of their days indoors: in offices, in their homes, in locations that may not provide the optimal amount of sunlight. Researchers from Fraunhofer in Germany are hoping to utilize that fact to their benefit with the development of a coating for window panes that lets in more sunlight.
Sunlight has been known to provide Vitamin D and elevate the mood. But with increasingly prevalent heat-insulators, for example, these window coatings prevent heat from entering or escaping. They also do not necessarily allow inside the optimal amount of light that governs our hormonal balance, and a significant portion of that light is reflected away.
The researchers aim to avoid pesky reflections, to optimize the transmission of the peak emission wavelength of sunlight, and to let in the most amount of blue light. This is because not all sunlight is equal when it comes to the human eye or mood elevation. The peak emission wavelength is the wavelength at which the human retina is most sensitive to light. Moods are most receptive to blue light, so the window lets in as much as possible of the blue portion of the light spectrum.
Why blue? The human retina and the hypothalamus, which controls the central nervous system, are connected through a nerve. The nerve has special receptors at the end, which are particularly receptive to blue light. Blue light helps the part of the brain that functions as our biological clock, and melatonin levels. High melatonin levels, caused in part by low levels of light, can lead to difficulty sleeping, seasonal affective disorder, and problems with concentration.
The coating for the window has a light transmissivity rate of 79 percent, compared with conventional triple glazing, for which the rate is 66 percent. But researchers are not yet satisfied, though the coating will be launched soon, and would like to up their rate to 95 percent.