Happy Glass: The Window Coating That Can Improve Your Life

​The Fraunhofer Institute for Silicate Research (ISC) in Germany has produced a new type of window designed to improve concentration, regulate sleep, and even improve people's mood. This "feel-good glass" is optimized to transmit wavelengths between 450 and 500 nm -- the blue wavelengths, usually blocked by traditional glass. The glass is treated by addition of a durable, inorganic coating only 0.1-micrometer thick; the application is barely noticeable. Office workers spend more than 90% of their day indoors. Spending time in the sun produces measurable health responses such as vitamin D production and elevated mood. Office windows with this special new coating would allow people to receive some of the benefits of direct sunlight all day while at work. Employees would feel better, perform better and in general have stronger immune systems. Such windows would also be useful in automobiles, malls, arenas, homes and various other locations. Currently, windows with "happy glass" let through 66-79 percent of light around the blue wavelengths. Eventually, windows transmitting 95 percent of blue light may become available. But what is so important about light's blue wavelengths in particular?

Daylight and the Circadian Rhythm

Light influences many functions of the human body such as temperature, heart rate, sleepiness, hormone secretion and gene expression. These internal processes gradually rise and fall every 24 hours or so. This endogenous (self-sustained) biological oscillation is known as the circadian rhythm. (The word "circadian" comes from Latin circa, "around," and diem or dies, "day.") Rhythms following a circadian clock have been observed throughout the plant and animal kingdoms. These rhythms are affected and adjusted by external cues in the local environment -- the most important of which is daylight. Light is the range of wavelengths in the electromagnetic spectrum visible to the human eye (approximately 390 to 700 nm). Different wavelengths appear to the eye and brain as different colors, ranging from violet and blue on the low end, through green and yellow, to orange and red on the high end.

The Blue Wavelengths

Various studies have shown that blue wavelengths -- relatively short and intense -- are more stimulating in humans than green wavelengths. Blues specifically are the strongest wavelength for entraining the circadian rhythms and suppressing melatonin production. Melatonin is produced by the pineal gland (a small endocrine gland in the center of the brain). Production of melatonin is reduced by light on the retina; blue light, from 460 to 480 nm, is principally responsible. The human retina is connected by a particular nerve to the hypothalamus (the control center for the autonomic nervous system). Special receptors on this nerve are sensitive to blue light, which is interpreted as light-or-dark. These nerve impulses help regulate melatonin levels. High levels of melatonin typically result in problems sleeping, difficulty concentrating, and possibly depression or other psychological issues. Seasonal affective disorder (SAD), or winter depression, is a possible outcome of abnormally high melatonin levels. Blue light therapy (e.g., goggles or panels) is commonly prescribed for patients suffering from SAD, as well as sleep disorders, jet lag, premenstrual syndrome, and skin conditions such as acne, rosacea, and psoriasis.