Intelligent Glass Solutions Summer 2020
Blinded by the Light: The dazzling and disturbing glare from glass buildings
Glare is a visual sensation caused by an uncontrolled light far brighter (2) than its surroundings creating an excessive range of luminance in the eye’s field, or because there is simply too much light over all. It is divided into two categories: Disability Glare which impairs vision, and Discomfort Glare which is annoying and causes eyestrain.
The refraction of light gives the human eye its sense of vision. Light as we use it in architecture is perceived not directly, but through reflecting surfaces. Sunlight allows space and form of architecture to change. Through light and shadow architecture acquires shape and meaning. Light reveals a building’s contours and shadow, its depth.
The range of light perception by the human eye (3) is from about 0.001 lux – in black space/ night sky – to 100,000 lux – bright sunlight. But eyes need time to adapt (4), so sudden glare is potentially dangerous for the aircraft pilot, a vehicle driver at night, the train driver trying to read coloured signals, and for the pedestrian or driver in a city of glass towers.
Architects clearly delight in the play of light and play with light, reflected and refracted, both inside and outside buildings. In large modern cities, characterised by tall buildings with ever more geometrically complex and reflective facades, the interplay of multiple reflection and refraction, light and shadow, from and between buildings, can become as mathematically complex as it is visually beautiful. It is important to remember that members of the public also often find beauty in the reflective facades of urban architecture. Some of the acclaimed artist Brendan Neiland’s work – paintings of reflections in the glass and mirrored architecture of the 21st-century city reveals the dynamic of this living, shifting, visual architectural intricacy, a subject that John Cage, writer and composer, also found enchanting.
The same light that delights the eye can also blind or burn when concentrated and reflected from highly reflective glass or metal, as Archimedes, who is said to have used parabolic reflectors during the Siege of Syracuse to set fire to approaching Roman ships, was well aware. Architects intoxicated by the visual delight of the shapes and forms they are designing often neglect to consider the potential negative impacts of highly specular facade surfaces, including the reflective coatings used on glass to reduce solar gain and glare inside buildings by reflecting it as heat and glare into nearby public spaces and buildings.
Do architects consider glare and the potentially dangerous and annoying impact that reflected light can have on pedestrians, car drivers, adjacent properties and their occupants when designing buildings wrapped in glass or shiny metal? Over the last thirty-odd years there have been many examples indicating they seldom do. If not, why not?
I suspect that most do not bother with such considerations or analysis because there has been no statutory requirement or, for that matter, any common understanding of what amount of candela would define glare, though most would accept that looking into the sun would qualify, or scientific agreement on the amount of difference between a bright light and its surroundings which would constitute glare.