3 November 2017

Chimneys That Help You Sleep

Huge numbers of people around the world are familiar with Battersea Power Station’s four famous chimneys. They featured prominently in the opening and closing ceremonies of the 2012 London Olympics. They have appeared in countless films and TV shows. They dominated the famous cover of Pink Floyd’s seminal 1977 album, Animals. When architects and designers buy architectural models for their personal collections, Battersea Power Station is the most popular choice. The chimneys have even been recreated using toast.

Those in the know about the chimneys will be aware that over the past few years they have been carefully taken down and completely rebuilt, as the original structures had deteriorated to the point where they couldn’t be repaired. The new chimneys are outwardly identical to the old ones: the only differences are that their concrete was not mixed using salty Thames water, so it won’t cause the steel reinforcement to rust – this was one of the problems besetting the originals – and the reinforcement is to modern patterns, rather than the esoteric spirals used by the builders of the 1930s. The paint has even been colour matched with the old chimneys, and the outer coats were applied all at once to get identical weathering effects.

So the new chimneys are, in most important respects, completely the same as the old ones: but there is one slight difference. The new chimneys will help people living nearby to get to sleep at night and will stimulate their production of the important hormone melatonin, boosting their health and happiness in a variety of ways.

How can chimneys do this?

The answer lies in their new night illumination system, turned on for the first time for the Fireworks celebrations at Circus West Village, the newly opened first phase of the Power Station’s redevelopment. It’s the subtle colouring of the light reflecting from the chimneys at night which will provide such important benefits for people living in the area around them.

This is because white light is made up of a mixture of different frequencies with different colours. The human body reacts very differently to different mixtures: in particular it is sensitive to the presence of higher frequencies towards the blue end of the spectrum. For almost all of the last million years, since humans started to use fire, the absence of blue in lighting has meant that the Sun was not up. Fires and flames are comparatively cool, emitting light mostly at the red end of the spectrum: but the Sun is extremely hot and emits a lot of blue. (Yes, ‘warm’ red-orange-yellow light is actually from cooler things, and ‘cold’ blue light is actually from hotter ones.)

What this means is that the human body uses the presence and absence of blue light to keep its internal clock aligned with the rhythms of day and night. This helps us get a proper, restful sleep at night and then keeps us alert, active and at top performance in the day. The vital hormone melatonin, which has many beneficial effects and may even help to protect us from cancer, is produced mostly during sleep: disruption to the body’s circadian rhythm also disrupts melatonin production.

Lighting is nowadays often measured on a temperature scale, representing the colour of light emitted by a perfect ‘black body’ at the given temperature. A ‘black body’ gets its name because it is a theoretical body which is completely opaque and reflects nothing back. At room temperature it is actually black to the human eye, as it is emitting only infrared radiation which we cannot see. As it gets hotter, however, it becomes visible and its colour mixture shifts from red to blue with rising temperature.

In the last century or so, humanity has learned to produce much bluer, hotter shades of light at will. Yellow candle flames have colour temperatures below 2000 Kelvin, or K. Old-school incandescent light bulbs with their ‘warm’ white light are in the range 2000-2500K, not all that much higher. But fluorescent tubes are more like 5000K, into the low daylight range: a good choice for an office where you want workers to be wakeful and alert, but not so pleasant in the bedroom or sitting room. Not many people care to live under fluorescent lighting in the evening, unless perhaps the lights are the new ‘soft’ or ‘warm’ compact fluorescents nowadays encouraged by the authorities on energy-savings grounds. These are in the neighbourhood of 3000K.

Oddly enough, however, what people often seem quite happy to do is look at electronic gadgetry in the evening – or even after going to bed. And a modern backlit display can easily have a colour temperature above 9000K, well up into the daylight range. This can have a serious disruptive effect on sleep patterns and melatonin production.

A 2014 scientific study compared two groups of people, one of which read a printed book under normal home lighting before going to bed. The other group read a book on a light-emitting electronic device.

According to the study authors:

The use of light-emitting electronic devices for reading, communication, and entertainment has greatly increased recently. We found that the use of these devices before bedtime prolongs the time it takes to fall asleep, delays the circadian clock, suppresses levels of the sleep-promoting hormone melatonin, reduces the amount and delays the timing of REM sleep, and reduces alertness the following morning. Use of light-emitting devices immediately before bedtime also increases alertness at that time, which may lead users to delay bedtime at home.

This hasn’t stopped everyone looking at their gadgets, but it has led to a lot of people installing special apps designed to reduce the amount of blue light that their screens emit after sunset – it’s simple for the device to know when sunset happens, as it has an accurate clock and a good idea of its location. Apple has even gone so far as to build this feature into the latest versions of its iOS operating system, under the name ‘Night Shift’. It remains to be seen how effective the various software fixes may be, but Adrian Williams, professor of sleep medicine at Kings’ College and the London Sleep Centre, told the New Statesman that sleep experts have been prescribing ‘blue-blocking’ apps for years.

‘I recommend them all the time – they’re strongly backed up by evidence,’ said Williams.

Nor have gadget makers been the only ones to notice the effects of colour temperature on human health. The WELL Building Standard, a set of building rules focused on human health and wellness, includes provisions intended ‘to provide lighting conditions that reinforce the natural patterns of the human circadian cycle’. Best practice now requires that lighting in the evening should be of a lower colour temperature, suited to ‘the melanopsin age’. Melanopsin is a chemical pigment thought to be an important part of the mechanism by which the eye detects the presence or absence of blue light and transmits this information to the brain’s body clock.

Accordingly, the new illumination system of the Battersea Power Station chimneys is programmed to be aware of sunset and sunrise. As the sun sets, the chimney floodlights illuminate to 2800K, not dissimilar to an old-fashioned ‘warm’ white lightbulb and well down out of the blue range. This provides an impressive spectacle until the lights shut down at the end of the evening to save power, but it won’t delay anyone’s sleep cycle, reduce their melatonin production, or impair their alertness and performance the next day.

It may or may not be OK to check your phone obsessively during the evening: but it will be perfectly OK to look at the Battersea Power Station chimneys.