Interiors of all descriptions are routinely overlit. There is no need for these absurdly high levels of light and we would all benefit from darker spaces. In this article we will examine the rise of too much light, and how darkness rather than light can be used as a positive design tool, together with the benefits of doing so.

It is important to note in this context that bright and dark are relative terms. They need each other to exist. The contrast theory of meaning (Ernest Gellner, Words and things, 1959) states that objects can only be understood with reference to their opposite; for example  if everyone was tall, no-one would think of themselves as tall, just normal. You need a reference point, a short person to look down on. Similarly, there can be no light without dark. It should also be noted that darkness is relative in magnitude as well. What we mean by dark depends on how bright the light is and the relative light levels. A dull grey day could still register 2,000 lux in absolute terms, very high for an indoor space but very low compared to the 100,000 of a sunny day.

Historically, spaces were much darker than they are now. Shops for example were lit by candles or gas lanterns. In recent years there has been an inflation of light levels - an arms race of illumination. We only need look a few years back in time to see how high and how arbitrary the current recommended light levels actually are.

Almost without exception, there was a steady increase in recommended lux levels from the 1930s to the early 1970s.

Among the more dramatic cases, the UK’s retail lighting level recommendations increased from ~100 lux in 1936 to ~500 lux in 1972.

In the former Soviet Union, the recommendation for general office lighting was ~25 lux in 1930, but had risen to 300 lux by 1979.

In North America, recommendations for chalkboard lighting rose from ~150 lux in 1938 to 1,400 lux in 1972.

Limited evidence indicates that levels were even lower prior to 1930, e.g. 35 lux for detailed drafting in 1915.
(American Energy Efficiency lighting association figures)

Our eyes, it should not be forgotten, happily work at levels between 0.1 to 100,000 lux, and they will compensate for any increase. If 1 lux is ok for safe movement in an emergency, why do we need 100 lux in corridors normally? Part of the reason for this increase is the risk – averse culture. If in doubt, ‘overlight it’ seems to be the motto, and we are terrified of being sued if someone trips up.

The benefits of less lighting are immediately apparent. Firstly, spaces will look better – more interesting and more evocative. Uniformly bright spaces are uniformly bland spaces. They present a washed-out appearance, lacking in focal points and the high light levels remove any drama. Leaving whole areas dark but lighting specific points creates more dramatic spaces (the “play of brilliants” as Richard Kelly would have called it). In addition, there are many effects you can only do in the dark, such as image projection. Simple things such as mood are more easily created with a blank canvas – a candlelit restaurant will only work in the evening; in lunchtime it is only a restaurant with candles, a significant difference.

Secondly, less light means less energy required to produce this light. If we stop lighting retail areas to 1000 lux and instead light them to 100 lux, we have achieved an immediate 90 % saving in energy use, with equivalent savings in CO2 emissions, starting us down the road towards a more sustainable future.

It can be seen therefore that we could and should light our buildings a lot less than they are lit. But what are the possibilities and what are the effects of the various types of darkness? In this next section we discuss the possibilities.

Dark ceilings lower the apparent height of the space. This in turn creates greater intimacy and allows focus to tables, or verticals – creating a more luxurious feel if you have expensive wall coverings. There are of course night-time parallels – at night the outdoor “ceiling” is dark, and our evolutionary history has adapted us to this environment.

Alternatively, the walls can be left dark. Keeping a lit ceiling and a lit floor is the default hotel lighting design with downlights and coffers. This solution allows you to add colour to ceilings and drama to floors or objects and to create an intimate space that is also quite bright.
A dark floor makes a space light and airy space but without being overlit. If the floor here was lit as well, it would be too bright but as it is left darker, the space works.

A dark floor and ceiling creates a bright lit space with a relatively low light level. It paradoxically makes space seem bright whilst not being lit brightly. I have used this effect at more than one project where practical considerations prevented lighting to or from the ceiling; we simply washed the walls brightly to compensate, and the space appeared bright whilst having a lux level on the floor of around 10 lux – greatly below guidelines.

Dark sections are a more dramatic example of darkness. One area is left entirely dark, others are bright. The light at the end of the tunnel is the best example of this, the sense of adventure and discovery created is palpable.

How then, to best achieve a lower-luminance world? Asking companies to adopt lower light levels might work, but would be too slow. Legislation is the only answer. In the UK it would only take a small tweak to Building Regulations to achieve this, and a lower carbon future is ours. For example, we could limit energy use for lighting to a maximum wattage per square metre, such as 10 watts/m2. for retail areas, with no exceptions. This could easily allow for drama, interest and accenting – as long as you adopt maximum light levels of around 50 lux for ambient lighting. This would save around 80-90 % of retail lighting energy costs immediately.

Offices should be limited to 50 Lux maximum, with supplementary lighting on desks allowed if you actually want to read a paper document – in this world of internally lit screens with documents, emails and CAD drawings, you don’t actually need much light on the desk at all.
In conclusion, I would like to say that by their contribution to global warming, high light levels do much damage to the environment. It is time we stopped overlighting buildings, time we used less light, and time we stopped being afraid of the dark.

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