OPINION Your views from across the built environment


LET’S LOOK ON THE LESS BRIGHT SIDE


Lighting is under pressure from energy savers and our response simply won’t do, argues Peter Boyce


There can be little doubt that lighting is under pressure. Most


of this pressure is coming from those who are concerned about global warming/sustainability. What these people want to see is a reduction in the use of electricity, particularly electricity generated through the burning of fossil fuels. Their impact is evident in the de facto banning of the incandescent lamp in many countries. But why lighting? Are there no other users of electricity to be considered? There undoubtedly are, but what makes lighting an attractive target for electricity savings are four characteristics. Lighting installations constitute a


major user of electricity; they have a much shorter life than buildings; they are easy to modify in existing buildings, and they are conspicuous, so changes in lighting makes it obvious that the authorities are doing something.


26 CIBSE Journal May 2011


Faced with this onslaught, the initial


response of the lighting community is usually to emphasise the importance of maintaining lighting quality. This is followed by suggestions about how to lower electricity consumption. There are usually


three possibilities suggested: a greater use of daylight, combined with better controls on electric lighting, the development of more energy efficient lighting technology, and a higher proportion of carbon- free electricity generation in the fuel mix. Unfortunately, these three possibilities will not do. They are, respectively, too slow, too uncertain and too expensive. The only honest answer to a demand for rapid and


major reductions in the electricity consumed by lighting is a reduction in the illuminances used in new and existing installations. Would this be a disaster? The first


The only honest answer to a demand for rapid and major reductions in the electricity consumed by lighting is a reduction in the illuminances used in new and existing installations’


thing to say in answer to this question is that illuminance recommendations are not set in stone. There have always been differences in illuminance recommendations between countries and, even for the same country, the recommendations have varied over the decades. The second is that, as regards visual performance, illuminance is a second order effect relative to visual size and contrast. This means that if you are concerned that reducing illuminance will lead to deterioration in visual performance, you can always offset it by increasing either the size or contrast of the target details. The third is that for self-luminous computer displays, decreasing illuminance will improve visibility.


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