The face value of lighting for building services is to provide adequate light for the built environment. This is typically quoted in terms of lux (lumens).However, there are several other qualities to consider including colour.
The second tier of qualities to consider are ‘glare’ and ‘colour rendering’.Glare typically defines the permitted quantity of nuisance / obstructive / intrusive light presented from the light source to the area.Colour rendering defines the quality of light falling upon a surface, reflecting the surface colours.This is typically increased for displays within art galleries and shop displays, and more so for where precise works are required such as within hospitals or precision maintenance workshops.
Other such colour considerations have been given to human and animal habits to help make life easier and non-disruptive to life cycles. Some examples follow . . .
Fish, where certain species for example, have a very low perception of light at the red end of the spectrum. Hence red coloured lighting is ideal for human observation during night without disturbing the aquatic life.Depending on the intensity of night time monitoring, the quantity of read lighting can be varied from a low minimum illumination of 20 lux to a more operational value of say 100 lux.This pending the species of aquatic life kept.
During the day, normal lighting levels can be maintained and even controlled to mimic the path of the sun passing overhead.Daylight colour temperatures may be a first line of thought, however, aquatic life understandably live in the blue end of the spectrum. Indeed, these days, lighting manufacturers are promoting colour temperature change luminaire controllers within the LED market (Trilux WW Control).
A natural level of UV will also be required to maintain plant life in an in-natural location.
Turtles, renowned for their yearly migratory patterns around the globe, returning to the same location to lay their eggs are believed to be attracted and guided by the light of the moon.A decline in numbers of turtles was suspected as being the result of off-shore and coastal engineering rigs fitted with bright ‘white’ lights possibly distracting attention of the turtles. Proven or otherwise, a diligent effort in the engineering of lighting systems was required and through research, alternative solutions were adopted.Along with glare control, energy saving sensors, aiming of luminaire light beams and selective site locations, it was found that long wavelength light was least distractive. i.e. Red and Yellow light.
People have a daily bodily rhythm, which when affected can lead to being grumpy, stressed, unable to think clearly and even affect our health if disturbed for long periods of time.The best way to recover of course is SLEEP.The two body systems we have are ‘homeostasis’ to determine sleep-wake cycles and the ‘circadian biological clock’.The circadian biological clock is believed to be controlled by the Suprachiasmatic Nucleus within the brain that responds to signals from the eye, determining how light or dark the ambient is.Various attempts of controlling the natural rise and setting of the sun have been produced for working environments without apertures to the daylight of the outside world using dimming control gear.However, the latest approach adopts the colour of the sky into the luminaires, all inclusive of solar flare by Nano-technology, available from Coelux , used as skylights, the affect is as if they were openings to the Blue sky of the outside world. Having seen it, it looks very impressive, . . . Of course, the best way of obtaining your vitamin D is to get outside daily.
The method of dimming lighting at dawn and dusk is of course also beneficial to places housing animals.
Note that I have separate such qualities as energy efficiency (lumens per watt) and light output ratios as these can be considered as part of the luminaire selection process, not the design of the built environment.
Russell Fox Chartered Electrical Engineer B.Eng.(Hons), C.Eng., MIET, CPEng(Aust), MIEAust, NPER.