November/December 2020
LR&T Symposium
Zurich Innovation Center of Givaudan, lighting by Lightsphere/Filipa Peixeiro
JOHN MARDALJEVIC: HOW CAN NATURAL LIGHTING NECESSARY FOR HUMAN HEALTH BE IMPLEMENTED?
HUMAN LIGHTS The Lighting Research and Technology Symposium this month will focus on the theme of lighting and human health. Based on their presentations, John Mardaljevic and Peter Raynham examine the roles of natural light and electric lighting respectively Twitter: @sll100
Let’s begin by imagining that we know just how much ‘natural lighting’ (daylight) is necessary for human health – of course, we don’t, but let’s pretend for now that we do. Just how much is likely to be some absolute measure of (daylight) illumination received at the eye. It will be an amount, or perhaps a varying amount over time (sometimes called a profile). Whatever the amount, or profile, it probably won’t be of the common or garden lux variety; rather, it’ll be one of the (now several) non-image forming light metrics. That’s another way of saying that the spectral character of the illumination needs to be accounted for. Maybe the changes in the spectral character of daylight need to be tracked also, in order to properly effect circadian lighting. At this point, you might be thinking: 'Hold on a moment, isn’t daylight "circadian" to begin with?' You would, of course, be quite correct. In fact, it would be perfectly reasonable to call for a halt in this progression of reasoning much earlier on. And, instead, begin to ask rather more fundamental questions, for which we need answers before we can even begin to progress meaningfully with any of the above. Although not explicitly indicated, the title refers to natural illumination inside buildings. As long as we spend moderate amounts of time outdoors, we probably don’t have to worry about getting too little natural light. Unless our intention is to synthesise vitamin D from exposure to sunlight — but (mercifully) that is outside the scope of this short article. Prepandemic, we were probably all spending far too great a proportion of our waking lives indoors. For many, the ‘lockdown’ may have afforded the opportunity to take daytime walks that, under normalcy, would not have happened. It’s also likely that many swapped a dingy spot in a deep-plan office for a better-daylit home alternative (even if what they sit on in the kitchen isn’t quite as comfy as the expensive ergonomic chair which their lower-back has fond memories of). Whichever way, pre-, during or (fingerscrossed) post-pandemic, it is the daylight inside buildings that is important to us.
E
5
