Are Lux/Watt and Lumens/Kilo New Environmental Norms?

ERCO’s lux/watt graphic and IGuzzini’s lumens/watt Palco upgrade

On my first day at the Light and Building fair in Frankfurt, I came away with two new and very interesting explorations into labelling light fixtures that could potentially become norms to assess a lighting products compliance to sustainability and its impact to our environment.

The first is an “escalation” of measuring the efficiency of a light fitting. We are all very familiar with the lumens per watt as a measure of lighting efficiency. However that never provided lighting designers with information on how much of that “efficient” light output was actual useful light! ERCO is one of the manufacturers who is floating the idea of Lux/ Watt, which clearly aims to determine how much of these lumens actually reaches a pre-determined surface (and as such how much of it is actually wasted light). In the context of the trendy light pollution and dark sky subjects, a useful metric to know. As a lux is a lumen per square meter, this way of expressing efficiency would give us a far more precise indication of real efficiency. As lux levels are relative to distance, this would have to be somehow factored in, but creating photometric diagrams that shows the lux levels at 1,2 or 3m distance relative to watts should be easy to do.  

The second approach to providing an insight of a light fittings environmental impact is to measure its lumen output against the amount (and weight) of the materials used to create the housing. The reasoning is the lesser the amount of materials used, the smaller the material footprint needed to manufacture a light fitting, which of course is good for our planet. While several companies promote the reduction in the material usage of their fixtures, IGuzzini was the only one to promote this by linking the lumen output to the fixture weight, introducing the lumens per kilo. In other words, a light fitting producing the same light output (lumens) for a lesser weight of a fitting would technically be more environmentally friendly. I have yet to get my head around this concept, but at first sight it seems a very interesting and relevant approach to identify sustainably designed light fixtures. 

If you throw the TM66 guidelines that describe a products’ circularity in as part of the equation, it is clear that many manufacturers are becoming more and more environmentally responsible. This should very much support lighting designers in messaging that to our clients!

Let me know what you think of the lux per watt and lumens per kilo labelling of light fixtures!