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contours across the entire fl oor area, so that we can compare daylight performance with that of electric lighting with minimal effort. So, with all this computational power at


our elbows, why are architects not beating a path to our door for advice? Why are they doggedly hanging onto control of everything to do with windows? The answer to that, I submit, is because they have not detached their brains from that intuitive sense of what the experience of daylight is all about. Our glossy print-outs of DF distribution leave them cold. As well as the delights of daylight, all


of us have, at some time, experienced its capricious nature. We have been exposed to debilitating sun glare, intolerable summertime overheating, winter down-draughts, puddles of condensate and traffi c noise – there is so much scope to get it wrong. However, developments in glazing technology, window frame design and shading devices offer an ever-growing range of ingenious opportunities for maintaining the visual openness of windows, while minimising their negative effects. But before we can make any useful contribution towards balancing these confl icting demands, we absolutely need to recognise that there is far more to daylighting than delivering lumens onto a work plane. The daylight factor has got us into a hole,


and it is getting deeper. Sustainability rating systems are taking daylight into their scope by specifying measures, such as requiring some value of DF contour to extend over some substantial percentage of the fl oor area, and of course this is just another way of reducing daylight to work plane lumens. While these systems used to be advisory, they are increasingly being imposed through the consent process, making then unavoidable. We cannot blame the regulators for this situation. Sustainability has to be a worthwhile goal, and in devising these systems they have referred to the guidelines and reference documents published by the lighting profession, and have, quite reasonably, assumed these to be the distillation of our knowledge. It is us who have misguided them. The unavoidable conclusion is that


we, the lighting profession, have got it absolutely wrong and are continuing to do so, and the only people who have a chance of getting it right are those who ignore


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If we fi nd ourselves involved on a project where someone mentions daylight, we forget all that intuitive stuff and switch into technocrat mode – Kit Cuttle


everything the lighting profession proclaims through daylighting codes, standards and recommended practice documents. The progressive imposition of sustainability regulations is making it increasingly diffi cult for anyone to do that.


● KIT CUTTLE is an author and lighting academic Go to www.kit-lightfl ow.blogspot.com for discussion by Kit Cuttle on a new basis for lighting practice


THE STANDARDS- BASED APPROACH JOHN MARDALJEVIC


While I share many of Kit Cuttle’s concerns, emphatically made in his jeremiad, I’d like to offer something that is rather more positive than a blanket recommendation to ‘ignore everything the lighting profession proclaims’. Early on he makes the reassuringly democratic statement that: ‘Really, we all understand daylight.’ What follows suggests that the experts’ transition to daylight ‘technocrat’ is akin to a fall from grace. I am not convinced. Many of us do, indeed,


value the daylighting qualities afforded by, say, Victorian dwellings with high ceilings and commensurately proportioned windows. However, many of the selfsame people who occupy and enjoy those buildings will, when given a free hand, select a conservatory extension that is woefully overglazed, rendering the space uncomfortable – if not unusable – for much of the year. I don’t believe that ‘we’ would be any less error-prone in our daylighting judgement, given projects larger than a domestic extension. I do, however, agree with Kit Cuttle that


the daylight factor (DF) is a crude measure of actual daylighting performance. A half- century or more of uncritical use of the DF


December 2012 CIBSE Journal 15


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