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Viewpoint Part L

On the surface, the requirements for lighting in Part L (2010) have been raised. A shift from 45 to 55 luminaire lumens per circuit watt for office, industrial and storage; the same raise in lamp lumens per circuit watt for general areas and display lighting up to 22 lumens per circuit watt from 15. So this is all good isn’t it? The weaknesses with the building

regulations then perhaps lie a little below the surface and they are threefold: the classification of spaces, the requirements for lighting and recommended controls. We still have the three sector types we’ve

grown accustomed to: Office/Industrial/Storage; General and Display. The definition of office is for desk-based tasks so classrooms would fit this classification. Display lighting is perhaps self-explanatory and everything that isn’t in those categories is ‘general’. General lighting covers circulation, mixed-use, sport and arguably healthcare, that’s a pretty wide range of tasks and design requirements to be all mixed into a single category. Turning to the efficacy requirements, 55 luminaire lumens per circuit watt for offices might sound efficient but assuming most specifiers are still using fluorescents, any luminaire with a LOR above 0.7 meets this. It’s not exactly going to get the manufacturers breaking into a cold sweat.


– Does it measure up?

The changes to the Building Regulations, which came into force in October of last year, seemed to raise the bar for lighting but will they really measure up in their aim to reduce energy consumption? Liz Peck, director of LPA Lighting, takes a look at the detail.

Twenty-two lamp lumens for display lighting probably won’t either; it cuts out some of the least efficient sources but that’s as good as it gets. General lighting is where Part L starts to fall apart. For a huge range of spaces and tasks, luminaire optical performance doesn’t matter so long as the lamp complies with 55 lumens per circuit watt. This brings its own problems of course: theoretically you could have a black-box luminaire with zero LOR and it would meet the requirements of Part L. Worse, it could even allow you to add lots of inefficient sources to the project as the calculation is for the whole area!

If you think that’s a weakness, then have a good look at the controls section. Hidden in a plethora of jargon are the recommended controls for a variety of rooms. For a cellular office, this amounts to a manual switch by the door – On/Off. For meeting rooms, storeroom and WCs, again it’s a manual switch; this time within 6m of any luminaire. So the switch might not even be by the door! Open plan offices should have pull cords so users can manually control the lighting at their desk. These are the 2010 recommended controls: not a PIR or photocell in sight! PIRs and photocells, of course are in the “advanced controls” section. If you employ either or both of these so-called

sophisticated lighting controls, you can apply a control factor to your lighting efficacy. So a room which has, god-forbid, both in, would only need a luminaire performance of 45LL/cw. Back to 2006 then. The somewhat cursory requirements for controls (the light switch, revolutionary indeed) mean of course that an empty office at 2am with all the lights on complies because it had a manual switch by the door that was left on. It doesn’t matter how efficient those luminaires were, at 2am in an empty office they are nothing but the height of inefficiency. Let’s be clear, Part L is designed to “further the conservation of fuel and power” but it falls a long way short of that lofty ambition in its current form. The way forward seems to be a move towards systems-based targets that embrace proper lighting controls and measure energy consumption, not installed performance. The LENI calculation tool can help to facilitate this through benchmarking and estimation, but the lighting industry must act now if changes are to be made to the next edition. Maybe then the 2013 edition really will further the conservation of fuel and power.

Contact LPA Lighting 01273 239 052


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