John Bullock Lighting Design
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The Future for Part L 2013


The consultation documentation is out for the next iteration of Part L, as part of the 2013 edition. There are huge changes being proposed for the lighting of commercial buildings the old idea of just having to ask the lighting rep for the luminaire efficacy of your preferred fixture are GONE!

Firstly, let's confirm that this will only apply to non-domestic buildings, so the current nonsense of allowing lighting fixtures that can be retro-fitted with filament lamps to comply with Part L1A and L1B will still be there. But for non-domestic buildings there will be two methods available for meeting the energy efficiency requirements.

The first method is based on luminaire efficacy, much as the 2010 edition, but with a far greater emphasis on lighting controls. Hoorah! Lighting designers have been going on about the importance of lighting control in energy management for years, so it's good to see it being taken seriously at last.
To begin with, the minimum luminaire efficacy (for general illumination of offices, industrial, storage and other types of space) will increase from 55 to 60 luminaire lumens per circuit-watt.  This will be measured across the entire applicable floor area. 
However, once we apply some form of lighting control to the installation, we find a more relaxed situation. For example, if an office space has daylight photo-switching combined with occupancy control, that figure of 60lm/cct-w minimum efficacy can be pulled down to a possible 45 luminaire lumens per circuit-watt, which opens up the aesthetic options for the more sensitive lighting designer.

The second method offers an entirely new concept of efficacy assessment. This is LENI brought in from the cold at long last. The Lighting Energy Numerical Indicator (LENI) is a calculation tool that works in terms of energy per square metre. The new edition of Part L will include a Lighting Energy Limit table that is based on design illuminance and hours of operation. The LEL table then provides the maximum permissible lighting energy consumption (kWh) per square metre for a given condition.
But it doesn't stop there. The Lighting energy Limit figure only describes the maximum energy consumption figure; part L requires the ACTUAL LENI figure for the project. This is in the form of a calculation (free downloadable software available, folks!) and takes into account such things as lighting controls, daylight availability, maintenance factors and so on.
It sounds complicated and cumbersome and possibly too expensive for the smaller project (the more mathematically-inclined lighting designers are already rubbing their hands in anticipation) but here's a statistic that I read recently; a project that engages a specialist lighting designer typically uses in the neighbourhood of 30% LESS energy than one from a non-lighting expert; and as De Niro once said that's a very respectable neighbourhood.

Just don't get me started on lighting schemes designed by lighting manufacturers!

RIBA CPD in 2015

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