Legal Illuminating measures
There are other – often better – rules for promoting energy efficiency in lighting than those contained in Part L of the Building Regulations, argues Hywel Davies
L
ighting is a significant user of energy in offices, schools, shops or factories. According to the International Energy Agency, 19% of electricity worldwide is used for lighting. So one might
expect Part L of the Building Regulations – which covers ‘Conservation of Fuel and Power’ – to encourage the use of the British and European Standard developed by the lighting industry and lighting professionals to enable energy efficient lighting to be specified. But it doesn’t. In only a few paragraphs, Part L sets limits on equipment efficiency through installed power density. It says: ‘Reasonable provision shall be made for the conservation of fuel and power ... Fixed Building Services [shall be] energy efficient [and] have effective controls.’ By contrast, BS EN15193, the British and European Standard for the design of energy efficient lighting for buildings, describes the Lighting Energy Numeric Indicator – LENI – which demonstrates the efficiency, or otherwise, of a lighting system. LENI specifies the annual lighting energy per sq m, and is a measure of consumed energy, embracing all aspects of the building, Nor does the Approved Document (AD) currently supporting Part L particularly encourage good building design. But this AD is only for guidance and not mandatory – as, too, is the related Compliance Guide. What we need is a system-based energy consumption
target instead. This view is supported by the Society of Light and Lighting (SLL), the Professional Lighting Designers Association (PLDA), the Lighting Industry Federation and several other industry bodies. This position also aligns with the lighting industry’s input into a European Commission report entitled Working document on possible measures targeting the energy efficiency of lighting in the tertiary sector. Faced with the shortcomings of Part L and the accompanying guidance documents, what should a professional designer do? Many lighting professionals consider the daylight element of the current guidance to be extremely weak, taking no account of location, orientation, shading or dirt. The guidance on lighting controls is also inadequate.
Automatic controls are essential and should not be optional, which in the AD and Compliance Guide they currently are. Effective controls for heating systems are required by
26 CIBSE Journal November 2010
Part L1b(ii). And that refers to all fixed building services, including lighting. It should not be an option not to have automatic lighting controls under Part L 2010. Enough studies have shown that humans do not switch off lights, either on leaving a room or when there is enough daylight without them. Perhaps it is time for professional lighting designers to
point to the requirement for lighting systems to be energy efficient and have effective controls, look up BS EN15193 and use it. They should also point out to the client, the building control officer and anyone else who cares to ask that this is the European Standard method for designing energy efficient lighting, and therefore makes reasonable provision for the conservation of fuel and power in buildings. In other words, it meets the requirements of the Building Regulations. In the meantime, the SLL, PLDA and other industry bodies will continue to argue for the formal introduction of LENI as the design metric for non-domestic buildings, allowing the designer to demonstrate that lighting is both suitable and efficient. BS EN 15193:2007 should be the actual basis for all calculations of energy performance, and its outputs should be incorporated into SBEM or whatever carbon compliance tool applies when Part L is next revised in 2013. There is validated software already available to calculate LENI, so its adoption is no burden on the industry. The industry standard is the SLL Code for Lighting. A
Perhaps it is time for Part L to catch
up with LENI, the SLL Code and the industry
lighting designer following the Code will be very well placed to argue that they are following good practice, and that the design will be energy efficient, effectively controlled, and will deliver a lighting system that creates visually pleasing healthy environment for the occupants. Perhaps it is time for Part L to catch up with LENI, the Code and the industry. l
Hywel Davies is technical director of CIBSE.
www.cibsejournal.com
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