Recognising the benefits of controlled lighting

Legrand, lighting, LENI, control, Part L, Building Regulations
The energy-saving benefits of controls — Alastair Ramsay.

Alastair Ramsay of Legrand, discusses the impact expected updates to Part L of the Building Regulations focusing more attention on delivering opportunities for energy efficiency from lighting and controls.

­Publication of the 2013 update to Part L of the Building Regulations is targeted for Summer 2013. At the time of writing, the contents seem very much in line with the proposals laid out in the consultation document of 2012. This clearly indicates the important role that lighting will play in contributing to the Government’s energy and carbon targets, which aim to ensure that new-build residential properties are zero carbon by 2016, with non-domestic new buildings following suit by 2019.

Lighting efficiency requirements feature in both current and previous versions of Part L, but the focus has always been on the energy performance of luminaires, with minimal consideration of the benefits of control systems. This approach has limited the capacity for lighting designers to be creative in providing high-quality and safe schemes that offer long-term, sustainable energy savings.

In the proposals for the 2013 updates to Part L, the focus on energy-efficient luminaires will remain, with a higher targeted efficacy of 60 luminaire lumens per circuit watt; however, a wider range of control factors will be allowed for the different types of control systems installed. For instance, the target minimum efficacy of the luminaire will be reduced by 30% (from 60 to 42 luminaire lumens per circuit-watt) when installing controls for daylight auto dimming in conjunction with absence detection. This will give greater lighting design flexibility for quality and task appropriate schemes, enabling specifiers to balance controls and energy efficient luminaires in a much more holistic way.

Central to the new approach to lighting efficiency in the regulations is LENI (Lighting Energy Numerical Indicator), an alternative way to demonstrate compliance. The LENI calculation generates a performance figure in terms of energy per square meter per year for the lighting system. Compliance is achieved when the LENI calculated figure of the planned building is equal to or below the maximum figure detailed in a look-up table that allows for different occupancy rates and target lighting levels. The LENI calculation, which is detailed by the standard EN 15193, includes factors for standby loads, the total potential power load of the lighting, the planned occupancy rate of the space, the amount of daylight available and the saving available through dimming to achieve constant illuminance levels for the installed lighting.

Legrand, lighting, LENI, control, Part L, Building Regulations
The all-important function of control for lighting is combined with the delivery of power by Legrand’s Electrak Buscom trunking.

The proposed changes to Part L mean that lighting designers will have more flexibility to develop a much more creative and user-focused installation. This is true whether the enhanced control factor method or the LENI calculation method is used. Automatic controls are a significant factor in energy saving for lighting schemes. However, it is important to remember that providing users with options for a ‘manual on’ switch with the potential for ‘manual off’ (and with ‘auto off’ built into the system) is also a key factor in energy saving, because, where manual controls are suitably placed and there is user buy-in, lights are likely to be turned on later and off earlier than through a pure automated system. Only by ensuring that the power-distribution network is capable of accommodating a more complex control system can the true benefits of Part L 2013’s more progressive approach to lighting efficiency be realised.

The choice of power infrastructure is mainly between cabling or some form of busbar system. While busbar is often perceived as more expensive, the reduced installation times and ease of reconfiguration that busbar offers makes the actual cost of the two alternatives very comparable. This is particularly true when using a busbar with combined power and communication circuits on a shielded twisted pair communications bus, such as Legrand’s Electrak Buscom trunking.

The proposed updates to Part L should allow lighting designers the freedom to create lighting schemes that provide users with energy-efficient installations that also meet aesthetic and optimum lighting level expectations. Here, at last, are legislative changes that combine environmental requirements with a clear focus on improving the practicality and aesthetics of the built environment.

Alastair Ramsay is sustainable development manager with Legrand.

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