Roundtable debate Lighting efficiency Guide to lighting terms Marc Draper Bob Cervi Simon Wootton Lee Barker-Field
Lumens per circuit watt: This is a measure of a lighting system’s ‘luminous efficacy’ – ie, efficiency. Luminaire: This is the lighting fixture and lamp combined. Part L 2010: Building Regulations Part L 2010 sets tougher minimum requirements for lighting efficiency levels in different types of environment. Efficiencies must be at least 55 lumens/circuit watt for general lighting in non-domestic buildings. Part L 2010 also sets tougher targets for buildings’ ‘notional’ carbon emissions, which are to be 25% lower. Lux: This is a measure of ‘illuminence’ – how much light falls onto a surface. The Lighting Code: This is published by the Society of Light and Lighting (SLL).
www.sll.org.uk Sources: CIBSE Journal, SLL
Iain Trent
it could be in the Part L, with its focus on thermal performance. While most of the group felt that the rules could
set tougher requirements for energy efficient lighting, in reality it is building occupiers and users who will determine just how much energy is saved or wasted. However, it was felt that Part L’s requirement for a 25% reduction in carbon emissions from buildings would be a key driver of change over time.
Topic two Are ‘ultra-efficient’ lighting technologies the answer, or are they oversold? There is a role for more highly efficient lamps, particularly when it comes to refurbished properties, which generally can’t depend on adding more daylight to reduce energy use, argued Tulla. But he agreed with the group that there is genuine concern about possible misselling of new products. Wootton said: ‘Manufacturers are convincing us that LEDs are the energy efficient source.’ But the danger from overselling new lamps, said Ridler, is that clients won’t do other stuff such as daylighting. He added: ‘I do think that manufacturers are
going for BREEAM Excellent or Outstanding, you’ve got to put lighting into the equation in a much bigger way.’ ‘But BREEAM credits are too easy to get for lighting,’ added Simon Wootton of NG Bailey. One key problem with inefficient lighting is the level
of light required by building tenants and users. Iain Trent of Land Securities suggested that, if offices are designed with a level of lighting at the lower end of the range of 300 to 500 lux, the ceilings will have to be stripped out to put in extra lighting. He suggested it was better to ‘design for 500 lux and then bring this down to 300’ when the building is occupied. The discussion on regulations and codes highlighted
some of their limitations when it comes to trying to legislate for bringing about a reduction in energy use in larger commercial and domestic properties. In particular, the role of natural light is not as strong
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overselling LED lighting,’ said Robinson. ‘This convinces clients that LEDs are the most efficient lighting source, and that’s not right.’ ‘There’s a whole world of hurt coming from people
badly specifying and installing LEDs,’ warned Trent, adding: ‘But when we get LEDs right, they’re a very efficient light source.’ When it comes to office lighting, said Tulla, ‘a T5
lamp and a properly designed luminaire with proper control gear is pretty efficient’. Tulla pointed out that the lighting industry had
recently produced a three-page guide on how to specify LED lighting, which was freely available, and is also working on a definition of ‘ultra-efficient’ lighting. Barker-Field argued that a system powered by
electricity, with all the wasted energy that occurs along the supply chain, was ‘inherently inefficient’. If we are
> September 2010 CIBSE Journal 29
There’s a
whole world of hurt coming from people badly specifying LEDs
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