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A new era in lighting design

Jun 17, 2005
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The latest lighting design guidelines stress the need for quality of lighting in the working environment, but can they be reconciled with demands for increased energy efficiency? Leighton James looks at the issues involved.

Following the original publication of CIBSE Lighting Guide 3 in 1989 and its subsequent update in 1996, it became commonplace for commercial lighting schemes to be designed around luminaires fitted with Category 2 louvres. In most cases, these louvres were successful in achieving their intended purpose of reducing unwanted reflections on VDUs. However, the consequent dark ceilings and walls tended to create an oppressive ‘cave’ effect, resulting in an uncomfortable working environment. Yet, very often the ‘Cat 2’ louvre would be specified by default, with little thought to the actual needs of building users.

New guidelines and standards

In an effort to address this situation, the Society of Light & Lighting, which acts as the professional body for lighting in the UK, issued an addendum to LG3 in 2001. Taking into account the advances made in display-screen technology, the addendum re-emphasised the need to consider the whole visual environment and withdrew the ‘category’ system for selecting luminaires. Instead, luminaires were to be chosen according to the type of screen likely to be used.

In addition, to improve the environment for users, the addendum introduced recommendations for walls and ceilings to be illuminated uniformly and in proportion to the average level on the working plane - namely 50% on wall surfaces and 30% on ceilings*.

Following these changes, 2003 saw the introduction of the BS EN12464 European standard for lighting of indoor workplaces. The aim of the standard is to ensure that lighting quantity and quality create a suitable lit environment that satisfies the human need for visual comfort, visual performance and safety. In the standard, this lit environment is defined by reference to the following parameters: luminance distribution, illuminance, glare, directional lighting, colour aspects, energy and daylight, and display screen equipment.

While the standard states that “good lighting practice is to be used”, it neither provides specific solutions, nor restricts the designer’s freedom from exploring new techniques or the use of innovative equipment.

Market response

In response to these changes, manufacturers and specifiers initially sought a ‘one fit solution’ to satisfy the new criteria. Uplighting from suspended luminaires would have been ideal, but typical UK ceiling heights as low as 2.4m effectively ruled out this option in many applications. Furthermore, it became clear that the number of variables involved in each application – e.g. task, available daylight, colour scheme and furniture – meant that there was unlikely to be one luminaire design alone that would meet the requirements in full.

In essence, the new guidelines aim to encourage the designer to look more closely at the working environment required and to create a comfortable and balanced lighting solution, rather than reverting to a default luminaire for all applications. It is the finished lighting scheme that needs to comply with the requirements, not the individual luminaire. Therefore, for most commercial lighting applications, designers should be looking at a  combination of the following types of luminaire:

  • suspended luminaires with an upward light component (where ceiling heights permit)
  • recessed or semi-recessed direct/indirect luminaires
  • wall- or ceiling-mounted wall washers.

In short, the general response to the new guidelines has been to design ‘in the spirit’ of LG3, attempting to provide as much ceiling illumination as possible within the physical and aesthetic constraints of the application.

Energy efficiency

However, the emphasis on providing indirect lighting, i.e. lighting reflected from ceilings and walls, raises important questions relating to energy efficiency. The plain fact is that lighting already accounts for some 20% of UK electricity use, and in a typical office environment, it consumes more energy than either heating or ventilation.

The government’s desire to cut lighting-related energy consumption is reflected in the Scottish Building Regulations Part J, which stipulate that lighting in office, industrial and storage premises should have a minimum efficacy of 65 lumens per circuit watt, while in Northern Ireland, the DOE (NI) Technical Booklet F specifies a minimum of 50 lumens per circuit watt.

As already indicated, the new LG3 and BS EN12464 lighting design guidelines encourage designers to throw additional light on to ceilings and walls, while maintaining existing light levels on the working plane. But indirect lighting is inherently less efficient than direct lighting, so its increased use is potentially counterproductive in terms of energy conservation. So, what is the solution?

Lighting control systems

Rather than compromising the design of a good lighting scheme to achieve energy efficiency requirements, the answer is to ensure that lighting is dimmed down or switched off when it is not needed. Wherever practical, lighting controls should be fitted to encourage the maximum use of daylight and avoid unnecessary lighting during times when spaces are unoccupied. At the most basic level, lighting controls can include manual switches and time clocks, but with the cost of more sophisticated controls falling rapidly in the last few years, automated control is now viable for even the smallest installations.

Generally, such automated controls use either presence-detection or daylight-sensing technology, and in some cases, both. Presence detection - automatically turning luminaires on when an area is occupied and off when people have vacated the area - can cut energy consumption by 20-40%, while in rooms with good fenestration, the use of a daylight-sensing photocell can produce energy savings up to 50-70% in the areas closest to the windows.

While such lighting controls can be implemented with individual components, this approach does necessitate additional cabling between the components and the luminaires, and subsequent reconfiguration can be costly and difficult.

A simple, easy-to-use alternative is the intelligent luminaire, which has automatic controls integrated into the fitting itself. The more sophisticated versions have both presence detection and photocell control built in, providing maximum flexibility and energy savings. Top-of-the-range products have luminaire communication as an added feature, ensuring that lighting is uniform and that a comfortable visual environment is maintained. Some also offer programming of user defined requirements via simple infra-red programming tools. Easy to install and set up, sophisticated intelligent luminaires can often reduce energy consumption by more than 50%, compared with conventional installations.

Conclusion

The aim of the latest lighting guidelines is to make a significant improvement to the working environment. By using appropriate lighting control systems, this can be achieved at the same time as reducing energy consumption.

Cooper Lighting and Security has produced a new colour brochure outlining the key aspects of lighting design relating to safety, environment and energy efficiency. For a free copy, please call the literature hotline on 01302 303200 and ask for the SEE brochure or e-mail marketing@cooper-ls.com.

* CIBSE and SLL have now split LG3 into LG7 (covering office environments) and a new version of LG3, which will be written to cover non-office working environments. The content of LG7 is effectively the same as the existing LG3. For more information on the guide change, visit www.cibse.org.

Biography

Leighton James is product marketing manager for mains lighting and lamps at Cooper Lighting and Security. He has over 16 years’ experience with the company, having originally joined Crompton Lighting as an engineering apprentice. After completing his apprenticeship, he was appointed to the position of production engineer – a role in which he was responsible for manufacturing efficiency, manufacturing processes and equipment procurement. He then spent four years as a product designer, specialising in the mechanical and optical design of luminaires. In 2001 – shortly after the acquisition of Crompton Lighting by Cooper Industries Inc. – he was appointed product marketing manager, with responsibility for product development, management and marketing.