FMJ Facilities Management magazine providing industry-specific intelligence to FM and property professionals
Using a combination of four elements can help you achieve the most visually comfortable and affordable lighting within the modern workplace says Paul Coggins of Zumtobel Group
Effective commercial lighting needs to combine the requirement of a visually comfortable and motivational working environment along with a low cost of ownership.
Whatever the requirement, an effectively designed commercial lighting scheme has to be varied to meet the needs of today’s workplaces. Workplaces haven’t just become more flexible they have also become more dynamic, changing in terms of layout and purpose on a more regular basis than used to be the case. With more businesses now favouring open plan office spaces, one of the key elements is to provide a uniform, well-lit environment for the workforce, while building operators are looking for an energy saving system that will require minimum maintenance.
There are four key elements that have to be taken into consideration when choosing a lighting scheme:
- Colour Temperature
- Light Distribution
- UGR
- Lifetime
COLOUR TEMPERATURE
Previously, in the days of the old style fluorescent lighting, 3500K was taken as white and 4000K represented the cool white option. With the introduction of LED technology, 4000K has become the preferred choice for office installations and is seen as white, which means that cool white is now 5000k. However this 5000k cool white has too much blue content and is not suitable for office installations.
LIGHT DISTRIBUTION
Because all luminaires don’t have the same light distribution, the choice of which to use has to be made on each individual project requirement. It is always important to be aware that the light distribution of each luminaire will have an impact on the overall lighting scheme. The choice has to be made whether to choose a flat panel or technical optic. Flat panel luminaires are all similar and give a very bland and uninteresting appearance. Technical optic can give a more interesting visual appearance and add differentiation to the overall scheme.
UNIFORM GLARE RATING (UGR)
Visual comfort is critical in the working environment and it is a fact that excessive glare can be the cause of very uncomfortable conditions, causing strain on the eyes and contributing to headaches. Glare may seem subjective but it is actually calculated using a precise formula that measures the luminance of a lamp and divides it by the background of visible luminance from the room. UGR ranges from 5 to 40 and the lower the number, the less glare. For example, a low UGR of 10 means the glare is so discreet it will go unnoticed, whilst a UGR of 30 will definitely cause discomfort. Reflected glare is excessive luminance reflected from objects or surfaces within view, which includes reflections from interior surfaces and from the luminaires themselves.
The new European standard sets UGR = 19 as the maximum permissible value for offices. Very bright LED panels with no control can help create glare and in a world of short cuts, we need to be aware that UGR 19 is NOT just the luminaire but also how it is used in the space.
LED LIFETIME
Unlike traditional lighting sources, LED’s are a much more reliable source of illumination than its predecessors and, with technology constantly improving, failure rates are getting smaller and smaller. This means that the life of the LED cannot be defined in terms of its time to failure, as previously used.
To overcome this, the lighting industry defines the loss in light output over time, shown as Lx at NN hours. So for example L70 @ 50,000 hours, means that at a time of 50,000 hours the light source will have 70 percent of its initial output. This is a prediction of lumen depreciation but NOT luminaire lifetime. The LED package may not be dominant in determining product lifetime, which means that we should take into account:
- Optical quality
- Mechanical construction
- Cooling system
- LED quality
- Lifetime and stability of the driver
Luminaire life, on the other hand, has to do with the reliability of the components of a LED luminaire as a system. It is also relevant to consider the provision of the correct lighting levels and the quality of the lit effect, combined with the energy efficiency of the solution. Warranty is also a consideration, along with what it actually covers, conditions of use and reliability of the supplier.
Ultimately, putting all of these factors in place will enable lighting specifiers to be more creative and to achieve better solutions that meet the client’s aesthetic, energy-efficiency and lifecycle requirements.
