Lighting offices can strike the necessary balance

Successfully illuminating a commercial office needs to take into account a number of considerations. Here, Richard Holt, Managing Director at Trilux explores how building services engineers can achieve an intelligent lighting solution that is not only functional but also aids visual comfort.

Building services and environmental engineers have a difficult job to do. With a variety of responsibilities and often with an incredibly wide remit, balancing all the requirements necessary to deliver a safe, comfortable, energy and cost efficient building can be hard to achieve.

Without question, lighting is one element of a building that can have significant impact on long term energy efficiencies however it is vital that the quality of lighting is not compromised and we fully appreciate its primary function.   

People spend a large proportion of their lives at work, and most of that time is spent at a desk in an office. Lighting has a fundamental role to play in creating a comfortable environment and lighting conditions need to be optimal, however this is no easy task.

Comfortable environment

The requirements for lighting in modern offices are eminently diversified. On the one hand, the task must be suitably illuminated and deliver maximum light quality but at the same time, building services and environmental engineers must ensure that they have an intelligent lighting solution in place that is functional and visually attractive to create a comfortable environment that promotes a sense of well-being.

This need is very much the focus of the Society of Light & Lighting’s, Code for Lighting 2012: Lighting of Indoor Workplaces, which now incorporates the European Standard EN 12464-1, and looks at achieving visual comfort and performance that enables people to perform tasks efficiently and accurately.

This is, of course, determined by a number of parameters. First of all, it really is about getting back to basics and thinking about how the space is going to be used. If you know exactly how the work area will be set up, then it is worthwhile selecting the best level of illuminance for the task, often 500 lux for this defined area, which could be a desk or even as small as an A4 piece of paper.  The half metre band around the task is known as the surround area and can be lit to a lower level, probably 300 lux, but then the remaining area is known as the background area and the average light level here can be as low as 100 lux.

This new way of treating the space will result in significant energy savings.  However, if it is too early to know or if the work area has to be flexible then the sensible option would be to install a lower level of lighting, around 200 lux, across the board and then bring in additional task lighting around workstations.

Take control

Luminance control is also an important consideration as a common complaint in the workplace is often the glare on computer screens. EN 12464-1 can offer guidance as it does specify requirements. For normal workstations, a luminance limit (the brightness of the luminaire surface) applies of 3000 cd/sq m or 1500 cd/sq m depending on the type of computer screen that is being used. This limit applies for angles starting from 65 degrees all around and for critical computer screen activities, this starts from 55 degrees all around.

When it comes to visual comfort and performance, understanding how we react to light can also be incredibly helpful. Knowing what we do about how the human eye has evolved to respond to daylight and its need for variation, an optimal lighting scheme should be one that provides a balance between diffuse and accent light, and ideally with changes in colour temperature and intensity

When lighting a room there should be enough light on the desk (horizontal illuminance) and enough light on the walls (vertical illuminance). Cylindrical illuminance is required to illuminate the faces of the people using the space. This is especially important to aid communication through facial expressions. Also helping this is the need for the light source to provide good colour rendering.  For an office environment where people tend to spend long amounts of time, lamps with a high colour rendering index, around 80 Ra, should be selected.

LED lighting

When trying to meet the myriad requirements for office lighting, building services and environmental engineers should now be looking to LED technology for the solution.

In the past few years there has been understandable hesitance to switch to LEDs as although their potential was much publicised, the technology was still evolving in order to fulfil its true capabilities. However, LEDs have done just that and so quickly and to such an extent, that they can absolutely meet the requirements of a modern office environment.

LEDs are an increasingly economic and environmentally compatible form of lighting, offering energy efficiency, a high level of colour rendering and performance, and crucially, LEDs are easy to control and can be used in conjunction with daylight sensors. You may well have an efficient LED, but without understanding how to utilise the technology properly, you could be missing out significantly on its benefits. Controlling and dimming the lights wherever possible can help to ensure both energy costs and maintenance cycles are minimised. 

Ideal solution

The Belviso Set is a range of LED luminaires from Trilux that offers an ideal solution for office environments. Available as recessed, surface mounted and free standing luminaires the LED range offers a low surface brightness which is ideally suited for this new way of lighting task orientated work spaces. With constant colour stability, 98 lumens per watt, a colour rendering index of 80 Ra as well as a homogeneously illuminated light effect, it helps to create a pleasant working environment. Furthermore, compliant with EN 12464-1, Belviso luminaires offer reduced luminance values of 1500 cd/sq m so do not cause an issue when it comes to glare on computer screens. 

Aurista is another EN 12464-1 compliant LED that has been designed to meet Zhaga specifications. Those already looking into LEDs as a possible light source may already be familiar with Zhaga, a consortium whose goal is to develop interface specifications for LED light engines. Aurista is an innovative recessed reflector luminaire utilising LED light stars and offers a range of colour temperatures – achieving the balance between performance and aesthetics.    

So many factors come into play when creating a comfortable workplace environment but arguably, none have quite the same level of impact as lighting.

Implementing a well thought out lighting scheme that has taken into consideration the function of the room; illuminance; luminance distribution; direction of light; colour rendering as well as glare reduction will help to create a workplace that doesn’t just benefit from reduced energy and running costs, but one that is quite simply pleasant and comfortable to work within.   

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