Curtis O’Donnell, Lighting Design Manager at Dextra Group plc. discusses…
It is widely recognised that lighting can be at the heart of many debates in the workplace, at home and at play. Even before I started working in the industry, I was guilty of looking up at ceilings in shops and commenting on the quality of the lighting and offering my opinion on a far better solution.
There is no doubt that there are many different demands and needs from lighting relating to how we carry out our everyday tasks-especially in relation to our work. So it is no wonder that lighting is a very common topic of conversation in offices and workplaces.
While considering our personal opinions and individual needs we have to remember that there are often ‘guidelines’ to follow. In my opinion, it is these guidelines that restrict lighting designers in their ability to diversify and widen the scope of the type of lighting that is frequently used in our workplaces. In some respects, it is those guidelines that are restricting development and innovation.
In offices twenty-five years ago it would have been very common to see batten luminaries with diffusers or recessed modular fittings with prismatic panels in a suspended ceiling delivering the light. Then came a proposal to change the guidelines that were written specifically for areas of the office where visual display terminals-or computers as we now know them-were being used.
Guidance was there to ensure the use of specifically designed optics that were developed to help eradicate the glare on computer screens.
The category system as it was then known, used three types of louvres – Cat 1, 2 and 3.
The most common and most suitable one for an office was the Cat 2. This avoided the luminance of the fitting exceeding 1000 cd/m² at 65 degrees elevation at all angles of azimuth. It kept the health and safety departments of companies happy while avoiding headaches for the staff using the computers.
The other guides for lighting designers – CIBSE, BSEN12464 etc., mirrored these requirements. In 2005 the Lighting Guide 7 reduced the luminance limit to 1500 cd/m² and gave further guidance on lighting the ceiling relative to the horizontal task area. In addition to many other lighting factors the guides gave specific illuminance levels that needed to be achieved. But some of these guides were written in the 1990’s when office workers were still blessed with using computers with fixed position monitors, dark background with DOS based software on Cathode Ray Tube (CRT) monitors made of highly reflective screens.
Just like anything else we do in life, whether it’s driving a car, building an extension to our house, wiring in a socket or plumbing a bathroom, there will always be rules we have to follow and guidance that is written to ensure that our practices and technologies work in harmony.
My opinion is that the guidance written for lighting design needs to be brought in line with the modern working and living practices we are part of today. Modern computer monitors, for example, are now non-reflective enough to allow luminaires to exceed the current limit of 3000cd/m². The screens are adjustable as well as being able to be tilted and we generally utilise a light coloured software background whilst carrying out work on our computers. If these guidelines are more flexible, less stringent and are more in line with modern equipment we could open up a new concept of lighting and luminaire design enabling the customer to have more dynamic and varying light sources within their work space.
It is far too easy to space recessed light fittings at the ‘normal’ 2.4m x 2.4m centres, whilst there are LED products that can easily achieve wider spacings. In order to maintain the current 300 -500lux, designers are restricted to higher LED lumen packages in order to comply with the guidance. I think with today’s precision engineered optics, the ground breaking efficiencies that can be gained from LED light sources and the general high quality of the lighting available, the levels of illuminance could be reduced within many areas including offices. The guidance says between 300- 500 lux but more often than not the specification is closer to 500lux as that has now become the acceptable norm. It is this acceptance that 500 lux is required in order to perform office based tasks that should be carefully considered in the future if you look at the impact on power usage and increased energy bills.
The most obvious way of reducing illuminance is to employ a lighting control strategy and dim the level of illuminance according to the natural daylight or user requirements. But this could be lowered even more and only by recognising an acceptable lower top end illuminance will lead to bringing power consumption and bills down.
There are some truly incredible luminaire designs with ground breaking performance and efficiencies and it seems a shame to not utilise them to their maximum potential. If we were to review the illuminance levels we actually need, energy levels could be driven down even more than the present requirements and guidelines.
It is time to design and not just simply follow methods of the past.
