Comment, Office

Redefining localised lighting in the office

The 'clunky' definitions of 'localised lighting' need to be redefined, argues Lux's applications editor John Bullock. Image: Courtesy of GE

The International Commission on Illumination (CIE) defines localised lighting as:

‘Lighting designed to illuminate a functionally defined area with higher illuminance at certain specified positions, for instance those at which work is carried out.’

This is surely one of the most clunky descriptions of an exciting inovation that you are ever likely to hear.

To be fair to the CIE, it’s never been a boundary smashing organisation, it instead tends to move at a grandfatherly pace towards the development of a comfortingly bland definition of whatever new ground has been broken.

In a few years’ time the CIE is going to need a whole new definition of ‘localised lighting’.

A horribly wasteful way of lighting

It has been a design norm when dealing with an office space to always provide a working illuminance across the entire floorplate with a draconian uniformity of 0.7 – a figure that is usually met only by cheating with the calculations.

This process is based on the idea that no one knows how the interior landscape will be planned, so the best thing to do is to make sure that there is sufficient working illumination everywhere.

Throwing light into unnecessary corners

Lighting schemes designed to deliver ‘minimum measured illuminance’ have always been a gift to energy companies, as the designers strive to shove illumination into the deadest of corners, where no one will ever need it.

Happily, the Society of Light and Lighting is taking an active role in discussing localised lighting, acknowledging the potential savings that can be achieved by targeting illuminance patterning across an office floor.

So, let’s come back for a moment to the argument that office planners may not have finished their designs before the lighting is planned, so a blanket illuminance level is the only way forward.

It doesn’t have to be like this

Every new interior office space has a working furniture design within it just ready to be teased out. The building does not have to be completed in order to do this. All it takes is for the inevitable office circulation spaces to be sketched in and for the dead corners to be acknowledged and, suddenly, a localised lighting scheme is already underway.

If we add to the mix the prospect of introducing lighting via desk-based luminaires or re-locatable ceiling tile systems we begin to see how the future of energy-efficiency lies in a localised lighting approach to office design.

The numbers are falling

Before the introduction of the T5 fluorescent lamp and the LED, the target figure for office lighting was often as high as 12-15W/m². The launch of the more efficient fluorescent lamp brought that figure down to below 10W/m² and for a while it was thought that was as good as it was possible to get.

Localised lighting schemes have cut that figure in half. In 2015 Cundall won the Low Carbon Project of the Year award for their office in Birmingham; a localised lighting scheme delivering a stunning 4W/m².

That was done by using T5 fluorescent lamps and effective controls. Since LED technology has proven as effective source for office lighting, there are reports of localised lighting schemes that are working at less than 3W/m².

Why localised lighting isn’t task lighting

SLL provides the best differentiation between lighting for task and lighting for a local area:

‘A localised lighting scheme should deliver a uniform illuminance across the defined space, with a uniformity of 0.8 or better.’ 

And we thought that 0.7 was an issue?

Task lighting refers to supplementary lighting that is usually intended to double the illuminance level on a specific task area. It is spotlighting on a desk – that is all.

This is a new design philosophy

Localised lighting is not just a new way of seeing an old way of lighting. The designers who are pushing the boundaries on what localised lighting might become are aiming for even lower figures. For that to work it is essential that clients buy-in to the process and that will require the CIE to find another definition entirely.