KNOWLEDGE

With energy costs soaring, it’s time for a fundamental reassessment of the way in which we light offices. Jill Entwistle investigates the return of the humble task light

The arguments in favour of task lighting are becoming harder to refute. Offices are not only overlit, but as much as 70 per cent of office downlighting can be ineffective – illuminating the carpet and the unoccupied desk is unforgivably wasteful and pointless. As well as that, workers’ individual needs and preferences vary, so blanket uniformity is as unhelpful as it is dreary.

And why are we so obsessed with a horizontal surface when our working plane has largely shifted to the vertical? Reducing ambient light levels to 200 lux and letting individuals add their own light according to their needs makes more sense on all counts, but primarily on energy efficiency.

Power density

‘In a recent project study we compared a task lighting plus 200-250 lux design with a 450 lux ceiling design,’ says Mark Ridler, director of BDP Lighting, which uses lower ambient plus task lighting in its London and Manchester offices. ‘The power density was respectively 3.9W/m2 versus 7.4W/m2. We will have real in-use power studies in the years to come but we expect even greater savings because our experience in our own offices is that most people turn on their task lights only occasionally.’

Andrew Bissell, director of lighting at Cundall, has seen similar savings. ‘Where we have used task lighting we have seen reductions of 30 per cent in the energy consumption, without including for any daylight linking and presence detection,’ he says.

When you combine that with presence detection, especially in small zones, you can start to see 50 per cent savings over a blanket array of lights. Hands up who wants a cooler-looking office and 50 per cent savings in energy? Um, apparently not many.’

The barriers are largely about perceived disadvantages, hidebound attitudes and short-term thinking. But the drive to conserve energy means the case for task lighting has to be re-examined.

The first barrier is the speculative office building culture in the UK. Iain Carlile of DPA Lighting Consultants says: ‘Designing a building’s base illumination to a lower level and then telling prospective end users – who will be spending a lot of money to rent the space – that they need to provide additional task lighting will not be well received. They will potentially see it as substandard design which they need to supplement, and not a way of saving energy in the running of the building.’

Reaping the benefits

As Carlile points out, this is particularly pertinent if utility charges are included in the rent, and it is therefore the building’s owner rather than the end user who reaps the benefits of the saving.

‘The speculative UK office market is structured around providing compliant Cat A infrastructure and task lighting would be seen as an additional tenant cost and the provision of a 200 lux environment would be perceived by letting agents as non- compliant,’ adds Ridler.

‘Agents do love their 2.4 x 2.4m fully recessed lighting schemes and they do push clients to take on offices lit this way,’ says Bissell. ‘We need to educate clients and agents.’

Contractors may not be too keen on the prospect of installing task lighting. ‘From a procurement and installation perspective, 1,000 recessed plug- in fittings are a far more attractive and profitable solution than 800 lower power ceiling fittings and 400 task lights,’ says Bissell.

Even after the task lights are installed, staff may not turn them off when they are not needed, or leave them on at night. ‘Staff, whether users or cleaners, need to be educated to switch them off,’ says Carlile. ‘Alternatively, it’s possible to link the task lights to the lighting control system – still with a local switch for individual control – and switch power on or off based on occupancy detection in the immediate area.’ The floorstanding/desk-mounted, direct/indirect or ‘stalk’ versions often have integral presence and daylight dimming.

Next is cost. ‘The capital cost of task lighting is seen as an addition even though in terms of project costs this should be set against the fewer ceiling- mounted units required,’ says Ridler. ‘The LED versions of portable desk lamps are expensive at the moment, although the CFL equivalents are better value and in some ways better for glare.’

High capital cost

Carlile agrees. ‘Potentially, in large, open-plan speculative offices you will still require the same number of luminaires to ensure sufficient uniformity of the base 200 lux. The cost difference between the two luminaire types required to achieve the different levels of illumination is likely to be marginal. The additional cost of local task lights is likely to make the capital cost of equipment high.’

Luxo’s Ninety fitting in an office application

Luxo’s Ninety fitting in an office application

‘Controlling portable desk fittings can be more complex although not impossible,’ says Ridler. ‘They do need dedicated sockets – not 13A – to avoid plugging them into non-controlled power supplies.’

Another obstacle is the British Council for Offices (BCO) and lighting guides. ‘Like the agents, BCO certainly loves its 1,500-grid strategy which doesn’t necessarily lend itself to putting the lights only where they are needed,’ says Bissell.

‘Architects don’t like the ‘forest of stalks’ although if fully implemented it results in a much cleaner ceiling,’ says Ridler. ‘There are sometimes concerns over desk clutter for portable task lighting although these now often sit below typical computer screen heights. If properly mounted on to desks this should not really be a significant issue.’

Bissell ran into this problem recently at a high spec office in London where both he and the architects wanted a task lighting scheme. ‘Unfortunately the client has said no. The main reason was the cost of the task lights – despite a £9 million refurbishment budget – and the desk clutter they created.’

Taking task lights home

Also, clients believe that task lighting is liable to damage because it is in the public realm, says Ridler, and ‘bizarrely they think that the staff they employ and trust to conduct their business are going to take the task lights home. Our experience is that maintenance is not a problem and I have never heard of an instance of theft.’ However, portable appliance testing means there is a maintenance cost that ceiling-mounted lighting does not have.

Glare can be a concern for lighting designers and end users, although it may not usually be understood by clients, according to Ridler. ‘The flat-optic LED portable desk lights are quite glarey when angled to direct light. The more traditional CFL versions are better in this regard. The stalk task solutions are normally excellent for avoiding glare.’

Integrating task lighting into furniture, fixtures and equipment may be a problem. ‘Electricians and furniture suppliers rarely have a need to talk to each other and operate on different programmes,’ says Ridler. ‘If desks need to accommodate mounting requirements then this can be a problem on site even if specifications have been co-ordinated.’

Traditional values

Finally, tradition. ‘As bad as blanket arrays of lights are, people are used to it now,’ says Bissell.

Despite the long list of barriers to task lights, Jonathan Rush of Hoare Lea says it is time to reconsider them. ‘Part L 2018 will require buildings to have a negative carbon impact, meaning that they will have to create their own energy through combined heat and power systems internally.

‘Lighting is going to be massive and if you look at the current best practice we have a long way to go. Buildings will need to maximise daylight and provide intelligent control of lighting. But there is only so much that can be done and reducing illuminance will be a big step forward.’

 

More than an Anglepoise

The term task lighting invariably evokes an image of an Anglepoise or the many permutations that have followed in its pioneering wake. But the options are broader than that – a ceiling-mounted or suspended light positioned over the desk or task, a floor-mounted luminaire positioned next to the desk or task, an integral desk fixture – and each can be more or less appropriate according to the context.
‘We do find ourselves explaining the principle that a task light is a light dedicated and positioned specifically for a task,’ says Bissell. ‘There are pros and cons for each option. Clearly mounting a task light to the ceiling means the luminaires need to be moved when the desks are moved – but then again how often does that really happen? Desk-mounted fittings put the light closer to where it is required so a lower output lamp is required, but they tend to light a smaller area of the desk.
‘The floor-mounted light sits between those two concepts. It is easy to move as the desks move, can use a lower output lamp and lights a larger surface area. As with all aspects of lighting design, it is about understanding the client business operation and staff requirements, and giving them what they really need.’

 

The case for task lighting

  • It results in much lower installed energy
  • It gives the end user greater control
  • It gives different demographics personalised control
  • Cleaner ceilings and a more varied lighting environment
  • The Cat A/B conundrum can be resolved by capital transfers or design responsibility devolved to the tenant
  • Portable lighting can be moved to new premises

CASE STUDY

Vodafone headquarters, Q-Port, Amsterdam, DPA LightingDPA Vodafone‘This scheme puts a slightly different angle on task lighting,’ says DPA’s Richard Bolt. The oversized pendants were used for project/ workshop breakout spaces and were specific to the task as well as creating a statement.
Because the light fixtures are closer to the working plane, a lower wattage can be used compared with a light source mounted on or very close to the ceiling. ‘The difficulty is allocating a particular area for this purpose in a speculative office development,’ says Bolt.
‘But it could be that a basic infrastructure of recessed track could be integrated in the ceilings in specific locations to allow for such lighting.’

 

TEN BARRIERS TO TASK LIGHTING

 

1 Speculative offices

Telling prospective users they need to provide extra task lighting will not be well received. In the speculative office market in the UK, task lighting would be seen as another tenant cost and a 200 lux environment would be considered non-compliant.

2 Cost

The capital cost of task lighting can be high, but fewer ceiling fixtures are needed – most of the time at least. LED versions of portable desk lamps are expensive, but their CFL equivalents are better value and can create less glare.

3 Contractors

Many electrical contractors might consider the procurement and installation of 800 lower power ceiling fittings and 400 task lights considerably more onerous – and less profitable – than simply fitting 1,000 recessed plug-in fittings.

4 Lights left on

Staff might not turn off their task lights when they are not needed, or when they leave at night. They can be trained to turn them off, or the task lights can be linked to a lighting control system that switches based on occupancy in the area.

5 BCO and lighting guides

The British Council for Offices is, according to Andrew Bissell, wedded to its 1,500-grid strategy. That, he says, doesn’t lend itself to putting lights only where they are needed.

6 Aesthetics

Architectsjust aren’t fond of the ‘forest of stalks’ that sprouts up around an office with task lighting – but most fittings sit below the typical height of a computer monitor.

7 Maintenance and theft

Clients believe that because task lighting is in the public realm it is liable to be damaged or stolen. This is rare, but portable appliance testing will be a significant ongoing maintenance cost for anyone who has such a system.

8 Glare

Although many lighting designers and end users are concerned about glare from fittings such as flat-optic LED portable desk lights, conventional CFL versions are better in this regard and stalk task lights are great for preventing glare.

9 Integration into furniture, fixtures and equipment

Building mounts into desks on site can be problem when electricians and furniture suppliers rarely have a need to talk to each other and operate on different programmes.

10 Tradition

Arrays of uniform lights hanging from the ceiling may be ghastly, but everyone is used to them now. Why change?

RELATED
Keeping up appearances

There’s a maintenance plan. It’s just that no one follows it. Francis Pearce looks at whether it’s possible to design out one of lighting’s biggest bugbears.

RELATED
Colour gamut

Colour gamut is a measure of how colourful a scene will appear under a given light source. Sources with a high colour gamut generally make objects appear brighter and more colourful.