Lighting accounts for one-third of the energy used in commercial spaces. About half of the lighting is wasted either through inefficient bulbs, poor design or improper maintenance.

The main reasons are:

  • older bulbs and reflectors use inefficient technology and give off more heat than light (which in summer has to be removed by the air conditioning system, using more energy)
  • companies don't effectively plan their lighting needs when they design their buildings or offices
  • tenants don't move existing lighting to suit their changing layout needs
  • over-lighting is a waste of energy.

Plan your lighting carefully

  • Look for opportunities to maximise natural light by placing offices in areas that get the most natural light. Placing open plan offices around the building perimeter maximises daylight. Cellular offices block out the light to other areas. Place cellular offices and meeting rooms near the core, or middle of the building so they don't block light.
  • Work out how the office is going to be used and then allocate areas by:
    • general lighting to illuminate the office (the Green Star guide is 400 lux)
    • task lighting for desks or work stations to localise light to where it is really needed
    • accent lighting if required to create mood or to highlight a feature. Be economical with accent lighting as it generally isn't efficient to run.

Install a lighting control system

  • Timers that switch lights off after a preset period are a suitable solution in open plan offices or large conference rooms where it is difficult to make a particular individual responsible for turning off lights.
  • Occupancy sensors are another solution. These sensors turn lights off when they have not detected movement for around 15 minutes.
  • Daylight dimming control systems can be very cost-effective over time. Ask your electrical engineers about DALI (Digital Addressable Lighting Interface) and similar systems.
  • Ensure that switching to individual areas is provided and labelled so that during after-hours use, a whole floor doesn't need to be switched on.

Upgrade fittings or bulbs

  • Install reflectors into fittings to redirect light. Without them about half the light from a fluorescent tube is absorbed by the inside of the fitting.
  • Clean fittings regularly.
  • Install 'occupancy sensors' in rooms that are infrequently used (toilets, store rooms, meeting rooms etc).
  • Install electronic control gear and more efficient new-generation lamps to increase efficiency.
  • Replace bright lamps with lower power ones in over-lit areas, or remove some lamps altogether.

Encourage energy saving behaviour

  • Obtain "Switch Off when not in use" stickers for light switches from the Energy Efficiency and Conservation Authority.
  • Remind people to switch off lights in meeting rooms and other rooms that are used only part of the time

Useful resources and information

Case study: lighting

Lighting accounts for about 30% of the total energy consumed by an office building.

Most of the fittings at the Ministry are T5 fluorescents running off high-frequency ballasts with a highly reflective (KRN) fitting which maximises the amount of light reflected. The building's lighting control system includes occupancy sensors for intermittent-use areas such as stairs, toilets, utility areas and meeting rooms. Large numbers of switches for different areas enable specific sections of lighting to be turned off and on as required, rather than having to light entire floors.

The Ministry considered installing a lighting control system that would enable automatic sensing of daylight conditions, variable control in different areas and so on. The Digital Addressable Lighting Interface (DALI) system originally envisaged for the building:

  • allows lights to be individually dimmed from 1% to 100%
  • automatically dims lights near windows
  • uses predetermined levels in meeting rooms so users can choose a level suited to the need
  • sets reduced lighting levels (usually 15%) for cleaners, security rounds and so on.

This system has been successfully installed in the Treasury building but did not meet the cost/benefit assessment for inclusion during the construction process at Environment House. The Ministry is looking at the possibility of a gradual rollout of DALI or a similar system during the first couple of years of its occupancy.

The Energy Efficiency and Conservation Authority has an excellent guide available on improving office lighting [PDF, 117 KB].

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