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Introduction

You need sufficient levels and quality of light for staff to perform tasks. But that's not all – these people also have to interpret the lighting effect as a pleasant environment. With this in mind, there are a number of basic steps you can take:

• Maximise natural daylight levels, while avoiding glare
• Light walls and ceilings with bright room surface finishes, so people can efficiently and safely move around the space
• Provide the correct colour rendering and colour temperature to improve the feeling of comfort
• Allow zoning so people can dim lights or switch them off when they are not required, thereby saving electricity..

The right amount of light
Reflectance
Cellular office
Large office
Conference/Meeting/Boardroom
Controls
Next steps

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The right amount of light

Significant savings can be made if the lighting is designed to work in conjunction with the desk layout, since circulation areas need only half the light as work areas. Although office work that involves finer levels of detail sometimes requires more lighting, most small and open plan offices only need to be lit to 320 lux over the entire floor area. Rather than wonder if you have too little lighting, you might like to ask if you have too much (this is the case in many New Zealand offices

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Reflectance

Reflectance is the amount of light that bounces back off a surface (eg. wall or ceiling).

A lighter coloured room with a ratio of 90/70/20% reflectance (ceiling/walls/floor respectively) requires 70% less energy for equivalent illuminance as a darker room with a ratio of (70/40/20%). These figures compare with the absolute minimum reflectance recommended by the New Zealand Green Building Council (65% ceiling reflectance and 40% wall reflectance).

Lighter-coloured rooms provide better daylight distribution and improve brightness ratios, thereby creating spaces that are more visually comfortable. These significant improvements are possible at little or no additional cost – rooms need to be repainted every few years so why not try lighter tones to brighten your space?

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Lamps

Linear fluorescent lamps, available in a range of colours to achieve a natural appearance. These are the first choice for office environments.

There are two main types of fluorescent lamps: the older T8 and new technology T5. Both technologies have merits and limitations that your lighting designer can discuss in more detail.

A cool colour temperature of 4000K is suitable for offices and other work areas. Then change to warmer lamp colours in areas that are more relaxed and informal, such as staff rooms and entrance foyers. Fluorescent tubes are available in 2,700K, 3,000K, and 3,500K, all of which would be suitable for use in the informal areas, depending on décor and style required.

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Cellular office

In a small office it should be possible to vary the lighting level to suit the task at hand and the amount of daylight entering the space. Typical reading and writing work in such an environment requires lighting to 320 lux.

Switching or control systems should be configured so that staff can adapt the lighting levels as necessary. An occupancy detector can also be used to switch off lighting when no one is in a room.

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Large open plan office

In a large open plan office, you need to think about a broad range of people and task requirements: there are workplaces, conference and meeting spaces, material storage and circulation spaces.

Work to limit glare from light fittings, windows and other bright surfaces from any viewing angle. This is easier said than done in offices where desk locations aren't able to be moved around. To maximise the efficiency of the lighting system, its design and implementation should be carried out on an integrated fit-out level, where lights are designed with desk location and orientation in mind.

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Conference/meeting/boardroom

In conference and meeting rooms the lighting should be adaptable to meet the range of tasks that go on (eg. fine detail work, informal discussions, slideshows and video conferencing).

Lighting on the meeting table should be at least 320 lux but you should be able to reduce this to around 240 lux when tasks require less detail. You may need to be able to reduce light levels further if a data projector and screen is to be used. Avoid too much directional lighting over the central table if you don't want people’s faces looking unnatural due to shadowing. And keep the surrounding vertical walls brightly lit to avoid contrast between people’s faces and the background.

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Controls

In small offices
Retro-fitting a wall-mounted occupancy sensor in line with your standard switching is a good idea if there's no one about a lot of the time - although dimmable lighting provides the best flexibility. If you choose a dimmer be sure to fit a secondary light switch so you can easily switch off some lamps when you don't need them. (Just check the type of control gear within the light fitting.)

In large offices
Put lighting on separate circuits so staff can turn on lighting in zones that ideally are less than 100m². Doing so is a particularly good in open plan offices where people work late – they can switch lighting on in their immediate work area without having to flood the entire office.

In open-plan offices
Use ceiling-mounted occupancy sensors for each zone. For more energy savings, try a combination of daylight-reactive dimming control and occupancy detection.

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Next steps

If you want to take the lead on energy efficient lighting for your business:

• Talk with a qualified lighting professional to assess your specific needs and ask for their qualifications – ideally they should be IES accredited (illumination Engineers Society)

• Ask them to specify the most appropriate energy efficient lighting designs and lamp options to meet your business needs

• Make sure you get a clear cost/benefit analysis of the different efficient lighting options available including payback period/ROI and lifecycle costs (including maintenance costs).

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