IAEEL newsletter 3/96

Give People Control Of Lighting Controls

Automatic lighting controls-with suitable manual overrides-offer major opportunities for improving performance, occupant satisfaction, and energy efficiency. However, systems sometimes perform disappointingly because insufficient attention has been given to how people react to and make use of them.

Lighting controls continue to develop rapidly, with systems becoming increasingly sophisticated. They have the potential to produce significant benefits through energy savings, increased occupant comfort, and greater planning flexibility, as well as by making it simpler to design and install lighting systems. The recent inclusion of lighting controls in the UK Building Regulations (1995 edition) has focused attention on the need to provide appropriate controls for energy-efficient operation and is also the subject of new guidance from CIBSE, the Chartered Institution for Building Services Engineers in the UK. However, the full benefits of the control system will only be realized if the occupants find it easy to produce the lighting environment they require.

A recent Building Research Establishment (BRE) study indicated that in many buildings there was still considerable room for improvement in energy efficiency, occupant satisfaction, and usability by both users and management. Problems frequently arose because the technology itself had been seen as the solution, without sufficient understanding or analysis of how management, visitors, occupants, and other users of the building (such as cleaners) would react to it and want to use it. In existing buildings, opportunities to learn from pilot projects have often been missed, the study concluded. A need was identified for clearer problem definition, better understanding of occupancy and management requirements, and better ergonomic design at both the strategic and detailed levels.

MATCHING OCCUPANTS' NEEDS
High user satisfaction and high energy efficiency were generally associated with high levels of local control (i.e. down to the level of the individual user or small group), plus high awareness (by both end-users and the facilities managers) of how the controls operated. Conversely, where users had little or no control over lights in their work space or low awareness of the proper use of the controls, low satisfaction and energy wastage were common.

People often refer to abstract "users", but in fact there are many users with different-though sometimes overlapping-requirements which also change with circumstance and task. When making provisions for unknown occupiers one can use the principles below, while also aiming for as much adaptability as possible within the cost constraints.

Maximize control where needed. More user control over a situation reduces uncertainty and increases satisfaction: People may adapt to inappropriate conditions, but quality or productivity tends to suffer. It is usually easier to provide individual control over lighting than over other aspects of the internal environment; however, lighting of the whole space and the comfort of other occupants must also be taken into account.

Provide good information and feedback. A mistrust of new technology will be exacerbated if people do not understand what it is supposed to do, or if the user interfaces are poor. Occupants need to understand how a system works, preferably intuitively, but if not, then by receiving a clear briefing or instructions. Stress and frustration will occur if control functions are not clear and the lighting does not adjust to its desired state as soon as a control is operated. Poor usability or feedback can quickly form a barrier to effective use and can easily lead to system features being overridden or even disconnected.

Consider safety requirements carefully. Safety is essential, especially on stairs, when using machinery, and when handling valuable or potentially dangerous objects; and if the lights all go off suddenly almost any situation may become hazardous. However, an unthinking concern for safety can easily lead to an unnecessary and wasteful over-provision of lighting, as in several of the offices surveyed where stair, corridor, atrium, and toilet lights throughout the building were switched on if there was only one person there, and sometimes regardless of available daylight too!

WHO ARE THE USERS?

The need for and appropriateness of lighting controls are influenced not only by the physical characteristics of the space, the availability of daylight, and the task and appearance requirements, but also by the ways in which spaces are occupied and managed. In addition to the normal occupants of the building, whose interactions with the lighting controls will vary with context, as described in the next section, the following users should also be considered:

Building management will want systems to operate smoothly, reliably, and economically to ensure comfort, safety, and sometimes energy efficiency. If difficulties occur, case studies indicate that the management response is usually to simplify the operation in order to minimize complaints. In practice, this nearly always means that the lights end up being on longer than necessary. This makes it particularly important for operational and management issues to be carefully considered at the design stage and for the solutions developed to be as user-friendly and as self-managing as possible.
The management of individual tenants (and occasionally departments) may require their own intermediate-level interfaces. Otherwise, if there are administrative difficulties in communicating their requirements to building management, control features will often be overridden for convenience, and the lights will be on longer than necessary.
People in the building outside normal hours need to be thought about carefully, or too much lighting may be used, not only in the areas concerned, but in common and circulation areas as well. In some buildings, the global "sweep"-intended to switch off all the lights in a floor or zone-could not be used if people stayed late in one area, and other lights in the zone stayed on unnecessarily. The lighting preferences of night-shift workers may differ from those occupying the building during the day.
Cleaners and security staff may need additional facilities, such as "pilot" lighting (less concentrated than the normal circulation lighting) so they can move about the building safely. They may also need to control larger areas than individual users, for example, to switch off the lights in an area when they leave, and possibly to turn them on easily when they arrive. A system that monitors which lights are on and whether they should be on, can also facilitate security efforts.
People who do not have their hands free, for example, when carrying objects, pushing trolleys, or driving vehicles. Occupancy sensors, which switch lights on when people arrive and switch them off or dim them afterwards, can be particularly valuable.

CONTEXTS OF CONTROL USE
The most appropriate division of functions between individual occupants and management varies with context, and particularly with the amount of "perceived ownership" the occupant can reasonably have over the space and its controls. Situations range from the quasi-domestic, such as cellular offices (where individuals can decide what they want, have the power to control it, and do not want anyone to interfere!)to a concourse of an air terminal, where passengers would not expect to control anything directly (though they might complain if they thought conditions where poor).

Six categories of space have been identified:

Owned spaces: small rooms for one person or a few colleagues
Shared spaces: multi-occupied areas such as open plan offices
Temporarily owned spaces: meeting rooms, interview rooms, etc.
Occasionally visited spaces: storerooms, bookstacks, toilets, etc.
Unowned spaces: circulation areas, etc.
Managed spaces: atria, entrance halls, restaUrants, libraries, etc.

Each category has different requirements. Various control techniques are available, including: time switching, occupancy sensing, daylight linking and local switching. The most appropriate should be used for each space. Guidance documents are available to help with this choice.

Modern lighting control technology, sensitively applied, offers great potential to improve occupant satisfaction, save energy, provide flexibility, and make life easier for management-and all at the same time. Case studies show that relatively simple systems can perform well. However, if occupant needs have not been carefully considered, even sophisticated controls can disappoint.

Anthony Slater
Bill Bordass
Tanya Heasman
©UK Crown Copyright

The authors are working with the following three UK organizations: UKBuilding Research Establishment (BRE), W. Bordass Associates, and System Concepts Ltd.

Contact: Anthony Slater, BRE
Tel: +44 1923 66 44 72 Fax: +44 1923 66 40 95
E-mail: slaterai@bre.co.uk

References and suggestions for further reading:

Occupant use of lighting controls: a review of current practice and problems, and how to avoid them.
Proceedings CIBSE National Conference, 1995.
CIBSE,
222 Balham High Road,
London SW12 9BS, UK
Fax: +44 181 673 3302
Comfort, control and energy-efficiency in offices, BRE Information paper IP3/95, and People and Lighting Controls: BRE Information Paper IP6/96.
BRE papers ordering: Construction Research Communications Ltd,
151 Rosebery Avenue,
London EC1R 4QX, UK
Fax: +44 171 505 6606

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