LED Office Lighting: The Potential for Occupant Benefits

Volume 17, Number 2, June 2012

Lower energy consumption, longer life, and the possibility of exciting new ways to use light are some of the advantages of light-emitting diodes (LEDs) over other light sources. Although the initial cost of LEDs remains higher than that of their conventional counterparts, lower lifecycle and maintenance costs will make the technology more attractive, especially as manufacturers continue to economize and increase efficiency.

LED technology is radically different from existing light sources and opens new directions in lighting design. Market acceptance will require that it be trusted as healthful and safe, and that its features be valued by users.

NRC Construction scientists recently completed a four-year study with two overlapping activities: the conceptualization of new ideas for office lighting, and laboratory experiments assessing how people would use and respond to the colour-tuning capabilities of these systems. They brought together people from diverse backgrounds and expertise to imagine and discuss what a novel LED lighting system might be like.

Human Factors Experiments

Researchers began with a scale-model experiment in which they studied the range of colour temperature and spectral power distributions of participants’ preferred lighting conditions during a short-time (one hour) exposure (Figure 1). Next, they conducted full-scale experiments, asking occupants to create their preferred white light, using custom software during a full workday exposure (Figure 2). They concluded with an experiment seeking to determine how various LED sources affect colour appearance.

Preliminary observations from the research include:

  • People have a wide range of light spectrum preferences, which they could not previously demonstrate with fluorescent lighting systems.
  • Although they have the ability to create extremely saturated coloured lights, most participants created reasonably white lights with high colour rendering quality.
  • People like being able to choose their light spectrum, but are unfamiliar with it and need more experience with the interface to develop stable preferences.
  • A high-quality LED can render colours as well as an incandescent lamp of the same correlated colour temperature.

Like cost, lack of familiarity is a barrier to the successful market penetration of the LED technology. NRC researchers built two types of LED luminaires in full scale to demonstrate novel uses and future applications of this technology.

  1. A corridor demonstration was designed to show how one might use LEDs to provide a visual fire alarm. In an emergency, the LEDs flash red and guide occupants to the closest exit by scrolling through the corridor from one luminaire to another. During normal office conditions, the LED luminaires function as regular indoor light sources and emit a high quality white light (Figure 3).
  2. A 1.2 metre x 1.2 metre LED lighting panel was designed and built to play back, in real time, a low resolution image of the sky captured from the outside with 289 individual LEDs (Figure 4). Research shows that in a windowless space, having a sense of outside conditions contributes to occupants' well being.

The demonstrations were installed in a building at the NRCan CANMET Energy Ottawa Research Centre, where visitors can learn about LED lighting and its role in energy-efficient buildings. Feedback will contribute to future refinements in the technology and its uses.

For more information

Contact Erhan Dikel at erhan.dikel@nrc-cnrc.gc.ca or 613-993-9625.

Figure 1. The scale model

Figure 2. Experiment setting for the full-scale experiment

Figure 3. LEDs showing the nearest exit in case of an emergency (scrolling red light can be seen on the closest luminaire)

Figure 4. The square LED luminaire, used as a skylight