Home > Articles By Issue > Space Planning & Interiors > Energy & Environment > Article June 2003

Light Brings Power (Special Report)

Between 80% and 85% of peoples' impressions of the world are visual. Light makes sight; vision requires a human eye and light. While light is for seeing, lighting is for perception.With Americans spending an average of 80% of their time indoors, most lighting that shapes the inside world is therefore electric-created, designed, and controlled by humans. The question should then be, "How do facility managers make the correlation between lighting and worker productivity?"

The laws of mathematics and economics can determine if an energy efficiency upgrade is a wise investment. But historically, it has been extremely difficult to generate factual evidence of a causal link between the qualitative aspects of better lighting and worker performance.

Now a landmark research project indicates that giving building occupants personal control over their lighting can result in greater satisfaction and motivation among office workers.

Previous Studies

The first major research in this area, conducted by the Lighting Research Center, demonstrated manual dimming energy savings of 6% in its eight-week study at the National Center for Atmospheric Research in Boulder, CO. The Center is a 250,000 square foot complex with three buildings. Each office was lit with two 2' x 4' recessed troffers housing three 32W T8 lamps driven by dimmable electronic ballasts.

Using various lighting controls, the Lighting Research Center reported energy savings of 61%, with 43% from occupancy sensors, 6% from manual dimming, and the rest from other methods. Three out of four of the occupants used the manual dimmers at least once and used the desktop dimmer over the wall-mounted unit by a ratio of six to one. The occupants also used their manual controls to switch the lights and work under daylight entering the room through window blinds.

Overall, the Lighting Research Center was able to conclude that participants preferred manual lighting lighting controls to automatic controls because the manual controls allowed people to tailor their lighting needs.

New Research

Evidence from a more recent field simulation study conducted by the Light Right Consortium (LRC) may help facility managers glean a way to increase worker productivity and energy savings at the same time. Formed in 1998, the LRC has set out to establish a link between lighting quality and worker performance and satisfaction. Before undertaking the full field simulation study, the LRC conducted an exploratory survey to determine if there actually was sufficient demand for increased lighting quality with economic benefits. Professionals involved in the specification, installation, and ownership of lighting systems participated in this survey.

Owners, while having the highest degree of influence and frequency of involvement in lighting decisions, perceived the value of lighting quality to be low. Facilities managers, on the other hand, considered the value of quality lighting to be fairly important. Furthermore, they indicated their level of influence in lighting decisions was fair with new construction and slightly higher with renovations.

The LRC found that 87% of respondents reported flexibility in lighting budgets; however, only if a ROI could be demonstrated. Also, 75% of respondents said if factual evidence indicated a positive effect by lighting on worker productivity was available, this would influence lighting systems purchasing decisions. Respondents reported occupant satisfaction as more important than worker output, retention, and absenteeism.

The Field Simulation Study

Next for the LRC was to isolate lighting as a single design factor and demonstrate its impact on worker satisfaction and performance using a scientific method. The primary variables included room surface brightness and personal control. Later, glare would be addressed.

The research centered on a field study with simulated tasks and a high degree of experimental control (typical of laboratory studies). This approach was chosen to maximize realism and validate the results. To confirm the results and gain more information, an actual field study is planned for 2003/2004.

An office in Albany, NY was set up as a typical space for nine workers. The open office plan featured perimeter windows and access to a view, although translucent window shades were used to alleviate the impact of daylight at work stations. The space allowed researchers to change the lighting between different lighting systems without the subjects' knowledge.

The lighting scenarios included:

• Best practice: Linear system of direct/indirect fixtures together with wall washing to brighten the walls.
• Switching control: The same as best practice, but with a moveable desk lamp with three manually switched light outputs and some individual control.
• Dimming control: Direct/indirect fixtures suspended over the center of each cube, together with wall washing system. The direct component of each could be dimmed using the interface on the occupant's computer.
• Parabolic base case: array of three-lamp parabolic-louvered fixtures.

Subject Observations

Test subjects were temporary employees hired to work under different lighting conditions during a typical eight hour day. They performed set tasks to simulate elements of office work and completed questionnaires linked to the productivity metrics being studied.

Output measures ranged from the subjective (occupant opinion) to objective (quantitative performance), resulting in a large data set. When asked whether they agreed with the following statements at the end of the day, the workers gave the following responses:

"Overall, the lighting is comfortable." (91% reported this for direct/indirect lighting with dimming control; 71% reported this for parabolic base case.) "The lighting is uncomfortably bright for the tasks that I perform." (11% for direct/indirect with dimming control; 33% for parabolic base case.)

Current Findings

Based on analysis to date, the LRC has discovered that occupants appreciate quality lighting and have preferences that are consistent with the organization's predictions and prior research. The study indicated personal dimming control resulted in occupants performing better on certain productivity metrics.

In the objective segment of the research, the LRC discovered that the presence of control had a measurable impact on motivation, which in turn was represented in the study in measure of persistence and vigilance. Persistence at a difficult or impossible task is an indicator of motivation at the task; people who are not motivated to do the task will not continue at it when it becomes very difficult.

The study subjects were more able to sustain their persistence and vigilance over the day in the personal dimming scenario compared to the baseline and best practice conditions. The probable reasons for this included:

• The ability to fine tune the lighting conditions to meet individual needs-both with respect to horizontal light levels and the brightness on the surrounding partitions;
• The ability to satisfy the preferences of individuals-the function of satisfaction in the workplace; and

other psychological impact of control on motivation. "Perhaps the simplest and most profound message with respect to personal control is that we are learning that personal control significantly improves our ability to optimize the satisfaction and performance of office workers," says Carol Jones, LC, program manager.

The results related to the effects of room surface brightness are still being analyzed along with the personal control data and both will be announced in August at the IESNA Annual Conference. The LRC also plans to analyze a lensed-troffer base case, with results available later this year. The conclusion of this portion of the study will mark the end of the project.

Once the full study is complete, Jones says the LRC is going to develop tools that have the potential to benefit occupants, facilities managers, owners, and the entire lighting industry. These tools will include lighting analysis software that integrates potential productivity benefits with energy savings. The end result will be life cycle cost analysis for various lighting approaches under consideration.

Completing The Transformation

This landmark field research supports the theory that workers are more motivated and satisfied when they are able to control their own lighting. While these results are important, it's significant to note that a causal link between lighting and worker satisfaction

and performance goes beyond providing just enough light for a worker to see and do a task. As an added benefit for facility professionals, personal lighting controls also represents an opportunity to generate incremental energy savings. For many years, representatives of the lighting industry have argued that lighting has a larger role to play in productivity.

There is now solid evidence that supports the belief that lighting does have a positive effect on worker satisfaction and performance. As this evidence is likely to be translated into practice, it has a strong potential to have a deep and lasting impact on how facilities are lighted in the future.