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Personal Control: Boosting Productivity, Energy Savings

Productivity has traditionally been regarded and measured as work output per man-hour. Today, in non-industrial organizations, productivity is being regarded as a broad range of positive outcomes, with job satisfaction being a leading outcome. Job satisfaction has become increasingly important, particularly for office workers, due to the lengthy period of time required for new employees to reach maximum efficiency, and turnover costs that can erode profitability and competitiveness.

Numerous research studies have shown that workplace design is a major contributing factor to how satisfied and motivated workers are, how well they perform individually, and how they perform as a group. A majority of office workers, however, are not satisfied with the quality of their workplace design, including leading environmental quality factors such as lighting, thermal comfort and acoustics. While people demonstrate highly variable preferences for temperature and light levels, for example, thermal and lighting systems are designed as fixed output systems that will be comfortable for a majority, but not all, occupants.

Since people costs outweigh building costs by a ratio of 13:1, organizations can generate desirable financial outcomes through investments in productivity, in particular by addressing workplace design. Studies indicate that workers relate comfort to workplace design, and that increasing job satisfaction can correlate to productivity increases. As a result, organizations today are highly aware of the need for integrating emerging technologies with innovative design to maximize satisfaction and performance among space occupants.

To bridge the gap between a fixed workplace design and highly variable need for lighting and temperature among individuals in a group and for each individual based on changing tasks, time of day and other factors, designers have increasingly adopted personal control solutions. Regarding lighting, this generally entails establishing a dimming system with each occupant in the space being able to interface with the lighting system (through PC, handheld remote, etc.) to control his or her local light levels.

A number of studies demonstrate that personal dimming can result in higher productivity—specifically in the metrics of vigilance, motivation and satisfaction—and also in energy savings. This dual impact can result in an improved bottom line and more satisfied employees and tenants. These advantages are resulting in a significant new trend towards adoption of personal dimming solutions among designers and building owners.

This white paper makes the case for personal control, in particular giving occupants the ability to control their own light levels through dimming.

The Modern Definition of Productivity
Productivity among the complex jobs held in modern offices can be measured in many ways, from forms completed per hour to ideas generated per week, at both the individual and organization level. Today, productivity includes quality of work output, employee attraction and retention, comfort, financial success and job satisfaction. According to the Light Right Consortium, this has resulted in an emerging approach to studying worker productivity that focuses on mental building blocks (attention, vigilance, memory, creativity, mental computation, comprehension) and psychological processes (motivation, persistence, effort).

In the Industrial Era, worker productivity was typically measured in the proverbial “widgets per hour,” a metric comprised of production output, efficiency and accuracy. In the Information Age and the modern office, worker satisfaction and motivation are now more important metrics due to the complex nature of many office jobs and the high costs of turnover.

According to Harris, Rothberg, LLC, a performance consulting firm, research indicates that the turnover cost for an exempt employee is about 1.2-2 times his or her annual salary. This includes, according to Douglas T. Phillips, author of “The Price Tag of Turnover” (Personnel Journal, 1990), inefficiency of the replacement and co-workers working with the replacement; inefficiency of the employee who is leaving and co-workers working with that employee; organizational inefficiency during the time the position is vacant; and processing costs. According to Harris, Rothberg, new employees do not reach maximum efficiency and performance for 13.5 months.

Businesses are sensitive to these costs. In 1999, Canadian Business reported that CEOs considered “attracting and retaining high-caliber employees” to be second only to “increasing profitability” as a top corporate priority, ahead of “market expansion” and “mergers and acquisitions.”

Job satisfaction may be the key to retaining top employees. A study in the Journal of Occupational Health Psychology reported that job satisfaction accounts for 63% of variance in organization commitment, which accounts for 80% variance in intent to turnover. As stipulated in the study, job satisfaction incorporates satisfaction with the work environment, which brings us to the role workplace design plays in job satisfaction in the next section.

Even without the relationship between job satisfaction and turnover and its impact on the bottom line, CEOs and facility executives want a satisfied workforce and consider this an important factor in the built environment, more important than employee retention, in fact. A 1999 market research study by Ducker Research interviewed end-users responsible for making decisions involving the quality of the office environment and physical facilities, including CEOs, facility executives and real estate managers responsible for a total of 232 million square feet. The study found that worker satisfaction ranked higher than worker output, employee retention and absenteeism.

Personal Control Boosts Productivity, Energy Savings

A Ducker Research study of CEOs, facility executives and real estate developers found that worker satisfaction ranks higher than worker output, employee retention and absenteeim as factors that these decision-makers consider when making decisions regarding the quality of the built environment. Source: Light Right Consortium

In addition to having higher job satisfaction, a more productive office worker demonstrates greater individual and group performance. A more productive office worker performs tasks with greater accuracy, for longer periods of time without tiring, are more creative, can handle stress and unexpected situations better, can interact with other employees more effectively, etc.

Workplace’s Relationship to Productivity
Workplace design has been found to be a major contributing factor to how satisfied and motivated workers are, in addition to how well they perform.

A 1987 study in the Journal of Applied Psychology reported that workplace characteristics account for as much as a 31% variance in work satisfaction. The Buffalo Organization for Social and Technological Innovation (BOSTI) Associates, an organization that researches the office’s effects on productivity and job satisfaction, reported in 2000 that the workplace makes an 8-32% (smallest to largest) contribution to job satisfaction (average 24%), 3-10% contribution to individual performance (average 5%), and 6-15% contribution to team performance (average 11%)—according to a survey of about 13,000 people in 40 business units conducted between 1994 and 2000. And in September 1999, Sales & Marketing Management reported the results of a survey of 150 executives, which found that the work environment has become the most important factor in fostering employee satisfaction.

In 1995, The Office of Science and Technology Policy, an arm of the Federal government, stated that better-constructed facilities can result in a “30% improvement in productivity and comfort.” The Office’s Biennial Report also stated that better-constructed facilities can result in “50% reduction in delivery time; 50% reduction in operating, maintenance and energy costs; 50% fewer occupant-related injuries and illnesses; 50% less waste and pollution; and 50% more durability and flexibility.”

The 2002 Steelcase Workplace Survey of more than 1,500 corporate executives, facility managers and design professionals from various industries reported that more than three-fourths (79%) of respondents believe that “physical comfort has a serious impact on worker satisfaction,” while more than one-half (53%) believe “their organizations had minimal information regarding the level of satisfaction people have with their physical work environment.” This illustrates an alarming disconnect between the organizational goal of productivity and understanding of a key element of that productivity—physical comfort in and satisfaction with the workplace.

A Building Owners and Managers Association (BOMA) study found that Class A spaces are not only likely sell and rent faster, but that tenants in these spaces are much more satisfied with the environment.

Studies Find Widespread Dissatisfaction with the Workplace
While many organizations have failed to connect workplace satisfaction with productivity, the building industry has been unable to satisfy most office workers in regards to thermal comfort, lighting and acoustics. Research indicates that large percentages of workers are not satisfied with their physical workplace.

Besides the actual design of the space (whether it facilitates interactions, communication, ergonomics, privacy, etc.), key elements of the workplace include lighting, thermal comfort and acoustics, which together are components of Indoor Environmental Quality (IEQ). Currently, the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) defines acceptable indoor air quality as “air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction” when temperature is set at 22 ºC (72 ºF). Similarly, the lighting industry addressed the issue of glare, which can impair or cause discomfort to vision, and established the Visual Comfort Probability (VCP) rating system, which indicates what percentage of the occupants in the poorest location in the area would not be bothered by direct glare caused by a uniform lighting system of identical lighting fixtures. A VCP of 75, therefore, means 75% of the occupants in the poorest location would not be bothered by glare. Generally, office environments require that fixtures have a VCP rating of 70 or more, although this figure has been revised by some in recent years to 80 or more for environments where computers (vertical tasks) are used.

Satisfying the majority is a common-sense approach when thermal and lighting characteristics of the space are fixed. But it also means that the building industry, by design, accepts a one in five dissatisfaction ratio among workers with two key workplace design elements that may directly impact their job satisfaction.

However, even ASHRAE’s definition for acceptable indoor air quality and the lighting industry’s VCP metric are no guarantee of satisfaction with thermal comfort and lighting for the majority. Studies have found that large percentages of office workers are dissatisfied with thermal comfort, lighting and acoustics in their workplace.

A 1997 American Society of Interior Designers (ASID) study determined that 68% of employees complain about the light in their offices. A 1991 Steelcase survey conducted by Louis Harris & Associations discovered that 44% of office workers and 64% of computer users considered eyestrain (due to glare) to be the leading hazard to their health in the office—ahead of asbestos and even exposure to AIDS. Similar studies document significant dissatisfaction with heating, ventilation and air conditioning (HVAC) and acoustics. A 1983 study by Merck revealed a 43% dissatisfaction with HVAC, and 1992 Social Security Administration study found that 56-89% of government workers regarded HVAC as a problem. An ASID study found that 70% of office workers claim they would be more productive if their offices were less noisy.

The benefits of increased productivity are obvious in terms of individual performance, group performance and job satisfaction. According to a five-year BOSTI Associates study of 6,000 office workers conducted in the 1980s, employment costs exceed building costs by a ratio of 13:1 for owner-occupied buildings and 5:1 for leased space. Therefore, if facility owners, property managers and facility managers can find a way to bridge the gap between building design and worker comfort, they may realize higher productivity and less turnover of employees/tenants. With a 13:1 ratio of people costs to building costs, an investment in building costs to produce even a small increase in productivity can result in a significant impact to the bottom line, helping organizations become more profitable and competitive.

Connecting Building Systems to Individual Need: Personal Control
Studies, such as those performed by Dr. David Wyon of the National Institute of Occupational Health in Copenhagen, Denmark, have demonstrated that people respond very differently to their environment. Wyon showed that workers who are satisfied with their environment are up to 15% more productive compared to people who are not.

Numerous studies have shown that workers are more satisfied with their working environment when they have control over thermal comfort and lighting. Personal control bridges the cap between a building design that attempts to satisfy the majority and people who have very different needs based on a range of factors.

Thermal Comfort: Wyon estimates that group performance can realize an improvement of 2.7-8.6% by providing individual control over the environment rather than trying to reach a temperature acceptable for all or most workers. Carol Lomonaco and Dennis Miller of Johnson Controls, in an important white paper, “Environmental Satisfaction, Personal Control and the Positive Correlation to Increased Productivity,” write, “When office workers are satisfied with their environmental conditions, when they can work in greater comfort and control, they will be more productive. Additionally, the cost of employment per worker will drop, and the cost of facilities operation will decrease … a growing body of research supports these conclusions.”

Lomonaco and Miller cite several studies supporting the hypothesis that individual control of thermal comfort leads to greater productivity. In a study conducted at the University of California in Berekely and a similar study conducted in 12 air-conditioned offices in Townsville, Australia, occupants exhibited a wide range of preferences for thermal conditions. The Office of the Environment Study (United Kingdom) examined several variables and their effect on productivity, including number of people in a given room and job type, and level of personal control. The study found that productivity decreased as the number of people in the room increased. The study also found that productivity increased as the level of personal control increased, independent of the number of people in the room.

The Johnson Controls authors provide a clear, comprehensive and persuasive argument for individual control of thermal conditions in offices, backed by a considerable amount of research and references. To see their study, click here. The rest of this white paper will explore the correlation between personal control over light level and productivity.

Personal Control Boosts Productivity, Energy Savings

Analysis of Environmental Satisfaction-Productivity Studies. Source: “Environmental Satisfaction, Personal Control and the Positive Correlation to Increased Productivity,” Carol Lomonaco and Dennis Miller, Johnson Controls, Inc.

Lighting: People vary significantly in their preferences of lighting. Age is a significant factor in how much light an individual needs to perform a given task accurately and efficiently. It has also long been known that various tasks demand different light levels depending on contrast, size and time allowed for the task. Depending on location, workers may be forced to suffer from the effects of glare, which causes eyestrain, which in turn is considered a leading health hazard by many office workers. Daylighting can be beneficial but the lighting system must be able to respond to changing light levels to save energy and eliminate glare. In addition, workers today are expected to perform a greater variety of tasks in the same space, use computers (vertical in addition to horizontal tasks), and handle greater workloads that previously had been the responsibility of a larger workforce. To accommodate these working conditions, they need optimum lighting conditions perfectly tuned to their needs—essentially, the ability to tune their lighting according to changing tasks, mood and ambient conditions (such as time of day and amount of daylight).

Personal lighting control satisfies these needs. It has been demonstrated in numerous studies to increase job satisfaction, motivation, vigilance and performance—by bridging the gap between a fixed building design and a highly variable individual need. Advancements in lighting technology now provide cost-effective personal control capabilities to buildings that can improve productivity as well as energy savings.

Let’s look at the research in this area, which supports the claims that:

  • Workers have varied lighting needs
  • Personal dimming control can save energy
  • Personal dimming control can increase worker satisfaction and performance

Much of the research in this area focused on various aspects of personal control. A number of these studies found that workers like having personal control, but its presence may not lead to increased productivity. It wasn’t until the Light Right Consortium’s landmark productivity study was published in 2003 that the claim, linking personal control and worker satisfaction and performance, received validation.

Personal Dimming Control: Research Study #1
According to the California Energy Commission, automatic lighting controls generate typical energy savings of 35-45 percent in commercial and institutional buildings. Personal dimming control in private offices can accelerate energy savings while increasing occupant satisfaction and enhancing the value of the space.

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 of 58 private offices at the National Center for Atmospheric Research (NCAR), a three-building, 250,000 sq.ft. complex in Boulder, CO.

The project was sponsored by The Watt Stopper, GE Lighting, Motorola, Environmental Protection Agency, Bonneville Power Administration, CIEE, NCAR and Prescolite-Moldcast.

Each office was lighted with two 2×4 recessed troffers housing three 32W T8 lamps driven by dimmable electronic ballasts. The lighting controls included a wall-mounted manual unit for on-off and dimming; a portable manual dimmer on the desktop; and a PIR occupancy sensor mounted in a corner for automatic switching.

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 dim the lights and work under daylight entering the room through window blinds.

The biggest reason they dimmed their lights? Computers, they said. “Compensation for daylight,” “read printed text,” and “create an atmosphere for work” were other important reasons to 10-20% of the survey participants.

Whatever their specific reasons, the Lighting Research Center concluded, “Employees … prefer manual lighting control to automatic controls because the manual controls allow them to tailor the lighting to their needs.”

Other key findings in this study were that occupants preferrred desk-mounted dimmers over wall-mounted dimmers due to greater convenience, and that occupants used the dimmers more often when they were mounted on the desk.

Personal Dimming Control: Research Study #2
In 2002, National Research Council (NRC) Canada published a research study, “Preferred Surface Illuminances [light levels] and the Benefits of Individual Lighting Control: A Pilot Study,” authored by Guy R. Newsham, C. Arsenault and Jennifer A. Veitch. The researchers established two different lighting conditions in two workstations in a mock-up open-plan office. One was fitted with conventional ceiling-recessed parabolic lighting fixtures that were dimmable (A). The adjacent workstation was fitted with a dimmable “partion-washer” system designed to preferentially light vertical surfaces in the worker’s view, supplemented with light from overhead fixtures (B).

Twenty-two participants, all of them lighting experts, performed a task in one of the two spaces and then completed a questionnaire about their satisfaction with the lighting. They then dimmed the lighting to their own preference using an interface on their PCs and repeated the task and the questionnaire. After that, they switched workstations and repeated the entire process.

The researchers observed that the participants preferred a wide variety of light levels. While preferences clustered at around 19-28 footcandles (fc) (200-300 lux) on the desktop in Workstation A, preferred light levels overall ranged from 5-84 fc (50-900 lx). While preferences clustered at around 28-37 fc (300-400 lx) on the desktop in Workstation B, preferred light levels overall ranged from 5-74 fc (50-800 lx).

“While we would expect a wide range in the preferred luminous conditions produced by individuals, we would predict broad agreement that control, not matter how it is used, is beneficial,” noted the authors. “On average participants agreed that their own lighting choice improved their ability to do the job well compared to the lighting they started with … These positive effects associated with individual control and receiving preferred lighting conditions are expected, and agree with other recent research work on individual lighting control.”

Personal Dimming Control: Research Study #3
The most significant research about the effects of personal dimming control was conducted by the Light Right Consortium. The Consortium’s landmark study, formed to address the benefits of quality lighting, indicates that personal control of lighting can result in a significant improvement in occupant satisfaction and performance.

The Light Right Consortium’s goal is to transform the lighting market by using research to investigate the link between lighting quality and the performance, satisfaction and productivity of workers. The Consortium, formed in 1998, is managed by the Pacific Northwest National Labora tory and operated by Battelle for the U.S. Department of Energy. Board members include the Alliance to Save Energy, the Illuminating Engineering Society of North America, the International Association of Lighting Designers, the International Facility Managers Association, Johnson Controls, the National Electrical Manufacturers Association, the New York State Energy Research and Development Authority, Steelcase, the U.S. Department of Energy and the U.S. Environmental Protection Agency. Project sponsors who contributed equipment included Armstrong, Birchwood Lighting, Cooper Lighting, Day-Brite Lighting, Engineered Lighting Product, General Electric, Ledalite, Lightolier, Lutron, OSRAM SYLVANIA, Peerless Lighting and Philips Lighting. The Lighting Research Center and the National Research Council of Canada were contracted to perform the research.

“Central to the success of the Consortium is establishment of a link, based on sound research results, between quality lighting and economic benefits,” says Carol C. Jones, LC, Program Manager. “Market transformation goals include 1) influencing customer decisions so that they are designing, purchasing and installing higher-quality and more energy-efficient technologies, 2) going beyond the technology issues to delve into the dynamic of customer and market behaviors, and 3) creating enduring market changes.”

First, the Consortium conducted market research to provide proof of concept. A survey was conducted among professionals who specify, install and own/use lighting systems. It was not surprising that 87 percent of respondents reported flexibility in lighting budgets if a return on investment could be demonstrated. But 75 percent said if factual evidence indicating a positive effect by lighting on worker productivity was available, it would influence which lighting systems they would buy. These results validated the need for Phase II, which was to provide this factual evidence validated by scientific method, and to study which lighting approaches were the most effective at influencing workers.

With Phase II’s implementation, a research program was formulated to address the question, “Can different forms of realistic office lighting affect the performance of office work or the well-being of employees?” The primary variables included room surface brightness and personal control. The study indicated that personal dimming control resulted in occupants performing better on certain productivity metrics.

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 workstations. The space was planned and furnished to allow the researchers to change the lighting between five different lighting systems without the knowledge of the subjects. The workers were temporaries hired to work under the different lighting conditions for a typical eight-hour day. A range of output measures were collected that ranged from the subjective (occupant opinion) to objective (quantitative performance), resulting in a large data set. The study was conducted in the field, but with simulated tasks and a degree of experimental control. This approach was chosen to maximize realism and the validity of the research.

The four 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 having three manually switched light outputs and providing 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”: Regular array of three-lamp parabolic-louvered fixtures.

“Lensed Troffer Base Case”: Regular array of recessed lensed troffer fixtures.

Personal Control Boosts Productivity, Energy Savings

The Albany, NY study personal control/dimming scenario. Courtesy: Light Right Consortium

The temporaries worked for a complete day on set tasks to simulate elements of office work, and on questionnaires linked to the productivity metrics being studied.

Personal Control Boosts Productivity, Energy Savings

Workers in the Albany, NY study who had personal dimming control exhibited a wide preference for light levels, a phenomenon typical of personal control studies. Courtesy: Light Right Consortium

When asked whether they agreed with the following statements at the end of the day, the workers responded:

“Overall, the lighting is comfortable.”

Direct/Indirect with Dimming Control – 91%
Parabolic Base Case – 71%

“The lighting is uncomfortably bright for the tasks that I perform.”

Direct/Indirect with Dimming Control – 11%
Parabolic Base Case – 33%

“The lighting causes deep shadows.”

Direct/Indirect with Dimming Control – 12%
Parabolic Base Case – 7%

“The lighting fixtures are too bright.”

Direct/Indirect with Dimming Control – 19%
Parabolic Base Case – 38%

“Reflections from the light fixtures hinder my work.”

Direct/Indirect with Dimming Control – 29%
Parabolic Base Case – 21%

Personal dimming control with linear suspended direct/indirect fixtures yielded a 30-point spread in response to whether the workers believed the lighting was comfortable, and produced the lowest incidence of workers perceiving their lighting to be uncomfortably bright for the tasks they performed.

Personal Control Boosts Productivity, Energy Savings

Personal dimming control with linear suspended direct/indirect fixtures yielded a 30% spread in response to whether the workers believed the lighting was comfortable. Courtesy: Light Right Consortium

Participants were also asked:

“How does the lighting compare to similar workplaces in other buildings?”

Worse Same Better
Direct/Indirect with Dimming Control 7% 43% 50%
Parabolic Base Case 8% 69% 24%

In the objective segment of the research, the Light Right Consortium discovered that the presence of control had a measurable impact on motivation, which in turn was represented in the study in measures of persistence and vigilance.

Personal Control Boosts Productivity, Energy Savings

Personal dimming had a positive impact on workers' persistence and vigilance, metrics of motivation. Courtesy: Light Right Consortium

The Consortium concluded:

“People with dimming control reported higher ratings of lighting quality, overall environmental satisfaction, and self-rated productivity … people with dimming control showed more sustained motivation, and improved performance on a measure of attention … In addition, on average, people with dimming control chose lower illuminances [light levels] than current recommended practice. This implies that individual overhead dimming control has potential for energy savings.”

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. Vigilance is a state of watchfulness or careful attention, and is related to accuracy. 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 the needs of individuals, 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.
  • The psychological impact of control on motivation.

The study concluded:

“Dimming control participants showed steeper performance improvements over increasing contrast in the timed vision task and avoided motivation declines over the day. They also improved in vigilance performance over the day, whereas the Best Practice participants did not. There was additional evidence in interaction effects with Print size and time that typing performance also showed beneficial effects of having dimming control.”

“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 Jones. “We know from prior work conducted at National Research Canada that it there is a great variety of preferred light levels. This tells us that we have a tremendous opportunity, and a tremendous challenge, if we choose to raise the bar with respect to meeting the needs of the office worker population.”

References & Further Reading

A management report on the correlation between workstation lighting and computer vision syndrome. Lutron Electronics Co. Inc. P/N 366-625, 1998.

Baier, R.D. 1999. Customer service made easy: Deliver what office tennants want. HPAC Magazine. September: 41-45.

Benoit, Richard. Lighting in the healthy office white paper. Steelcase, Inc. 1996.

Boyce, P.R., Individual lighting control: Task performance, mood and illuminance. (PDF) Illuminating Engineering Society of North America 1999 Annual Conference: Proceedings. IESNA: New York, NY. 299-312.

Boyce, P.R., et al., Impact of the “personna” system on task performance, mood
and illuminance selected. Lighting Research Center. Rensselaer Polytechnic
Institute. March 1998.

IRC’s Lighting Quality Project. National Research Council Canada, Institute for Research in Construction, website, 2004.

Lighting Quality & Office Worker Productivity. (PDF) Light Right Consortium, November 2003.

Light Right Consortium website, 2004.

Lomonaco, C. and Miller, D., Environmental satisfaction, personal control and the positive correlation to increased productivity. Johnson Controls, Inc., 1996.

Maniccia, D., B. Rutledge, M. Rea, and N. Narendran. 1998. A field study of lighting controls, Troy, NY: The Lighting Research Center.

Maniccia, D. Rutlege, B., Rea, M.S., Morrow, W., Occupant use of manual lighting controls in private offices. (PDF) Illuminating Engineering Society of North America 1998 Annual Conference: Proceedings. IESNA: New York, NY. 490-512.

Morrow, W., B. Rutledge, D. Maniccia, and M. Rea. 1998. High performance lighting controls in private offices: A field study of user behavior and preference. World Workplace ’98 Proceedings. Chicago, IL: International Facilities Management Association.

Newsham, G.R., Veitch, J.a., “Individual control over office lighting: perceptions, choices and energy savings.” (PDF) National Research Council Canada, ISSN 1206-1220, September 1998.

Newsham, G.R., Veitch, J.a., “Individual control can be energy-efficient.” (PDF) National Research Council Canada, January 1999.

The value of quality lighting. (PDF) Light Right Consortium, May 2002.

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