Lighting control plays an essential role in every lighting system. First, it allows the lights to be turned ON and OFF using a switch. Second, it can also allow light output to be varied via the use of multilevel switching, dimming or other strategies.
A good lighting control system is one that satisfies the design intent and user’s operational needs for the lighting system. This often involves allowing flexibility in use of the system in terms of timing, spatial distribution and/or intensity. A good lighting control system will also enable the user, or an automated logic system, to minimize energy consumption while meeting all operational needs.
For the control system to realize these important goals, it should be designed to provide the right amount of light where and when it is needed.
In the past, the common wall switch was the primary means of controlling lighting in buildings. However, in response to growing demand for energy savings, flexibility in use, user control, and improved maintenance—coupled with dramatic advances in technology and falling costs—designers are beginning to select ever more sophisticated control solutions. As a result, lighting systems are achieving both greater levels of amenity and lower operating costs.
New control options and technologies, however, have also introduced greater complexity into the selection and design of lighting control systems. Given the flexible settings of many new control options, system logic can be adjusted and reprogrammed more easily and frequently than in the past. While this flexibility promises lighting control systems more precisely tailored to users’ immediate needs, it also makes it more difficult to predict energy use of the system or long-term performance.
According to the Carnegie Mellon University’s Center for Building Performance and Diagnostics, worker salaries and benefits can run up to $318/sqft per year in a typical commercial building, while energy costs run about $2.25/sqft per year. This means if a lighting strategy can be demonstrated to positively impact worker satisfaction, it is potentially much more valuable than those limited only to saving energy—even though the impact on the bottom line may be more difficult to predict or quantify.
Lighting Control Basics Figure 1. Worker salaries and benefits can run up to $318/sqft per year in a typical commercial building, while energy costs run about $2.25/sqft per year. Lighting strategies that support productivity are therefore potentially much more valuable than those limited only to saving energy. Source: Light Right Consortium Research Study, Albany, NY. Graphic courtesy of Pacific Northwest National Laboratory, managed by Battelle for the U.S. Department of Energy.
It also means if a lighting strategy is certain to generate significant energy savings but control the lighting in a manner that irritates occupants and causes complaints, it may do more harm than good. Most facility managers will disable automatic lighting controls rather than allow ongoing complaints go unanswered. For this reason, controls should be reliable, easy and intuitive to use, and non-intrusive. For example, while most users will not notice a gradual 15-25% reduction in illumination, any abrupt changes in light level can be distracting and should be avoided, particularly for occupants performing stationary tasks. Similarly, occupancy sensors that routinely turn the lights OFF while the space is occupied may be disabled by disgruntled occupants.
Many projects are primarily driven by visual needs, such as:
More recently, the benefits of lighting flexibility have begun extending its application into new spaces such as classrooms and office workspaces.
Many office workers are unsatisfied with their lighting conditions and believe having control over light levels in their personal workspace would make them more satisfied and productive. For example, the 1999 Steelcase Workplace Index Survey showed that about four out of 10 workers (38%) said light levels in their area were too dim (22%) or too bright (15%). Three out of four (75%) said they wanted more control over their lighting; nearly one-half (48%) said they wanted the ability to adjust light levels with a dimmer. Three out of four (75%) said they believed lighting improvements would improve their efficiency and productivity (Steelcase, 1999).
Despite these needs, in the past, facility managers in commercial buildings paid a great deal more attention to the thermal comfort of workers than they did to their visual comfort. If occupants had the ability to turn their lights ON and OFF, their control needs were considered adequately served. And most people would not formally complain about their lighting unless the lighting was so bad that they could not work.
This thinking is changing for three reasons.
First, computers have become a common tool in today’s workplace, presenting new lighting challenges and creating more demand for users to be able to control their own lighting conditions.
Second, temporary positions are becoming more common, higher “churn rates” are a fact of life, and corporations are constantly interested in finding ways to make people more productive using less space. Workplaces are rearranged more frequently, workers move around more, and group workspaces are more common, creating demand for more flexibility from lighting.
Third, the workforce is aging. A higher median worker age is creating demand for higher levels of illumination, as older workers generally need more light to perform the same tasks as younger workers, particularly when viewing paper tasks with small type.
Lighting Control Basics Figure 2. A 2004 Light Right Consortium study involving personal lighting control in an open-office environment found that people exhibit a wide range of light level preferences. Source: Light Right Consortium Research Study, Albany, NY. Graphic courtesy of Pacific Northwest National Laboratory, managed by Battelle for the U.S. Department of Energy.
Research studies have demonstrated that people are more satisfied in office work environments when they can control light levels in their personal workspace:
Lighting Control Basics Figure 3. A 2007 National Research Council Canada office lighting study found that participants with personal dimming control reported higher job and environmental satisfaction. Photo courtesy of National Research Council Canada.