Lighting Quality and Energy-Efficiency Effects on Task Performance, Mood, Health, Satisfaction, and Comfort
Many jurisdictions have legislated energy codes that restrict building energy consumption for all uses, including lighting.12 Quality lighting systems today must meet or better these energy-use levels so that both the environment and resources are conserved (meeting long-term human needs), while still meeting immediate task, social, behavioral, aesthetic, emotional, health, and safety needs. Maintaining this balance is important to building owners, employers, and occupants, for lighting is an important feature in office design and furnishings.5 ' 4 Although many lighting systems exist that meet energy-efficiency requirements, concern persists that more energy-efficient lighting design will result in poorer quality lighting. The absence of a common definition of lighting quality has been one impediment to progress on this issue. Vetch and Newsham5, 6 have proposed a behaviorally-based definition of lighting quality. According to this definition, lighting quality exists when the luminous conditions are suitable for the needs of the people who will use the space. They grouped these needs in six categories: visual performance; post-visual performance (e.g., reading, eating, sewing, and walking); social interaction and communication; mood state (happiness, alertness, satisfaction, preference); health and safety; and aesthetic judgments (assessments of the appearance of the space or the lighting).