Subjective responses to changes in spectral power distributions of LED light

Lighting is an indispensable element in buildings, which influences visual comfort, health, well-being, work performance and building energy consumption. Light emitting diode (LED) technologies for illumination have made rapid advancements. Commercially available LED lightings have high luminous efficacies ranging from 60 to 75 lumen per watt and their spectral power distributions (SPD) are easily controllable. This study aims to reveal the potential effects of spectral power distributions of LED lighting on subjective responses including the evaluation on likeness, comfort, preference, clarity, brightness, glare, skin colour, lighting colour, overall satisfaction and work performance. Wavelength controllable LED lighting system that can render the 4³²⁴ different SPDs has been developed in this study in order to achieve the aim and 26 people participated in the experiment. The experimental results indicate that the subjective evaluation on lighting changes would depend on different SPDs under the same illuminance. The participants would tend to prefer the red-colour emphasizing SPDs with a peak wavelength of 636 nm to the blue-colour emphasizing SPDs with a peak wavelength of 453 nm. This study should contribute to reducing carbon dioxide emissions from buildings without sacrificing visual comfort and satisfaction of occupants by encouraging a wider application of LED lighting in buildings.