A case study of lighting retrofit to improve building energy efficiency and lighting quality by using luminaires with nano optical coating

Lighting retrofit is a common technique to reduce lighting energy use and to improve lighting quality. It is usually performed by replacing the lamps in the existing luminaires with more efficient lamps. Despite the high potential to enhance lighting performance by improving other parts of the luminaires such as reflectors, lighting retrofits usually keep their designs unchanged and focus on the change of the lamps. In this case study, an alternative lighting retrofit method - the replacement of reflectors using a nano optical coating - was tested in a typical office in Hong Kong. The case study used a luminaire with a highly reflective nano optical coating. The pre- and post-retrofit illuminance level, illuminance uniformity, glare and lighting energy use were measured. The results show that the use of the nano optical coating enables the reduction of light tubes in the office and thus the lighting energy consumption without lowering the lighting quality. The lighting retrofit enhances the illuminance uniformity in the office by 14.6% while keeping the illuminance level and discomfort glare within the satisfactory level. It also lowers the lighting energy use of the office by 37.5%.