Indirect Lighting System with Luminaire Installed on Uppermost Part of the Wall to Achieve both Visibility and Energy Saving Performance

In this study, lighting environment under wall-installed indirect lighting method with high diffusive-reflective ceiling paint is examined. The authors studied desktop illuminance and vertical illuminance (height: 1200mm) in this lighting environment of the room (4000 × 4000 × 2700h mm). The average desktop illuminance is 844 lx (1.06 times greater than that under direct lighting method (employing luminaire of white reflector with white louver) with ready-made ceiling paint), and the average vertical illuminance is 560 lx (1.16 times greater than that under direct lighting method with ready-made ceiling paint). As to the appearance of photogravure paper on the desktop, slight reflection of ceiling (immediate area of the luminaire, luminance: 1990-2150 cd/m2) onto the photogravure paper is observed, but there is no difficulty in terms of visibility at any part of the letters, figures or photo images. Human faces and inner walls in the room appears to be brighter than under direct lighting method with ready-made ceiling paint.