Daylighting systems offer tremendous potential for reducing the energy consumption of electric lighting, but their usage has been inhibited by high costs and imperfect performance of current technologies. This paper presents predictions of energy savings for two proposed daylighting technologies, a daylight-sensing switch and an automatic blinds system, which employ simple, inexpensive components and designs. Assumptions of solar irradiance, blind position, blind operation behaviour, and light switching behaviour were combined with illuminance data and daylight factors to develop an algorithm for calculating the potential energy usages of six different systems in commercial private offices and open plan offices. Results show that the combined usage of the proposed technologies perform with an average annual energy saving of 24% compared with manual switching and blinds operation in Albany, New York. Compared with a photosensor-operated dimming system, the proposed technologies combined show better performance during summer months. Comparisons were also made for the systems in six US climatic regions.

Workplace lighting design is dominated by a perceived requirement for low-brightness luminaires, to avoid distracting reflections in display screen equipment (DSE). This paper presents measurements of the reflectance characteristics of current commercially available DSE. The results suggest that modern display screens cause less distracting reflections, and consequently that current workplace lighting guidelines could be significantly relaxed. The measurements of screen self-luminance, specular and diffuse reflectance followed the experimental method of EN 29241-7, and corroborate tendencies seen in previous studies. EN 29241-7 contains calculations for quantifying the subjective distraction effect to office workers, and these calculations were adapted to derive numerical values for the maximum tolerable luminance of office luminaires. The practical application of these measurement techniques to commercial workplace lighting design is discussed.

OA Howlett 295 method was based on EN 29241-7, I wonder if a source consisting of 600 mm square diffusing surfaces constitutes a 'worse case' for DSE in of ces. The use of small high luminance sources (T5 lamps or LEDs for example) in re ector optics for general of ce lighting may cause sizeable areas of much higher luminance than the test condition. Is the test condition truly representative of modern of ce conditions? Comment 2 on 'Re ectance characteristics of display screen equipment: application to workplace lighting design' by OA Howlett J Hugill (