Daylight exploitation and management were always important in the design of interior spaces. Daylight is superior compared to artificial light, not only due to its benefits for human body, but also because of the lighting quality and visual comfort it offers.

Given the high importance of energy consumption nowadays, daylight can significantly contribute to the reduction of energy costs, if this factor is taken into consideration during the design. There is a great variety of existing systems, delivering daylight to the core of a building according to the current needs. Such systems, combined with the use of wall or ceiling openings, can lead to an increase of daylight and shading autonomy, thus leading to the optimum lighting quality.

It is often difficult to balance between daylight and shading needs, as trying to increase daylight levels in a room can lead to shading problems and vice versa. Particularly in areas of low latitude, this balance is difficult to maintain during the whole year and ordinary daylight solutions can cause overheating during winter, lack of shading during summer or low light levels in certain, distant areas of the room.

In this student project, our research efforts mainly concern the behavior of a new daylight system: a rotatable light shelf, considered for a typical office room and optimized for the climate data of Athens. The project is divided in 5 main parts.

In the beginning, an introduction to basic daylight meanings and physical quantities, as well as its advantages to human being, is given. In the second part, the most important daylight systems are discussed, with emphasis in light shelves. The third part contains the main part of the project analysis concerning the rotatable light shelf, obtained through computer simulation data organized in charts, tables, and graphs. Daylight calculations were realized with the "Radiance", "Daysim" and "Solar Tool" computer programs and the results were organized using Microsoft Excel. Results include luminance and illuminance levels, the daylight factor and DGI glare index.

In the fourth part, calculations are repeated for a room with double length, in order to investigate the maximum distance where the benefits of the shelf are considerable and therefore the effectiveness of the rotatable light shelf. In the fifth part, the most important concluding remarks of our theoretical and computational research are presented and analyzed, along with the resulting restrictions and some possibilities for future research. Finally, the explanations of certain basic terms are summarized in an Appendix to facilitate their best comprehension.

The computational results are presented with rendered and photometrically calculated images (false colors) in an additional issue.