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Good natural lighting and unimpeded views out of a building belongs to the minimum standards required by guidelines for natural, healthy, productive workplaces. Attention, however, should be focused not so much on a simple maximization of the natural light available in a space, as on improving the quality of lighting by ensuring as even but intense distribution of illumination in all inner areas. An architectural means of optimal daylight distribution is by using so-called light shelf systems, horizontal shading and redirecting devices. They improve the uniformity of natural light in a space by reducing the level of illumination near the window and redirecting light deeply into the space. In most cases, systems of this kind consist of light-colored, reflecting or mirror elements in the area of the building facade. One problem in selecting and positioning elements of this kind is the facts that ultimately the amount of light available in the facade plane is merely redistributed and reduced a little with each reflection. This paper aims to provide the design guidelines for optimal light shelves based on their geometric and optical characteristics. Their role, that is, a tradeoff between optimal distribution of the daylight and glare control has been evaluated simultaneously. A series of computer simulation deals with the basic geometrical design elements of a commonly used light shelf and sky conditions. As is shown in the results, for best distribution, light shelves should be located as low in a space as possible without causing glare, typically above standing eye level. In addition, more uniformity of light distribution can be improved by extending of the shelf and reflectance of the shelf and higher ceiling height might play a role in increasing the effectiveness of light shelves.