Discomfort glare is one of the most important issues in the building planning process that is yet to be fully understood. Nowadays it is well known (Reinhart & Voss, 2002), that people tailor their sun shading devices to their visual needs. This means avoiding direct sunlight and glare at their workplaces, but also providing themselves with a view to the outside. The energetic impact of this typical behaviour is often underestimated. Modern architecture often applies highly glazed facades, so that a good sun protection is needed. In the planning phase, minimal total solar energy transmission values (g — values) referring to closed shadings are often used for the calculations — even if the user opens the shading for the view and the g-value could change significantly. The result from this is that overheating in summer occurs or the cooling energy required is much higher than expected.

As a conclusion from this, the main visual aspects of direct sun and glare should be taken into account in the planning phase of a building.

To avoid the direct sun on a workplace is only a geometrical problem and is quite easy to be solved. Much more difficult is the glare aspect.