Only in the past 20 years, with a growing awareness of the importance of natural lighting and the wish to save energy, has daylight planning established itself as a distinct discipline. Today, lighting planners reproduce the geometry of proposed buildings either in the form of models or through computer simulations, which are two mutually complementary techniques. The aim of this planning is to exploit the available daylight as efficiently as possible for purposes of illumination, while at the same time reducing the often undesirable side effects of heat gains through insolation. The basic design parameters include the orientation and layout of a building, its location and surroundings, and the shading to which it will be subject. Dynamic lighting situations are conducive to the well-being of the users of a building; in other words, contrasts are more important than constant, monotonous ergonomically correct lighting. In addition, the sleeping and waking rhythms of human beings and certain ailments from which they suffer, particularly in northern regions (seasonal affective disorder, sick-building syndrome, attentional deficit disorder, etc.), are assuming an ever greater importance in lighting design.