Combined Electric Light and Daylight Systems Ecodesign

Natural daylight in interiors has two main characteristics: It is extremely pleasant to humans, and it is a free energy. The electric lighting system has to be able to combine the daylight contribution with consequent savings on the energy bill. The application of sensors, control systems, and information technologies can reduce significantly the need for human work. Controlling the electric lighting in such a way that the daylighting penetration matches the lighting level to the actual need allows saving on the energy costs and improving the human comfort and efficiency. This paper highlights that lighting controls work with effectiveness if the lighting system is well structured both in luminaire arrangement and control group subdivision, according with a comprehensive approach that considers working zones and daylight contributions. At this aim, this paper suggests an adaptive criterion and a rule of thumb to evaluate the daylight availability and its internal penetration since the preliminary design.