Abstract
The evaluation of the energy performance of transparent components should not neglect their influence on the indoor thermal and visual comfort conditions. If the design choices are based only on the energy need optimization or the cost reduction, they could lead to solutions not suitable for the occupants’ comfort. The available design tools allow the realistic and detailed evaluation of the building energy performance in standardized use conditions, once the site climatic characteristics, the envelope thermophysical properties and the technical characteristics of the systems are known. The actual energy performance becomes more difficult to assess when the occupants behavior has to be included, as it is often influenced by their environment’s perception and the resulting reactions. The significant effect, often negative, of the occupants’ interaction on the real building energy consumption during its operational life, leads to the necessity of a careful assessment of both the building energy needs and the comfort conditions at the same time, since the early design phase. The use of indicators and metrics able to synthesize the different fundamental aspects of the performance, including the indoor environmental quality, becomes essential in order to carry on an adequate comparison between different options.