1. A Review of Long-Term Discomfort Indices

Over the past decades, several metrics and methods have been developed to assess human perception of the thermal environment and thermal response to different climatic conditions. In the last decade, a new type of discomfort index, intended to describe long-term thermal phenomena in buildings has been proposed in the scientific literature, standards and guidelines. Most of these new indices summarize the thermal performance of a building in a single value. A hopefully exhaustive review of the existing indices for long-term evaluation of thermal comfort conditions in buildings and for thermal risk assessment is presented here for several reasons: (i) there are considerable differences in their structure and significance, (ii) some of them are based on thermal comfort models whilst others derive from rules of thumb and (iii) a systematic collection of those is missing. In this chapter, indices are first grouped according to the assumptions on which they are based on, and then they are analyzed in order to identify their scope, strengths and weaknesses. Finally, some guidance is provided for future developments.