Outdoor human comfort and thermal stress: A comprehensive review on models and standards

Outdoor human comfort is an essential parameter to assess the quality of the urban microclimate, and to provide guidelines for sustainable urban development. This paper presents a comprehensive review of available tools for modelling outdoor human comfort and thermal stress, explains the physical equations that drive these models, and shows their applicability based on climate and the findings of previous research. The existing procedures are subdivided into three main categories: Thermal indices, Empirical indices and indices based on Linear Equations; for each approach, case studies are presented and subdivided according to Koeppen Climatic Classification (Polar, Cold, Temperate, Arid and Tropical). International regulations and software available to quantify outdoor human comfort and microclimate are presented, as well as a graphic thermal scale to compare the ability of each procedure to respond to the 11-point thermal sensation scale (from Sweltering to Extremely Cold). Finally, the models are presented as function of their ability to analyse climate, microclimate and human-related characteristics of the selected built environment. This paper aims at bringing a comprehensive introduction to the topic of the outdoor human comfort, helping the reader to understand the existing procedures and guiding the choice of the suitable options according to specific research needs.