Design of three outdoor combined thermal comfort prediction models based on urban and environmental parameters

Abstract

The current trend of urbanization growth, take along a substantial increase in the outdoor temperatures within built environments, affecting the liveability of outdoor space, reducing the thermal comfort of citizens. Outdoor thermal comfort is usually evaluated with complex models on large scale, considering neighbourhoods, districts, or cities, without focusing on local and accurate predictions. The present study is aimed at contributing to the topic by proposing a simple yet accurate combined prediction model, able to assess the outdoor thermal comfort around a theoretical isolated building. A set of parameters, such as wind velocity, relative humidity, solar irradiation, and building height, has been used to quantify their effect urban comfort at fixed air temperature. The same parameters have been used for the development of a predictive correlation for the three outdoor thermal comfort indexes (UTCI, PET and SET). Comfort data was calculated by CFD simulations where the environmental parameters was variated in a fixed range. The main contribution to outdoor thermal comfort is provided by solar irradiation affecting the comfort indexes values up to 50%, the second is the wind velocity affecting up to 25% the thermal comfort indexes. The variation of building height is less impacting (around 15% of comfort values) as well as the relative humidity (5%). At least, three correlations have been elaborated for each outdoor thermal index. Correlation’s quality has been evaluated using RMSE and percentage difference, obtaining a maximum average value of 0.71 and 1.48%, respectively.