Calibração do índice de conforto térmicotemperatura fisiológica equivalente (pet) paraespaços abertos do município de Belo Horizonte, MG

Abstract

Research on global climate change and on urban climate demonstrates that urbanization affects the local energy balance, causing changes in the climate of cities and influencing the thermal comfort of its inhabitants. In this context, this study aimed to propose procedures for measuring urban microclimatic variables, collect individual and subjective variables and treat data in order to calibrate the thermal comfort index known as physiological equivalent temperature (PET) for open spaces in the city of Belo Horizonte - MG. Tasks were conductedthrough the inductive experimental method. A population of adults who are healthy and acclimated to the climatic conditions of the city was considered. The variables were collected through field measurement simultaneously with administration of questionnaires in representative days of each one of the four seasons during the years 2009 and 2010 in two contrasting areas regarding morphological characteristics such as the sky view factor, the height of buildings, the type of floor, the presence of water sources and the vegetation. For field investigation, a portable and of easy assembly weather shelter was designed using lightweight, durable, sturdy and affordable material. The construction of the 40mm gray globe thermometer was based on information in the literature. The collected and measured data, as well as the calculated values of PET, were statistically analyzed through descriptive analysis and ordinal logistic regression. The results suggest that the methodology used provided satisfactory outcomes to obtaining the values of PET and to its calibration. The descriptive analysis of the collected data confirmed the importance of shading, air humidification and maintenance of channels of wind in the urban enclosures. In calibrating the PET index, three ranges were defined: the "comfortable" range had the upper limit value of 30.5°C, the "hot" range was defined by the values of 30.5ºC to 35ºC, and the lo wer limit of the "very hot" range was 35°C. Considering the winter of 2009, which was hotter than usual, and the resulting amplitude of the index PET obtained during the year - 20-41ºC, the intervals related to cold climatic situations, as well as the lower limit of the comfortable range, could not be defined. The calibration of the PET index will allow planners to evaluate the thermal adequacy of open spaces and to compare different design solutions ahead of time, directing decision making in urban projects.