An experimental investigation of the thermal usability of outdoor environments for urban heat mitigation, adaptation, and governance

Abstract

Abstract This study develops a quantitative method to assess the thermal usability (e.g. rideability, walkability, entertainmentability, exercisability, and workability) of outdoor spaces. The benchmark for thermal usability was assessed by four widely-used indicators (Wet Bulb Temperature (WBGT), Predicted Mean Vote (PMV), Physiologically Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI)). Among these five dimensions of thermal usability, exercisability was the most significantly thermally-affected, as WBGT was greater than 30℃, exercisability dropped to below 50%, while the other four usability dropped to below 75%. An empirical study based on field experiments in Changzhou, China was performed. The results indicated that the quantitative method was capable of assessing the thermal usability of various urban spaces (e.g. basketball court, badminton field, walkway space and natural lawn), and could guide people in spatial modifications, outdoor activities and site management. The empirical studies also showed that airflow and radiation were the two critical meteorological factors, associated with urban infrastructure affecting the thermal usability of outdoor spaces. Activity metabolism showed a positive correlation with participant heat stress and a negative correlation with the thermal usability. Guidelines are used to guide participants to avoid optional activities and to provide them protective recommendations for necessary activities during periods of low thermal usability. Overall, this paper promotes methodological understandings of thermal usability, and provide policy makers, urban planners and designers, and urban managers with implications on effective heat solutions.