Assessment of predicted versus measured thermal comfort and optimal comfort ranges in the outdoor environment in the temperate climate of Glasgow, UK

In a warming world, the risk of overheating is significant in temperate climate areas such as Glasgow, UK where adaptation to overheating is low. An easy-to-use thermal comfort evaluation is therefore a necessary first step towards developing effective coping mechanisms. In this study, we explore the effectiveness of Predicted Mean Vote, Predicted Percentage of Dissatisfied and Physiologically Equivalent Temperature, together with air temperature in mimicking actual thermal sensation votes of street users obtained in 2011 in Glasgow City Centre. The Predicted Mean Vote/Predicted Percentage of Dissatisfied indices developed for controlled indoors show a surprising similarity to actual thermal sensation votes derived from outdoor surveys, than the Physiologically Equivalent Temperature developed specifically for the outdoors. The method of calculation of mean radiant temperature is the key to improved performance of Physiologically Equivalent Temperature, with fish-eye lens photographs improving its performance. The results also show air temperature alone has nearly equal predictive power of the actual thermal sensation. A preliminary comfort range for Glasgow is also derived and its limitations are explored. Practical application : The strong relation between thermal sensation votes and air temperature (Ta) enables future thermal comfort studies to predict the thermal comfort using easy-to-access Ta only. A current thermal comfort study in Glasgow aiming at developing a link between urban morphology and Ta is already using this strong relation to predict outdoor thermal comfort in the city centre. This helps to establish a correlation between these three factors.