Towards a prediction of outdoor human thermal comfort adapted for designers of urban spaces: examining UTCI and APCI in the context of Algiers (Algeria).

Abstract

The aim of this article is to determine the ability of UTCI (universal thermal climate index) to assess summer micrometeorological comfort in the climatic and sociocultural context of Algiers (Algeria). This widely recognised thermo-physiological index is compared with a subjective index, APCI (average perceived comfort index), based on a definition of comfort established beforehand by the studied population. A new procedure was applied based on "micrometeorological walk" in order to collect objective and subjective experimental data simultaneously. From the data collected, both indices were calculated for 12 urban configurations. The correlation between UTCI and the subjective APCI shows that UTCI is able to correctly predict and assess the level of outdoor human thermal comfort felt in the south Mediterranean climate. However, the evaluation scale for heat stress in UTCI is inappropriate in the studied context, unlike that proposed by APCI, which takes sociocultural differences into account, as well as the different perceived environmental and urban aspects that may influence the perception of outdoor thermal comfort. However, this comparison of UTCI and APCI enables us to put forward a contextualised model of the prediction and assessment of perceived outdoor thermal comfort based on an APCI estimate, from which users' true perception can be assessed, derived exclusively from physical measurements. Designers can therefore evaluate their proposals using digital architectural and urban modelling tools that include calculation of UTCI, by adjusting the heat stress evaluation scale to match the sociocultural context of the project.