Towards local sustainability: A case study to evaluate outdoor urban spaces in Baghdad using physiological equivalent temperature index

Abstract

Improving environmental quality to promote outdoor activities, which also aims at providing social benefits, is an extensively researched field of study. In this study, a sustainable urban solution is evaluated as a prototype using the physiological equivalent temperature (PET) index. The literature demonstrated the local deficit of increasing social qualities through the development of a prototype that performs as a mitigation strategy to improve the urban thermal environment. To fill this gap, the aim of this experimental study is to create a neutral outdoor thermal comfort area that is suitable for social gatherings while minimizing local heat stress. We investigated six selected sites using ENVI-met 4.4 software, and we validated them with the observed data by two types of validation metrics. The sites were located near the Tigris River in Baghdad. The conditions at the sites were analyzed between 8:00 and 24:00. The simulation findings revealed the possibility of achieving thermal comfort during most of the working hours. A reduction in thermal stress by ∼18.4 °C was observed with a drop of 36.4% of PET results. The urban solution contributed to a decrease in the temperature by four degrees from the existing situation, which promotes a sustainable outdoor urban area. In hot climates, any outdoor activity between 12:00–16:00 is generally discouraged, whereas (8:00–10:00 & 18:00–00:00) hours are suitable for social interaction. However, multistoried buildings with sufficient orientation and shading could be ideal for achieving local sustainability, whereas the river's presence and its low albedo significantly raise the mean radiant temperature (MRT) by ∼7–8 °C, which proves its importance in heat reduction. The hybrid fabric altered the traditional courtyard's climatic characteristics, exacerbating its heat stress. The largest dip in PET in the courtyard area occurred at 17:00, with a drop of 13.6 °C, which was smaller than the rest of the areas. The additional sustainable prototype had a significant impact on influencing the microclimate and played a decisive role in determining thermal comfort. The prototype's high- albedo materials and dense, selective local trees have a direct effect on reducing the local air temperature and MRT. This, together with the physical characteristics of the surrounding area, helped to minimize PET outcomes and improve the local thermal environment. The findings of this study serve urban designers by verifying the success of the modelled design prototype spatially and environmentally.