Assessing the Impact of Urban Area Size on Thermal Comfort in Compact Urban Fabrics Considering the Saharan City of Ghardaïa, Algeria

Improving microclimate conditions is a pivotal aspect of urban design, particularly in hot, arid climates, where it directly influences outdoor comfort, mitigates the urban heat island (UHI) effect, and reduces the indoor cooling energy demand. The objective of this study is to quantitatively assess the impacts of neighborhoods’ urban size when combined with compact streets’ geometry regarding the outdoor thermal comfort generated in a typical vernacular settlement of the Saharan region of Algeria. The Ksar of Al-Atteuf in the city of Ghardaïa is taken as a case study. The related interior thermal conditions of buildings assumed to be potentially affected by the urban morphology are also examined. To study the effectiveness of the two urban morphology parameters (i.e., urban size and compactness) on outdoor and indoor thermal conditions, a mixed methods approach was adopted, integrating in situ climatic measurements and dynamic simulations. Indoor temperatures were examined in a traditional house located in the core of the Ksar. Year-round operative temperature (OT) simulations were achieved using the Ladybug tool within Grasshopper, and they were complemented by the Universal Thermal Climate Index (UTCI) values calculated during peak hot and cold weeks. Furthermore, a parametric analysis was conducted, focusing on the thermal performance of the compact urban fabric by varying progressively the neighborhood sizes from 20 m, 40 m, and 60 m. The results indicate stable indoor thermal conditions across the monitored residential building, which suggests that the architectural envelope is closely affected by its immediate surroundings. On the other hand, the UTCI analysis revealed significant differences in outdoor thermal comfort since the larger urban area provides better mitigation of heat stress in summer and cold stress in winter, the improved outdoor thermal conditions generated at the neighborhood level, being proportional to the size of the urban area. The findings underscore the value of compact urban fabrics in creating climate-responsive built environments and provide further insights into sustainable urban planning and energy-efficient design practices in hot, arid regions.