Urban microclimate analysis: residential block morphology impact on outdoor thermal comfort

In many cities, protracted exposure of urban structures to excessive solar radiation and the urban heat island (UHI) phenomenon may cause thermal discomfort for pedestrians in outdoor spaces, particularly in hot-arid regions. This study investigated the impact of urban residential block morphology on microclimate in Isfahan, Iran, using ENVI-met numerical models. The predicted mean vote (PMV) model for residential outdoor spaces was calculated using simulation data for the hottest day of the summer to assess outdoor thermal comfort. Comparison of the alternatives – namely, diagonal blocks, compact linear blocks, continuous curved blocks and dispersed cubic blocks – showed that the microclimate performance of the diagonal type was better than those of the other design options, as the PMV index represented the minimum distance from the ideal thermal comfort range due to a lower sky view factor (SVF) and optimal orientation. The curved blocks performed better in urban open spaces, promoting airflow and reducing UHI, than linear and cubic blocks. The results showed that the PMV index could predict thermal comfort in various urban design patterns and could be affected by the morphology of urban blocks. Variations in building morphology alter the SVF and microclimate parameters, which have an impact on outdoor thermal comfort.