Urban heat relief through sustainable design: Assessing outdoor thermal comfort in courtyards of multifamily housing in Dar es Salaam, Tanzania

Abstract This study examines the impact of vegetation strategies and courtyard geometry on outdoor thermal comfort in warm-humid climates. The research focuses on the Magomeni Kota housing blocks in Dar es Salaam, Tanzania, where population growth is outpacing housing development, and informal settlements are intensifying urban heat island (UHI) effects. The study used ENVI-met to simulate 30 simulation scenarios to investigate the outdoor thermal comfort of the courtyard, as well as testing the interventions to improve the outdoor thermal comfort. The scenarios were categorized into three main major groups, which are examining the existing situation, altering the building heights, adjusting the building heights and ratio while maintaining the optimal coverage of the building block, and adding vegetation for the selected building height. Results indicate the increasing tree coverage is an effective strategy for reducing courtyard heat stress, lowering physiological equivalent temperature (PET) by up to 18.98 °C (for a baseline) and 22.19 °C (for a 52 m building height) during peak daytime hours. Additionally, increasing building height up from 24 m to 52 m would help to reduce MRT and PET, even though this impact can easily be attained by adding trees even for the baseline. These findings highlight and demonstrate that ENVI-met can serve as a proactive design tool to inform and assist in decision-making regarding outdoor thermal comfort when upgrading thermal comfort for housing strategies.