The open spaces of cities have become hostile to citizens due to the high temperatures. Lack of thermal comfort hampers outdoor activities. It is imperative to combat these phenomena to bring life back to the streets and make spaces frequently used in the past more appealing to local citizens. The aim is to mitigate the severity of the outdoor climate to reach comfortable conditions in open spaces. For that, microclimate control based on natural cooling techniques is proposed to recover the habitability of these spaces of the cities. These techniques are characterised via experiments. Demostrando como es posible conseguir and integrated using simulation tools. Following this methodology, it is possible to design, size and define operation strategies for the ideal climate control system according to the type of need. This paper addresses a degraded and unused real space as a case study to demonstrate the feasibility of the methodology used. A system has been designed that stores water cooled at night by using the sky and night air and uses it during the day to produce cold air and cool cover. The experimental results test the efficiency of each solution that has been integrated into the complete system. The system operates every technology to keep the temperature radiant and the air of the occupants cool. For it, falling-film technology cools every night a volume of water below 18 °C and dissipation in a water pond by water sprinkler maintains a pond 10–15 °C below the outside air temperature. Also, results test how it is possible to guarantee thermal comfort conditions (operative temperature below of 28 °C) even when the environment surrounding the conditioned volume is at temperatures above 40 °C, and how the seismic allows maintaining these conditions during the worst summer hours. In conclusion, microclimate control allows for mitigating the severity of the outdoor climate to reach a degree of thermal comfort equivalent to that in enclosed venues.

Sanitary issues, combined with the effects of climate change, emphasize the comfort of outdoor spaces in cities. Numerous comfort models exist and can predict thermal sensation. However, these comfort indices need to be validated in hot zones and quantify the neutral range considering people’s thermal resilience. The present study investigates the outdoor thermal comfort of people who live in hot areas and are accustomed to this and quantifies this effect. For that, predictions provided by the COMFA thermal comfort model were compared with the occupants’ perceptions given in the field campaigns’ questionnaires. The field campaigns were associated with on-site monitoring of local climate variables. It was observed that during the survey period, the entire space was predicted to be uncomfortable by the COMFA model. On the contrary, the results of the questionnaires showed that the most frequently encountered thermal sensations were distributed between the comfort zone and the hot zone. The proposed methodology has been designed to be used by other researchers, and it is adaptable to other outdoor thermal comforts such as PET or ITS. The comparison between the model’s predictions and the users’ responses to space highlighted the tendency of the COMFA to overestimate the thermal sensations. This work’s results allow extending the neutral comfort band from 50 W/m² (value of literature) to 80 W/m². So, the paper quantifies that the effect of the thermal resilience of the people increases the thermal band of comfort by around 60%. These results will allow an accurate assessment of the effectiveness of future mitigation solutions implemented to improve outdoor thermal comfort in other world areas. It is due to the propose of a higher neutrality range researchers or designers could achieve outdoor thermal comfort in effective and reliable ways, even in hot climates.

Natural ventilation in hot climates represents a key strategy to reduce the dependence on mechanical cooling systems, especially in historic buildings, where it is essential to balance thermal comfort and heritage conservation. This study analyses the effectiveness of various natural ventilation strategies in a historic building located in Écija, Seville, which is characterised by a warm climate with nocturnal thermal dips. Experimental data obtained during a summer monitoring campaign were used to validate computational fluid dynamics (CFD) models and thermal simulations. In addition, an efficiency index was defined to quantify the indoor temperature reduction. The results show a cooling efficiency close to 40%, achieving an average reduction of 3 °C in the indoor temperature during the summer. Simulations of different modes of operation of natural ventilation show a 30% improvement in comfort hours according to Spanish regulations and a 50% reduction in the thermal difference during non-comfort hours. This work demonstrates that natural ventilation can significantly improve indoor conditions, offering a sustainable and replicable approach for historic buildings in hot climates.