## 5 Conclusions  
Improving indoor conditions in historic buildings requires specialised approaches that preserve their architectural and heritage value while optimising the thermal comfort of the occupants. In this context, the present study analysed the impact of night time cross-ventilation as a passive cooling strategy in a historic building in Ecija, Seville, a region characterised by a warm climate. The methodology involved the use of computational fluid dynamics (CFD) models and thermal simulations, calibrated against experimental data obtained from a monitoring campaign carried out over three summer months. The CFD simulations characterised the air flows entering the building, providing detailed information on flow rates and circulation patterns as a function of external wind speeds. Furthermore, a thermal efficiency parameter (\(\varepsilon\)) is defined which serves to quantify the impact of night ventilation on the reduction in indoor temperature. These data were incorporated into thermal simulations for the purpose of analysing the impact of airflow on indoor temperature. The combination of both simulations, validated with experimental data, permitted a comprehensive analysis of the indoor environment. Once the models had been validated, an analysis was conducted of the impact of different modes of natural ventilation operation. The findings indicated that night time cross-ventilation has the potential to reduce the indoor temperature by an average of 3.8 \({}^{\circ}\)C during the summer months, with maximum reductions reaching up to 6 \({}^{\circ}\)C under optimal conditions. The 40% reduction in temperature indicates that approximately 40% of the external air entering the building effectively contributes to the reduction in indoor temperature. It is crucial to acknowledge the influence of ventilation on temperature reduction, not only during designated ventilation nights but also during subsequent nights. It has been demonstrated that, as a consequence of the high thermal mass of the historic building, the indoor temperature remains lower than it would have been in the absence of natural cross-ventilation for up to 10 days. Conversely, the validated simulation models permit the analysis of a variety of scenarios concerning the impact of thermal comfort on the occupants. A notable enhancement in thermal comfort is evident across all typologies. Nevertheless, the most efficacious intervention is night ventilation, which is conducted on 66% of the nights of the month. A reduction of 14% in the number of hours spent outside the comfort temperature is achieved, with an average reduction of 20% in the temperature difference to the comfort temperature in those periods when the comfort temperature is not reached. From a regulatory standpoint, when the comfort temperature of 27 \({}^{\circ}\)C, as stipulated by Spanish regulations, is taken into consideration, it can be observed that an average of 30% of the summer hours fell within the comfort range. These findings indicate the potential for amendments to the normative references to enhance the perception of thermal comfort in hot climates, particularly when coupled with passive strategies. In conclusion, the findings of this study demonstrate that night time cross-ventilation represents an effective and sustainable solution to enhance thermal comfort in historic buildings situated in hot climates. The implementation of this solution not only reduces the reliance on mechanical systems but also respects the heritage and architectural values of these buildings. In future work, the impact of combining these measures with conventional systems on energy consumption will be evaluated, as well as their effectiveness in other seasons of the year. The methodology presented, based on the integration of experimental analysis and numerical simulations, can be replicated in other building typologies and seasons as well as in other climate typologies and regions throughout the world.