## 2 Materials and Methods
### Description of Case Study  
In order to analyse the effect of cross-ventilation in historic buildings, an old house located in Ecija (Seville), southern Spain, is used as a case study (Figure 2). Figure 1: Methodology for intervention. The house was constructed at the end of the nineteenth century, and therefore, its architectural style reflects the prevailing local trends of the period. In order to enhance the internal environment, thick walls were employed, thereby reducing the flow of heat from the exterior during the daytime and the loss to the exterior during the night time in periods of elevated temperatures. The construction of the walls is of considerable thickness, measuring 60 cm, which markedly increases their mass in comparison to contemporary construction. The construction of the wall follows the mud wall technique, whereby the majority of the wall is constructed from rammed earth with cement facing [34]. This technique was widely utilised for the construction of houses in the southern part of Spain [35]. Consequently, the building exhibiting a high thermal inertia, thereby enhancing its passive cooling potential through thermal storage within the walls. Conversely, the building features a central stone courtyard of 22 m\({}^{2}\), surrounded by arcades. The historic structure encompasses two floors, all of which are connected to the courtyard through extensive windows. In consideration of the geographical location of the structure in question, the climate designation according to the Koppen-Geiger classification is Csa [36]. The prevailing climatic conditions are characterised by high summer temperatures and low precipitation, with mild winters. More specifically, Figure 3 illustrates the mean daily and hourly temperatures for Ecija during the summer of 2023. The period under discussion extends from June to September, months which are customarily regarded as summer in southern Spain on account of the high temperatures they typically experience. The data were obtained from an existing weather station located in a rural area in close proximity to the building under study. This station belonging to the national network of climate stations is maintained by the Spanish Government [37]. The aforementioned stations are situated in the peripheries of urban areas; thus, the data obtained represent rural climate conditions. In order to accurately assess the impact of urbanisation on temperature, it is necessary to consider the urban heat island effect. It is noteworthy that daytime temperatures exceed 35 \({}^{\circ}\)C, with readings reaching 40 \({}^{\circ}\)C on the majority of days. However, temperatures decrease significantly during the night, with readings dropping to around 20 \({}^{\circ}\)C, or even lower. These observations highlight the potential for energy savings through the utilisation of external air flows in cooling systems, taking advantage of the low temperatures occurring at night. Figure 2: Situation of the ancient building study. In addition, the study of wind is of particular interest. The wind speed and direction values for the summer of 2023 were obtained from the same database. These data are presented in Figure 4, which illustrates the wind rise for the summer of 2023. It can be observed that the predominant wind direction ranges from the southwest to the west. The wind speeds are predominantly below 10 km/h, which equates to 2.8 m/s. A further analysis of the data indicates that wind speeds during the day vary between a minimum of 1 km/h and a maximum of 15 km/h, with an average speed of 7 km/h. During the night, wind speeds are somewhat lower, with minimum values of less than 1 km/h, which is classified as calm, maximums of 12 km/h and an average speed of 5.4 km/h.