## 4 Discussion  
The experimental campaign was performed in the period from July to September when the temperatures in the site were higher. The maximum recorded outdoor temperature was 39 \({}^{\circ}\)C, with an average of 27.7 \({}^{\circ}\)C. The maximum recorded temperature measured inside the building was 34 \({}^{\circ}\)C on the northwest-facing wall, and the average indoor temperature measured at the center of the building was 28 \({}^{\circ}\)C. The maximum solar radiation power was 928 W/m\({}^{2}\) and the average daily value was 573.6 W/m\({}^{2}\). For the relative humidity, its outdoor peak was 91% RH, measured during a rainy day, and the average was 58% RH. Inside the building, the maximum value was 71% RH, with an average of 58%RH. Considering the need to maintain the air temperature around the transformer at a maximum of 40 \({}^{\circ}\)C, it is necessary to install a forced ventilation system to mitigate the rise in temperature due to the power produced inside the environment. Therefore, in this study, two different layouts are proposed (open and con-fined transformer enclosures) and a total of five simulations were performed at different mass flow rates, as shown in Table 7. To avoid overtreatment, only the maximum and minimum possible air-flow rates are discussed (1100 and 2200 m\({}^{3}\)/h); the others are available in the ESM document. The boundary conditions used were obtained from the measurement campaign data, considering an inlet air with a temperature of 36.7 \({}^{\circ}\)C and a humidity of 48.7%RH. The open layout, with the transformer enclosure placed inside the building and cooled by air with an extraction fan system, shows bad performances in terms of temperature and humidity inside the building. The humidity notability decreases and the temperature rises compared to the external air temperature. This would lead to water rising from the walls, which can cause saline formations. At the same time, when the humidity is high and the temperature is lower, water can condense, allowing molds and fungi to grow. Therefore, this layout is not suitable for a historical building. Higher temperatures are reached on the ceiling when the temperature reaches ~46 \({}^{\circ}\)C and the humidity reaches ~37% RH when the air flow rate is 1100 m\({}^{3}\)/h. These conditions are far from optimal, resulting in temperatures that are too high and possible damage to the plasters and the transformer itself. At a flow rate of 2200 m\({}^{3}\)/h, the maximum indoor temperature is ~36 \({}^{\circ}\)C, but there is a humidity value of ~27%RH. Considering that the humidity of the inlet air is 48.78% RH, this results in a very high variation that can lead to the capillary rise of water on plasters and the consequent formation of saline formations. At the same time, when humidity is high and the temperature is lower, water can condense, allowing mold and fungal growth. Therefore, this layout is not suitable for a historical building. The second layout considers installing the transformer enclosure inside a paneled enclosure to physically separate the power transformer from the building interior. In this case, the cooling air is extracted from the enclosure by the same ventilation system as the open layout. Analyzing the results, this layout showed rather good performance, both in insulating the transformer enclosure interior from the building environment and in maintaining the temperatures inside the operative range. At the maximum flow rate, the transformer enclosure operates under 39 \({}^{\circ}\)C, and at minimum flow, the transformer enclosure's average temperature is 41 \({}^{\circ}\)C, slightly over the required 40 \({}^{\circ}\)C. Both cases allow for the preservation of the building, maintaining microclimatic indoor conditions at the same level as the external temperatures and humidities. Therefore, this layout is optimal for the preservation of the building because it does not alter the indoor environment and maintains the same environmental conditions as the outdoor environment [37].