## 1 Introduction  
Since 2002, European Directives have progressively set out requirements to enhance the energy performance of building stock, culminating in 2024 with the Energy Performance of Buildings recast [1, 2]. This latest update underscores the ambition for a zero-emission building stock by 2050, accentuating energy efficiency and the reduction in greenhouse gases. It stipulates new minimum standards, integrating life-cycle emissions assessments, solar energy utilization, and formulating comprehensive national renovation strategies, marking a significant step forward in sustainable building practices. The complexities in building performance design analyses necessitate numerical simulations, which offer practical and reliable means for enhancing design, energy efficiency, and comfort. At the same time, the proliferation of more rigorous building performance codes and standards [2] acts as a key catalyst for increasing reliance on computer simulation tools. These tools are essential for verifying compliance with building performance benchmarks, reflecting a shift towards more advanced evaluation methods in the construction and design industries [3, 4]. The push towards achieving high-performance energy-efficient buildings (i.e., nearly Zero-Energy Buildings, Zero-Emission Buildings, net Zero-Energy Buildings, and others) [1, 2] necessitates the expanded use of simulation tools in building design, construction, and operation. Concurrently, there is growing scrutiny of the accuracy of building simulation models and predictions, highlighting the importance of trust in the reliability of these simulation techniques, encompassing both the mathematical models and the input parameters used [3, 5]. In terms of establishing the thermal performance of the building envelope components, previous studies, such as the one conducted by [PERSON] et al. [6], have underscored the need to assess the surface heat transfer coefficient under various conditions to enhance our understanding of wall thermal performance. In their research, [PERSON] et al. utilized laboratory measurements to assess the thermal transmittance of walls, employing both the Heat Flow Meter (HFM) method, as outlined in ISO 9869-1 [7], and the Air-Surface Temperature Ratio (ASTR) method. The findings of their research highlight the importance of further investigating the surface heat transfer coefficient under various conditions to understand global wall thermal performance more accurately. On the same note, the investigation performed by [PERSON] et al. [8] on the constant value of the total internal heat transfer coefficient revealed that the actual values obtained in their experimental campaign differed significantly from the value suggested by the standard ISO 6946 [9]. The percentage differences ranged from about 40% to around 143%. This indicates that the constant value recommended by ISO 6946 may not accurately represent the heat transfer mechanisms of walls in different environmental conditions and with different surface finishes. The study also found that the total heat transfer coefficient varied with height, suggesting that the convective part is not constant. Another interesting related study was performed by [PERSON] et al. [10]. They evaluated the influence of environmental boundary conditions (temperature and air velocity) on the surface thermal resistance of walls under controlled lab conditions, making use of experimental measurements through a Guarded Hot Box (GHB). They found lower experimental convective coefficients in comparison to the conventional values suggested by ISO 6946 [9]. The differences between the measured convective heat transfer coefficient (\(h_{c}\)) and the constant conventional value provided by ISO 6946 (\(2.5\) W/m\({}^{2}\cdot\)K) ranged between \(-46.8\%\) and \(-32.4\%\). They also concluded that in real environments, the radiative and convective heat transfers could lead to even greater deviations; therefore, this issue needs to be further investigated.