## 1 Introduction  
The building sector accounts for about 40% of the global energy consumption [1]. In China, the energy consumption in buildings accounted for 27.6% of total national energy consumption in 1999, increasing to 45.5% by 2020 [2, 3]. This proportion means there is high energy-saving potential in buildings. A building envelope has the function of regulating and controlling the use of energy because it is on the boundary between indoor and outdoor environments; therefore, the improvement of its performance has attracted attention all over the world [4, 5, 6]. Related research has mainly focused on the following problems: (1) the development of building materials with excellent thermal performance; (2) the integration of the building envelope with renewable energy; and (3) numerical and experimental investigations into the thermal performance of building envelopes. Moreover, with rapid economic growth, the strategies adapted to regional climate and environment are more cost-effective for improving building performance in reducing energy consumption and reducing the associated CO\({}_{2}\) emissions [7, 8, 9]. Many research efforts took more into account climate characteristics when improving the thermal performance of building envelopes and verified their effectiveness in reducing energy consumption [10, 11, 12]. And the heating and cooling requirements of passive buildings varied considerably in different climate regions [13]. Rock is the most convenient and abundant material in mountainous regions. In terms of thermal comfort, traditional single-layer rock envelope cannot meet human demand with HVAC system; with regard to safety, it is prone to collapse owing to non-uniformity. Due to rock's good ecological expression and architectural value, gabion architecture was first introduced by designers to further overcome shortcoming of traditional rock envelope [14]. [PERSON] et al. [15] compared the thermal performance of traditional buildings and gabion buildings through dynamic simulation. They found that gabion buildings had better thermal performance in temperate climates. However, the mountainous climate is a special local microclimate with poor weather, characterized by high variations in wind speed and temperature [16]. [PERSON] et al. [14] analyzed case studies of massive single-layer stone masonry building solutions and found that, in terms of thermal energy performance, these solutions are appropriate for historical centers, maintaining urban cultural identity while ensuring energy efficiency and user comfort. [PERSON] et al. [17] compared the thermal performance of rubble, rammed earth, gabion, and traditional cement walls. The results indicated that gabions demonstrated the best thermal delay performance, with the most stable wall heat transfer, and the least fluctuation in inner wall temperature due to changes in outer wall temperature. Interestingly, gabion buildings were also found in the Yanqing area with typical mountainous climate in Beijing, and they also achieved excellent comfort in winter. These buildings have broken people's common sense. Thus, it is valuable to quantify the adaptivity and validness of a gabion envelope for low-energy and low-carbon buildings in the mountainous region. Thermal performance is the main approach to evaluating building envelopes. As one of the important thermal properties of the building envelope, the exterior convective heat transfer coefficient (CHTC) is a vital indicator in evaluating the thermal performance of building envelopes [18]. Besides experiments, the numerical approach is used to simulate the heat transfer between the building facades and external environments and analyze the effects of different parameters on CHTC by obtaining detailed velocity and temperature field information [19; 20; 21]. [PERSON] et al. [22] applied multiple exterior CHTC models to simulate the energy demand of buildings with different geometry in EnergyPlus software.