Traditional Architectural Heritage Conservation and Green Renovation with Eco Materials: Design Strategy and Field Practice in Cultural Tibetan Town

Abstract

With the rapid advancement of rural revitalization in China, protecting regional culture and construction techniques of traditional ethnic groups, while incorporating green energy-saving concepts, has become increasingly vital. With Sware ITES2023 as the simulation tool, this article conducts a comparative study on the green building technology and thermal comfort of traditional Tibetan residential houses in Songpan, Sichuan Province, and the new residential houses that villagers have incessantly renovated and built in the past two decades, thus demonstrating the advantages and disadvantages of traditional houses and newly-built houses in terms of green building technology elements, such as stone and wood structures, roof floors, walls, doors, and windows, therefore developing an optimized design scheme, which includes the eastern direction of a building’s orientation, concrete frame and wooden structure, brick wall and stone masonry, and optimized door and window size selection. This scheme will improve indoor thermal comfort by two to three times by calculation. Through preliminary simulation and deduction, the optimized design scheme combines traditional architectural culture and ethnic characteristics with green and energy-saving concepts. This provides a design paradigm that can be promoted and popularized for the construction of residential buildings in high-altitude ethnic areas of western Sichuan and also lays the foundation for future protection and research of traditional residential architecture.

1. Introduction

With the rapid development of large-scale urbanization and industrialization in China, the contradiction between protecting cultural traditions and embracing modern ways of life has aroused new attention to green building and sustainable development strategies. Technological innovation and economic development inevitably widen the gap between the traditional rural lifestyle and modern urban lifestyle. In Tibetan areas of western China, the environment of traditional buildings is being submerged by new buildings, and modern building technologies and materials are rapidly flooding in, which has made the construction techniques and eco-friendly wisdom of Tibetan traditional buildings difficult to inherit and develop, and the ethnic characteristics and regional culture of buildings are gradually eroded. This article studies the residential buildings in a traditional Tibetan settlement in western China (Songpan County, Aba Prefecture, Sichuan Province), explores the basic architectural form, functional characteristics, structural composition, and construction nodes of the local Tibetan traditional residential buildings in this area, extracts the traditional green building technology elements contained in them, and proposes suggestions for reference in contemporary architectural design, so that Tibetan traditional residential buildings can meet the requirements of modern living quality while having cultural identity and green energy-saving characteristics. This is of practical significance for the protection of traditional architectural culture and sustainable development in developing countries.

In the exploration of the relationship between architecture and culture, it is essential to recognize the issues and challenges faced by historically and culturally significant towns and villages in China during their conservation and development processes [1]. Understanding the historical significance, function, and urban morphology of a region is crucial for the revitalization of historical towns inhabited by ethnic groups [2], especially regarding the connection between architecture and culture. Architects are obliged to consider the cultural features of architecture and combine them with vernacular architecture to restore hidden features in architecture; at the same time, they must remember the indefinable role of culture in establishing connections between people and architecture [3]. Culture has a great influence on residential buildings, and the researchers analyze the influence of physical and social factors on residential buildings by focusing on rural residences. From the physical and social factors, the construction process of local dwellings from scale to location is investigated [4]. Culture has profoundly influenced the construction, function, form, and decoration of Kham Tibetan dwellings and overall vernacular architecture in Sichuan. Through case study, it is observed that the style and color of traditional Tibetan architecture are based on its unique geographical environment, climate characteristics, religious beliefs, and ethnic customs, with strong plateau characteristics. Some researchers even studied the color palette of Tibetan traditional dwellings, palace, temple architecture and its relationship with their cultural beliefs, in order to have a deeper understanding of the Tibetan traditional architecture [5].

In terms of planning, a multi-faceted approach is crucial. For the sustainable development of traditional villages, new perspectives on land use planning and architectural design can be provided based on cultural heritage conservation [6], and strategies for the tourism development of ethnic traditional villages can be adjusted accordingly [7]. Some researchers have proposed that the smart countryside concept helps to promote the sustainable development of rural areas, and have stressed that special emphasis should be placed on strengthening the relationship between rural communes and neighboring cities and towns [8].

In terms of structural materials, summarizing the traditional residential patterns of Tibetan residents can provide a basis for integrating renewable energy technologies into Tibetan residential architecture [9]. The application of advanced disaster-resistant construction technologies and materials can enhance the safety and stability of traditional buildings [10], while highlighting regional characteristics [11]. Yang et al. discussed the primary mechanical properties of old Tibetan poplar, new Tibetan poplar, and new Tibetan pine, and the variations in wood strength over time [12], emphasizing the urgent need to protect and renovate old Tibetan buildings. This study underscores the necessity of modernizing traditional building materials and structures, which can help improve the durability and functionality of traditional Tibetan architecture. Some researchers have analyzed the damp and heat properties of rammed earth walls in Tibetan buildings and established and verified the properties of rammed earth walls [13]. Some researchers have carried out reliability analysis on the prediction of residual strength and service life of wood components in Tibetan buildings and put forward two failure criteria to predict the service life of wood components based on the ultimate strength bearing capacity and allowable deformation [14]. Other researchers have highlighted the effects of thermophysical parameters such as phase change temperature, phase change plate temperature, thickness, and position in composite walls on the indoor thermal environment of Tibetan buildings [15].

As for the decorative art of Tibetan architecture, in order to have a deeper understanding of the connotation of religious culture, the researchers conducted a detailed study of the construction, materials, religious functions, and symbolic significance of religious architecture [16]. Some researchers have also gone deep into the decorative patterns of religious buildings [17], categorizing the themes and layouts of Tibetan architectural paintings and analyzing their artistic features [18]. For example, Hou et al. provided a quantitative research method for the protection of traditional village architecture, objectively defining the irregularity index range of wall textures in Xisu Village and analyzing the variation patterns and influencing factors of stone building wall textures. This study not only offers technologies and methods for preserving and inheriting the cultural textures of traditional buildings but also provides scientific evidence for protecting and promoting the unique charm of traditional Tibetan architecture [19].

The indoor environment is crucial for the residential comfort of traditional buildings. To enhance the potential for indoor thermal comfort, it is necessary to conduct field investigations of the indoor environment from the perspective of the building’s physical environment [20,21]. Subsequently, a series of energy-efficient building renovations can be optimized to reduce energy consumption and improve the indoor thermal comfort of Tibetan residences [22]. The study of outdoor factors is also indispensable, requiring an analysis of the building form and its unique environmental characteristics [23]. In the evolution of natural and building materials, architecture exhibits bottom-up adaptability [24]. The interactions between geographical and meteorological elements are significant [25], and in the harsh climate, traditional passive design must address major issues like cold protection, solar radiation, and heat storage to regulate day–night temperatures [26]. In such contexts, green design approaches are a wise solution [27]. Some researchers have studied the green, ventilated exterior walls that can effectively save energy in buildings and conclude that they can effectively improve living conditions and help mitigate climate change [28]. Other researchers use green roof technology for the sustainable green renovation of buildings [29]. Other researchers have integrated passive design strategies into the economic and environmental benefits of the building and have proposed that energy-saving is particularly important for the passive transformation of the building [30]. Some researchers have also studied the thermal comfort of rural buildings in cold climates by investigating the adaptability of residents, providing valuable references [31].

Determining how to efficiently improve indoor thermal comfort has become the key to sustainable transformation of traditional buildings. Current researchers focused mainly on active and passive modification measures to improve indoor comfort and reduce energy waste [32]; however, it is often difficult to afford the operation of active equipment and multi-purpose passive transformation strategies in this region due to its harsh environment and limited budget. Researchers have found that traditional houses in summer are characterized by high humidity and low temperature, and the indoor environment in winter is much worse, so it is necessary to improve the indoor comfort of Tibetan houses [22]. Some researchers in China have analyzed and tested the indoor thermal environment of Tibetan dwellings with different materials and pointed out the current status and characteristics of the indoor temperature change of Tibetan dwellings with different materials [20]. Through the theoretical analysis of the architectural form, structure, and materials, some researchers observed that the thermal characteristics of Tibetan vernacular architecture corresponds closely to the local climate conditions and put forward suggestions for architectural improvement [33].

With the aid of computer modeling and statistical analysis, the gradual disappearance of vernacular architectural traditions is recorded, and the historical evolution of housing functional organization is analyzed. This exploration aims to provide recommendations for contemporary architects [34] and support data for policies on architectural heritage, technical interventions, and targeted field surveys [35]. Huang et al. established a two-dimensional (2D) nonlinear finite element model of a soil–civil defense structure interaction system. This model provides a relevant reference for the seismic performance assessment, risk analysis, and seismic resilience evaluation of typical civil defense structures in soft soil areas [36]. Aliakba et al. developed a simplified holistic sustainability decision support framework applicable to existing building refurbishments [37]. Sun et al. employed low-cost unmanned aerial vehicles (UAVs) and Structure from Motion (SfM) algorithms for surveying Tibetan architectural heritage [38]. Liu et al. proposed dynamic TRNSYS simulations for quantitative performance assessment of low-energy buildings through practical applications of comprehensive heating systems on the Qinghai-Tibet Plateau [39]. Lu et al. utilized software such as Ecotect 2011, Grasshopper 2.0, Phoenics 2019, and TRNSYS 18 to numerically simulate models of Tibetan traditional dwellings, suggesting overall energy consumption is lower than modern building technologies and materials [40]. Applications of vernacular architecture in ecological aspects such as natural resources, solar energy utilization, and climate response in modern contexts [41] promote the integration of ecological wisdom with architectural science and technology [42].

Although many researchers have studied the sustainable improvement of traditional Tibetan dwellings, they often focus on the status quo of individual buildings and neglect the historical and cultural aspects of the architecture. Some researchers prioritize sustainable building renovation but overlook the overall architectural context. While their renovation methods meet green building requirements, they do not consider the unique requirements and usage scenarios of the buildings before the renovation, such as whether the random reconstruction by the local residents is reasonable or why local dwellings exhibit chaotic reconstruction patterns. These reconstructions often better meet the residents’ living needs. Therefore, sustainable renovation that meets both living needs and architectural context is an effective strategy.

Currently, few researchers use model simulation and data comparison to assess the rationality of spontaneous housing reconstructions. A scientific approach is to seek the best renovation strategy through multiple model simulations and energy consumption comparisons, combined with local cultural customs and usage habits. This study presents a method of model simulation and data comparison to directly show the necessity and feasibility of sustainable architectural renovation. It establishes a research route that spans from the evaluation of traditional dwellings and current reconstruction chaos to the verification of design optimization models. This provides a complete research idea and framework for the renovation and new construction of Tibetan dwellings in western Sichuan.

This study employs the indoor thermal comfort simulation software (Sware ITES2023) to calculate models of traditional dwellings, new buildings, and enhancement renovation plans. The results demonstrate a sustainable development model that reduces energy consumption, improves indoor thermal comfort, and preserves the architectural heritage of the region.

2. Conception and Methodology

2.1. Characteristics and Application of Traditional Tibetan Building Foundation Materials

The original Tibetan ancestors living in the Qinghai-Tibet Plateau in China used various stones distributed on the plateau as their building materials. They built stone walls in front of the caves, filled the gaps between the wall stones with fine stones and clay, applied a mixture of grass and mud for reinforcement, floored and rammed fine loess, small stones, and fine soil on the ground, covered it with small branches, and finally applied a floor of grass and red soil mixture on the small branches and the inner walls of the caves, and baked it to form a hard moisture-proof and thermal insulation floor.

This simple and environmentally friendly concept of building energy conservation is still applied in the construction of traditional Tibetan buildings today. Tibetan people use their wisdom to choose the most suitable construction method—mud-bonded timber frame walls. Wood is used as the building frame, and rubble stones are used to build the walls. Natural-colored soil is rolled, sieved, and filtered, and then mixed with water and a certain amount of adhesive material to be directly applied to the exterior walls. The floors and roofs of the buildings are compacted and flattened with mud and fine branches. In the harsh natural environment of the plateau, these primitive and simple construction wisdoms have ensured that Tibetan people of all ages have obtained basic living conditions in the simplest and most economical way.

Songpan County in Sichuan Province, southwest China, is located in the high-altitude underdeveloped area in the northeast of Aba Tibetan and Qiang Autonomous Prefecture, upstream of the Minjiang River, and is a border area between Sichuan, Gansu, and Qinghai, more than 300 km away from Chengdu, serving as a regional gateway in the northwest of Sichuan. Songpan is also an important transportation node for the “Jiuzhai and Huanglong Scenic Area” and a military stronghold for ancient wars. According to historical records, since the era of Cancong from the ancient Kingdom of Shu, Songpan has been the economic, military, and cultural center of the region, having repeatedly experienced the rule of different ethnic groups such as Diqiang, Mongolia, and Tubo for over 2000 years. The multi-ethnic culture of the west and the Han culture of the Central Plains have been exchanged and integrated for a long time. During the Qing Dynasty, Songpan became the border area between the Amdo Tibetan and Jiarong Tibetan cultural regions, with Tibetans as the main population, and Han, Hui, and other ethnic groups living there for generations. The relevant information is shown in Figure 1.

The traditional Tibetan dwellings in Songpan are quite different from those in Tibet and Kham Tibetan areas in Sichuan. The forms, techniques, and decorative elements of the dwellings are not completely unified. The closer to the Kham Tibetan area in the western Ganzi Prefecture, the closer the style is to the architectural style of Tibet. The closer to the east, the more Qiang and Han architectural elements there are, exhibiting obvious fusion characteristics. There are the most Tibetan traditional dwellings here, and the most typical architectural form is characterized by features of Ando Tibetan and Jiarong Tibetan dwellings, which, drawing on the architectural form of Han dwellings as the prototype, deploys the architectural techniques of Han dwellings to evolve into a local architectural style called “Bengkong” in Tibetan.

Its typical features are: the walls of the first floor are built with stone, while the upper floors are built with wood, and the roof is a combination of pitched roof and flat roof. The houses are built in a wooden-stone structure, generally with three floors. The ground floor is used for raising livestock, the second floor is the main living space, and the third floor is used for storing forage and other miscellaneous items. Through field surveys, we employed cluster sampling to develop a representative building model, as shown in Figure 2. This building is also used as the subject of our simulation. The houses are built along the mountains, staggered in height, and the architectural form adapts to the local semi-agricultural and semi-pastoral production methods, taking full account of the characteristics of the terrain, emphasizing livability, and allowing modifications and adjustments in terms of function, structure, materials, and construction according to specific conditions.

2.2. Green Construction Methods and Mechanisms of Traditional Dwellings of the Tibetan People in Songpan

The traditional Tibetan dwellings in Songpan embody the green energy-saving wisdom of Tibetan ancestors: livestock are raised on the first floor, which can make full use of the poorly lit space on the first floor and avoid unnecessary lighting; bedrooms and chapels are set up on the second floor, where some farming tools or miscellaneous items are stored in the entrance hall. This space serves as a western heat buffer zone, reducing heat exchange and lowering the indoor temperature caused by western sun exposure in summer, thus ensuring the thermal stability of indoor rooms. The chapel is a necessary space for the Jiarong Tibetan people to carry out religious belief activities. According to the traditional customs of the Jiarong Tibetans, when important religious activities are held in the family, many guests will live there simultaneously, so the area of the guest bedroom is set to be more than 20% larger than the master bedroom, generally reaching 30 square meters. The eaves space under the pitched roof on the third floor is usually used as a bedroom or grain silo, which not only helps to keep the living space on the second floor warm but also ensures enough ventilation for grain storage. The flat roof platform on the second floor is a drying area for drying grain. The related building structure is shown in Figure 3.

• Seismic-resistant structure with a flexible interior and rigid exterior. The structure of traditional Tibetan dwellings in Songpan adopts the load-bearing system of external stone walls and internal wooden beams and columns. This structural form of rigid exterior and flexible interior greatly enhances the overall connectivity and seismic resistance of the building. The stone wall is the vertical load-bearing structure, and the wooden beams supported on the stone wall are the horizontal load-bearing structure. Fine branches or wooden boards are used as the load-bearing support structure of the floor, which are laid as the base plate of the floor. The circular cross-section of the main wooden beams and columns of the building usually has a diameter of 200 mm, and the net height of a single floor is generally 2500–2800 mm. One or more cantilever platforms are commonly set up on the second or third floor of the building. There are no walls on the cantilevered part, and wooden boards or firewood are used for enclosure. Due to the thick stone walls and small bay, the usable area inside the building is much smaller than the floor area. The cantilever structure and semi-open space similar to balconies can increase the usable area and alleviate the problem of insufficient flat land in mountainous areas, as shown in Figure 4.

2.

Masonry wall of rubble stone for cold and earthquake resistance. The exterior walls of traditional Tibetan dwellings in Songpan are very thick, and the bottom of the walls can generally reach 1000 mm, which is sturdy and safe, resistant to attacks, and can also keep cold out and keep warm. The exterior walls of the building form a significant tapering as the height increases, and the thickness decreases to 600 mm at the top of the second and third floors. The significant vertical tapering can reduce the center of gravity and weight of the wall, and the shear force borne by the lower wall during an earthquake is relatively small, making it more stable. On the other hand, as the number of floors increases, the requirements for cold protection and resistance to external invasions also decrease accordingly. Tibetan craftsmen are particularly good at using various stone sizes and shapes to build the wall. With different stones in different places, the texture and color of the walls will vary, and each building and wall surface will have unique textures. This approach retains the rustic beauty of early Tibetan architecture. The wall surface is directly exposed, without pointing or plastering with mud, and without elaborate painting. Elaborate painting would require additional steps such as priming and leveling of the stone wall surface, increasing unnecessary labor costs. Additionally, in the cold, windy, sunny, and dry environment of the plateau, the exterior wall finish is prone to cracking and peeling.

The layout of load-bearing walls generally adopts a north–south horizontal bearing method, which does not affect the lighting of windows facing the main direction. The bottom of the wall has less tapering, while the upper part has more. The width of a single wall can also change according to different functions and load-bearing requirements. Before masonry construction, the location of doors and windows needs to be determined first. Then, stones and yellow mud are used for floored masonry. When the masonry reaches a height of 1500 mm, a horizontal wooden strip is set to level the masonry height while maintaining the integrity of the wall stones. The stones between the inner and outer walls are interlaced, and the four corners are generally partially raised above the wall with larger stones to enhance the strength and rigidity of the corners. Some traditional dwellings also use rammed earth walls. The formwork is first erected, and the earth is rammed once for every 2000 mm increase in masonry height. Branches, wooden strips, and other materials are also added horizontally into the rammed earth floor by floor.

Songpan is rich in timber, and both interior partition walls and decoration are made of wood, mainly using Chinese fir, pine, and cypress. The two sides of the second floor facing the courtyard of the building usually use wooden planks as walls, while the other sides use stone walls or rammed earth walls. There is also a method of using woven willow strips to form the wall surface and then applying mud on the outside, which is locally known as “wooden frame mud wall”. This method can prevent wind and cold, reduce the weight of the wall, and resist fire. The attic or grain storage room on the third floor generally adopts the craft of light and ventilated willow strip walls, which can maintain warmth while providing good air circulation, helping to naturally dry the stored grain, as shown in Figure 5.

3.

Roofing methods combining Han and Tibetan styles. The Songpan area is mountainous and rainy, with heavy rainfall during the rainy season. Tibetan dwellings mostly have double-pitched roofs with eaves extending 300 mm to 400 mm. Drawing inspiration from Han Chinese dwellings, the roofs are paved with small gray tiles, which facilitate drainage and prevent the wooden structures and rammed earth walls under the eaves from getting wet and rotting. Besides the small gray tiles, there is also a wooden plank roofing method. The wooden plank roof is composed of wooden boards overlapping each other. Boards are made of waterproof pine woods, such as Pinus tabuliformis and Pinus koraiensis, and are covered with thin wooden strips and stones. The board surface has small grooves formed by the annual rings, which are laid along the direction of roof drainage, allowing rainwater to drain away quickly along the grain. The intense sunshine in the Songpan area allows the wooden planks to dry quickly after rain, making them durable. The wooden plank roof needs to be manually turned over every 2–3 years to prevent the wooden tiles from decaying, as shown in Figure 6.

Tibetan houses have a tradition of setting up wooden columns in the center of a large room. The wooden beams and rafters are erected on the wooden columns to support the floor and roof. A wooden beam is arranged on the load-bearing wall every one meter, and the rafters are arranged vertically on the wooden beam to support the floor. Fine twigs and wooden boards are laid on the rafters, and then a 50 mm-thick coarse granular yellow mud floor is formed as a waterproof floor for thermal insulation. Wooden braces are set on this floor, wooden floorboards are laid, and gravel is filled under the floor. The construction method of the flat roof is basically the same as the second floor. The 150–200 mm-thick yellow mud floor is laid above a rammed 20 mm-thick floor of fine sand and grass residue. If there is leakage, another floor of yellow mud is paved and compacted on it. The renovation cycle of the floor is once every 1–2 years. The Tibetan houses in Songpan with a long history have undergone many renovations, and the thickness of the yellow mud floor of the roof can reach 500–600 mm, posing a serious safety hazard to the house.

4.

Energy-saving structure of doors and windows. Due to the need for military defense in history, the sizes of doors and windows in traditional Tibetan residential buildings in Songpan are generally small. The window openings are trapezoidal in both plan and elevation, and wood is used to make door and window components. The window opening size is generally about 900 mm high and 600 mm wide. Considering cold protection and insulation, there are generally few windows on the building walls, and windows are concentrated on the west wall of the building. Nowadays, this window style has been passed down as a traditional style. However, with the development of modern construction technology, the window size is gradually increasing, and the decoration style is also becoming more diverse and gorgeous, as shown in Figure 7.

2.3. Calculation of Indoor Comfortable Temperature for Traditional Tibetan Houses in Songpan

Based on the research of the function, structure, and materials of the traditional Tibetan houses in Songpan, this article uses Sware ITES2023 as a tool to calculate the proportion of indoor adaptive thermal comfort temperature compliance for a surveyed Tibetan house. The time proportion value of indoor thermal environment parameters in the adaptive thermal comfort zone of each functional room in the house is solved under the conditions of natural ventilation and combined ventilation. The time proportion of indoor adaptive comfortable temperature = (time when indoor temperature is within the thermal comfort range)/annual operating hours of the building. The meteorological data for Songpan were obtained from the “Special Meteorological Data Set for Building Thermal Environment Analysis in China”. We selected the period from January 1 to December 31, with detailed parameters shown in Figure 8.

The simulation was conducted using the Sware ITES2023 software. The specific steps are as follows: first, a floor plan was drawn in the software based on field survey data, as shown in Figure 9, with wall lines set and a floor height of 3 m. The total building area is 517.71 m², with a temperature-controlled area of 388.66 m² and a non-temperature-controlled area of 126.60 m². Next, the doors and windows were set: the exterior doors are single-layer solid wood doors with a heat transfer coefficient of 1.97 W/m²·K, the interior doors are single-layer wood doors with a heat transfer coefficient of 1.95 W/m²·K, and the windows are single-layer wood windows with a heat transfer coefficient of 4.70 W/m²·K and a shading coefficient of 0.65. The arrangement of doors and windows is shown in Figure 9. The windows used were of two sizes: 900 mm × 600 mm and 1800 mm × 1500 mm. The roof line was drawn to extend 600 mm outward from the external walls. Subsequently, the room search operation and building floor frame operation were performed, dividing the building into three floors and a roof layer, followed by a model check and project setup. The simulation period was set from 1 January to 31 December, with the software’s geographic location set to Songpan, Aba, Sichuan. The building type was set as residential, with a solar radiation absorption coefficient of 0.75. According to the “Green Building Evaluation Standard” GB/T 50378-2019 [43], the average heat transfer coefficient was calculated using the area-weighted average method, and the compass was set. Finally, the project construction settings were made, with the main materials and structures used shown in

Table 1. External wall structure.

Material Name (From Outside to Inside)	Thickness (δ)	Thermal Conductivity (λ)	Heat Storage Coefficient (S)	Coefficient of Correction	Thermal Resistance (R)	Thermal Inert Index
	(mm)	W/(m.K)	W/(m2.K)	α	(m2.K)/W	D = R × S
Rubble	150	2.910	23.348	1.00	0.052	1.204
Grass clay (ρ = 1600)	200	0.760	9.451	1.00	0.263	2.487
Rubble	150	2.910	23.348	1.00	0.052	1.204
The sum of each floor ∑	500	–	–	–	0.366	4.894
Solar radiation absorption coefficient on the outer surface	0.75
Heat transfer coefficient K = 1/(0.18 + ∑R)	1.83

and

Table 2. Roof construction.

Material Name (From Outside to Inside)	Thickness (δ)	Thermal Conductivity (λ)	Heat Storage Coefficient (S)	Coefficient of Correction	Thermal Resistance (R)	Thermal Inert Index
	(mm)	W/(m.K)	W/(m2.K)	α	(m2.K)/W	D = R × S
Concrete tile	20	0.93	10.583	1.00	0.022	0.228
Plank	80	0.058	1.627	1.00	1.379	2.244
Grass clay (ρ = 1600)	120	0.760	9.451	1.00	0.158	1.492
Plank	20	0.058	1.627	1.00	0.345	0.561
The sum of each floor ∑	240	–	–	–	1.904	4.525
Solar radiation absorption coefficient on the outer surface	0.75
Heat transfer coefficient K = 1/(0.18 + ∑R)	0.48

, and the room types and their parameters listed in

Table 3. Room type parameters.

Room Type	Transition Season Fresh Air Volume	Winter Fresh Air Exchange Rate	Summer Fresh Air Exchange Rate	Average Wind Speed	Personnel Density	Lighting Power Density	Electrical Equipment Power
	(Times/h)	(Times/h)	(Times/h)	(m/s)	(m2/Person)	(W/m2)	(W/m2)
Toilet	10	0.5	10	≤0.3	0	6	0
Vacant	10	0.5	10	≤0.3	0	0	0
Living room	10	0.5	10	≤0.3	36.6	2	4.3
Hallway	10	0.5	10	≤0.3	32	6	5

, including main spaces such as bathrooms, empty rooms, living rooms, and corridors.

Based on the above basic settings, subsequent improvements primarily involved simulating and comparing building materials, orientation, and window openings. The current building orientation is westward, with window openings sized at 900 mm × 600 mm. We hypothesized building orientation as the sole variable and conducted indoor thermal environment simulations for four directions: east, south, west, and north. On this basis, we also simulated and compared different window opening sizes by replacing the 900 mm × 600 mm windows with 1800 mm × 1500 mm windows. The indoor thermal environment under different conditions was analyzed and compared, leading to the determination of better improvement measures.

3. Renovation and Evaluation of Modern Tibetan Dwellings in Songpan

In recent decades, tourism in Songpan has experienced rapid growth, and the surge in tourists has placed a greater burden on the once-balanced ecological environment. The local government has encouraged villagers to utilize their homes to accommodate tourists through tourism support projects. To obtain more economic income, some local villagers have rebuilt, expanded, or newly built their own homes. The current situation is shown in Figure 10. With the introduction of modern lifestyles and construction technologies from outside, the lives of Songpan residents have undergone tremendous changes. Contemporary living functions have complicated and standardized living spaces, and the old architectural forms can no longer meet people’s living needs. While inheriting ancient crafts and retaining the simple and environmentally friendly construction concepts, villagers have randomly designed and renovated their homes in terms of functions, structures, materials, and forms. However, these changes have gradually caused a severe disturbance to the traditional architectural vocabulary and the overall look and style of Songpan dwellings. It is urgent to evaluate whether these modern renovation measures are reasonable and will bring about changes in building energy consumption and thermal comfort.

First, we evaluate the impact of modern functional transformation on building energy consumption. In traditional Tibetan dwellings in Songpan, livestock is raised on the ground floor, and the heat emitted by the livestock can effectively isolate the cold air from the ground, supplementing heat for the living space on the second floor. However, in the redesigned Tibetan dwellings by villagers, almost all of the livestock have been moved out of the buildings, and the ground floor has been converted into functions such as kitchens, reception areas, and bedrooms, greatly improving the living and hygiene conditions. With the popularization of tractors in agricultural areas, tractor garages have also appeared on the first floor of the dwellings. In traditional dwellings, heating is not provided on the first floor, while fireplaces are used for daily heating on the second floor and above. However, after the ground floor of modern dwellings is converted into living spaces, the entire house is heated using a combination of stoves and modern heating equipment, further increasing the demand for heating.

In recent years, a large number of Tibetan dwellings in Songpan have begun to add glass sunrooms on the balconies of the second floor. These sunrooms adopt a combination of color steel tile roofs, iron frames, and lead alloy windows, covering the entire second-floor balcony, as shown in Figure 11. The glass material allows excellent lighting and can quickly warm up in winter, resulting in a significant increase in the proportion of indoor adaptive thermal comfort temperature compliance. Some dwellings have also installed color steel tile canopies at the main entrance and set up new-style toilets in a corner of the house. While such additions undoubtedly improve the living environment, they are the artificially dominant results of local Tibetans pursuing a better quality of life and more efficient construction after economic and technological progress. However, they also undoubtedly severely damage the style and architectural beauty of traditional Tibetan dwellings.

Second, we evaluate upgrades of the wall structure and materials. The first-floor walls of traditional Tibetan dwellings in Songpan are built with yellow mud and rubble stones, and some walls can reach three or four stories high. The whole house structure is mainly divided into two systems: stone wall bearing system and wooden structure bearing system. There are wooden columns supporting the beams and frames inside the walls to form a bearing structure. The masonry method of stone walls is to use the upper surface of large stones as a reference plane and fill in gaps with small stones. This masonry method can increase the tensile force between stones and also has a certain resistance to disturbance. However, the multi-floor height of the rubble stone masonry walls, coupled with the high seismic fortification level in the region, poses a risk of falling stones. Modern building materials, such as reinforced concrete frame structure, are utilized to greatly increase the seismic safety factor and insulation efficiency. As for the traditional load-bearing material, stone has been transformed into the main material for facade decoration, and fly ash hollow bricks and red bricks have become the most commonly used filling materials, as shown in Figure 12.

Third, we evaluate the roofing practice. A floor of 80 mm reinforced concrete roof is built on the loess floor to enhance waterproof performance, and grain drying can be more sanitary. The floor structure generally consists of three floors. Wooden purlins, which are relatively thin pieces of wood, are placed on the wooden beams. The second floor is composed of scrap wood and small branches to flatten the surface. The third floor is a raw soil floor, which is leveled with yellow mud and also serves as a thermal insulation and waterproof floor. This kind of structure utilizes local materials, saves energy, and has good ventilation and moisture transmission properties. With the development of the economy, it is also common to lay plastic sheeting under the raw soil floor as a waterproof floor, similar to the inverted roofing practice. Nowadays, it is also common for newly built dwellings to have a cement floor laid on the top of the loess floor for the drying area, which is waterproof, sturdy, and more conducive to the use of the drying area. In recent years, some Tibetans have adopted more convenient and efficient color steel tiles as roofing materials. This is a result of human intervention after technological and economic progress. The extensive use of color steel tiles has damaged the architectural style of local traditional villages; however, it is more conducive to roof drainage and waterproofing and is easier to construct, thus becoming the choice for most newly built houses.

Finally, we evaluate the increasing trend of door and window sizes. Over the past decade, with the rapid development of tourism in Songpan, many villagers have transformed their ground-floor spaces into guesthouses and beautifully decorated main rooms to accommodate tourists. To improve comfort, a large number of dwellings have added more large window openings or floor-to-ceiling glass curtain walls to enclosed rammed earth walls on the ground floor, increasing lighting and pursuing the aesthetic of modern architecture.

This renovation has brought significant changes to the window-to-wall ratio. The doors and windows on the ground floor, which were previously designed for insulation and defense, have become a cultural symbol preserved over the years. Nowadays, villagers have broken the fixed sizes of traditional doors and windows, and the renovated door and window sizes are arbitrarily expanded according to the occupants’ preferences, even adopting entire glass curtain walls. To increase lighting and cater to tourists’ aesthetics, the windows of the wooden rooms on the second floor have also significantly increased, which has brought noticeable changes to indoor air circulation and the indoor air reaching the adaptive thermal comfort temperature standard.

4. Results and Discussion

Through software simulation, it is found that the thermal performance parameter of traditional Tibetan residences has a heat transfer coefficient of 1.83. The time compliance ratio of major functional rooms meeting the thermal comfort range is 3.03%, as shown in Figure 13. The thermal comfort of granaries, livestock rooms, and corridors is relatively good among all rooms, while the thermal comfort of storage rooms, living rooms, and toilets is poor. Especially in areas where people are frequently active, it is difficult to meet the thermal comfort requirements for habitation. These traditional Tibetan residences have significant room for improvement in terms of structural thermal performance and indoor adaptive thermal comfort temperature compliance. As shown in Figure 14, the time during which indoor thermal comfort is achieved is very limited.

According to the analysis and calculation, the heat transfer coefficient of the thermal performance parameter of the external wall envelope structure of the modern Tibetan residential buildings designed and transformed by villagers themselves is 0.64, as shown in

Table 4. The main materials of the exterior wall of the modern Tibetan residence are designed and transformed by the villagers themselves.

Materials	Thickness (δ)	Thermal Conductivity (λ)	Heat Storage Coefficient (S)	Coefficient of Correction	Thermal Resistance (R)	Thermal Inert Index
	(mm)	W/(m.K)	W/(m2.K)	α	(m2.K)/W	D = R × S
Gravel, limestone	150	2.040	18.099	1.00	0.074	1.331
Brick	200	0.810	10.551	1.00	0.247	2.605
Pine, wood, spruce (vertical wood grain in heat flow direction)	150	0.140	3.575	1.00	1.071	3.830
The sum of each floor ∑	500	–	–	–	1.392	7.766
Solar radiation absorption coefficient on the outer surface	0.75
Heat transfer coefficient K = 1/(0.18 + ∑R)	0.64

, and this index is lower than the 1.83 of the traditional residential buildings. The significant reduction of the heat transfer coefficient of the thermal performance parameter indicates that the introduction of modern building materials and construction technology can effectively reduce building energy consumption. The time compliance ratio of the main functional rooms meeting the thermal comfort range is 4.58%, as shown in Figure 15, which is 1.5 times higher than the 3.03% of the traditional residential buildings. This indicates that the building function, the increase of window-to-wall ratio, and the construction of glass lighting sheds can greatly increase the indoor adaptive thermal comfort of the house, and it has good promotion value.

As can be seen from the above research, Tibetan people have accumulated rich experience and wisdom in their long-term adaptation to nature, among which the ecological concept of adapting to and utilizing nature in residential buildings is worthy of our inheritance in modern design and construction. In the modern residential buildings designed and renovated by villagers themselves, the new functional layout adjustment and vertical stratification can be directly used for reference. The thickness, materials, and structural system of traditional residential external walls, as well as the materials and construction methods of modern concrete and brick wall structure with masonry veneer, are more energy-efficient and have higher construction efficiency. It is an optimized strategy to change building materials, adjust wall thickness, and learn from and combine relevant traditional construction methods. In modern renovations, the increase of window-to-wall ratio and the construction of glass lighting sheds have greatly increased the indoor adaptive thermal comfort of houses and also have good promotion value. However, the gradual loss of regional characteristics and styles of traditional dwellings in modern renovations, as well as the emergence of new products such as glass sunrooms, have become our concerns in continuing to optimize renovation measures, such as how to adapt to traditional culture, how to be more energy-efficient, and how to further improve indoor adaptive thermal comfort.

Based on the above calculations, we have attempted to further optimize the orientation and dimensions of doors and windows of the building. We simulated the effects of the building orientation on indoor thermal comfort. It is found that when the main entrance and the main facade of the house are oriented towards the east, the indoor adaptive thermal comfort temperature compliance ratio is higher, as shown in Figure 16. Figure 17 and Figure 18 are the statistics of indoor adaptive thermal comfort temperature compliance ratio when the building faces east and the window sizes are 900 × 600 and 1800 × 1500:

Based on the analysis and calculation, it is found that when the main entrance and the main facade of the house are oriented towards the east, and the window size is 1800 × 1500, the indoor adaptive thermal comfort temperature compliance ratio of the main functional rooms is 6.19%, as shown in Figure 18. Compared with the 3.03% of traditional dwellings and the 4.58% after the villagers’ self-designed renovation, this indicator has been increased by three times and two times, respectively, demonstrating a better living quality. For the glass sunroom, we suggest adding design elements of regional culture on the basis of the original materials and construction methods, using traditional roof styles and facade detail designs, so that this new function and new material building can better integrate into the traditional architectural features and protect the historical style of local architecture, as shown in Figure 19.

The results indicate that the design approach proposed in this study significantly enhances the indoor thermal comfort of buildings while preserving the local architectural characteristics and usage habits. Given the difficulty in obtaining building materials in ethnic minority regions, the design methods and materials identified in this study can provide purchasing recommendations for local residents and market guidance for building material suppliers. Furthermore, this approach can be widely promoted in similar ethnic minority villages, effectively improving the sustainability of buildings.

In summary, we conducted simulation comparisons on building materials, window openings, and building orientations. We selected four building orientations and two window opening sizes, along with the building materials currently used in local houses, and compared these combinations to find the optimal configuration, forming the improvement mechanism presented in the paper. To implement this approach, we fully considered the usage needs of local residents. Since most buildings in the area are oriented east and their doors and windows already use the 1800 mm × 1500 mm model, we sourced the renovation materials locally, making them easily obtainable. Therefore, adopting this improvement strategy can maximize the use of existing conditions for renovation, minimizing the impact on residents and the architectural landscape.

5. Conclusions and Prospect

In the past two decades, the initiative of rural revitalization in China has led to a construction frenzy in rural areas, especially those ethnic villages, where traditional residential buildings have been greatly undermined and drastically changed. Tibetan traditional dwellings are an important component of Chinese vernacular architecture, which showcases that the Tibetan people have accumulated rich experience and wisdom in adapting to nature. The research results indicate that: 1. the optimal building orientation in this area is to face east on the facade; 2. the building can adopt a combination of concrete frame on the ground floor and wooden structure on the second floor. The walls can be supported by concrete columns and brick walls with decorative masonry on the outside; 3. the roof can adopt a combination of a sloping roof with metal tiles and a concrete flat roof. The villagers’ addition of a second-floor glass sunroom can be upgraded with a steel structure frame to optimize the shape and more easily integrate with the building’s overall style; 4. the optimal size of windows is 1800 × 1500 mm.

This article proposes sustainable improvements to residential buildings through passive energy-saving methods. The design and deduction of building models can increase indoor thermal comfort by two to three times by calculation. The optimized design scheme combines traditional residential culture and regional characteristics with eco-friendly and energy-saving architectural design.

Songpan is located in the high-altitude mountainous areas of western China and is a microcosm of rural ethnic areas in underdeveloped western China. Its social environment and regional culture have strong peculiarities. Faced with harsh climate conditions, underdeveloped economy, high labor costs, and limited construction technology, this study tries to evaluate existing residential buildings through energy-saving calculations while protecting traditional residential buildings and regional culture and provides a feasible construction operation plan under the existing economic and technological conditions for the local people. The current results are a preliminary exploration of this subject, which we will continue to expand and strengthen in future studies: 1. this article selects the most common type of residential architecture in Songpan as the research object, and proposes optimization design suggestions through simulation calculations and data comparison. The next step is to promote the implementation of the design scheme in actual engineering and conduct on-site testing and data verification; 2. this article starts with the demonstration of advantages and disadvantages of current reconstruction and renovation scheme, then by model simulation finds the most appropriate optimization scheme, therefore providing a complete research framework for the renovation and revitalization of traditional Tibetan dwellings; 3. the method of combining aesthetics and technology by way of model simulation can be applied to such research topics as biogas utilization, traditional toilet renovation, and prefabricated construction design of rural dwellings in ethnic areas in the future. It has great potential; 4. by calculating and comparing the models of traditional residential buildings, existing newly built buildings, and the proposed upgraded buildings, a sustainable development design paradigm is derived that not only reduces energy consumption and improves building living comfort, but also protects regional architectural culture. This method can be applied and promoted in the design of high-altitude ethnic areas in western China.

This article conducts field investigations and surveys, using a research method that combines architecture, anthropology, and engineering technology to extract the ecological concepts and technical measures of traditional dwellings in adapting to and utilizing natural conditions. Through simulation and deduction using Sware ITES2023 software, a practicable design proposal comes into being, which actively reduces energy consumption, improves the living comfort of local people, protects regional architectural culture, and lays the foundation for future research and optimization of rural revitalization practices.