Climate Adaptability Research of Vernacular Dwellings in Jiangxi Based on Numerical Simulation—An Example from Nanfeng County

Abstract

Energy conservation and carbon reduction in buildings have become important concerns and, at the same time, the value of low-tech approaches employed in indigenous architecture is increasingly acknowledged as a pertinent reference for contemporary design practices. The research on vernacular dwellings in Jiangxi has many perspectives and fruitful results, but not enough attention has been paid to the research on climate adaptation. This article verifies the vernacular dwellings’ climate adaptation and summarizes the low-tech methods embedded in vernacular dwellings, aiming to provide guidelines for future exploration of energy-saving and carbon-reducing practices in architecture. By selecting different types of vernacular dwellings in Nanfeng County, this article verifies three aspects of the ecological characteristics of vernacular dwellings: the light environment, wind environment, and energy consumption, by comparing them with those of local modern residential buildings. It is concluded that the average daylight factor of the hall area of vernacular dwellings is better than that of the modern residential buildings in rural areas, and the vernacular dwellings regulate the indoor wind environment and maintain indoor comfort through natural ventilation in winter and summer seasons. Also, the annual energy consumption of the vernacular dwellings per unit area per year can be reduced by up to about 32% in comparison with modern residential buildings. Subsequently, the article concludes that patio space has a positive impact on the indoor physical environment through comparative experiments. Vernacular dwellings are well adapted to the local climate in terms of form, structure, and materials, and these low-tech methods should be applied to the design of rural dwellings in the future.

1. Introductory

Global warming and the energy crisis are among the most prominent issues facing the world today. The construction sector accounts for 30% of the world’s total greenhouse gas emissions [1]. In developed countries, the construction sector accounts for 40% of total greenhouse gas emissions [2]. In China, the carbon emissions from the whole life cycle of dwellings account for 51.2 percent of the country’s total carbon emissions [3] and the construction industry accounts for 40 percent of the world’s total energy consumption [4]. In developed countries, the building sector accounts for 40% of all energy consumption [2], of which 30–60% is used to regulate the indoor environment of dwellings [5]. The building sector accounts for 46.5 percent of total national energy consumption in China [6], with residential dwellings accounting for 61 percent of the total energy consumption of dwellings [7]. China has committed to peak carbon emissions by 2030 and become a carbon neutral society by 2060, while aiming to reduce energy consumption in dwellings to less than 1% to ensure comfort and health [8]. The use of low-tech methods in vernacular dwellings is an indispensable part of reducing energy consumption and achieving sustainable development. This is an important direction that cannot be ignored. In the process of this profound change, Chinese vernacular dwellings show the energy-saving potential and low-tech, low-cost passive designs, which are worth in-depth excavation, practical transformation, and application.

1.1. Relevant Research on Climate Adaptation

Vernacular architecture refers to both traditional and contemporary residential dwellings constructed spontaneously in rural areas, under a system of non-professional architects [9]. It is worth learning from the experience of vernacular architecture, as the main architectural system in rural areas, in reducing energy consumption and waste, using resources rationally and adapting to local climatic conditions [10,11].

Many scholars have studied climate-appropriate vernacular architectural design practices around the world. In Europe, the vernacular architecture coped with the high summer temperatures typical of the Mediterranean climate thanks to the materials of their construction elements, the thickness of their envelopes, and the orientation of their façades [12]. In Cyprus, vernacular architecture in its three different climatic zones employed a variety of design strategies to achieve optimal thermal comfort [13]. Simulations of the vernacular architecture of Pompeii show that the Romans felt comfortable in the summer but required heating in the winter [14]. In Asia, the semi-outdoor spaces of traditional Japanese houses acted as thermal buffers for promoting cross-ventilation as well as pre-cooling to provide “warm but breezy” conditions to the connected indoor spaces that can effectively cope with the hot and humid summer climate [15]. In India, Assam-type houses and stilt houses are highly responsive to the local climate, utilize locally available materials, and reflect the living style, customs, and socio-economic conditions [16]. Vernacular architecture in the Himachal Pradesh region of India adheres to the foundations of traditional Indian architecture while adopting new measures to adapt to nature [17]. In Malaysia, the courtyard forms that characterized their thermal environments were classified into five types and the different types of courtyards performed different functions with respect to improving the indoor thermal comfort in the CSHs [18].

Chinese ancestors constructed a diverse array of dwellings according to their geographical location and climatic conditions [19]. Due to the diversity of building materials, local people developed a wide range of house types, construction techniques, and climatic appliances to adapt to the local climate [20]. In China, there are a wealth of research findings on the climate adaptability of vernacular dwellings in different regions, and different emphasis is placed on the research level and the geographical and climatic areas.

(1) Research on vernacular dwellings in the Huizhou region.

Huang et al. [21] measured the physical environment of traditional vernacular buildings in Huizhou and concluded that slope roof and roof structure as well as the hollow brick wall construction in vernacular dwellings are of significance in heat shielding in summer. Zhu et al. (2020) [22] employed the climate adaptability technology of Huizhou residential dwellings to measure both the indoor and outdoor temperature and humidity of a residential property and took 24 solar terms as the cycle to change the indoor and outdoor temperature and humidity. The variation law of indoor and outdoor temperature and humidity with solar terms in hot summer and cold winter areas were studied. Gao et al. (2023) [23] combed the light aspects of vernacular dwellings in Huizhou to improve indoor requirements. Through experimental comparison, it was concluded that the height of the window side can improve the lighting effect of the window side, and the width of the window and patio can improve the overall lighting of the room.

(2) Research on vernacular dwellings in the Lingnan region.

Gao et al. (2015) [24] took the vernacular dwellings in the Lingnan area as a research object and conducted a digital simulation analysis of their natural ventilation. They concluded that the vernacular buildings rely on the combination of “patio—cold alley—courtyard” to provide good ventilation in the interior. Yao et al. (2018) [25] simulated the indoor lighting and wind environment of vernacular dwellings in Guangdong Province using Ecotect, Phoneics, and found that the living space of vernacular dwellings has a good lighting environment. Due to the reasonable layout of vernacular dwellings, ventilation can be effectively organized through the courtyard in summer. Xiao et al. (2018) [26] analyzed the characteristics of climate adaptation of villages in the Lingnan area, pointing out that cold lanes and courtyards form the spatial system as the main spatial elements. Then, they summarized the reasonable scale range and organization pattern.

(3) Research on vernacular dwellings of ethnic minorities.

Jin et al. (2021) [27] monitored the physics of Dong-nationality vernacular dwellings in real time. The results demonstrated that the Dong nationality’s vernacular dwellings have higher thermal comfort adaptability than urban residential dwellings under natural ventilation. Zhang et al. (2022) [28] summed up the advantages and disadvantages of residential physics to climate characteristics by using the indoor physics of Dong vernacular dwellings, measured and simulated the vernacular dwellings in the Dong-nationality area, and concluded that they are well adapted to the local climate in form, material, and structure. Dong et al. (2021) [29] measured the indoor and outdoor heat of typical Tujia dwellings in Chongqing during the extremely hot period. The results demonstrated that the ventilation roof structure of Tujia dwellings is unique and effectively utilizes the valley wind, which not only improves the heat insulation ability during the day but also is beneficial to the ventilation and refrigeration of the house at night.

1.2. Overview of Vernacular Dwellings in Jiangxi

The vernacular dwellings of Jiangxi represent a pivotal area of research within the field of Chinese vernacular dwellings, exerting a profound impact on the surrounding region. From the perspective of migration, Jiangxi has historically played a key role as the birthplace and transit point of many large-scale migrations. The three wars in the Central Plains, namely the Yongjia Rebellion, the Anshi Rebellion, and the Jingkang Rebellion, triggered large-scale population migration, and Jiangxi became one of the important destinations. The spatial distribution of Jiangxi dwellings as well as the innovation of dwelling types were greatly influenced by this. In the movement of “filling the lake with Jiangxi”, the migrants from Jiangxi not only brought the customs, language, and culture of Jiangxi to new settlements, but also spread the architectural style and construction techniques of dwellings [30].

Jiangxi is a relatively closed and complete geographic unit with the east, south, and west of Jiangxi surrounded by mountains and with the Yangtze River in the north. Since the Song and Yuan Dynasties, Jiangxi’s political changes have been relatively stable, ensuring the stability of the regional characteristics of dwellings [31]. In addition, some researchers [32] have sought to demonstrate the evolution of the dwelling form through a process of deduction. This approach offers more convincing proof of their assertions.

1.3. Present Situation of Research on Vernacular Dwellings in Jiangxi Province

Lu et al. [33] reviewed and summarized the research on Chinese dwellings from 1957 to 2007, and divided the research on dwellings into three periods; namely, the establishment period of dwellings in the 1950s, the surveying and mapping period in the 1960s, and the planned and organized research period from the 1980s to the beginning of the 21st century. Because of the inconvenient transportation and relatively backward economic conditions in the early stage, the research on the vernacular dwellings of Jiangxi started relatively late. In 1989, with the support of the policy, many scholars conducted in-depth research on vernacular dwellings in Jiangxi. Their research findings are mainly manifested in the form, characteristics, technology, culture, geography, and climate adaptability of vernacular dwellings, and so forth.

(1) Research on the form and characteristics of vernacular dwellings

Mr. Hao Huang’s research on Jiangxi dwellings is the earliest and most mature. In his book [34], he conducted profound research and exploration on the composition laws and architectural art characteristics of Jiangxi patio dwellings, summarizing the three types of dwellings in Jiangxi. And, he traced back the degradation and disappearance of patio dwellings from the plan form and elements. This is a useful exploration of the inheritance and development of dwellings. Pan et al. [35] pointed out the reasons for the formation of ancient Jiangxi dwellings in the Ming and Qing Dynasties and thought that ancient Jiangxi dwellings were formed in adaptation to the natural ecology and social circumstances of the Jiangxi region. Yao et al. (2015) [36] systematically discussed the history, type, distribution, and characteristics of vernacular dwellings in Jiangxi. They provided a microscopic discussion of architectural techniques, decorative arts, and material use.

(2) Research on residential technology

Li et al. mainly focused on the characteristics and decorative differences between vernacular dwellings in Jiangxi [37]. Lan et al. (2017) [38] took the brick masonry structure in Jinxi County as an example to reveal the internal relationships and structural language of this mixed masonry. Yi et al. (2018) [39] studied the evolutionary patterns of hall structures in Ming Dynasty residences in the Fu River, especially the plan, section, and node construction features, and analyzed the similarities and differences between the structures. By comparing cases in other regions, they revealed the technological inheritance and fusion, and the comparison of hall-type structures in the Qing Dynasty showed the development of a more open spatial layout and simplified support structure. Li et al. (2018) [40] systematically analyzed the characteristics of the construction techniques of vernacular dwellings in the Lichuan area in terms of plan layout, structure, roof form, dimensions, and construction techniques. They tried to define the absolute scale of the local vernacular rulers and explain the diversity and complexity of the vernacular dwellings’ ruler-making methods.

(3) Research on cultural geography of vernacular dwellings

Guo et al. studied the social background and architectural culture of ethnic areas in Hunan and Jiangxi based on the study of ethnic groups [41]. Pan et al. systematically extracted three types of elements: patio, courtyard, housing hall, and two types of basic units: row house unit, triple patio unit, and quadruple patio unit. From the perspective of typology and systematics, the level of vernacular dwellings has been divided into eight complex levels according to the multiple units involved in their construction and combination [42]. Kang et al. (2020) [31] systematically combed the formation of vernacular dwellings in Jiangxi since the Ming and Qing Dynasties by investigating the existing dwellings in Jiangxi and historical documents. The study revealed a close correlation between the distribution of Jiangxi dwellings and the water system, with dwellings exhibiting an asymmetrical distribution along the water system and watershed. Furthermore, this study highlighted a notable association between spatial distribution and population distribution.

(4) Research on climate adaptability of vernacular dwellings

Wang et al. clarified the livable characteristics of patio dwellings according to the form characteristics and spatial form composition of patio dwellings in different regions [43]. Chen et al. (2020) [44] studied the climate adaptability of vernacular dwellings along the Hunan–Jiangxi border from the material and structural level of architectural form and the architecture–climate interface. The study summarized the advantages and disadvantages of local climate adaptation from the thermal point of view by combining qualitative and quantitative analysis. Wu et al. (2023) [45] took the vernacular dwellings in Futian Town as the research object and summarized the climate adaptability strategy of local vernacular dwellings by actual measurement and simulation from the thermal perspective.

1.4. Research Review

In conclusion, the majority of domestic scholars engaged in research on Jiangxi dwellings have focused their attention on exploring the architectural aspects of the settlements, including their cultural characteristics, architectural forms, and so on. The research on the ecological characteristics of dwellings remains relatively limited. Moreover, the ecological performance of dwellings with different characteristics in this area is lacking. In terms of research methodology, the research on climate adaptability was initially limited to preliminary qualitative analyses of patio dwellings. In the last few years, although computer simulation has been introduced to study climate adaptability, some scholars focused on a single physical factor and ignored the overall comprehensive consideration. Not only that, the research lacks a comparative analysis between vernacular dwellings and modern residential buildings, making it challenging to combine the advantages of vernacular dwellings and modern residential buildings.

Therefore, this study takes vernacular dwellings in Jiangxi as the research object and employs digital simulation technology to verify the climate adaptability characteristics of vernacular dwellings in three aspects: light, wind, and energy consumption. This is accomplished by comparing the vernacular dwellings with local modern residential buildings. The purpose of this study is to refine ecological wisdom and provide practical guidance for the improvement of local vernacular dwellings and the construction of new residential dwellings in local villages. In addition, this study aims to reveal the scientific nature of vernacular dwellings and provide theoretical support for the scientific nature of construction ideas, while scientifically analyzing climate adaptability. Figure 1 illustrates the framework of this study.

2. Overview of The Study Population

Although there are many different types of vernacular dwellings in Jiangxi, such as patio-style dwellings, patio courtyard-style dwellings, halls, etc., the patio dwellings are more widely distributed with a substantial number in existence (Figure 2). The object of this paper is to study the patio-style dwellings.

Nanfeng County is known as one of the “cultural counties” in Jiangxi Province (Figure 3). It currently has 12 well-preserved, distinctive traditional villages, 11 national traditional villages, and 10 provincial traditional villages, accounting for 3.23% of the number of traditional villages in Jiangxi Province in China. The traditional villages in Fuzhou ranked fourth in terms of the number of traditional villages in Jiangxi. Nanfeng County ranks fourth in Fuzhou and eighth in Jiangxi in terms of the number of traditional villages, and Nanfeng Ancient City has been rated as a provincial famous historical and cultural city. Therefore, the traditional villages in Nanfeng County are typical representatives of the traditional villages in the whole of Jiangxi Province, both in terms of quantity and culture. This paper includes field research and consults classic works [33,34,36]. The patio-style dwellings are divided into three typical types: three openings with one entry and one patio, three openings with one entry plus half a patio, and three openings with multiple entries. (As

Table 1. Summary of different types of vernacular building plans and modern residential building plans.

Typology	Plan Map Prototype	Typical Instance
Three-room, single-entry, single-patio type
		Kangdu Village Guard Camp Dwelling	Lumin No. 130 in Shanggan Dwelling
Three-room, single-entry plus half-well type
		Meikengs’ Dwelling	Shiyou villagers’ Dwelling
Three-room, multi-entry type
		Former site of the Red Army in KangDu	Yaopu Village Zengjia Dwelling
Modern residential building type

).

2.1. Geography and Climate Conditions of Nanfeng County

Nanfeng County is mainly characterized by hilly landscapes, accounting for about 65% of the total area of the county. Nanfeng County has a subtropical monsoon climate, with an average annual temperature of 19.8 °C, the coldest month being January with an average temperature of 6.2 °C, and the hottest month being July with an average temperature of 29.3 °C. The annual precipitation is 1791.8 mm, and the main precipitation in the region is concentrated in April–June. Therefore, local vernacular dwellings are usually required to adapt to the needs of sun shading, ventilation, and cooling in summer, while also taking into account cold protection and warmth in winter.

2.2. Vernacular Dwellings Layout of Nanfeng County

2.2.1. Plan Form

The combination plan form of vernacular dwellings in Nanfeng County is centered on the patio and symmetrically distributed on the central axis. The upper and lower halls are sequentially placed on the central axis, and the upper and lower rooms are on both sides of the halls. The upper room has the highest rank and is usually inhabited by the elders, while the compartments on both sides of the patio have a lower rank and are usually inhabited by the children. This is in line with the social relationship of the feudal family and the feudal hierarchy. The patio carries the functions of drainage, ventilation, sunlight, and lighting inside the building. According to the system of vernacular dwellings in Nanfeng County, there are one-entry, two-entry, and multi-entry types of layouts. Among them, the three rooms with one entry and one patio type is the smallest type in Nanfeng County, which is characterized by simple composition and neat layout, and is widely distributed in Nanfeng County.

2.2.2. Structures

The structure of vernacular dwellings in Nanfeng County is mainly of the pierced-double type (Figure 4), followed by the inserted-beam type, which is generally used in higher-grade dwellings. And, the outer walls of vernacular dwellings are mostly cavity walls (Figure 5), their masonry is “one sleep one bucket”, a brick outer skin layer and a space between the bricks to form an air layer. The inner walls are mostly wooden partition walls.

2.2.3. Materials

The vernacular dwellings in Nanfeng County mainly use easily accessible materials such as wood, brick, and stone. Nanfeng County is located in a red hilly area, and red stone is an important material for vernacular dwellings in Nanfeng County, being widely used for door and window frames, column bases, wainscotting, forming a unique architectural style, and overall harmonization.

2.3. Low Technology

Low tech is a mature and traditional technology compared to high-tech. Low technology in the field of architecture is a kind of concept, strategy, and idea in the macro perspective, and a specific technical form in the micro perspective. Low technology is characterized by reverence for nature, ease of implementation, and economic use. In terms of spatial function, low technology is manifested in the use of building pattern design to create energy-saving effects, in order to achieve the purpose of maintaining human comfort and reducing energy consumption [46]. From the aspect of economy, low-tech represents the use of cheap local materials and use of certain technical means to achieve good construction results. As a result of Nanfeng County’s long history, the form of vernacular dwellings in Nanfeng County is constantly being perfected, containing low-tech methods such as plan layout, building structure, construction techniques, wall structure, and building materials.

3. Methods

This study constructs research ideas from climate adaptation, conducts research and mapping on six typical vernacular dwellings in Nanfeng County, and makes use of Ecotect (2011), Phoenics (2019) [47], and Energy plus (v8.7.0) software [48]. These programs are used to carry out mathematical simulation and analysis of the light environment, wind environment, and energy consumption in comparison with a selected modern residential building. By exploring the indoor physical environment of vernacular dwellings, the passive strategies involved in coping with the climate can be more accurately distilled.

3.1. Theoretical Basis

Climate adaptability originally refers to the interrelationship between living organisms and the climate environment in climatology and ecology, and belongs to the intersection of the two research fields. Later, the field of architecture quoted this research method, and formed the bioclimatological method of architecture [49].

Foreign exploration of the relationship between architecture and climate can be traced back to the Greek architect Vitruvius who compiled “Ten Books of Architecture”, which is the earliest documented description of the principles of architectural design interacting with climate. Later, as a pioneer in the climate adaptation of traditional dwellings abroad, Rudovsky explored the relationship between architecture and climate in different regions of the world, and carried out corresponding research on traditional architecture from the perspective of the climatic environment. “Climatic adaptability” in architecture refers to the ability of architecture to resist and adapt to the natural climate environment. Climate refers to the weather conditions in general or over a long period of time, which are characterized by stability and regularity, and it is a different concept to that of weather, which refers to the changes in the hot and cold state of the near-surface atmosphere in a particular region within a short period of time.

3.2. Physical Modeling

The data of three kinds of vernacular dwellings were compiled through field research and mapping. The specific data are shown in

Table 2. Statistics of physical modelling indicators for vernacular and modern residential dwellings.

Serial Number	M1	M2	M3	M4
Typical instance	Kangdu village guard camp residence	Lumin No. 130 in Shanggan village	Meikengs’ villagers	Shiyou villagers’ residence
Average building height (m)	4.5	5.57	5.54	5.49
width (m) × depth (m)	7.5 × 10.2	10.5 × 15	9.8 × 15.5	14.2 × 15
Patio1 Length-width ratio	2.2:1	3.2:1	3.2:1	3.3:1
Patio1 Width–height ratio	1:3	1:2.9	1:3.3	1:3.2
Hall Width (m) × depth (m)	2.8 × 4.5	4.3 × 6.3	3.9 × 5.2	4.4 × 5.5
Bedroom Width (m) × depth (m)	2.1 × 3.8	3.0 × 6.3	2.9 × 7.9	4.4 × 5.1
Serial Number	M5	M6	M7
Typical instance	The old site of the Red Army of Kangdu Village	Yaopu Village Zengjia grand house	Modern residential buildings in rural areas
Average building height (m)	5.73	5.82	6.3
Width (m) × depth (m)	14.5 × 19.8	15.7 × 19.2	8.2 × 12.2
Patio1 Length–width ratio	3.4:1	3.1:1	—
Patio1 Width–height ratio	1:3.1	1:3.5	—
Hall Width (m) × depth (m)	4.6 × 5.5	4.1 × 5.7	8 × 4.5
Bedroom Width (m) × depth (m)	5.2 × 5.4	5.2 × 5.7	4 × 3.3

.

Through field research, a modern residential building southwest of the guard battalion dwelling in Kandu Village, Taihe Town, Nanfeng County, was selected as the reference building, which is more similar in form to the residence of the Kangdu Village Guard Camp Dwelling with a sloping roof and the same orientation (Figure 6). The modern residential building has a two-story sloping roof and no internal patio, with a total width of 8.28 m and a total depth of 12.2 m. It adopts a brick–concrete structure, with steel security doors, single-glazed windows, and aluminum alloy frames, which is a relatively common form of modern residential building in the area. In order to simplify the model and accelerate the convergence speed of the calculation, this paper ignores all the minor bumps and various components in the simulation process, and mainly retains the main components of the building such as doors, windows, roofs, floor slabs, and walls [50]. Because the modern residential dwellings are located more towards the periphery of the village, the surrounding building density is low, while the vernacular dwellings are mostly concentrated in the middle of the village, with a high site coverage density. In order to control for the influence of the surrounding environmental conditions, the simulation experiments are carried out in an ideal environment with open and unobstructed surroundings for the calculation and analysis.

3.2.1. Light Environment Modeling

The light environment simulation is analyzed by Ecotect software, and the three-dimensional spatial model is established according to the actual mapping drawings. As the vernacular dwellings are affected by a series of factors such as climate, historical deposits, living customs, construction technology, etc., wall features such as textures and being out of true, grille ash accumulation, uneven reflections, and other irregularities may appear. However, to simplify, these difficult-to-control, small variations can be ignored [50]. In the simulation, the bedrooms and halls of seven dwellings are selected to simulate the value of the daylight factor. The grid is set at 750 mm from the indoor floor height, and each room is divided by a 0.1 m × 0.1 m grid cell specification. Grid independence is verified by spacings of 1.2 m × 1.2 m, 0.1 m × 0.1 m, 0.08 m × 0.08 m, and 0.06 m × 0.06 m. The bedroom of M1 is selected as the experimental object in this experiment, and compared to the average lighting coefficient and the computing time of different grid numbers. It was found that through the comparison (

Table 3. Grid Independence Verification Simulation.

Grid Cell Specifications	Daylight Factor Value (%)	Time (s)
1.20 m × 1.20 m	0.92	141
0.10 m × 0.10 m	0.92	206
0.08 m × 0.08 m	0.92	435
0.06 m × 0.06 m	0.94	920
0.04 m × 0.04 m	0.94	1929

), the grid cell specification of 0.08 m × 0.08 m is encrypted. The error of the average daylight factor is 2%, but the computation time is doubled. When the grid is encrypted again, the average daylight factor does not change, but the time is doubled. The grid cell size of 0.1 m × 0.1 m shows the same result, but the calculation time is shortened compared to the grid cell size of 0.08m*0.08m. Therefore, the simulation results using a 0.1 m × 0.1 m grid cell size can better reflect the light environment of the building and save computing costs.

3.2.2. Wind Environment Modeling

Since wind environment simulation uses Phoenics software, the study needs to set the corresponding calculation domain, based on the “DB22/T 5055-2021 green building design standards” [51], to ensure that the building coverage area is less than 3% of the area of the calculation domain. So, with the building as the center of the circle, the radius of the horizontal calculation area is not less than 5H (building height), and the calculation area of the upper part of the building is not less than 3H. After determining the calculation area, the built-in PARSOL function of Phoenics software creates a structured mesh division and, in order to improve the calculation accuracy, the mesh is encrypted in the space where the main body of the building is located and in the near-ground area. In order to verify the independence of the grid, which is divided into 100,000; 500,000; or 1 million cells, experiments show that a 500,000-cell grid can guarantee the accuracy of the calculation. We examined and compared the statistical analysis of the relative wind speed of the five measurement points in the three different experiments (Figure 7). Through comparison, it was found that when the unit number of the grid was increased for the first time (from 100,000 to 500,000), the relative wind speed of some measurement points changed remarkably. However, when further increasing the unit number (from 500,000 to 1 million), the error rate of the relative wind speed at each measurement point was less than 5%, which proved that a grid with 500,000 units could ensure computational accuracy. Therefore, this article employed a grid with 500,000 units for numerical simulation to improve the operational efficiency.

3.2.3. Energy Consumption Modeling

The simulation of building energy consumption is analyzed by EnergyPlus software, and the three-dimensional spatial model of vernacular dwellings and modern residential buildings is established according to the actual mapping drawings, and sets different enclosure structures such as doors, windows, exterior walls, roofs, interior walls, floor slabs, and so forth. Then, the weather file (EnergyPlus Weather File, EPW) of Fuzhou City Meteorological Station in Nanfeng County is then downloaded from the official EnergyPlus website, and set as the year-round meteorological parameters for the vernacular dwellings and modern residential buildings. After completing the 3D modelling in Sketchup, the idf file was exported, and the EnergyPlus software’s idf editor was used to define the delamination, thickness, material thermal conductivity, and light transmission properties of the building envelope, as well as to set the parameters of the lighting, personnel, electrical equipment, and HVAC system. The simulation of the building’s energy consumption was then carried out.

3.3. Model Setup and Parameters

3.3.1. Light Environment Parameters and Mathematical Modeling

1. Parameter Setting

The light environment was modeled using Ecotect Analysis. According to the Chinese light climate zoning standard, Nanfeng County belongs to the class IV light climate zone. The lighting critical illuminance of its areas are all 4500 Lux, and the design illuminance value is 13,500 Lux. The most unfavorable lighting conditions were calculated by using the full-coverage model of the International Commission on Illumination. Vernacular dwellings with wood roofs have an albedo ratio of 0.2, brick wall interior surfaces have an albedo ratio of 0.6, and cinderblock floors have an albedo ratio of 0.23. Modern residential buildings have concrete roofs with an albedo ratio of 0.7, brick wall interior surfaces have an albedo ratio of 0.6, and concrete floors have an albedo ratio of 0.23.

2. Mathematical Modeling

Ecotect uses the Building Research Establishment (BRE) shunt method, a widely accepted and very useful technique for calculating daylight factors. The method assumes that direct sunlight is ignored and that three separate components of natural light arrive at any point inside the building:

Daylighting Factor (DF)—represents the daylighting factor at a given point;

Sky Component (SC)—represents the portion of the room that receives light directly from the sky through the window;

External Reflectance Component (ERC)—represents the portion that reflects back from the ground, trees, or other dwellings;

Internal Reflection Component (IRC)—represents the internal reflection of the first two components on the interior surface.

The Daylight Factor calculation uses the following expression:

$$\begin{array}{c}DF=SC+ERC+IRC\end{array}$$

(1)

3. Range of the light environment simulation

The simulation range of the light environment of the seven dwellings is mainly based on the regularity of the range of human daily activities, which can be divided into the bedroom and the hall (Figure 8). In this paper, the simulation range of the bedroom in the vernacular dwellings is in the upper main room area on the left side of the hall, and the simulation range of the hall in the vernacular dwellings is in the area of the hall, because the hall in the vernacular dwellings is the main space for people’s daily activities.

3.3.2. Wind Environment Parameters and Mathematical Modeling

1. Meteorological Parameters

The main evaluation of the wind environment conditions in summer and winter for the seven dwellings involves drawing up the main technical parameters by referring to the “Air Conditioning Design Manual (Third Edition)” and consulting the Nanfeng County Meteorological Bureau. The dominant wind direction in summer is south-easterly with a wind speed of 2.7 m/s and an outdoor design temperature of 28.3 °C whilst the dominant wind direction in winter is northerly with a wind speed of 2.1 m/s and an outdoor design temperature of 7.2 °C.

2. Mathematical Modeling

This article adopted the standard k-ε model. It has the characteristics of low cost, small fluctuations, and a high numerical calculation accuracy. When the iteration number of the standard k—ε model is set to 200, the residuals of the continuity and momentum equations are less than 10⁻⁴, and the residuals of the k and ε equations are less than 10⁻⁷, hence the model’s judgment is credible. In this article, assumptions are made based on air flow: (1) room temperature, low velocity, incompressible fluid flow, (2) steady-state flow is studied, and (3) the fluid is considered isotropic. The numerical solution process is shown in Figure 9. All the control differential equations include the continuity, momentum, k and ε equations [52,53], and the simplified equations after considering the steady state incompressibility of the fluid are:

Mass conservation equations:

$$\begin{array}{c}{\displaystyle \frac{\partial u_i}{\partial x_i}}=0\end{array}$$

(2)

momentum equation (math.)

$$\begin{array}{c}{\displaystyle \frac{\partial \left(\rho u_{\mathrm{i}}{u}_{\mathrm{j}}\right)}{\partial x_{\mathrm{i}}}}={\displaystyle \frac{\partial }{\partial x_{\mathrm{i}}}}\left({\mu }_{\mathrm{e}\mathrm{f}\mathrm{f}}{\displaystyle \frac{\partial u_{\mathrm{j}}}{\partial x_{\mathrm{i}}}}\right)-{\displaystyle \frac{{\partial }_{\mathrm{p}}}{\partial x_{\mathrm{j}}}}+{\displaystyle \frac{\partial }{\partial x_{\mathrm{i}}}}\left({\mu }_{\mathrm{e}\mathrm{f}\mathrm{f}}{\displaystyle \frac{\partial u_{\mathrm{i}}}{\partial x_{\mathrm{j}}}}\right)\end{array}$$

(3)

the conservation of energy equation

$$\begin{array}{c}{\displaystyle \frac{\partial \left(\rho u_{j}T\right)}{\partial x_i}}={\displaystyle \frac{\partial }{\partial x_i}}\left({\Gamma }_{T,eff}{\displaystyle \frac{\partial T}{\partial x_i}}\right)+S_T\end{array}$$

(4)

T represents the temperature; Γ_T,eff represents the effective diffusion coefficient; S_T represents the heat generation term; ρ represents the fluid density; u_j represents the velocity vector; and x_i represents the coordinate position.

3. Calculation Area

The size of the calculation area was set according to the Green Building Design Standard and affects the speed and accuracy of the software calculation. The area covered by the building should be less than 3% of the whole calculation area, the size of the horizontal calculation area should be a radius of 5H (with the building as the center of the circle), and the calculation area above the building should be more than 3H (H is the height of the main body of the building).

4. Wind Environment Boundary Conditions

(1) Inlet boundary condition

In practice, the wind speed near the surface decreases with height due to friction at the surface. The pattern of change in wind speed at the incoming surface is expressed as an exponential rate:

$$\begin{array}{c}{\mathcal{u}|}_{inflow}=U_z\end{array}$$

(5)

$$\begin{array}{c}{\displaystyle \frac{U_z}{U_o}}=({\displaystyle \frac{Z}{Z_o}}{)}^{\alpha }\end{array}$$

(6)

U_z is the wind speed in the horizontal direction at height Z; U_o is the wind speed at Z_o of the reference height; and α is a power index determined by the roughness of the terrain. According to the relevant Chinese standards and norms, traditional villages in Jiangxi belong to the field, countryside, jungle, and hilly areas, and the value of α is taken as 0.16.

By referring to “Air Conditioning Design Manual (Third Edition)”, consulting Nanfeng County Meteorological Bureau, and by other means, it is known that in the typical climate of Nanfeng County in summer the dominant wind direction is south-easterly, with a wind speed of 2.7 m/s; the dominant wind direction in winter is northerly, with a wind speed of 2.1 m/s. For example, for a northerly wind, the north side of the calculation area is set as the “velocity inlet”, and the east, west, and south sides are set as the “pressure outlets”.

(2) Outlet boundary condition

The exit boundary condition uses a chi-square Neumann boundary condition, im-plying that at the exit boundary the normal gradient of all variables is assumed to be zero, i.e., the flow is sufficiently developed to be no longer affected by the flow near the exit. The equation can be expressed as:

$$\begin{array}{c}{\displaystyle \frac{\partial \mathcal{u}}{\partial \iota }}=0\end{array}$$

(7)

$\mathcal{u}$ represents the fluid velocity; ${\displaystyle \frac{\partial }{\partial \iota }}$ denotes the partial derivative of the flow direction along the outlet boundary.

By assuming that the flow on the outlet surface is sufficient and has returned to the normal conditions, free from obstruction by buildings, the outlet pressure is set as the standard atmospheric pressure. The equation can be expressed as:

$$\begin{array}{c}{{\rm P}}_{amb}=101,325 \mathrm{Pa}\end{array}$$

(8)

(3) Wall boundary conditions

The wall and underlay of the building are set up as no-slip movement conditions, conditions that correspond to actual physical phenomena. Due to the viscous interaction between the fluid and the wall, the velocity of the fluid immediately above the wall can be assumed to be zero. The equation can be expressed as:

$$\begin{array}{c}{\mathcal{u}|}_{wall}=0\end{array}$$

(9)

5. Thermal Environment Boundary Conditions

In this simulation, the research object is placed in an ideal environment, and there are no other sources of heat and cold in the vicinity, so in the temperature field simulation, the first type of boundary conditions are used in this simulation. The equation can be expressed as:

$$\begin{array}{c}{\rm T}={{\rm T}}_{boundary}\end{array}$$

(10)

${{\rm T}}_{boundary}$ is the constant temperature at the boundary.

By means of reference to the Air Conditioning Design Manual (3rd Edition) and consultation with the Nanfeng County Meteorological Bureau, it can be learned that the average outdoor temperature for a typical summer climate is 28.3 °C, and the average outdoor temperature for a typical winter climate is 7.2 °C.

6. Wind speed detection point setting

According to the flow field area of the wind environment of the building and the daily activities of people, the simulated wind speed detection points in different types of dwellings are determined (Figure 10). Point A is located at the main door of the building to detect the wind environment on the windward side; Point E is located at the doorway of the bedroom to detect the wind environment at the doorway of the bedroom; Point F is located in the center of the bedroom to detect the wind environment in the bedroom space; Points B, D, and G in the vernacular dwellings are located in the center of the hall to detect the wind environment in the main public activity space, and Point B in the modern residential building is to detect the main wind environment in the main public activity space.

3.3.3. Energy Consumption Parameters and Mathematical Modeling

1. Meteorological Parameters

In the simulation, the number of people using lighting and appliances and the electricity load are proportional to the building area. The population number is set to eight people, and according to the Energy Saving Design Standard for Residential Buildings in Jiangxi Province, it is known that the lighting and equipment loads are 5.0 W/m² and 3.8 W/m², respectively. The daily opening time is set to 6 h/day, the indoor summer air conditioning cooling temperature is set to 26 °C, and the intended winter indoor heating temperature is set to 18 °C. Combined with the local climatic conditions, the cooling time is set from 1 June to 1 October each year, with daily cooling times of 12:00–14:00 and 20:00–24:00, and the heating time is set from 15 December each year to 1 March of the following year. According to the “Energy-saving Design Standards for Residential Buildings in Jiangxi Province” and the results of the field research of the simulation object, the parameters of the enclosure structure of the vernacular building and the modern residential building are set separately.

Table 4. Digital Physical Models of the Study Buildings in Energyplus Software.

Energyplus Model
			M7
M1	M3	M5
M2	M4	M6

shows the building’s established three-dimensional model. The specific values are shown in

Table 5. Parameter Settings for the Envelope Structure of the study buildings.

Building Envelope	Construction Method	Material Thermal Index
		Thickness (mm)	Density (kg/m3)	Specific Heat kJ/(kg·K)	Heat Conductivity W/(m·K)
cavity wall	Atmosphere		1.3	1005	0.0023
	Blue brick	240	1900	1050	0.265
Brick wall	1. Lime cement	15	1800	1050	0.93
	2. Clay brick	240	1800	1050	0.81
	3. Lime cement coating	15	1800	1050	0.93
Wooden Wall	Wooden board	30	500	2510	0.17
Door	Wooden door	40	550	2301	0.343
Floor	1. C20 fine aggregate concrete	60	2300	920	1.51
	2. Soil pile	150	1600	1010	0.81
	3. 3:7 Lime soil	300	1795.6	884	0.72
Window	Single-glass wooden board K = 4.7 (W/m2 K)	6	2500
Roof	1. 15 mm gray tile roof	15	2044	1050	0.96
	2. Rafters	80	2300	656.9	0.753
	3. Purlin	100	2300	656.9	0.753

.

2. Mathematical Modeling

In this study, Energy Plus is used to simulate the energy consumption of a residence to calculate the total energy consumption of the building in one year, and the energy consumption per unit area of the building is compared because of the different sizes of the building areas of different buildings. The total energy consumption of the building in Energy Plus is composed of Heating, Cooling, Lighting, Equipment, and Fans, respectively, Pumps and other energy consumption system, due to this paper using the ideal air conditioning system in the simulation, does not take into account the energy consumption of air conditioning systems or ventilation equipment, so the total energy consumption of the building is simplified into air conditioning load, personnel equipment, and indoor lighting.

The equation for energy consumption per unit area of a building is as follows:

$$\begin{array}{c}{\mathcal{Q}}_{Total}={\displaystyle \frac{{\mathcal{Q}}_{HVAC}+{\mathcal{Q}}_{Equ}+{\mathcal{Q}}_{Light}}{A_{Total}}}\end{array}$$

(11)

Energy Plus is composed of a building module, an air module, and an HVAC system module, with real-time feedback between the three using an integrated synchronization method. The indoor air energy conservation equation and the building wall energy conservation equation are the two basic equations used in the calculations performed by the energy simulation software.

$$\begin{array}{c}{\displaystyle \sum _{i=1}^N}{q}_{i,c}{A}_i+{\mathcal{Q}}_{other}+G_a{C}_p\left(T_{a-out}-T_m\right)-{\mathcal{Q}}_{heat-extra}=\rho V{C}_p{\displaystyle \frac{d{T}_{in}}{dt}}\end{array}$$

(12)

The building wall energy conservation equation is as follows:

$$\begin{array}{c}{q}_{i+}{q}_{ir}={\displaystyle \sum _{k=1}^N}{q}_{ik}+q_{i,c}\end{array}$$

(13)

i is the number of individual surfaces of the building envelope; $q_{i,c}$ is the convective heat transfer through the ith surface; $N$ is the number of surfaces of the envelope; $A_i$ is the actual heat transfer area of the ith surface of the envelope; ${\mathcal{Q}}_{other}$ is the latent heat caused by the convective part and evaporation of water in the heat balance equation of the surface, sunlight, equipment, lighting, and heat gain of the personnel; $G_a$ is the sum of air volume of the fresh air and infiltration air; $C_p$ is the constant pressure-specific heat capacity of the air; ${\mathrm{T}}_{\mathrm{m}}$ is the temperature of the zone; ${\mathcal{Q}}_{eat-extra}$ is the amount of heat lost from the inside air to the outside; C_p is the constant pressure-specific heat capacity of the air; ${\rho VC}_P{\displaystyle \frac{d{T}_{in}}{dt}}$ is the heat capacity of the room air; T_a.out is the outdoor air temperature; $q_i$ is the heat transfer from the wall to the wall i; $q_{ir}$ is the radiant heat from the internal heat source and the sun.

Energy Plus uses the heat balance method to calculate the air conditioning system load. Based on the first law of thermodynamics and the law of the conservation of energy, the air conditioning system supplies hot or cold air to each indoor area to satisfy the indoor heat or cold loads under non-linear outdoor conditions by assuming that the room air temperatures and the surface temperatures of the enclosure are balanced and consistent. The instantaneous load of the room is calculated by solving each surface and room air temperature through the heat balance equations for the external surface of the building, the internal surface of the building, the heat balance of the building body, and the outdoor heat balance.

The formula for calculating the instantaneous load of a building by the heat balance method is as follows:

$$\begin{array}{c}{q}_i\left(t\right)=h_i\left(T_R\left(t\right)-T_i\left(t\right)\right)+{\displaystyle \sum _{k=1}^n}h{r}_{i,k}\left(T_K\left(t\right)-T_i\left(t\right)\right)+R_i\end{array}$$

(14)

$$\begin{array}{c}Q\left(t\right)={\displaystyle \sum _{i=1}^n}{s}_i{h}_i(T_i(t)-T_R(t))+m(t)C_P(T_o(t)-T_R(t))+{\mathcal{Q}}_S(t)\end{array}$$

(15)

The energy consumption formula for building HVAC systems is as follows:

$$\begin{array}{c}{{\rm P}}_{HVAC, total}={\displaystyle \frac{Q\left(t\right)t_{HVAC}}{{COP}_{ref}}}\end{array}$$

(16)

The energy consumption formula for indoor lighting in buildings is as follows:

$$\begin{array}{c}{{\rm P}}_{Light}={\rm P}\left(t\right)t_{Light}\end{array}$$

(17)

The energy consumption formula for building indoor equipment is as follows:

$$\begin{array}{c}{{\rm P}}_{Equ}={\displaystyle \sum _{e=1}^n}{n}_e{\rm P}\tau \end{array}$$

(18)

$q_i\left(t\right)$ is the heat gain of the ith surface at moment t, (kw/m²); $h_i$ is the heat transfer coefficient of the ith surface; $T_R\left(t\right)$ is the calculated indoor temperature, (K); $T_i\left(t\right)$ is the temperature of the ith internal surface; $R_i$ is the radiant absorption of the ith surface (kW/m²); $Q\left(t\right)$ is the cooling load at moment t, (kW); $s_i$ is the area of the ith surface, (m²); m(t) is the fresh air volume at time t, (kW/s); $C_P$ is the constant pressure-specific heat capacity, (kJ/kg); $T_o\left(t\right)$ is the calculated temperature of the outdoor air, (K); $Q_S\left(t\right)$ is the heat generation from the indoor heat source at time t, (kW). $t_{HVAC}$ is the HVAC turn-on time. ${COP}_{\mathrm{r}\mathrm{e}\mathrm{f}}$ is the rated cooling factor of the building’s HVAC system. $t_{Light}$ is the indoor lighting runtime. P is the average power of a device in operation. e is the total number of device types. n is the quantity of a particular type of equipment. $\tau$ is the equipment runtime.

4. Results

4.1. Light Environment Simulation

According to the Chinese building lighting design standard (GB55016-2021 [54]), the lighting coefficient of bedrooms and halls in residential buildings should not be lower than 2.0%. According to the specification, the minimum value of daylight factor C_min = standard value × light climate coefficient K (K = 1.1) for residential lighting in Nanfeng County, the minimum value of daylight factor for bedrooms and halls shall not be less than 2.20%.

Comparing the light environment of the hall of seven dwellings (

Table 6. Simulation of daylighting coefficients for different dwellings.

Typology	Three-Room, Single-Entry, Single-Patio Type	Three-Room, Single-Entry Plus Half-Well Type	Three-Room, Multi-Entry Type	Modern Residential Building Type
Light environment simulation diagram.				M7
	M1	M3	M5
	M2	M4	M6

and

Table 7. Table of light environment indicators for bedroom and hall areas in different buildings.

Area		M1	M2	M3	M4	M5	M6	M7
Hall area	Average light factor (%)	5.45	4.7	6.48	5.45	5.77	7.51	4.38
Bedroom area	Average light factor (%)	0.83	0.75	1.21	1.06	1.02	0.87	5.12

, and Figure 11 and Figure 12), M7’s hall has a lower percentage of areas with a daylight factor value of not less than 2.20% of M1. The average daylight factor value (1.07%) is lower than M1’s, in which the difference in the average value of daylight factor is 1.07%, so M1’s hall light environment is better than that of M7. Due to M1 and M2 being of the same type with little difference in their daylight factor, it can be concluded that M2’s hall light environment is better than M7. By comparing the light-environment-related indicators of different types of halls, it is clear that the light environment of M7 in the hall area is lower than that of the vernacular dwellings.

Comparing the light environment of the bedrooms of the seven dwellings, M7’s bedrooms have a much higher percentage of areas with a daylight factor value not less than 2.20% than M1, and the average daylight factor value (4.29%,) is much higher than those of M1, so the difference in the average value of the daylight factor is 4.29%, so the light environment of the bedrooms of M7 is better than that of M1. In the same vein, it appears that the light environment of M7 in the bedroom area is better than that of the vernacular dwellings.

4.2. Wind Environment Simulation

Comparing the wind speeds at different points in the six vernacular dwellings under ideal conditions in summer (

Table 8. Table of wind speed values at each test point simulated in different dwellings in summer.

Serial Number	Point A (m/s)	Point B (m/s)	Point C (m/s)	Point D (m/s)	Point E (m/s)	Point F (m/s)	Point G (m/s)	Point H (m/s)
M1	1.2–1.4	0.6–0.8	0.6–0.8	0.4–0.6	0.4–0.6	0–0.2	/	/
M2	1.4–1.6	0.6–0.8	0.6–0.8	0.4–0.6	0.4–0.6	0–0.2	/	/
M3	1.4–1.6	0.8–1.0	0.8–1.0	0.6–0.8	0.2–0.4	0–0.2	0.4–0.6	/
M4	0.2–0.4	0.6–0.8	0.2–0.4	0.4–0.6	0.2–0.4	0–0.2	0.4–0.6	/
M5	1.4–1.6	0.6–0.8	1.2–1.4	0.2–0.4	0.2–0.4	0–0.2	0.2–0.4	0.8–1.0
M6	1.4–1.6	0.8–1.0	1.2–1.4	0.2–0.4	0.4–0.6	0–0.2	0.4–0.6	0.8–1.0
M7	1.4–1.6	0.2–0.4	/	/	0.6–0.8	0.2–0.4	/	/

and

Table 9. Simulated wind speed clouds for different dwellings indoor wind environments in summer.

Typology	Summer
Three rooms with one entrance and one patio
	M1	M2
Three-room, single-entry plus half-well type
	M3	M4
Three-room multi-entry type
	M5	M6
Modern residential buildings type
	M7

), it was found that the indoor wind environment improves with the increase in the number of patios. M1 and M2 are of the three-room, single-entry and single-patio type, except at point A where the wind speed gap is obvious, but the wind speed difference in other areas is not significant. M3 and M4 are of the three-room, single-entry plus half-patio type; however, due to the main door of M4 being on the west side, the range of the wind speed of point A of M4 is much lower than that of M3, and also the wind speed difference between the two at point C is larger. Points B, F, and D have smaller differences in wind speed ranges. Comparing the wind speed situation of M1 and M2, the wind speed range of M3 and M4 at points E and F tends to be the same, the wind speed range of points A and C has a small difference, and the wind speed at point B is slightly higher. By comparing, it can be concluded that the wind environment of M3 and M4 in the hall area is better than that of M1 and M2. M5 and M6 are three-room multi-entry types and, by comparing the range of wind speeds at different points, the difference in the internal wind environment is not large, and the difference in wind speed is larger only at point D. This is because there are corridors on both sides of the upper hall of M5, which create a wind pressure that reduces the wind speed in the upper hall area. Comparing the wind speed situations of M1 and M2, the wind speed range of M5 and M6 at points A, B, and C is slightly higher, and the wind speed range of points E and F tends to be the same, while the wind speed at point D is lower than that of M1 and M2. This is due to the fact that there is an open door on the north side of M1 and M2 to form a through-traveling wind, and the wind speed at point H is higher than the wind speed of M1 and M2 at point D. By comparing these, it can be concluded that the wind environments of M5 and M6 in the hall area are better than those of M1 and M2.

Comparing the vernacular dwellings with the modern residential buildings, the scale ratio of M1 and M7 is not much different. Comparing the wind speed range at point A, M7’s wind speed range (1.4–1.6 m/s) is higher than the M1’s wind speed range (1.2–1.4 m/s). Comparing the wind speed at point B, M7’s wind speed range (0.2–0.4 m/s) is slightly lower than M1’s wind speed range (0.4–0.6 m/s). Comparing the wind speed range of M7 at points E and F, the wind speed range of M7 is higher than that of M1. In summary, although the wind speed is higher in M7’s bedroom area than in M1’s bedroom, its hall area wind speed is lower than that of M1’s hall area.

Under the ideal conditions in winter, comparing the wind speeds at different points of the six vernacular dwellings (

Table 10. Table of wind speed values at each test point simulated in different dwellings during in winter.

Serial Number	Point A (m/s)	Point B (m/s)	Point C (m/s)	Point D (m/s)	Point E (m/s)	Point F (m/s)	Point G (m/s)	Point H (m/s)
M1	0.55–0.69	0.28–0.41	0.28–0.41	0.14–0.28	0.14–0.28	0–0.14	/	/
M2	0.55–0.69	0.28–0.41	0.28–0.41	0.14–0.28	0–0.14	0–0.14	/	/
M3	0.55–0.69	0.28–0.41	0.14–0.28	0.14–0.28	0.14–0.28	0–0.14	0.14–0.28	/
M4	0.14–0.28	0.41–0.55	0.55–0.69	0–0.14	0–0.14	0–0.14	0.14–0.28	/
M5	0.55–0.69	0.41–0.55	0.55–0.69	0–0.14	0.14–0.28	0–0.14	0.41–0.55	0.41–0.55
M6	0.55–0.69	0.55–0.69	0.55–0.69	0.14–0.28	0–0.14	0–0.14	0.14–0.28	0.41–0.55
M7	0.68–0.83	0.41–0.55	/	/	0.83–0.96	0.2–0.4	/	/

and

Table 11. Simulated wind speed clouds for different dwellings indoor wind environments in winter.

Typology	Winter
Three rooms with one entrance and one patio
	M1	M2
Three-room, single-entry plus half-well type
	M3	M4
Three-room multi-entry type
	M5	M6
Modern residential buildings type
	M7

), it was found that their internal wind environments tend to be the same. M1 and M2 are three-room, single-entry and single-well types so, except for the obvious difference in wind speed at point A, the difference between the points in other areas is not significant. M3 and M4 represent the three-room single-entry plus half-well type, and M5 and M6 represent the three-room multi-entry type. Although they are different types, by comparing the wind speeds at different points, it was found that the internal wind environment conditions tend to be similar. Compared with the three-room, single-entry, single-well type represented by M1 and M2, the greatest difference is that the wind environment at point B is slightly higher than that of M1 and M2.

M1 and M7 were also compared. By comparing the wind speed at point A, the wind speed range of M7 is higher at 0.69–0.83 m/s than that of M1, which is 0.55–0.69 m/s. Comparing the wind speed at point B, the wind speed range of M7 is about twice as high as that of M1 (0.41–0.55 m/s). In particular, at point E, the wind speed range of M7 reaches 0.96–1.1 m/s, which is much higher than that of M1 at 0.14–0.28 m/s due to the formation of a penetrating wind. Comparing point F, the wind speed range of M7 (0.28–0.41 m/s) is higher than the wind speed range of M1. In summary, the overall indoor wind speed of M7 is higher than that of M1, especially the wind speed in the hall area and bedroom area of M7 is higher than in M1.

4.3. Energy Consumption Simulation

The comparison the six vernacular dwellings (

Table 12. Different dwellings of energy consumption simulation comparison.

Serial Number	Unit Area Energy Consumption Annual Energy Consumption (kWh/m2)	Lighting System Unit Area Energy Consumption (kWh/m2)	Energy Consumption of Equipment System Unit (kWh/m2)	HVAC Unit Area Energy Consumption (kWh/m2)
M1	23.73	3.66	5.88	14.20
M2	25.89	4.11	6.37	15.41
M3	24.82	3.84	6.29	14.69
M4	23.94	3.61	5.77	14.56
M5	25.76	4.13	6.07	15.56
M6	25.47	4.31	6.74	14.42
M7	32.83	5.13	7.80	19.9

) reveals that their annual energy consumption per unit area is relatively close. The highest annual energy consumption per unit area was in M2, with a difference between M2 and M1 of 2.16 kWh/m². The residential energy consumption for both is the highest for the unit area energy consumption of the HVAC system, and the lowest energy consumption is the unit area energy consumption of the lighting system. The energy consumption of M2 is 9.1% higher than that of M1, qwithin which the energy consumption per unit area of the lighting system is 12.2% higher. The energy consumption per unit area of the equipment system is 8.3% higher, and the energy consumption per unit area of the HVAC system is 8.5% higher.

Comparing the annual energy consumption per unit area of the vernacular dwellings with the modern residential building, M1 and M7 are selected for comparison. The energy consumption of M1 is better than that of M7, with the main difference in energy consumption coming from the HVAC system. The total annual energy consumption of M7 is 32.83 kWh/m². The annual energy consumption per unit area of M7 is 1.32 times higher than that of M1; the energy consumption per unit area of the lighting system of M7 is 1.22 times higher than that of M1; the energy consumption per unit area of the equipment system of M7 is 1.24 times higher than that of M1; and the energy consumption per unit area of the HVAC system of M7 is 1.35 times higher than that of M1. In summary, the annual energy consumption per unit area of the six selected vernacular dwellings is relatively close, and the annual energy consumption per unit area of M1 is lower than that of M7. Thus, it can be concluded that the annual energy consumption per unit area of vernacular dwellings is lower than that of modern residential dwellings.

5. Discussion

Through the simulation of three aspects of light environment, wind environment, and energy consumption of vernacular dwellings and modern residential buildings, the following results are obtained:

(1)

In comparison to modern residential buildings, vernacular dwellings exhibit a superior lighting effect in the living hall area, although the natural lighting effect in the bedroom area is suboptimal.

(2)

In contrast to modern residential buildings, vernacular dwellings have limited natural ventilation in bedrooms. However, the main activity areas can regulate indoor wind conditions through natural ventilation in summer, adapting to climate change in hot and cold regions. This maintains indoor comfort.

(3)

Vernacular dwellings are more energy-efficient than modern residential buildings.

5.1. Analyzed Aspects

5.1.1. Light Environment

The light environment simulation reveals that the vernacular dwellings use patios to provide good lighting for the hall area while avoiding direct sunlight. As the number of patios increases, the lighting effect of the hall area improves. However, due to the emphasis on security and privacy, the bedrooms of vernacular dwellings only have small windows to receive direct light from the outside, and indirectly receive weak light from the patio through the inner windows. Consequently, the lighting in the bedroom fails to meet the minimum requirements of the code. In contrast, modern residential buildings are more flexible in setting up windows and doors, and the windows and doors in each area are set up more reasonably, but the lighting effect in the hall area is far from being as good as that of vernacular dwellings. The hall area is the primary location for human activities, and thus requires specific lighting conditions. Good lighting uniformity not only provides a comfortable visual experience but also enhances the sense of openness and warmth in the space. The top lighting method is more straightforward than the side lighting method for achieving better lighting uniformity within the interior. The light environment in the bedroom area of modern residential buildings is superior to that of vernacular dwellings. While the light environment in the bedroom areas of modern dwellings is superior to that of vernacular dwellings, vernacular dwellings exhibit a superior light environment in the hall area due to their patios.

5.1.2. Wind Environment

The wind simulation reveals that the clever use of the patio in the vernacular dwellings significantly enhances the efficiency of natural ventilation in the hall area, effectively reducing the heat and stuffiness in the room. In contrast, although the bedrooms have internal windows facing the patio, the cooling effect is far less obvious than that of the halls due to the location and airflow channels. The principle behind the patio design lies in the fact that external airflow is first brought in through the main door, and then smoothly discharged through the patio under the dual driving effect of wind pressure and heat pressure to achieve heat exchange. Particularly in the daytime, when there is plenty of sunshine, the room temperature rises, prompting the hot air to rise and be released through the patio. If the external wind is strong at this time, the indoor air is driven to form a negative pressure in the area of the patio, and the air is discharged under the effect of wind pressure. On the other hand, modern residential buildings have more windows and doors and, if they are fully opened, it is easy to trigger the phenomenon of a through- wind, although it can improve the overall air circulation speed, but it may also bring the problem of uncontrolled indoor wind speed and living discomfort.

5.1.3. Energy Consumption

The energy simulation study reveals that the vernacular dwellings are superior in energy saving performance, and this advantage comes from the comprehensive effect of their unique construction features: the first factor is that the vernacular dwellings use low-thermal conductivity building materials, such as wood, bricks, and rammed earth, which have smaller thermal conductivity compared to the building materials used in modern buildings, effectively blocking the transfer of heat to reduce the loss of energy, and reduce the energy consumption of the HVAC system. Secondly, the wall masonry method also has a certain impact on the energy consumption of the dwelling. The walls of Nanfeng County are mostly hollow bucket walls, with a masonry method of one outside wall and one cavity wall. Secondly, the masonry of the building wall also has a certain impact on the energy consumption of the building, the walls of vernacular dwellings in Nanfeng County are mostly empty cavity walls with masonry for a sleep a bucket, an outer skin brick layer and a space between the bricks to leave an air layer between the bricks; that is, to maintain better structural stability, but also to enhance the structure of the adiabatic properties. Furthermore, the two-story building around the patio of vernacular dwellings creates a narrow and high space that facilitates heat and pressure ventilation. It means that the indoor temperature of the building will fall, and the HVAC energy consumption of the building will be reduced. Compared with modern residential buildings, the annual energy consumption per unit area can be reduced by up to 32%.

In particular, a study of Dong dwellings shows that the full use of wood-based materials can achieve energy savings of 39% compared to brick-based materials. However, the results obtained in this paper are lower than the above data, and the reason for the difference can be attributed to two points: firstly, the difference in building material selection strategy, i.e., the aforementioned study used brick for the external walls and wood for the internal walls, whereas in this paper, the same building material was used for both the internal and external walls; secondly, there are differences in the floor plan and wall masonry, which have an impact on the final results of the energy consumption simulation.

5.2. Comparison Experiment

By analyzing the results of the experiment, this paper finds that the patio has an impact on the indoor physical environment of vernacular dwellings. In order to investigate how it has an impact, this paper will conduct a comparative experiment. The experiment selects one of the examples from different types of vernacular dwellings. The indoor patio space is closed by a roof, and the light environment, wind environment, and energy consumption are analyzed and compared to explore how the patio space affects the indoor physical environment of the vernacular dwelling. Considering the light environment analysis, the material of the roof used to enclose the patio space is made of glass, which is a single-layer glass aluminum frame with a transmittance of 0.753.

Table 13. Comparison table before and after the light environment of the experimental subjects.

Light Environment Simulation		Pre-Laboratory	Post-Experimental
Diagram
Hall area	Average light factor	5.45	4.54
Bedroom area	Average light factor	0.83	0.83

illustrates the light environment results.

Table 14. Comparison table before and after wind environment of experimental subjects.

Wind Environment Simulation	Pre-Laboratory	Post-Experimental
Wind environment in summer
Wind Environment Simulation	Pre-Laboratory	Post-Experimental
Wind environment in winter

illustrates the wind environment results.

Table 15. Comparison table before and after energy consumption of experimental subjects.

Energy Consumption Simulation	Pre-Laboratory	Post-Experimental
Diagram
Unit area energy consumption annual energy consumption (kWh/m2)	23.73	24.47
Lighting system unit area energy consumption (kWh/m2)	3.66	3.54
Energy consumption of equipment system unit (kWh/m2)	5.88	5.92
HVAC unit area energy consumption (kWh/m2)	14.20	15.01

illustrates the energy consumption results.

In a comparative experiment, this paper observes that the average light factor in the room decreases by 16% when the patio is enclosed with glass. This change stems from the reflectivity and light transmittance of the glass. On the one hand, some of the light is reflected from the glass surface to the outdoors; on the other hand, a part of the light passes through despite the high transmittance of the transparent glass used, which permits the penetration of most of the visible light.

In addition, the indoor wind environment of the building is more affected in summer and winter, especially in summer when the indoor wind speed decreases more. This phenomenon is attributed to two reasons. First, the natural ventilation path is restricted. In other words, the closure of the patio blocks the natural path for the free influx of outside air, thus reducing the indoor air flow rate. Secondly, the effect of thermal pressure ventilation is weakened. In other words, the hot air cannot be discharged through the patio, resulting in a reduction in the difference between indoor and outdoor heat pressure, and the power of natural ventilation is weakened, thus reducing the indoor air speed.

The energy consumption simulation experiment showed that the energy consumption increased by 3.1% after the experiment compared to before the experiment. The main reason behind this is the obstruction of ventilation. The patio is originally used as an important channel for natural ventilation, which could promote air circulation, a fall the indoor temperature of the building, and reduce the reliance on air conditioning. When enclosed, the effect of natural ventilation is reduced, which may increase the need to use mechanical ventilation or air conditioning systems, thus increasing energy consumption.

In summary, enclosing the patio spaces has a negative impact on the indoor physical environment, which not only reduces indoor living comfort but also leads to an increase in building energy consumption.

5.3. Innovation

The innovation of this paper is, first of all, at the research methodology level. In recent years, although the research on the climate adaptation of vernacular dwellings in Jiangxi has been introduced to computer simulation, the research focuses on a single physical factor, ignoring the consideration of the overall environment. This paper, on the other hand, analyses the light environment, wind environment, and energy consumption at three levels to better analyze the reasons behind them. Not only that, this paper uses comparative experiments to summarize the advantages and disadvantages of vernacular dwellings and modern residential buildings in Jiangxi. Vernacular dwellings in Jiangxi have a pivotal position, and the study of the climate adaptability of vernacular dwellings in Jiangxi helps to excavate the principal mechanism behind it.

Secondly, this paper concludes that the patio has a positive impact on the indoor physical environment of vernacular dwellings through a comparative experiment with and without an enclosed patio space. This low-tech approach not only effectively reduces energy consumption and costs, but also embodies the concept of sustainable development, demonstrating the unique value of the low-tech approach in contemporary Chinese rural construction. A low-tech approach achieves a more appropriate and sustainable construction model compared to high-tech paths with low cost, low environmental burden, and minimal interference with the local ecology.

5.4. Recommendations

The findings of the software simulation analysis indicate that vernacular dwellings offer several advantages in terms of energy efficiency and comfort. These advantages come from the layout, patio, traditional materials, and the design of doors and windows. These designs are worth learning and borrowing from modern residential buildings. However, vernacular dwellings also have some disadvantages, including inadequate sealing and an unfavorable humidity environment. It is necessary to enhance vernacular dwellings with modern architectural design methods to facilitate their effective accommodation of the ecological environment.

(1)

In terms of optimizing the light environment, vernacular dwellings can take measures to improve indoor light conditions by increasing the brightness of roof tiles, adjusting the size of windows and patios, and enhancing the reflectivity of interior finish materials. Moderately lowering the elevation of windowsills can strengthen the effectiveness of natural lighting in the area adjacent to the windows. The enlargement of windows and patios not only increases the total amount of light in the room but also ensures an even distribution of light. The application of highly reflective materials to the interior walls serves to enhance the lighting effect within the interior space. When implementing these improvements, care needs to be taken to maintain a reasonable window-to-ground area ratio and to ensure consistency between window design and decorative style, maintaining the windy condition of the original facade.

(2)

In terms of wind environment improvement, vernacular dwellings make skillful use of patio design to promote heat and pressure-induced natural ventilation, ensuring a stable airflow environment in the main living space. Modern residential buildings can learn from this experience by adding ventilated roofs or skylights in order to enhance the effect of non-powered ventilation. In addition, for poorly ventilated spaces in vernacular dwellings, the performance of natural ventilation can be enhanced by combining it with light optimization, such as increasing the number of windows and opening skylights on the roof to expand the ventilation area and optimize airflow channels.

(3)

In terms of energy consumption control, vernacular dwellings are characterized by their thick peripheral walls, small and few windows, and lower energy consumption brought about by the structure of the cavity bucket wall, with the latter’s internal air layer acting as a certain degree of thermal insulation. Nevertheless, there is still a considerable gap between the thermal conductivity of the cavity bucket wall and the current standard (thermal conductivity < 1.0 W/(m²K)). In order to enhance the thermal insulation performance of external walls, several strategies may be employed. These include the incorporation of an additional thermal insulation layer within both the internal and external walls, or the filling of the interior of the cavity bucket wall with high-efficiency thermal insulation materials. The general lack of airtightness observed in vernacular dwellings, particularly in the gaps between windows and doors and in structural joints, can be effectively addressed through the adoption of sealing materials. Such methods have the potential to prevent the infiltration of cold air and reduce the dissipation of energy through air exchanges, thus contributing to the goal of energy saving and emission reduction.

This paper examines the climate adaptation of vernacular dwellings in Nanfeng County with the objective of providing a reference and database for the design of new and improved vernacular dwellings in rural areas of Nanfeng County. It should be noted that this study is not without shortcomings and limitations. Firstly, the research methods employed in this study are primarily field measurement and digital simulation. During the field measurement process, errors may occur due to human factors, which could result in deviations in the digital simulation. Secondly, the optimization strategy proposed in this paper has not been verified in real projects. In addition, the factors influencing the outcome of this study are limited to light environment, wind environment, and energy consumption. These factors warrant further investigation, particularly in relation to temperature, humidity, PET, and other variables. Future research should adopt advanced measurement tools and multi-faceted analysis of the physical environment to provide a comprehensive summary of the low-tech approach to vernacular dwellings.

6. Conclusions

The vernacular dwellings of Jiangxi represent a set of practices that have been developed and refined over centuries by Chinese ancestors. These practices aim to achieve a harmonious relationship between humans and nature. This paper employs a variety of simulation software to analyze the indoor physical environment and energy consumption of different types of vernacular dwellings. The aim is to compare these dwellings with local modern residential buildings in order to verify the climate adaptability of vernacular dwellings. The results of the simulation are analyzed in this paper, with particular attention paid to the reasons behind them. In addition, the article explores the low-tech methods embedded in vernacular dwellings.

• The simulation results demonstrate that the vernacular dwellings in Jiangxi have a better climate adaptation capability. The vernacular dwellings represented by the guard camp dwellings in Kandu Village exhibit an average natural lighting illuminance in the hall area that is 21% higher than that in the living hall area of modern residential buildings in terms of the light environment. In terms of wind environment, the main activity area can adjust the indoor wind environment through natural ventilation in summer, thus adapting to climate change toward hot summer and cold winter areas. In terms of energy consumption, the vernacular dwellings consume 32% less energy than modern residential buildings.
• The utilization of patio spaces, the application of wall masonry techniques, and the incorporation of local materials permit vernacular dwellings to be modified to accommodate local climatic conditions. Such low-tech methods of vernacular dwellings enable them to operate with low energy consumption while maintaining a satisfactory physical environment indoors.