Interior/Exterior Form and Property Research on Wu-Style Residential Houses from the Perspective of Sustainable Development

Abstract

Research on regional residential buildings is an important means of exploring the natural climatic adaptability of buildings and the sustainable development of culture. It is also an important path of sustainable social development. However, current research methods for architectural space find it difficult to clarify the internal and external relations of space, and the function of architectural space to adapt to the regional climate and cultural heritage is difficult to quantitatively analyze and measure. This study constructs a new research method of architectural interiors/exteriors, takes the traditional residential buildings in Wu-style architecture in the Jinhua area as a case study, summarizes the types and characteristics of the interiors/exteriors of Wu-style architecture, and reveals the spatial construction rules of the internal and external types realizing environmental sustainability and traditional residences. The results show that: (1) the architecture of the Wu style has five typical types of interior/exterior, and the regional representation of its interior/exterior is affected by both the human and the natural environment; (2) influenced by traditional Confucian culture, the architecture of the Wu style shows a central axial secondary buckling type and an enclosed type of interior/exterior form, which has the value of the times to coordinate the relationship between people in today’s society; (3) in terms of ventilation, daylighting, and heat dissipation, Wu-style buildings flexibly use the slender gray space form and wide cornice for the internal and external space transition, which effectively improves the ecological efficiency of the buildings’ ventilation, lighting, heat dissipation, etc., and has important reference value for the development and utilization of traditional buildings and the architectural design of new dwellings. At present, this new research method for the internal and external spaces of buildings still has considerable potential and needs to be deepened and improved through further research.

1. Introduction

During its long process of development and evolution, traditional Chinese residential architecture has been influenced by the natural environment, such as topography and natural climate, as well as the humanistic environment, such as local customs and living customs, gradually forming a number of regionally representative architectural cultures and architectural representations characterized by environmental adaptability. Traditional residential architecture often constitutes a unique local cultural heritage and is an important carrier of sustainable cultural development; at present, with the deepening of the sustainability concept, the design concept and method of traditional architecture based on environmental adaptability are of great reference value in the process of ecological construction of modern architecture. This is a typical case of inheriting and developing excellent traditional culture and reviving the regionality of architectural space. Therefore, traditional residential architecture is an important means of summarizing the wisdom of the people’s ancestors and of introducing innovations into the practice of residential architecture. Studies have shown that sustainable spatial forms such as patios that exist in a large number of traditional residential buildings not only have certain family culture symbolism significance but also afford convenient ventilation and lighting of buildings and improve the comfort of living architecture; the form of gray space, such as an open hall or an entrance hall, forms an effective transition between the internal and external spaces to create more diverse and flexible public spaces, and the traditional form of doors and windows can be adjusted to better suit the needs for privacy and openness of different functional spaces through means such as proportional materials and strengthen the public–private distinctions of spaces. A large number of examples demonstrate that there is a regional expression in the relationship between internal and external spaces in traditional residential buildings from which environmental and cultural sustainability can be seen. Accordingly, the study of the internal and external spaces of traditional residential buildings is of great significance for innovating architectural space design techniques, enhancing the connotation of architectural space, and promoting the sustainable development of architecture.

The research methods for the interior and exterior spaces of architecture are diverse, but for the complex object of the interior and exterior spaces of architecture, it remains difficult to comprehensively demonstrate the connection between the internal and external spaces within the building, and most research methods can only be derived from the perspective of a part of the space inside and outside the building, such as gray space and architectural detail space. The building as a whole, including its internal space, gray space, and external space of the plane composition relationship, has a direct impact on the architecture, while the properties of door and window openings on the space boundary line and the function of internal and external spaces are closely related to the surrounding environment. Based on this, this study summarizes and innovates the existing methods, combined with existing examples and research, with the purpose of dividing the flat space of residential architecture into the interior, gray space, and exterior and locating the dividing line between internal and external spaces. Further, it seeks to establish the research method of the architectural interior/exterior, construct the form and properties of the architectural interior/exterior, and comprehensively reveal the commonalities and characteristics between the internal and external spaces of residential architecture. As a vital representative traditional residential form in Jinhua, Wu-style architecture has great research value in transmitting regional culture and adapting it to the regional climate. As a typical and representative case, it has positive reference significance for the sustainable development of contemporary architecture. This study classifies and determines the space form and properties of buildings by innovating the research methods of architecture, taking Wu-style architecture as the research object to clarify the commonness and characteristics of the spatial composition of this style of architecture; its characterization of cultural and climatic adaptability is explored, which, to a certain extent, reveals the residential architectural means of sustainable development and provides a new perspective for the comprehensive study of the internal and external spaces of architecture.

2. Literature Review

2.1. Internal and External Spaces of Architecture

Research on the internal and external spaces of buildings is rich and diverse, covering different aspects such as architectural plane relationships, architectural functions, and architectural detail design, and architectures of different regions, cultures, and functions have been studied. Japanese scholars spearheaded the research on the internal and external spaces of architecture and have had a profound impact on the development of space research [1,2,3,4,5,6]. Yoshinobu Ashihara’s Structure of Exterior Space focused on the design of the external space of the architecture, providing new ideas and methods for the design of the external space [7]. After that, Alexander pointed out from a behavioral point of view that the external space was closely related to human needs, further revealing the internal logic of external space design [8]. He took different scenes as model languages, created new spatial forms through different combinations, and brought human factors into them to construct the life structure of the living environment, thus changing the form and appearance of the human environment and further exploring the possibility of human-oriented space [9]. Kisho Kurokawa’s Japanese Gray Tone Culture defined the transitional space between the internal and external spaces of the architecture as gray spaces and explored the social uses, privacy creation, and function of gray spaces [10]. Kijuro Yahagi’s Spatial Architecture focused on bodily perception and spatial cognition, providing a variety of methods and possibilities for spatial research. As a result, a research framework for the internal and external spaces of architecture was initially formed [11]. On this basis, starting from the architectural details, taking the openings such as doors and windows as the starting point, the composition of architecture was elaborated by Keiko Hirata, Hiroyuki Moriyasu, and others from the two sides of the internal and external spaces of architecture and the consciousness field of human activities, and such research has focused on the relationship between the residential space and the consciousness field [12,13,14]. Mustafa et al. adopted spatial syntax theory and its techniques for the integration, isolation, functional partitioning, and accessibility of the internal spaces of the traditional Iraqi architecture of Kurdish courtyard houses, suggesting that traditional practices have a direct impact on the function of the interior space of the architecture [15]. Yusuke Itami et al. focused on the composition of residential architecture plans in the south of Hunan, China, adducing the relationship between the configuration of the internal space and external environment-related studies [16]. Yui Ushiyama et al. conducted a study of the configuration mechanism between the internal space and the external environment caused by the action of gray space [17]. Park analyzed the plane space of traditional Chinese Hui-style architecture, summarizing the typical plane types, and argued that the spatial relationship of Hui-style architecture is closely related to its use function and family culture [18]. The study of the internal and external spaces within the architecture was thereby further enriched.

Domestic research on the internal and external spaces of architectures started late, but in recent years, with the increase in attention to this issue, a wealth of research results has been presented. Liu et al. focused on the plane types and combined relationships of traditional residential courtyard spaces in eastern Henan and clarified the typological characteristics of traditional residential courtyards there [19]. Zhang et al. revealed the typological characteristics of Xi’an residential architecture from the aspects of spatial composition, architectural form, and ratio scale. At the same time, the study of the function and layout of gray spaces is also more prominent [20]. Xiao explored the function and role of gray space in public architecture from the perspective of human behavior and psychological patterns [21]. Du and Guan studied the application of gray space in residential space design and analyzed the expression form, function, and construction method of gray space in the application of modern residential space design [22]. However, most of this research remains in the descriptive stage of space and applies a single method with less attention to the design and function of architectural details [23,24,25,26,27], and the research methods for the internal and external spaces of architecture need to be further articulated.

2.2. Architectural Regionality

From Mumford’s “regionalism,” through the presentation of the term “critical regionalism” by Chuniss, to the six elements of critical regionalism proposed by Frank Dune [28], the perspectives of research on architectural regionality have gradually diversified. They recognized real life and technological development but emphasized the mandatory application of technology, and also respected context, environment, history, and culture. Later, Poulsen et al. explored the landscape and climate response of architecture in terms of vernacular, modern, regional, and ecological sustainability from the perspective of architectural climate adaptation [29]. Tang et al. conducted a study of six typical forms of residential architecture in China from the perspectives of history, geography, structure, and color and argued that natural and cultural factors were important factors affecting their regional changes [30]. Lawrence reviewed the study of regional architecture over the past 100 years and constructed a framework for regional architecture [31]. Based on this, Vietnamese scholar Le elaborated on the different architectural styles of traditional architecture in different parts of Vietnam as adaptations to the local climate [32]. Jeon et al. summarized the regional and epochal characteristics of architectural remains in northern Korea [33]. The Russian scholar Pilyak explained the regional characteristics of traditional Russian wooden architecture, such as large undersides, miniature top surfaces, and hierarchical arrangements [34].

Domestic scholars benefit from a richness of local examples, and their research perspectives on the regionality of architecture are more diverse. Zhang et al. explored the creation method of regional architecture based on the cultural background and regional architectural examples of southwest China [35]. Xu explored the regional evolution of residential courtyard spaces in Bashu from the perspective of historical change and cultural inheritance [36], while Wu et al. combined contemporary and traditional architectural examples to explore the regional expression of materials in terms of architectural structure, architectural environment, and architectural skin [37]. Ge studied the characteristics of local materials such as walls, tiles, and bluestone in Huizhou cultural architecture and their roles in regional expression [38]. In addition, there are many other regional-related studies that reveal regional expressions from perspectives such as environmental climate and architectural materials [39,40,41,42,43,44].

2.3. Traditional Dwellings

China has a profound history and a large number of historical and cultural heritages. Domestic scholars started their research on traditional residential architectures earlier, and the research scope basically covers the existing forms of residential architectures. Lu, a well-known scholar, once summarized the research process and achievements of traditional dwellings in the 50 years after the founding of the People’s Republic of China. He pointed out that the research on traditional dwellings in China could be traced back to about the 1920s and 1930s [45]. Long mapped cave dwellings in northwest China and started the research journey of Chinese dwellings [46]. Later, Liu studied the traditional dwellings in Sichuan and Yunnan, defined the dwellings as an architectural type for the first time, and affirmed the important value of the research on the dwellings [47], laying a foundation for the research on the traditional dwellings in China. Before the 1980s, a large number of studies on traditional dwellings were confined to architectural mapping and characteristic investigation. Among them, “An Introduction to Chinese Dwellings” by Liu was the first study on traditional dwellings in China, comprehensively summarizing the types of traditional dwellings throughout the country [48]. Li broke through the traditional research perspective of architecture and integrated geography, sociology, and other perspectives to study residential architecture [49], marking the gradual diversification of research perspectives and methods of residential architecture in China.

In recent years, the research perspective of traditional dwellings has been continuously expanded, from the basic architectural forms, materials, process characteristics, passive energy-saving means, and other aspects of the research to traditional dwellings with the social, cultural, environmental, and other types of multidisciplinary integration, in order to explore the sustainable development and inheritance of traditional dwellings. Cao et al. explored the adaptability of traditional Miao dwellings in western Hunan to the local unique mountain climate by means of orientation, terrain, the layout of quadrangle courtyards, sloping roofs, deep eaves, patios, and building materials, which led to the study of passive energy-saving methods of traditional dwellings [50]. Jin et al. pointed out that northern residential architectures create a pleasant indoor living environment by using the simplest methods such as the plane layout, window and wall materials, and extremely low energy consumption [51]. Chen et al. clarified that decentralized courtyards in traditional Chinese dwellings play a good role in natural lighting and ventilation organization [52]; Lu et al. adapted to the local climate through the design of the ground floor stilts, terrace, loggia, retreat, functional layout, and roof slope [53].

After a long time of evolution and development, traditional dwellings have made many adaptations to the natural and cultural environment through continuous trial and error and modification by generations of ancestors, which also show the sustainable development connotation of traditional residential architectures.

2.4. Review

In summary, there are already abundant research results on the internal and external spaces and regionality of traditional residential architecture; however, there are still some deficiencies: (1) the research methods of the internal and external spaces of the architecture are diverse, but they are still not systematic, and there is a lack of comprehensive analysis methods to clarify the connection between the internal and external spaces within the architecture; (2) research on regional architecture has mainly focused on the regional representation of the architectural structure and decoration, but research on cultural and climatic adaptability from the perspective of spatial composition is insufficient; and (3) there are abundant studies on space design energy-saving methods of traditional residential houses, but there is a lack of in-depth thinking on the architectural form and cultural characteristics and of an in-depth analysis from the perspective of sustainable development in which architectural features and cultural elements meet the requirements of sustainable development. In this study, based on existing research methods and angles of internal and external spaces, we construct a new research method for the architectural interior/exterior, conduct research on Wu-style architecture from all aspects of the form and properties of the interior/exterior, further subdivide the characteristics of Wu-style architecture, and summarize its characteristics and commonalities so as to dig deeper into the regional expression of the culture and nature of Wu-style architecture, and to clarify the characteristics of the Wu-style architecture in order to develop innovative research methods of the internal and external spaces within the architecture, thereby contributing to the excavation of architectural regional expressions and traditional residential protection and utilization as well as the sustainable development of new exploration.

3. Research Subjects

Wu-style architecture is a representative traditional residential name in the Jinhua area. Historically, the traditional dwellings in Jinhua were referred to as Hui-style architecture because they were similar to those in southwest Anhui and Zhejiang. However, after the influence and development of Wu culture for a long period of time, the traditional dwellings in Jinhua have a certain uniqueness in the architectural details such as the gable shape, yard scale, building scale, and indoor and outdoor decoration, so they are considered as a special form of traditional dwellings independent of Hui-style architecture. Wu-style architecture has five characteristics: a horse head wall, an open hall, a large courtyard, a large house, and fine decoration, reflecting its cultural personality and regional expression to a large extent [54,55,56,57]. However, compared with the research on other regional traditional dwellings, there are few studies on Wu-style architecture. In order to further explore the form characteristics and connotation value of Wu-style architecture and protect and inherit the spatial characteristics of Wu-style architecture, through field investigation and existing data collection, this study selects representatives of Wu-style residential architecture in Jinhua as research materials according to the architectural form and regional distribution and collates and brings together drawings and photo materials of the various floor plans and architectural features of a total of 20 Wu-style residential buildings as research objects.

4. Definition

Interior/exterior refers to the spatial fields composed of the interior, gray space, exterior, and interior/exterior boundary lines of the architecture. Of these, the interior refers to the space field that is covered by the roof and other structures and completely enclosed by the walls, doors, and windows; the gray space refers to the space field in the architecture that is covered by the roof and other structures but not completely enclosed by walls, and the space field that is in contact with the exterior air but not exposed to rain; the exterior refers to the space field inside the red line of the land when the interior space and gray space are removed (Figure 1). The characteristics of the interior/exterior areas within the architecture are concentrated in two aspects: the interior/exterior form and the interior/exterior properties.

4.1. Definition of Interior/Exterior Form

The interior/exterior form refers to the planar space formed by the interaction of the interior form, the gray space form, and the exterior form of the architecture (Figure 2). Through the classification and combination of different spatial forms of the architecture, the types of interior/exterior forms are revealed.

4.2. Definition of Interior/Exterior Properties

The properties of the interior/exterior represent an integration of the four relationships between the spatial use of the interior, gray space, exterior of the architecture, and the property and perimeter ratio of the interior/exterior boundary elements on the interior/exterior boundary lines. Of these, interior/exterior boundary elements refer to the categories of physical elements such as walls and openings (doors, windows, etc.) that make up the interior/exterior boundary lines. Properties refer to the daylighting, ventilation, sight, throughway, and other properties of the interior/exterior boundary elements (Figure 3), and the perimeter ratio refers to the proportion of interior/exterior boundary elements in the perimeter of the room in which they are located.

5. Methods

5.1. Extracting the Interior/Exterior Form

The extraction of interior/exterior forms requires the extraction and classification of plane forms for the interior space, gray space, and exterior space of the architecture. The preliminary analysis of Wu-style architecture indicated that its gray space has important usage features and is more inclined to the properties of the interior; therefore, in the overall extraction process, the gray space and the interior were first treated as a whole for interior/exterior form extraction, and on this basis, the different plane forms of the gray space were extracted for classification. The extraction classification method was as follows.

When extracting the interior form, the gray space and interior are considered as a whole. The basic type is a square, homogeneous form. When compared with the basic type, the internal inside corner appears, that is, the architecture plan contour is convex inward for the flexing type, which is divided into zero order (basic type) and secondary buckling type according to the number of inside corners. In addition, when the interior contains an open-air courtyard, it is an enclosed type, and it is divided into singular and plural according to the number of courtyards. According to the above standards, the interior form of Wu-style architecture can be divided into the flexing type (two), enclosed type (singular), and enclosed type (plural; Figure 4).

On this basis, we extracted the gray space form. When the gray space partially or completely surrounds the interior, it is an inclusion type; otherwise, it is an included type, and it is divided into four sides, three sides, and two sides according to the contact relationship. The adjacency between the gray space and internal space determines the adjacency type and is divided into two sides and one side according to the contact relationship. In addition, complex gray spaces can be formed by these three forms individually or in combination with each other to form a composite form. Specifically, it can be divided into seven composite types: inclusion type + inclusion type, inclusion type + included type, inclusion type + adjacent type, included type + included type, included type + adjacent type, adjacent type + adjacent type, and inclusion type + included type + adjacent type. According to the above standards, Wu-style architecture can be divided into seven types of gray space form: included type (four sides), included type (three sides), compound form (inclusion type + inclusion type), compound form (inclusion type + adjacency type), compound form (inclusion type + included type), compound form (adjacency type + included type), and compound form (inclusion type + included type + adjacency type; Figure 4).

When extracting exterior patterns, the exterior is fully or partially contained in the interior as an included type. According to the contact relationship, it is divided into four sides, three sides, and two sides. According to the above standards, the exterior form of Wu-style architecture can be divided into the included type (three sides) and included type (four sides; Figure 4).

In summary, the forms of the interior, gray space, and exterior of the research object are extracted layer by layer and combined to construct the interior/exterior form of the research object.

5.2. Extracting the Interior/Exterior Properties

First, the extraction of the properties of the interior/exterior takes the room as the basic unit to extract the interior, exterior, and gray space functions of different rooms (

Table 1. Different spatial functions of the architecture.

Interior Function			Gray Space Function		Exterior Function
Master bedroom (MB)	Secondary bedroom (SB)	Study (S)	Living room (GLR)	Corridor (GC)	Atrium (A)	Atrium and corridor (A&C)
Living room (LR)	Side hall (SH)	Lobby (L)	Lobby (GL)	Side hall (GSH)	Neighbor (N)	Road (R)
Storeroom (SR)	Dining room (DR)	Kitchen (K)

). Analysis shows that Wu-style architecture has nine main types of interior functions, five types of gray space functions, and four types of exterior functions.

Second, to determine the properties of the interior/exterior boundary elements of the inner and outer boundaries, the interior/exterior boundary elements are classified according to the indicators of daylighting, ventilation, sight, and throughway in the open and closed states. Using the above indicators, we extracted the interior/exterior boundary elements of the study object. In Wu-style architecture, there are mainly 15 interior/exterior boundary elements (Figure 5).

Finally, the proportion of the interior/exterior boundary element, which is the ratio of the interior/exterior boundary element to the perimeter of the room in which the element is located, is calculated (Figure 6).

In summary, according to the internal space use, gray space use, and external space use of the architecture, and the proportional relationship between the interior/exterior boundary elements on the inner and outer boundary lines occupying the perimeter of the room, the properties of the interior and exterior are extracted.

6. Classification Analysis of the Interior/Exterior Form and Properties of Wu-Style Architecture

6.1. Classification and Analysis of the Interior/Exterior Form

Taking the external space form of the architecture as the horizontal axis and the internal space form and gray space form as the vertical axis, we created an interior/exterior form type table and analyzed different types of form one by one.

Eight types of interior/exterior forms were arranged as types A to H (Figure 7). The interior and gray space forms of types A, B, and C are all of the flexing type (two), the exterior forms are all of the included type (three sides), and their internal spaces are distributed around the south courtyard, which serves as an entrance hall; the outer and inner spaces progress layer by layer, and the public and private fields are in a reasonable transition. Type A has a relatively large internal space and does not have direct contact with the external space; however, it uses gray spaces such as corridors for transition. It can be seen that it pays more attention to the privacy of the internal space. Type B, relative to type A, has a reduced proportion of internal space; the proportion of gray space increases as it plays a more functional role. The openness of the internal space is further enhanced. Type C has a clearer internal public–private boundary. The internal space on the south side is in direct contact with the external space, has stronger openness, and is greatly influenced by the external space. The internal space on the north side is connected to the rest of the space through the gray space, which is more private. The internal spaces of types D, E, F, and G are all of the enclosed type (singular), and the exterior spaces are of the included type (four sides). Such spaces are less affected by the surrounding neighbors and roads, and the use of an atrium space forms an independent residential system with both internal and external spaces without interference; these types of atrium space no longer play a specific functional role, playing a more important role in adjusting the indoor microclimate as well as strengthening the indoor ventilation and lighting. The gray space of type D occupies a large proportion, not only supporting a large number of open functions but also serving to organize the various functional lines of the house; such spaces are organized freely and openly, while the internal space with strong closure can still maintain a certain amount of privacy. Type E internal spaces are distributed on the east and west sides of the atrium, and the central public space axis of the house is represented by the layout of the atrium gray space. Compared with the previous two types, F and G have a higher proportion of internal space, presenting stronger attributes of the private domain. The internal space of type F half-surrounds the gray space and the external space. Compared with type F, type G has a circular layout in its internal space, and the functional organization of the internal space is better. The internal space form of type H presents a unique enclosed type (plural), which has two atrium spaces allowing greater external communication to the internal space, and part of the gray space is used to separate the internal and external spaces, such that the communication between the internal and external spaces has a certain difference, where some more extroverted internal spaces can actively communicate with exterior spaces, and some internal spaces with stronger private attributes can still maintain a certain degree of independence.

An overall analysis of the interior/exterior form of the architecture shows that Wu-style architecture continues the axial symmetry, closure, and enclosure in traditional Chinese architecture and creates family public space and etiquette space through the vertical sequence of gray space such as a foyer, atrium, and hall, showing a certain cultural regionalism. The combined layout of the gray space and external space forms a good ventilation circulation space, which adapts to the climate characteristics of the high humidity in the rainy season in the Jinhua region, and uses good ventilation and the climate adjustment effect of the gray space to cope with the hot summer, showing the strong adaptability of traditional residential houses to the climate.

6.2. Classification and Analysis of Interior/Exterior Properties

The research yields the following properties of the interior/exterior types a–e (Figure 8): type a, space openness and strong connectivity; type b, space openness, strong visual permeability, and no public–private difference; type c, space openness, weak public–private difference, spatial connectivity, and visual permeability balance; type d, medium openness and strong public–private difference; type e, lack of gray space function, extreme oneness, and closure.

In type a (Figure 9), the proportion of interior/exterior boundary elements in the form of doors ①–⑥ is quite high, especially in living rooms and lobbies with strong public attributes. There are almost no interior/exterior boundary elements in the form of windows ⑦–⑭, and there are only some rooms with strong openness, such as dining rooms. A certain number of windows show a distinction between public and private. In general, the functional organization of the type a space is simple; a large number of passing boundary elements make the communication between the internal and external spaces more convenient, and the integration of the internal and external spaces is strong.

In type b (Figure 10), there are many interior/exterior boundary elements in the form of windows ⑦–⑭, and their proportions are high, presenting the public and private attributes without distinction. There are many types of windows. Typical paper-pasted windows exist in the traditional architecture. Paper is used to adjust the daylighting, and there is an interior/exterior boundary element in the form of a window opening ⑬. Such window openings are generally treated with wooden fences to prevent theft. The exterior is mostly neighbors and roads. Although visible, the high height of the window still ensures the privacy of the interior. In addition, the proportion of space walls with strong private attributes, such as bedrooms, is significantly higher than that of spaces with strong public attributes such as dining rooms. Benefitting from the addition of interior/exterior boundary elements such as windows, the private space is more open than in type a. At the same time, a large number of interior/exterior boundary elements exist on the boundary of the gray space, which plays an important role in organizing the internal traffic of the architecture. In general, such spaces present a high degree of visual unity, without distinction between public and private spaces.

Type c (Figure 11) presents a high degree of openness. In the communication between the internal and external spaces, the number of interior/exterior boundary elements in the form of doors and windows is large, and the difference between public and private attributes is small, which is only reflected in the space communicated by the interior/exterior boundary elements. It is connected to the external space through the gray space. Spaces with strong public attributes such as the living room directly communicate with the external space, presenting a richer spatial organizational form. Although the interior space presents strong openness, the proportion of walls is still high, in line with the characteristics of the traditional architecture. At the same time, there are many rooms and functions in this type of space, showing a complex spatial organizational relationship. In general, type c shows high openness with a weak public–private distinction.

In type d (Figure 12), there are obvious differences in the openness of different functional spaces. Spaces with strong private attributes such as bedrooms are only related to the external space in terms of sight, ventilation, and daylighting. In terms of traffic, space communication is carried out by setting up internal functions such as corridors. The lobby, living room, and other open spaces are directly connected to the external space, which enhances the openness of these public spaces. The proportion of walls in storage-type spaces such as storerooms is extremely high, and the closeness is strong, which is in line with their use function. In general, type d reflects different open attributes of different functional spaces.

In type e (Figure 13), the amount of gray space is small, and the function is simple. At the same time, the internal and external spaces are in direct contact, and the gray space transition function is weak. To ensure that the internal space has a certain degree of privacy, the proportion of interior/exterior boundary elements such as doors and windows is generally low, and the proportion of closed elements such as walls is further improved, showing extreme closure, especially in the bedroom and other areas requiring privacy; the space even appears without an opening part, with only the opening within the interior, and the independence of the indoor space is further strengthened. In more open spaces such as lobbies and living rooms, interior/exterior boundary elements such as doors and windows also appear to limit the line of sight. Overall, type e has a strong degree of closure and independence. Owing to the lack of gray space function, this type is strengthened by reducing the proportion of openings to ensure public and private properties, and the independence of the internal space is strengthened.

Based on the overall analysis of the property, it can be found that spatial functions of Wu-style architecture are arranged around the basic living needs, and the visibility as well as proportion of room openings is adjusted according to the actual needs to show different public and private characteristics, from the completely open living room space to the privacy of the bedroom space, to meet the living needs of different spaces. At the same time, in order to better cope with the climate of the region, some special boundary elements such as paper-pasted windows are adopted. By adjusting the visibility of the window, the lighting needs of the room are met, and the dynamic balance between living quality and privacy is achieved, laying a foundation for the contemporary adaptation of regionalism.

7. Characteristic Analysis of the Interior/Exterior of Wu-Style Architecture

7.1. Interior/Exterior Type Analysis

Based on the above analysis, we can summarize interior/exterior form and properties of the research objects (Figure 14). A distribution table for the interior/exterior within the architecture was created with the “interior/exterior form” type as the vertical axis and the “interior/exterior property” type as the horizontal axis, according to the form and properties of the interior/exterior determined for the research object. The placement in the table indicates the distribution of the architecture that was analyzed to obtain five interior and exterior types of the building.

In type 1 (Figure 15), the proportions of interior and gray spaces are similar, and the gray space undertakes important use functions, such as living rooms and dining rooms, and serves important family public activities, while the public space is distributed around the courtyard, creating a more open sense of use. By facing the gray space, each room has an entrance and exit, it is easy for the internal space and the gray space to communicate, and the moving line is convenient. Long and narrow gray spaces such as corridors build the ventilation system of the house, which is conducive to the lighting and ventilation of the internal space. The proportion of the window in the interior space is low, and the proportion of the wall is high, which ensures that private spaces such as bedrooms have a certain degree of privacy. The south-facing layout of the external space is conducive to the overall lighting of the house, and at the same time, it is regarded as the main entry space, connecting the living room, playing the role of communication between the inside and outside spaces, greatly improving the openness of the space.

In type 2 (Figure 15), the gray space proportion is reduced, but the interior space has entrances and exits facing the gray space, and the gray space undertakes a traffic role communicating between the indoor and outdoor spaces; in addition, with the reduction in the proportion of gray space, it supports fewer public events as there are only important spaces such as the living room. At the same time, the proportion of internal space increases, and the internal space directly faces the external space with doors and windows, which support daylighting and ventilation for the indoor space. The distribution of internal space reflects a certain attribute of public and private differences, and the main space around the external space is the internal space with stronger openness, such as the dining room, which is directly connected to the external space using high windows and other interior/exterior boundary elements; spaces with strong privacy, such as the bedroom, are laid out in the north of the architecture, so that the overall privacy increases from south to north and from the middle to the east and west sides.

In type 3 (Figure 15), the proportion of internal space is low, and the internal space is broken, with the parts showing strong independence from each other; as the gray space proportion is extremely high, it plays an important role and can facilitate rich family activities. At the same time, the courtyard is in the center, and the space is arranged around the courtyard, which is conducive to family activities. The internal space presents a function-based difference in openness, including more privacy-based spaces such as bedrooms, and communicates with the outside world with only a door; the dining room and side hall with strong openness also have window line-of-sight communication with the outside world. The doors of the internal space do not directly face the living room and the lobby, making the sense of enclosure of the living room stronger, and the semi-enclosed space creates an open and solemn sense of space. The hall is connected to the courtyard, and the widened cornice is used to ensure the lighting of the hall and adjust the intensity and angle of light in the summer and winter, so as to adapt to the climate environment of a high temperature in the summer and a low temperature in the winter in Jinhua.

In type 4 (Figure 15), the internal space form is of the enclosed type, and there is only a gate to contact the surrounding neighboring road with no windows around, ensuring the overall independence of the house; while a small atrium is set up inside the house that plays a role in daylighting and ventilation, there is a partial gray space transition between the courtyard and the interior space. Some rooms, due to public activities, have directly open windows facing the atrium to communicate between the indoor and outdoor spaces, strengthen the openness of the space, and enrich the interior space. At the same time, the bedrooms are connected to each other through the interior corridor, ensuring better privacy. Additionally, there is only a gate to contact the surrounding neighboring road with no windows around, ensuring the overall independence of the house. At the same time, the overall layout of the house is more compact and closed, reflecting the concept of saving land. The exterior space is centered, and windows of the house open to the atrium, which greatly improves the ventilation effect of the space and meets the needs of humidity ventilation in the plum rain season in Jinhua.

In type 5 (Figure 15), the internal spatial form is also of the enclosed type, and like type 4, it ensures the strong independence of the house; unlike type 4, type 5 not only has no windows or other openness interior/exterior boundary elements around it but also faces the atrium. The proportion of doors and windows is also extremely small, the proportion of walls is extremely high, and only the gray space such as the living room that exists in the overall house is more open. The rest of the rooms are extremely closed, and there are more internal rooms; the functional organization is complex, but with the external space and gray space, there is very little communication, mainly through the internal corridor, playing the function of transportation, among other functions. The layout of the exterior space and the gray space corridor regulates the microclimate of the house in the middle of the building, avoiding direct sunlight in the summer while satisfying the lighting and ventilation, and forming a warm living environment in the winter that becomes cool in the summer.

7.2. The Relationship between the Interior/Exterior Type and the Regional Environment

The interior/exterior type of the architectural space is influenced by both humanity and the natural environment, and the regional expression of the boundary is remarkable.

7.2.1. Adaptability to Cultural Environment

Represented by types 3 and 4, the courtyard is in the middle, which reflects the concept of family etiquette in traditional Chinese culture. Dining and living are carried out around the atrium to enhance family cohesion. In types 1 and 2 versus types 3, 4, and 5, the atrium is located on the south side of the house in the former, while in the latter, it is located in the middle of the house; compared to the former, the latter’s spatial centripetality is more pronounced, and as such, most buildings are inhabited by large families.

Types 4 and 5 are more independent; except for the gate, there is almost no other interior/exterior boundary element to communicate with the surrounding environment, whose purpose is mainly to ensure the safety of the family’s property and their life needs. In ancient times, the Jinhua area benefited from good water transportation, and the resultant commercial prosperity produced a large number of rich merchants. The boundary form of high walls and no windows in residential buildings reflects the traditional idea of “wealth is not exposed”. At the same time, because the merchants went out for business, in order to ensure the safety of the women and children of the family, the opening of the external space was reduced, and the atrium was set up inside to ensure a safer living environment under the conditions of ventilation and daylighting.

The proportion of external space in types 4 and 5 is low, with hilly terrain accounting for 70%, the water system accounting for 10%, and arable plains accounting for 20% of the total area in Jinhua, and the contradiction between man and land is prominent. Therefore, during building and village planning, construction land should be fully saved, and agricultural land should be protected.

In types 1 and 2, most of the important functional spaces such as those for residential hospitality are located on the north side of the house, while the functional spaces such as those for living are mostly located on the south side of the house, which happens to coincide with the ritual thought of “the front hall and the back room”. Type 3 is the most prominent expression. As an important ceremonial and hospitality space inside the residence, the hall is enclosed on three sides, further emphasizing the ceremonial hierarchical order of the space; the living spaces such as bedrooms are extremely private, and invisible windows, doors, and other elements are used to enhance the privacy of the living spaces.

Comparing type 1 with type 2, type 4, and type 3, the internal gray space is further reduced. The main purpose of enhancing the closure is to maintain the privacy of personal life, so as to ensure the freedom of individual life. In summary, for the sustainable development of culture, there are two common treatment methods in terms of form (Figure 16). First, the internal space, gray space, and external space of the architecture are axisymmetric, in line with the traditional concept of etiquette. Second, the swirling layout of the internal space has centrality and reflects the family concept. At the same time, there are two more common treatment methods in terms of properties (Figure 16). First, the interior/exterior boundary elements facing the neighbors and roads are extremely closed, which is consistent with the introverted property of traditional culture. Second, the lobby and living room are centered, the private space is located on the north side of the residence, and the public space is located on the south side of the residence, showing the traditional pattern of a front hall and a back room.

7.2.2. Environmental Adaptability

Jinhua is located in a subtropical region, which has a subtropical monsoon climate with four distinct seasons, abundant heat, and rainfall. Rainfall is concentrated in late spring and early summer, and summer is long and hot.

In terms of the interior/exterior form, type 1 and type 3 use the design of the gray space, long corridors, and an atrium to form a good ventilation system for residential buildings and place doors and windows at both ends of the narrow corridor to form a “narrow pipe effect,” whereby wind is used to take away the moisture in the house. Contrariwise, in types 2 and 3, a large number of internal spaces have open windows to the corridor and atrium; this type of interior/exterior boundary element with good ventilation is coordinated with the atrium to form an upward airflow using the principle of atmospheric pressure to promote an indoor airflow. At the same time, the above design can form an indoor and outdoor air pressure difference in the hot summer weather, forming an airflow and removing the heat.

Because the outer walls of the houses are not interior/exterior boundary elements for daylighting, the interior space mainly relies on the atrium for daylighting, so in all types, the courtyard spaces are located in the south-central area, and the interior/exterior boundary elements such as windows are mostly posted with paper to ensure indoor privacy while daylighting.

In order to cope with the summer heat in the Jinhua area, types 3, 4, and 5 set up a gray space corridor around the atrium, and outside, pick eaves are used. In the summer, when the angle of the sun is high, the sunlight cannot directly hit the house, alleviating the rise in the room temperature; in the winter, the sun is low and can directly shine into the house, increasing the room temperature and forming an indoor microclimate that is warm in winter and cool in summer. Wu-style architecture also includes more loft areas to form an insulated space under the roof, further avoiding summer exposure. In response to the concentrated precipitation in the Jinhua area, traditional houses form a good drainage system through sloped roofs and atriums, and all interior/exterior types revolve around the atrium space; under the eaves, a sunken drainage ditch and a sewer pipe outlet are set up to quickly drain the water, and water collection vessels such as water tanks are placed in the atrium space to collect rainwater to meet household needs during periods of drought and little rainfall, playing the role of a fire pool.

In summary, the sustainable development of the Wu-style architecture environment mainly reflects the following strategies. For the daylighting conditions in the Jinhua area, there are two more common treatment methods (Figure 17). First, in response to the daylighting situation on the south side, the external space is concentrated on the south side of the building; second, the gray space depth is used for daylighting adjustment under different daylighting conditions in the summer and winter. At the same time, there is one more common property treatment method (Figure 17). In the inward layout of the interior space interior/exterior boundary elements, the room facing the central courtyard is arranged with a large number of interior/exterior boundary elements with good daylighting, while that facing the surrounding neighboring road space is arranged with a large number of closed interior/exterior boundary elements such as walls. In view of the high-humidity conditions in the rainy season in the Jinhua area, there are two more common treatment methods in terms of form (Figure 18). First, a large number of slender space forms, such as long corridors, enhance the indoor air circulation. Second, the included-type exterior form is combined with the enclosed-type interior form, and the atrium is used to introduce wind into the interior space. At the same time, there is one more common treatment method in terms of properties (Figure 18). The end of the slender space is equipped with a highly ventilated interior/exterior boundary element to form a ventilation corridor. According to the characteristics of the summer and winter monsoons in Jinhua, there is a more common treatment method in terms of form (Figure 19). Residential buildings are mostly clustered and distributed, and the ventilation spacing is insufficient; the external space is laid out internally to strengthen the ventilation of the residence, and a complex gray space system is formed.

8. Conclusions

In this study, the forms and properties of the interior/exterior of buildings were classified and analyzed through the study of the interior/exterior of the architecture. It was put forward that there are five types of Wu-style architecture: internal and external moving line integration; centered public spaces; gray space oneness; centripetal interior spaces; and weak connections between internal and external and complex functions.

The research results show that Wu-style architecture in all types of interior/exterior shows a strong idea of sustainable development of regional culture and sustainable construction strategies concerning the environment and climate adaptability.

Regional culture: (1) The spatial forms of axis symmetry and central courtyards in Wu-style architecture are influenced by traditional Chinese culture and show a strong concept of clan etiquette. (2) The internal forms of the flexing type (two sides) and enclosed type reflect the planning idea of gathering families and enhancing harmony. (3) The form of the boundary elements inside the external space and the windowless walls are influenced by traditional farming and commercial culture. (4) The layout of the gray space reflects the concept of harmony between man and earth. Based on this, Wu-style architecture shows strong spatial characteristics in the construction of etiquette space, the construction of public and private spaces, and the shaping of the family concept, which is conducive to the inheritance and development of regional culture.

Environmental and climatic adaptability: (1) Wu-style buildings form a complete internal circulation and ventilation system by using the built-in external space and corridor gray space. (2) In the enclosed space form, the high open boundary elements face the courtyard, and the orientation and type setting form the internal lighting system of the building. (3) A gray space with wide eaves adapts to the high temperature in the summer in Jinhua, forming a thermal insulation and heat dissipation system that is warm in the winter and cool in the summer. (4) A gray space corridor is set up around the atrium to form the automatic heat dissipation system of the building. Based on this, the various climate-adaptive means of Wu-style architecture, such as heat dissipation, thermal insulation, ventilation, and lighting, are of great significance to the sustainable ecological development of building energy conservation and emission reduction. Meanwhile, the dynamic adjustment of water and heat conditions in different seasons is of enlightening significance to the sustainable ecological development of contemporary buildings.

To sum up, Wu-style architecture has significant internal and external characteristics, and its cultural sustainability and environmental adaptability have been verified in reality.

The main contributions of this paper are that it establishes a set of research methods for the internal and external spaces of architecture and analyzes the responses of architecture to natural and cultural impacts through the form and properties of the interior/exterior. Our research will enhance the analysis of regional architecture in order to deepen our understanding of the cultural and climatic adaptability of regional architecture. The research results are also of great significance for innovation in architectural design methods and provide a theoretical basis and guidance for sustainable cultural development and low-carbon, energy-saving architectural design orientations.

There are several potential directions for future research. Firstly, in terms of the ecological sustainability of traditional buildings, many scholars at home and abroad have conducted quantitative analysis on the energy-saving characteristics of traditional buildings by constructing relevant parameters, proving the passive energy-saving wisdom of the spatial layout of traditional buildings [58]. On the basis of quantitative research, this paper conducted a qualitative analysis of Wu-style architecture from the aspects of the layout design of the building space, the determination of internal and external functions of the building, and the type and proportion of the opening part, so as to put forward the possibility of its ecological sustainability. Although this paper focused on qualitative research, the necessity of quantitative research methods is highlighted by a large number of studies in the literature. Therefore, scholars should further strengthen the quantitative analysis of energy-saving methods of Wu-style architecture in the subsequent research process. Secondly, in the context of national development, with building construction in full swing, a large number of modern means of architectural space have wreaked havoc for existing traditional architectural styles, and the regionality of local-style dwelling house building is at stake; at the same time, the existing residential buildings have been unable to meet the needs of modern life, and cultural heritage is facing interruption. Therefore, making the regional architecture adapt to contemporary life is of great significance for sustainable development. At present, a large part of regional modern translation is still stuck in the application of traditional materials and techniques, and the repetition of traditional cultural symbols [59,60,61,62,63]. Such partial and superficial imitation of regionalism does not really understand the core of regionalism and does not really penetrate into the core of culture. Therefore, this study will continue to study the traditional cultural symbols and characteristics on the existing basis and study their regional expression from a more in-depth perspective of architectural space, so that regional abstraction can be combined with modern technology and life, in order to achieve the balance between architecture, humans, and the environment. This research is also of great significance for regional modernization translation and innovation in architectural design methods, providing a theoretical basis and guidance for sustainable cultural and environmental architectural design orientations. In order to further improve the research methods of architecture, future research should further expand the research object and further analyze the region, in order to provide guidance for contemporary architectural design.