Sustainable Design Methods Translated from the Thermodynamic Theory of Vernacular Architecture: Atrium Prototypes

Abstract

In the context of China’s sustainable development and dual carbon goals, research on thermodynamic architecture theory and vernacular architecture increasingly aligns with international trends, developing distinct characteristics. This research addresses the challenge of rapid changes in the built environment by focusing on climate adaptability and passive technologies. However, the development of thermodynamic theory in vernacular architecture faced technical limitations in the early 21st century and was later overshadowed by the industry’s reliance on active technologies to meet green building standards, resulting in a reduced role for architects in the green building field. This article traces the origins of passive architecture, rooted in vernacular architecture, and applies thermodynamic theory to explore architectural prototypes. It examines the theoretical feasibility of architectural design in achieving low-carbon and sustainable goals, aiming to fill a gap in thermodynamic theory within the broader context of sustainable architectural development. After demonstrating the various passive prototypes inherent in vernacular architecture, this paper proposes a courtyard prototype focused on residential comfort for design translation and analysis. The research methods employed include bioclimatic charting, balance point temperature analysis in time series, and extensive computer simulations. Through the process of prototype extraction, performance analysis, validation, and optimization, the paper systematically discusses sustainable design methods within the framework of thermodynamic architecture theory. It also provides practical demonstrations of these methods across four distinct climate regions in China. By translating vernacular architectural designs, this research systematically organizes the theoretical framework for architects’ early involvement in low-carbon and green building design, offering a theoretical foundation for initiating the design process through prototype translation while guiding the generation of green ecological buildings.

1. Introduction

1.1. Background Overview: Current Status of Thermodynamic Theory in Vernacular Architecture under China’s Sustainable Development

This section clarifies three conceptual layers: first, the current state of modern sustainable development theories in architecture in China; second, the development of vernacular architecture theory; and third, the integration of thermodynamic theory as part of modern sustainable architecture with vernacular architecture.

1.1.1. Current State of Modern Sustainable Development Theory in Architecture in China

The development of architectural sustainability theory stems from widespread concern about global energy and climate issues. Since the 20th century, countries worldwide, including China, have begun researching how to reduce the high energy consumption throughout the entire design and construction process in the architectural industry.

The earliest relevant research can be traced back to 1963 when A. Ogaya introduced the Bioclimatic Design Method, leading to the evolution of bioclimatic architecture. This innovative and systematic approach quantitatively analyzes design elements, addressing factors such as building orientation, form, ventilation, and spatial relationships [1]. Following the 1970s oil crisis, a new research avenue emerged, emphasizing energy-efficient buildings that reduce the use of non-renewable energy and adopt passive technologies. The Chinese architectural community actively participated in promoting energy-efficient building theories [2,3,4].

Since the 1980s, green building theory, derived from ecological architecture, advocates for “design following nature”. This approach emphasizes efficiency, environmental friendliness, and interaction with the environment, considering the relationship between nature, people, and buildings. Various countries have established standards, such as LEED in the U.S., BREEAM in the U.K., and CASBEE in Japan. In China, the “Green Building Evaluation Standard” [5] promotes green building concepts through a series of evaluation criteria that award 1–3 star ratings, accompanied by supportive policies for builders in administrative approvals and economic subsidies.

In the early 21st century, the concept of ultra-low-energy buildings, characterized by passive technologies, began to take shape in China. In 2015, the Ministry of Housing and Urban-Rural Development released the “Technical Guidelines for Passive Ultra-Low-Energy Green Buildings (Trial)” (residential buildings), defining these buildings as those that adapt to climate characteristics and natural conditions through high-performance insulation and air-tight structures, maximizing renewable energy use while minimizing heating and cooling demands. This guideline subsequently led to standardized technical guidance with the “Near Zero Energy Building Technical Standard” [6], aiming to guide the construction sector to focus more on utilizing passive technologies and renewable energy to meet energy efficiency requirements.

In recent years, global climate change has prompted heightened awareness of building carbon emissions. Green buildings achieved through active technologies alone can no longer meet low-carbon requirements, prompting a shift in design concepts to align with contemporary developments. Building thermodynamics, environmental control, and climate response theories have evolved, giving rise to the concept of “thermodynamic architecture” [7,8,9]. This field investigates energy flow relationships, encompassing climate factors, building form and materials, and human sensory perception. The primary goal is to identify building forms that efficiently organize relationships between buildings, climate, and the environment, thereby informing design methodologies. As a crucial component of sustainable development theory, thermodynamic architecture is gaining increasing attention from scholars in China [10,11].

1.1.2. Current Development of Vernacular Architecture Theory in China

On the international stage, architects like Alvar Aalto and Le Corbusier have integrated studies of vernacular architecture into their modernist works. This renewed focus on regionalism under critical regionalism has sparked fresh vigor. The evolution from traditional regionalism to critical regionalism has led many architects to reexamine “contemporary vernacular” or “new vernacular” architecture [12,13,14,15,16], encouraging global architects to actively reshape local vernacular architectural cultures.

China’s interest in vernacular architecture emerged somewhat later, around the 1930s, initiated by the Construction Society, which aimed at rescuing local environments. In 1944, Liang Sicheng’s “History of Chinese Architecture” [17] presented a comprehensive view of Chinese architectural history to global audiences, establishing a foundation for systematic research in Chinese architectural history. Subsequent works, such as Liu Dunzhen’s “Overview of Chinese Residential Architecture” [18] in 1956 and Liu Zhiping’s “Types and Structures of Chinese Architecture” [19] in 1957, laid the groundwork for vernacular architecture research.

Since the 1990s, vernacular architecture has increasingly gained attention from architects and theorists in China. In 1993, Professor Han Dongqing published “Types and Vernacular Architectural Environments” [20] in the Journal of Architecture, clearly distinguishing between “types” and “prototypes”, emphasizing the need to consider users’ subjective spatial needs and their interaction with existing natural and social conditions. In 1998, Professor Wu Liangyong’s “Modernization of Vernacular Architecture, Regionalization of Modern Architecture” [21] argued that research should focus on “regions”, recognizing the distinct regional cultural characteristics and various residential and climatic factors. In 1999, Chen Zhihua’s article “On Vernacular Architecture Research” [22] in “Notes from the North Window” considered vernacular architecture as encompassing all types of buildings within a rural environment.

Entering the 21st century, systematic studies on vernacular architecture have matured, with publications like “Complete Collection of Chinese Traditional Residential Types” (2014) [23] and “Luban’s Measuring Tools: A Survey of Chinese Vernacular Architecture” (2017) [24]. Furthermore, advances in digital and climate analysis tools have expanded research focus beyond forms and styles to include spatial structures, climate responsiveness, and dialectal variations of vernacular architecture.

1.1.3. Development of Thermodynamic Theory in Chinese Vernacular Architecture Research

Introducing thermodynamic architecture into vernacular architecture studies is a natural progression. Initially, scholars focused on the hot summer climates of southern China. Chen Boqi explored traditional housing from a climate adaptability perspective, translating his research into new design practices [25] (1965). Similarly, Lu Yuanding studied the siting, form, and materials of traditional southern buildings through physical measurements of environmental conditions [26] (1978).

Around the turn of the 21st century, domestic academic research on the thermodynamic theory of vernacular architecture deepened, systematically organizing foundational knowledge of thermal environments in architecture [27]. Experimental work included detailed environmental testing and continuous monitoring of traditional residences’ indoor thermal conditions [28]. With the rise of urban renewal projects in China, applying thermodynamic theory to uncover the value of preserving vernacular architecture has prompted further development of the theory toward offering more design-oriented guidance.

Existing studies reveal a broad foundation in data collection, surveys, and climate monitoring concerning the thermodynamic theory of vernacular architecture. However, several issues remain: (1) an emphasis on measurement over practice, as academic research often focuses on experimental buildings and environmental monitoring without strong ties to professional architectural practices; (2) a qualitative rather than quantitative approach, as current climate-based studies often merely compile case studies without utilizing thermodynamic and energy perspectives for in-depth analysis; and (3) an indicator-centric view that sometimes leads architects to compromise design quality to meet predefined standards.

1.2. Importance of the Research: Filling the Theoretical Gap in Sustainable Architectural Design

Thermodynamic architecture theory is a vital component of sustainable development theory. The theoretical development of vernacular architecture aligns with contemporary energy agendas focused on low-carbon sustainability, given its inherent passive technological characteristics responsive to climate. However, prior to the 21st century, limitations in technological means hindered development, while post-21st century reliance on active technologies for achieving green building standards has led to the neglect of thermodynamic principles in vernacular architecture, creating a theoretical gap in the energy discourse.

This study aims to elucidate the climate adaptability characteristics of vernacular architecture through thermodynamic theory, exploring architectural paradigms in both qualitative and quantitative ways. The research focuses on the energy logic and mechanisms of vernacular architecture’s climate adaptability, utilizing climate adaptability analysis tools and environmental parameter simulation software to investigate the thermodynamic features of vernacular architecture across various climates, thereby providing practical guidance for climate strategies in regional architectural design.

2. Methodology

2.1. The Presentation of Thermodynamic Forms in Architecture

2.1.1. Thermodynamics as a New Formal Principle

Energy, or combustion, actually begins with construction. Fire, as the essence of combustion, is tied to the origins of technological civilization and the rituals foundational to cities. Fire is also a symbol of architecture itself. As Vitruvius suggested at the beginning of Book 2 of De Architectura, it is hypothesized that fire—or rather the maintenance and control of fire—established human social civilization. The making and burning of fire brought people together, facilitating the rapid development of language and ultimately promoting the construction of stable settlements [29]. However, this genealogy of thermal architecture—interwoven with energy, sociality, and architecture—has not been widely recognized. In fact, 1500 years later, architect Leon Battista Alberti offered a more pragmatic and consistent view in De Re Aedificatoria. Contrary to Vitruvius’s view, Alberti believed that the “principle of human gathering” was not a simple bonfire but “roofs and walls”. It was the architectural elements that protected the heating and continuity of the fire from external forces, allowing people to gather around the flames [30]. Therefore, from Alberti’s perspective, architecture (or structure) preceded fire; it was this factor that ensured human comfort and led to the emergence of architecture. Although these two views are, in a sense, opposing, they share a common assumption: human civilization incorporates the natural environment and must create a controlled microclimate within an unpredictable climate. As Luis Fernández-Galiano states in his seminal work Fire and Memory, comfort is an equal combination of energy and architecture: it depends on both combustion (energy regeneration) and architecture (protection and selection) [31].

Since the 19th century, as classical beauty theory gradually declined and eclecticism ended, architectural development played a role in a kind of “reconciliation” between Schinkel and Le Corbusier. Climate, health, and scientific arguments introduced through the development of disciplines like physics have led architecture toward a rigorous, identifiable, operable, and unprecedented architectural form. Consequently, critical architectural questions—that have long been dwelled upon and debated—emerged: Can architectural form be subjected to calculations in the same way a “machine” can, thus inaugurating a tradition of conversion from Viollet-le-Duc to Le Corbusier? Can architectural forms be synthesized from a series of quantifiable parameters, such as program, climate, or ventilation needs? Could the interaction between thermodynamic architecture and vernacular wisdom become a source of inspiration for new forms?

Since modernist architecture emerged, this human-centered focus and interest in how design improves human comfort has become widespread. Finnish architect Alvar Aalto talked about reconciling global post-war anxiety with the potentially alienating forces of technology and scientific knowledge by starting with human touch. Rudolf Wittkower’s Architectural Principles in the Age of Humanism [32] and Colin Rowe’s The Mathematics of the Ideal Villa [33] also advocate a universal human-centered concept, derived from the Renaissance, thereby encouraging new architectural approaches. Colin Rowe even relies on the typology of cities and chart analyses to establish historical continuity. Meanwhile, Le Corbusier proposed his modular system in the late 1940s, updating the familiar Vitruvian Man into a framework for modern design [34]. Ogaya’s research also originates from the relationship between architecture and related environmental factors; although this relationship is largely metaphorical, these environmental factors are ubiquitous in the development of modern architecture. After World War II, many architects designed buildings to maximize residents’ exposure to light and air in response to the urgent need for environmental improvement. Many architects, such as Walter Gropius, Frank Lloyd Wright, and Richard Neutra, have experimented with different types of architectural forms and design parameters in an effort to improve human health under these conditions.

Although modern architecture largely inherited the ideal of houses being both mechanical and elegant from the 19th century, this approach was not free from problems. Modern architecture often requires abstract and controlled environments due to the homogeneity of space, with heating pipes and radiators confined to hidden areas such as the ceiling. Although radiators were once a coveted object for modern people, especially in the kitchen and bathroom, the equipment that provides energy for them is hidden under the floor or behind walls, leading to a lack of consistency between energy and spatial forms. In traditional vernacular housing, energy is not guided through pipes or covers that are visually integrated into the interior space; instead, it is accepted in a natural way. That is, in vernacular architecture, spatial forms and thermal continuity reach a certain degree of consensus, regardless of climate or environment. In previous studies, only single energy variables were considered, and corresponding strategies were proposed. However, architecture is a non-equilibrium, instantaneous-dissipative structure [35], meaning that it simultaneously faces multiple climate energy and environmental needs, requiring it to respond accordingly.

2.1.2. Thermodynamic Forms in Vernacular Architecture

Iñaki Ábalos’ concept of a thermodynamic prototype suggests that all buildings can be developed based on this prototype and its variations. The definition of architectural space changes with the climatic differences of regions, leading to two fundamental architectural prototypes based on two broad regional climates (cold regions and warm regions). These prototypes manifest through different typological variations, materializing the thermodynamic relationship between the interior and the exterior. They can be broadly categorized into two forms: the “source” of heat and the “sink” of heat; these are commonly understood as the sunspace and the greenhouse, each representing distinct architectural genealogies [36].

The thermodynamic principles of vernacular architecture can be traced back to ancient societies and classical Rome, where early architectural forms reflected these two prototypes in various spatial configurations, such as caves, huts, wind towers, hot pools, kang beds, and courtyards. Below, we analyze examples of these thermodynamic types in vernacular architecture, referencing Reyner Banham’s three environmental control modes: insulation, selection, and regeneration. The insulation mode corresponds to cave spaces, the selection mode to huts and wind towers, and the regeneration mode to hot pools and kang beds.

The “cave”, a typical example of the insulation mode, served as humanity’s earliest form of shelter, before the development of architecture. Early humans utilized the natural contours of caves to create spaces guided by invisible factors such as temperature, humidity, wind, and thermal radiation. According to relevant studies, in the hot summer months, the depth of a cave is correlated with the gradual decrease in its internal temperature; meanwhile, the humidity increases, creating a more comfortable environment than outdoors. Various forms of cave-type spaces have also been found in vernacular architecture, such as the ancient Persian ice pits (Yakhchāl, Figure 1) which were used to store ice and food during the hot summer, stone caves in Central Spain, the Mandan tribe’s earth lodges in the United States, and the familiar Inuit igloos.

“Sheds”, representing the selection mode, are described by architectural historian Marc-Antoine Laugier in An Essay on Architecture as the prototype of human architecture [37]. Laugier argued that walls were not initially necessary. The separation of walls and floors define the logic of space, a principle that has long been fundamental in architecture. However, exceptions exist; in many tropical regions with high humidity and heat, walls are often unnecessary and do not form the primary structure. This concept is evident in stilted wooden houses in Southeast Asia and in structures that are similar to granaries. In Spain, traditional stone granaries (hórreos), dating back to around 700 AD, are elevated on stilts to provide ventilation and protect against ground moisture. These granaries respond to regional humidity, maintaining stable conditions that are ideal for grain storage. The materials used—locally sourced stone and wood—meet the demands of local construction, while the elevated design helps prevent humidity and pest damage. Hórreos are typically spaced evenly among homes, oriented to face well-ventilated, open slopes. Research indicates that their environmental parameters are influenced by geographical location, elevation, wind exposure, and orientation [38]. For instance, when outdoor humidity exceeds 90%, the internal areas of hórreos reach an average humidity that is 5.2% lower. Conversely, when outdoor humidity is below 65%, the humidity inside the granaries can increase by an average of 3.2%, providing better conditions for grain storage.

Another example of the selection mode is the wind tower, a ventilation structure that is commonly seen in vernacular architecture. For instance, in Arab regions, wind-catchers are designed to draw fresh air into buildings [39]. In Hyderabad, known as the “city of wind-catchers”, these structures are ubiquitous, sometimes incorporating water jars to increase humidity. Other examples include openings at the tops of domed buildings, as shown in Figure 2, which utilize curved surfaces to accelerate airflow and facilitate the exchange of hot indoor air with cooler external air. The Pantheon in Rome is an example: its large opening does not leak during rainfall; instead, raindrops are carried upward by the air.

“Hot pools” and “kang beds”, as examples of the regeneration mode, rely on combustion or heat to make spaces comfortable and usable. These features are common in traditional vernacular architecture across various cultures. The ancient Roman baths are a prime example, where the concept, design, and usage were entirely thermodynamic [33]. Ancient Roman craftsmen developed baths with central heating systems, utilizing pipes laid under floors and within walls to distribute hot air and exhaust smoke. These baths were central to Roman daily life, where people spent hours bathing and enjoying amenities such as libraries, lecture halls, gardens, and markets. The bathing process typically involved a warm–hot–cold progression, perfectly aligning with thermodynamic principles.

The kang bed, also known simply as “kang”, can be found in Northern China, Japan, Korea, and Europe. Its concept originated from heated “fire walls”, created over 2500 years ago for use during the spring and autumn months [40]. The kang is believed to have originated in the Changbai Mountain region, developed by the Wujiu tribe, and became increasingly sophisticated over time. The earliest kangs were narrow, single-flue structures centered within homes, but their position later shifted to the side to provide more efficient heating as families grew. The fire stove, kang bed, and chimney together form an efficient energy system that creates a comfortable indoor environment even in the coldest conditions.

2.2. Thermodynamic Design Methods for Vernacular Architecture Based on a Climate Adaptability Analysis

Climate-adaptive design methods and relevant tools allow architects to understand the climatic conditions of the building site in the early design stages, analyze the relationship between the building and energy balance, and propose appropriate passive design strategies for energy balance throughout the year or within a single day. These strategies might include passive solar heating, natural ventilation, shading, and thermal mass storage. Further coordination with other design factors ensures that these passive design strategies integrate seamlessly into an overall architectural design.

Since the 21st century, there has been significant progress in architects’ understanding of building performance, primarily due to the development of complex analytical tools. Firstly, the once cumbersome and time-consuming performance analysis of building designs has become faster and more accessible, enabling performance analysis to commence from the conceptual stages of design. Secondly, the growing awareness of the negative impacts of buildings on the environment and energy issues has made designing climate-responsive buildings critically important. Lastly, the effectiveness and practicality of empirical vernacular bioclimatic design methods have long been questioned. Therefore, verifying which climate-adaptive measures are truly effective in vernacular architecture and translating them into modern architectural design has become a focal point for many architects.

In climate-adaptive design, the climate (including climate characteristics, climate limiting factors, and climate potential for gain) and occupants’ thermal comfort are the two main driving forces for building thermal regulation (Figure 3). These two elements work together as the foundation for climate-adaptive design processes, and influence the selection of technical and design strategies as the third element. Together, these three elements are ultimately validated and expressed through bioclimatic design strategies and climate-responsive design measures in building design.

The key idea behind this design process relates to a building’s architectural characteristics and its interaction with regional environment, culture, society, and general climatic conditions. However, the methods of bioclimatic design in architecture are often not analytical and are directly derived from the empirical knowledge of vernacular architecture for three main reasons: firstly, raw climatic data are challenging for architects to process and even harder to translate into specific design solutions; secondly, it is difficult to link the thermal comfort requirements of occupants with a specific set of architectural design measures; thirdly, the technical responses to climate in vernacular architecture have not been effectively validated in translation to contemporary practices.

Although the empirical methods of vernacular architecture might successfully design climate-adaptive buildings, it remains unclear whether the most appropriate and effective bioclimatic design strategies were chosen; the final performance of the building cannot be predicted from the outset. Therefore, certain tools, such as bioclimatic charts—which link climatic parameters at a specific location with the thermal comfort of occupants—will be used to define the required design characteristics, marking the starting point and a crucial element of the analytical bioclimatic design process. In other words, the input requirements will be the thermal comfort needs and selected climatic parameters (including temperature, wind speed, and relative humidity), and the output will be the degree of bioclimatic adaptation of the building at the target site [41]. Thus, the preliminary assessment of bioclimatic adaptation is one of the key elements of the analytical bioclimatic design process, although it remains a rough estimate and not a prediction of building energy performance.

2.3. Design Process Based on Climate Adaptation Analysis

The energy-oriented climate adaptation analysis and thermodynamic design of architecture comprise a dynamic process. This process includes extracting traditional spatial prototypes from vernacular architecture, analyzing the thermodynamic performance and climate adaptability of these prototypes, conducting climate and energy demand analysis using bioclimatic charts, calculating energy balance temperatures for spaces, evaluating energy demand curves, proposing responsive strategies, and performing performance feedback evaluations.

The first step involves extracting and studying prototypes of vernacular architecture. This requires combining the regional characteristics of vernacular architecture with the cultural demands of the area to extract traditional spatial prototypes that are specific to that region. This step largely reflects the relationship between an architect’s design intent and the sociocultural environment.

The second step involves analyzing the thermodynamic performance of a prototype space. This involves defining the performance of the extracted vernacular architectural thermodynamic prototypes based on climate adaptation diagrams and related studies. The analysis includes a thorough examination of the prototypes’ roles in regulating wind, heat, light, and humidity.

The third step involves verifying the thermodynamic performance of the spatial prototypes. Based on the energy flow patterns of energy capture, energy exchange, and energy gradient, the thermodynamic performance of the prototype space is studied, including the relationship between specific spatial scales, spatial types, interfaces, and corresponding energy in order to obtain an optimized prototype that is adapted to the corresponding climate and energy needs.

The fourth step involves adjusting and optimizing the process of the architectural climate design based on energy balance analysis. This step requires iterative adjustments in conjunction with the design process to optimize the energy performance of the extracted vernacular prototypes. This includes using bioclimatic charts for outdoor climate analysis and conducting energy balance analysis for the architectural form.

Climate adaptation analysis involves plotting the climatic data of the city and region where the building is located on a bioclimatic chart to form a simple qualitative analysis. This helps an architect gain an initial understanding of the site’s climate environment and develop a general concept of the strategies needed. This analysis should be conducted alongside the overall architectural planning and site analysis. In addition to bioclimatic charts, other methods such as psychrometric charts analysis and climate data tables can be used. The results of the climate adaptation analysis can be combined with the design and bioclimatic chart to select appropriate energy strategies.

The calculation of energy balance includes determining the energy balance temperature and analyzing the energy demand curves. This is performed after the initial climate analysis has provided a preliminary architectural plan and form. The calculation considers the preliminary design of a particular architectural form (including building type, area, volume, enclosure shape, materials, and window placement) to calculate the energy balance temperature. This involves accounting for the building’s energy gains and losses over a specific period, including factors such as the building envelope, occupant usage, equipment usage, and ventilation. Evaluation of the energy demand curves defines the energy balance over a set period (such as a year, a month, or a day), determining the appropriate heating or cooling strategies for different times. This step is a further analysis of the existing building volume based on the initial architectural form.

Having gained an understanding of the basic climate conditions and energy balance requirements, it is necessary to use an energy-strategy-judgment framework to propose targeted strategies and consider their feasibility. Finally, the adopted strategies and measures can be summarized and evaluated; they can be expressed using relevant architectural symbols to form a more complete climate design building scheme. It is worth noting that climate adaptability analysis and energy balance analysis are complementary and distinct from each other. The former is an understanding of the climate conditions of the building’s location to clarify the relationships between various climate variables and what climate elements should be given priority at what time; the latter emphasizes the relationship between the building’s form, space, occupants, and equipment, and energy balance in the initial stage of the building’s formation, in order to propose targeted strategies and improvement measures for the building’s form.

3. Presentation of the Design Method

This section provides a detailed analysis of the design method “prototype extraction—performance analysis—prototype verification and optimization” as applied to courtyard spaces in vernacular architecture.

3.1. Prototype Extraction: Atrium Prototype and Spatial Structure in Traditional Vernacular Architecture

3.1.1. Thermodynamic Prototype Concept in Vernacular Architecture

Quatremère de Quincy provided a profound definition of “prototype” and “type”. He described a “prototype” as something that can be exactly replicated, whereas “type” refers not to a precise image to be copied but rather an abstract model that guides design without the necessity of exact reproduction. From a practical standpoint, the concepts of “type” and “prototype” are nearly opposite [42]. “Type” implies that one can derive entirely different works from it, while the construction of a thermodynamic genealogy involves identifying and categorizing different climatic types to propose corresponding thermodynamic prototypes for vernacular architecture, thus providing diverse and adaptable design references. Therefore, this article will extract form elements and energy patterns from the dimensions of “climate–culture–thermodynamics” to further explore the scientific wisdom and energy utilization methods inherent in vernacular architecture’s climate adaptation. This exploration aims to inform contemporary architectural design transformation by introducing the concept of “thermodynamic prototypes” from vernacular architecture.

3.1.2. Extraction of an Atrium Prototype in Vernacular Architecture

The atrium is neither entirely outside nor inside a building; it is enclosed within a defined volume, representing a desire to open up while attempting to restrict openings in a dark, confined space. This article selects the atrium as a typical traditional spatial structure and thermodynamic prototype in vernacular architecture for in-depth study for the following reasons:

• Global presence: The atrium, as a prototype [43], appears in vernacular architecture worldwide and in contemporary architectural design, serving as a model for studying the transition from traditional vernacular architecture to modern architecture. Examples include various Chinese traditional courtyard houses adapted to different climatic environments, as well as Roman noble villas and European courtyard houses.
• Climatic and cultural significance: The atrium has evolved into various forms as it intersected with regional cultures [44], but the question remains whether the construction of atrium spaces is merely a romantic, irrational strategy or if hidden climatic science and thermodynamic principles underlie its design. These aspects warrant deeper exploration.
• Thermal and microclimatic effects: Although many studies have noted the climatic effects of courtyards—such as sunlight capture, wind protection, shading, and seasonal thermal regulation [45,46,47]—the temperature and microclimatic environment within the atrium and the building’s interior are often evaluated using external climatic data. Due to the complexity of the thermodynamic phenomena and processes within an atrium, technical quantification is challenging when using external temperature data and simple formulas.

The origin of the atrium space is debated. It is generally believed to have originated from Roman rural villas around 2000 BC, with similar open central atrium houses found in ancient Egypt’s city of Kahun during the same period. Others suggest that the early forms of courtyard spaces originated underground, as seen in the troglodyte dwellings of Matmata, Tunisia. These structures were built to withstand harsh climates and defend against external threats, with spatial organization and design heavily reliant on the courtyard. In the third chapter of the sixth book of De Architectura, after discussing the impact of climate on architecture, Vitruvius specifically studied the forms and functions of courtyards, including the Tuscan atrium, Corinthian colonnades, four-columned structures, split-water atriums, and vaulted atriums. Despite this, it was not until the 20th century that the West truly began to associate courtyards with sustainable and energy-related architectural science or technology research; even today, studies on the thermodynamic characteristics of atriums remain relatively scarce.

Atriums can be categorized using different standards, such as by style, use (public, private, etc.), or geographical location. However, the geometric structures and spatial relationships within atriums are difficult to categorize completely by type, as they are influenced by cultural and social factors, and the varying needs of architects and clients. Based on the relationship between the spatial structure, atriums can be roughly divided into three categories:

• Directly enclosed atriums: Characterized by atriums directly surrounded by rooms, the directly enclosed atrium is the prototypical form of Roman courtyard houses. Examples include traditional Beijing courtyard houses and Shaanxi pit courtyards in China, as well as Tunisian troglodyte dwellings, commonly found in colder climates requiring protection against extreme weather.
• Corridor-connected atriums: Characterized by atriums connected to rooms via corridors or exterior galleries, examples of corridor-connected atriums include urban dwellings in Egypt and Iran and courtyard houses in the Jiangnan region of China. These are often found in regions with significant climate variations that require buffering and regulation.
• Partially connected atriums: Characterized by atriums that are partially connected to corridors and partially to building walls or rooms, typical examples of partially connected atriums include the Chinese siheyuan courtyard houses.

3.1.3. Contemporary Research and Transformation of Traditional Atriums

Many modern architects—such as Rudofsky, Hassan Fathy, and Le Corbusier—were influenced by courtyard housing, forming a distinctive design philosophy [48]. Bernard Rudofsky, an American architect deeply influenced by Mediterranean courtyard houses, extended his passion for vernacular architecture to atrium spaces. He studied and redesigned vernacular architecture in Procida, Pompeii, and Herculaneum, drawing on critical experiences from contemporary housing projects and his vision of Mediterranean architecture. He then produced a romantic vision of the courtyard in his housing project in Procida.

Le Corbusier, during his travels in Italy, similarly sketched architectural designs influenced by the Roman houses of Pompeii, characterized by perspectives aligned with the central axis of the atrium, where each progressing space varied in door size, with the atrium as the focal point for light and vision, creating a dynamic play of light and shadow.

In some of Hassan Fathy’s designs and research, he connected the interior spaces of courtyard houses with traditional Arab homes. For example, in his designs for Cairo city houses, two courtyards are arranged in sequence: the first is sunlit and the second is shaded and cool, thanks to the presence of trees and plants that provide shade and evaporative cooling. These two courtyards are connected by a gallery, both serving climate control purposes, forming a unique spatial arrangement of “hot and cool courtyards”. The connecting space, known as Takhtabush, enhances indoor–outdoor ventilation. Fathy also applied the hot and cool courtyard concept in the design of New Baris Village in 1964, where multiple courtyards were arranged between buildings. Some courtyards were planted with various plants (including palm trees) to provide shade and cooling, forming “cool courtyards” that offered comfortable resting spaces for the elderly. Other “hot courtyards” were designed to maximize solar exposure, serving as popular central markets that promoted ventilation through temperature differences between hot and cool areas. The buffer space—Takhtabush—between the hot and cool courtyards was designed to facilitate social activities and brief stays.

Furthermore, by studying more atrium design projects and experiments, it can be observed that atriums not only serve as the foundation for many contemporary urban organizations (particularly in European cities) but also play a unique role in high-density urban environments by integrating private and public spaces. Examples include the renowned Mies van der Rohe Courtyard Houses located within urban blocks and the Tuscolano neighborhood in Rome designed by Adalberto Libera. Architects have reintroduced the courtyard house in a singular form, as seen in Rem Koolhaas’s residential project in Fukuoka, Japan, completed in 1991. This concept explicitly references the compact urban blocks of ancient Greek and Roman cities and the courtyard house prototypes of Pompeii. The project consists of 24 individual courtyard houses, each three stories high, combined to form two city blocks. Each house is penetrated by a private vertical atrium, which brings light and space into the interior of the building.

In the renovation of Zhangyan Village in Shanghai, the “Artist’s Courtyard” project reconstructs and updates the courtyard structure of the late Qing Dynasty residence “Wang’s House”. Within the limited space, two distinct types of spaces are introduced—a lively, open snack shop and a quiet, private guesthouse. The circulation design takes inspiration from traditional gardens, using winding corridors and deep courtyards to create a spatial sequence that transitions from bustling to tranquil (see Figure 4). The courtyard acts as a buffer zone between spaces with different functions, allowing guests to experience varying views as they move from the street-facing shops to the guesthouse area.

The courtyards and buildings are arranged in a harmonious manner, with the layout achieving organic combinations of concealment and exposure, sparseness and density, and emptiness and solidity. The courtyards serve as private open spaces for the guest rooms of the homestay, which can be used exclusively by the guests, and serve as transition spaces between the guest rooms and the snack bar and catering store (as shown in Figure 5). The project has achieved the reconstructed continuation of modernization of rural architecture and showcases the strong vitality of the courtyard space. The project was completed in 2020 and is currently an important node in the rural revitalization demonstration project of Zhangyan Village, Zhongfu Town.

Therefore, the contemporary adaptation of traditional atriums can be summarized into four key points:

• Demand for natural outdoor spaces: The enclosed nature of the space creates an inherent inward focus, which can add specific green spaces to the building and offer more opportunities for outdoor activities.
• Spatial hierarchy: The division and connection of spaces—both physically and visually—create areas that are either enclosed or open, private or public.
• Atmospheric environment: By introducing light, the interior of the building primarily receives reflected light and some direct light, creating a comfortable and serene atmosphere within the indoor spaces.
• Thermal comfort maintenance: Whether through narrow light wells or more spacious atriums, courtyards can create comfortable microclimates both indoors and outdoors, varying by time of day and climatic conditions.

Reintroducing this typology in contemporary architecture not only represents a cultural reassessment that aligns design with the traditional context that truly connects with environmental conditions; it also offers a solution for adapting buildings to local climatic environments.

3.2. Performance Analysis: Thermodynamic Performance and Climate Adaptability of the Atrium Prototype

The atrium embodies both climate adaptability and social adaptability. In terms of social adaptability, atriums often feature shared, social, and familial spatial characteristics. In vernacular architecture, they typically serve important functions for religious ceremonies, family gatherings, and guest receptions. The spatial structure of an atrium is based on the continuous relationship between internal and external spaces, connecting with intermediary spaces such as cool corridors and passageways, naturally creating an environment distinct from private family spaces. As an open external space, the atrium meets the functional needs of social interactions and family gatherings, offering flexible and versatile space utilization. The multifunctionality and flexibility of this space grant it an elasticity that allows it to adapt to both climate and social changes.

This section explores the strategies linking the thermodynamic performance of atriums with climate adaptability using bioclimatic charts. These strategies specifically address natural ventilation, thermal storage, evaporative cooling, shading, and passive cooling in atriums. The effectiveness of these strategies is influenced by factors such as the geometric shape of the atrium, the cross-ventilation patterns, as well as the facade and wind intensity.

3.2.1. “Cold Storage”: Ventilation Performance in Atriums

In terms of climate adaptability, beyond promoting air circulation through the use of hot and cool courtyards, courtyard houses also function as “passive energy cooling systems”, maintaining environmental sustainability and comfort. In hot climates, atriums often appear as a key feature of courtyard houses because the open atrium can cool the surrounding environment during hot seasons. Additionally, the courtyard’s design ensures natural ventilation within the building, as the principle of air movement is based on the fact that warm air is less dense than cool air, causing it to rise. When the atrium is connected to other openings in the building, such as doors or windows, cool air replaces the warm air, creating a continuous airflow within the building.

According to Viktor Olgyay’s bioclimatic chart, courtyards can utilize both natural and mechanical ventilation for air cooling and purification (see Figure 6). The light wells and courtyard spaces act as air-handling systems with thermodynamic properties that lower the temperature. Specifically, air flows and circulates through the limited external courtyard space, and the design of fountains or ponds can further cool the air through evaporation. When combined with shading systems, vegetation, and passive solar energy utilization, the effectiveness of this cooling system can be enhanced. Therefore, the atrium space functions as a “cold storage”, storing cool air and distributing it to surrounding spaces while also serving as an entry point for fresh air ventilation.

3.2.2. “Heat Source”: Thermal Storage and Night Ventilation Performance in Atriums

The thermal storage and night ventilation of a building are primarily based on the thermodynamic properties of the wall materials surrounding the atrium (see Figure 7). As the central space of the building, the atrium experiences peak temperatures at midday when the sun is directly overhead, with a high solar altitude angle, making the atrium the hottest external space of the building. The thermal inertia and heat storage capacity of the building’s walls and roof help maintain cooler indoor temperatures distinct from the outdoor climate. At night, the cooled air in the atrium is indirectly heated by the stored heat in the walls, causing it to rise, while the cooler night air gradually replaces the warm indoor air. The direction of airflow is not fixed; due to the thermal buoyancy effect, warm indoor air is expelled upwards, allowing cool air to flow in from the atrium and cool the surrounding rooms.

3.2.3. “Light Regulator”: Solar Gain and Shading in Atriums

In courtyard houses, residents select different spaces within the courtyard to provide shading or solar gain based on the position and height of the sun throughout the day or different seasons. For example, the external corridors of the courtyard can offer cool and comfortable spaces during the day, while residents may use different parts of the courtyard depending on the movements of the shadows of the trees. The seasonal “migration” around the courtyard was mentioned earlier. In some traditional Arab houses, summer living spaces are located on the ground floor, while winter spaces are situated on the upper floor, where the ceiling height is lower to minimize heat loss. In some cases, underground spaces are used during the hot season, while the upper floors or courtyards are utilized in the cold season to enjoy the warmth of the winter sun. Many vernacular examples demonstrate how to improve the climate efficiency of courtyards. The systems and devices used for shading include screens, canopies, eaves, verandas, pergolas, and vegetation (see Figure 8).

3.2.4. “Humidifier”: Evaporative Cooling Performance in Atriums

Figure 9 illustrates a passive cooling system within an atrium, utilizing a pond for direct evaporative cooling. As water evaporates, it absorbs heat from the environment, thereby lowering the air temperature. This increases the air density, causing the cool air to sink and flow into the connected building spaces. Additionally, trees and plants in the courtyard play a significant role in this process by helping to induce and transport the moist airflow. In hot climates, they provide shade, and through transpiration, they further cool and humidify the air.

3.3. Verification and Optimization of the Atrium Prototype

Traditional vernacular dwellings are notable for their efficient use of natural energy. In the pursuit of energy conservation and the optimal use of natural resources, it is essential to explore the indeterminate factors in architectural design and establish a balance between minimizing costs and maximizing performance. Contemporary vernacular architecture, when combined with climate adaptability research, can achieve self-sufficiency in energy supply and seamlessly integrate with architectural forms. Therefore, by applying Odum’s energy diagrams [49], buildings can be conceptualized as open systems in which energy exchanges define the boundaries of the system, distinguishing between the internal and external environments. These boundaries are not merely physical objects or structures; instead, the boundary of a building’s energy system should be understood as an exchange zone characterized by dynamic thermodynamic energy gradients and exchanges. In the context of vernacular settlements, energy gradients within vernacular architecture can vary based on factors such as the location and organization of the settlement, the building envelope, and the internal spatial configuration.

Thus, based on thermodynamic energy capture and regulation at the spatial level, the spatial structure of courtyard houses and their associated thermodynamic phenomena exhibit the following “prototype” relationships, where each component influences and is closely interconnected with the others:

• Central opening structure for energy capture from the external environment: This includes the atrium or light well.
• Building envelope for energy exchange between internal and external environments: This encompasses interface structures such as windows, walls, and roofs.
• Spatial structure creating energy gradients within the building: This includes buffer spaces such as verandas, corridors, and entrance halls; isolated spaces such as bedrooms, living rooms, and attics; and regulating spaces such as backyards and front yards.

3.3.1. Energy Capture of Light, Heat, and Wind in Atriums

Energy capture refers primarily to the structures that capture natural energy from the external environment, including light, thermal radiation, wind, and humidity. Given that the shape coefficient of courtyard-style vernacular architecture is larger than that of compact standalone buildings, analyzing its thermodynamic performance solely based on the shape coefficient would be ineffective. Therefore, in courtyard-style vernacular architecture, the central opening structure (i.e., the atrium or light well) is primarily considered as the main source for energy capture, including light, radiation, and air.

Firstly, the natural lighting in the atrium space of courtyard-style vernacular dwellings is influenced by several key factors: the amount of natural light available under local climatic conditions; the height, width, and depth of the atrium; the area and position of windows facing the rooms; the light-transmission capacity of the glass; the reflective properties of interior surfaces; any shading elements in the building envelope. Among these factors, the most crucial is the ratio and dimensions of the light well [45]. The aspect ratio of courtyard plans in vernacular architecture generally ranges between 3:1 and 1:3, with square atriums being the most common. The height-to-width ratio is significantly related to the climate and geographical distribution: in cold climates, the height-to-width ratio is typically lower, often below 0.5, whereas in hot climates, the ratio is significantly higher, sometimes resulting in extremely narrow atriums. The amount of natural light entering an atrium depends partly on local climatic conditions, with hot, low-latitude climates generally receiving more natural light than cold, high-latitude regions. Additionally, the Sky View Factor plays a role; atriums that are tall and narrow have a lower Sky View Factor and thus receive less natural light and solar radiation. For central atrium spaces, when the height-to-width ratio is around 2, square atriums provide 7–10% more natural light than rectangular atriums with a 2:1 aspect ratio.

Secondly, the solar radiation heat gain in the atrium space of courtyard-style vernacular buildings is closely related to local solar radiation and the openness of the atrium, which is primarily influenced by the Sky View Factor, itself determined by the height-to-width ratio (spatial depth) of the atrium. East–west-oriented atrium spaces have a larger surface area exposed to the sun, with less shading, allowing more sunlight to reach the walls and floor of the atrium. For instance, in the northern hemisphere (at 24° N latitude), the east and west walls and the floor of the atrium act as the main surfaces for receiving solar radiation. When the height-to-width ratio of the atrium exceeds 2:1, the amount of solar radiation received by the lower half of the east and west walls decreases significantly. Furthermore, atriums with the same height-to-width ratio but different aspect ratios exhibit noticeable differences in ground-level solar radiation distribution. In a 2:1 aspect ratio atrium, the ground-level radiation is concentrated in the southern–central area due to reflections from the northern wall; in contrast, in a 1:2 aspect ratio atrium, the radiation is primarily influenced by direct sunlight and is concentrated in the northern part of the ground. Based on the different radiation distributions on the building’s surfaces, one can optimize the placement of windows, material selection, and the zoning of vegetation and public spaces.

Lastly, the airflow in the atrium space of courtyard-style vernacular buildings is influenced not only by the local prevailing wind direction and the building’s shape but also by the temperature differences caused by solar radiation. Regarding prevailing wind direction, wind speed within the atrium is mainly affected by the height-to-width ratio along the wind direction (i.e., depth) and the height-to-width ratio perpendicular to the wind direction (spatial depth). Buildings can block wind by reducing wind speed, increasing turbulence, and creating internal circulation, thereby forming areas with relatively calm wind conditions. Generally, the wind speed within the atrium increases as the depth along the prevailing wind direction increases, while a higher windward-facing wall reduces the wind speed within the atrium [46]. When wind acts on the windward face of a courtyard-style building, the flowing air splits over the roof and gradually returns to the ground on the leeward side, with the wind speed within the atrium decreasing as the depth of the atrium increases. For example, in hot and humid regions or during summer, a light well oriented 45° to the prevailing wind direction can maximize wind speed within the courtyard while optimizing the building’s wind pressure and ventilation conditions. In climates where heating is dominant and there is less demand for interior lighting and sunlight, a height-to-width ratio of less than 1 in the atrium provides better wind protection.

3.3.2. Energy Exchange of Light, Heat, and Wind in the Atriums

Energy exchange primarily refers to the process of exchanging energy between the external climate and the internal environment through the thermodynamic properties of the building’s envelope, including the shape and materials of the structure. However, in a building, energy exchange is not limited to the envelope and building outline; the presence of energy gradients between different spaces within the building also leads to energy flow and exchange. Therefore, the energy exchange that constitutes the thermodynamic prototype of courtyard-style vernacular architecture includes the building envelope that facilitates energy exchange between the interior and exterior (such as windows, walls, roofs, and other interface structures), as well as their overall construction and openings.

Firstly, natural light entering the interior through the atrium space is significantly influenced by the shape of the atrium and the placement of windows in the walls, the presence of verandas, and shading structures. Generally, rooms on the ground floor of the atrium receive the least natural light, so their design must consider the required lighting coefficient. Additionally, for tall and narrow atriums, mutual reflection between the side walls absorbs some light, thereby reducing the efficiency of natural light reaching the interior rooms. Therefore, the lighting efficiency of an atrium depends on the reflectivity of the light well walls and the shape of the light well. Figure 10 shows the relationship between the atrium well index and the lighting efficiency of rooms of different sizes and proportions. This metric can be used to analyze the direct lighting efficiency of the atrium space as it relates to the atrium’s interior and surrounding spaces, particularly when the exterior walls of the atrium do not extend vertically to the ground—this aids in evaluations of the impact of the eaves structure above the atrium well on the entry of light into the building.

Secondly, the heat gain and loss in the atrium space are influenced not only by the shape of the light well opening but also by the floor area or spatial volume and the thermal resistance of different materials used in the interior space. The presence of the atrium opening increases the surface area of the building envelope in contact with the external environment. For buildings with the same volume, the heat gain and loss through conduction and ventilation in courtyard-style buildings are greater than in more compact buildings. Buildings with a larger shape coefficient have more solar radiation hitting the walls, windows, and roofs. In winter, a larger south-facing surface area can capture more sunlight, but in summer, it is crucial to avoid the orientation of the main building facade being east–west and to ensure proper insulation of horizontal surfaces. The heat exchange on the exterior surface of the building shows a positive linear relationship with the ratio of surface area (S) to floor area (F). For buildings with high insulation performance, the variation in heat loss is minimal, but for buildings using materials with low thermal resistance, the impact of the building’s shape needs to be carefully considered. Additionally, the size and arrangement of window openings on the exterior walls of the atrium significantly influence the natural lighting and solar heat gain.

Lastly, in terms of airflow, openings leading to the courtyard are typically created between the light well space and the interior spaces to increase wind speed through these openings, especially when they face the prevailing wind direction or when there are multiple openings that allow air to flow out of the light well. This effect is more pronounced in narrow light wells with a high height-to-width ratio. Additionally, the connecting spaces between courtyards also influence airflow. For example, in “hot and cool courtyards”, the combination of shaded and sunlit courtyards accelerates the movement of air from one courtyard to another due to the temperature differences, creating pleasant ventilation. This phenomenon is actually driven by differences in solar heat gain, which cause temperature variations between spaces and result in different energy gradients.

3.3.3. Energy Gradients of Light, Heat, and Wind in the Atriums

In nature, thermodynamic energy gradients are almost universally present, such as pressure gradients, chemical concentration gradients, or temperature gradients. If external gradients disrupt the equilibrium between a system and its natural environment, the system will respond by resisting and altering its state accordingly. Simply put, the more a system is forced out of equilibrium, the more energy is required to maintain that balance. Therefore, for living organisms, from a thermodynamic perspective, if entropy affects them, their state is one of continuously acquiring energy from the environment to maintain their own gradient balance [45]. As D’Arcy Thompson wrote in On Growth and Form [50], “All forms of matter, and the manifest changes of form that occur in their motion and growth, can be reduced to the action of forces. In short, the form of an object is a ‘diagram of forces.’ An organism, regardless of its size, is not only a representation of the movement of living matter that must be interpreted in the language of force (according to dynamics), but it also manifests in the form of the organism itself, a form whose invariance or equilibrium can be explained by the balance of forces”.

The form of matter in nature is closely linked to thermodynamic energy exchange and is often achieved by maintaining energy gradient balance. In Professor William Braham’s Architecture and Energy: Performance and Style [51], the author discusses an example from landscape ecology studies on the shapes of biological patches, noting that their forms are influenced by a range of parameters. These parameters reveal possibilities from historical development to species diversity and energy exchange with the surrounding environment. For example, the shapes of hares in extreme climates (such as the jackrabbit and the Arctic hare) illustrate this concept. The elongated and curled shape of the jackrabbit maximizes heat exchange with the surrounding environment, making it well-suited for cooling needs; in contrast, the Arctic hare tends to adopt a spherical shape, which minimizes thermodynamic exchange and allows it to adapt to cold environments. If we consider that buildings, similarly to living organisms, have the purpose of maintaining their own balance and comfort, then buildings can also achieve gradient balance. Constructing a building that is isolated from its environment while maintaining a comfortable interior environment essentially involves creating an energy gradient to resist the increase in entropy over time.

Regarding the spatial division of energy gradients in courtyard-style vernacular dwellings, the location and connection of different spaces play distinct roles in guiding and utilizing energy. In Europe, the changes in lighting gradients differ significantly across atriums with different shape indices, as shown in Figure 11. Taking the typical courtyard-style dwellings of ancient Rome as an example, the energy gradient of light variation in the atrium and its directly connected surrounding spaces largely depends on the shape of the atrium as a capture space, the filtering of light by buffer spaces, and factors such as the solar altitude angle. Based on previous studies on the lighting efficiency of light wells, it is possible to determine the variation in lighting gradients within atrium spaces in specific vernacular buildings. This variation is mainly influenced by the height-to-width ratio [52]. The energy gradient in the atrium space of Roman courtyard dwellings, based on the lighting coefficient, is illustrated in Figure 12. In the distribution of light energy gradients within the atrium spaces of vernacular architecture, the lighting coefficient is directly proportional to the aspect ratio, the shape index of the atrium, and the local illuminance at the corresponding time, while being inversely proportional to the height-to-width ratio of the atrium space.

The atrium space, as the temperature regulator in courtyard-style dwellings, can effectively mitigate the extreme heat of summer and the discomfort of winter cold. In summer, due to the high solar altitude angle, traditional Roman courtyard houses use shading, evaporative cooling, and ventilation between the north and south courtyards to lower the temperature within the atrium space by 2 to 4 °C compared to the external air temperature. Corridors and entrance halls, which serve as buffer spaces, can be 1 to 3 °C cooler, while the attic, functioning as an insulating layer, tends to have higher temperatures due to its role as an energy isolation space.

The variation in the energy gradient of solar radiation heat within atrium spaces in vernacular architecture can be analyzed through two methods: on-site spatial measurement and thermal radiation software simulation. In recent years, the former has increasingly utilized thermal imaging recorders for on-site measurement and analysis of built spaces [53], while the latter can involve modeling and analysis using environmental performance simulation software, such as Ladybug Tools (version 1.8.0).

3.4. Theoretical Innovations in the Thermodynamic Design Method of Vernacular Architecture

This section focuses on vernacular architecture as a starting point, aiming to address the role architects can play in creative architectural design when faced with contradictions between globalization and regionalism, tradition and modernity, and energy efficiency versus energy consumption. As the architectural field increasingly engages in discussions on energy issues and ecological sustainability, architects’ creative autonomy has weakened, leading to a collective silence and perceived incapacity when addressing energy efficiency and relying on energy-saving regulations. When “ecological anxiety” and “energy-saving standards” flood into the design field—along with prefabricated, intelligent buildings and digitalization—if future designs aim solely to meet singular energy-efficiency comfort standards by piling up technology and assembling metrics while neglecting considerations of regional, traditional, and humanistic needs, will future architecture become a monotonous display of technology? If so, this is clearly both dangerous and unfortunate.

In response, this section introduces the concept of a “Thermodynamic Prototype of Vernacular Architecture” based on the courtyard typology, one of the most distinctive features of vernacular buildings. It establishes a thermodynamic design method of “prototype extraction–performance analysis–prototype validation–energy optimization”, analyzing the thermodynamic performance of courtyard spaces adapted to different climatic conditions, including four performance types: “cold storage”, “heat source”, “light regulator”, and “humidifier”. This approach reveals that energy-oriented, climate-adaptive analysis and thermodynamic architectural design is a dynamic adjustment process. It involves extracting traditional spatial prototypes from vernacular architecture, analyzing the thermodynamic performance and climate adaptability of these prototypes, conducting climate analysis and energy demand assessments using bioclimatic charts, calculating energy balance temperatures for the derived spaces, evaluating energy demand trends, and finally proposing responsive measures along with performance feedback evaluations.

4. Practical Analysis

Applying the sustainable design translation of the atrium space prototype based on the thermodynamic theory of vernacular architecture, we will discuss the optimization of design strategies through the atrium prototypes in four different climatic regions.

This section analyzes four typical cities in China with different climatic types—Haikou, Turpan, Shanghai, and Harbin—based on the thermodynamic prototypes of courtyard-style vernacular architecture. It elaborates on the bioclimatic adaptability analysis of traditional courtyard dwellings and the design research process during the early design stages. The aim is to provide architects with a workflow that transitions from abstract to concrete, based on climate adaptability analysis, thereby offering guidance for achieving more efficient and sustainable architectural design.

It is important to note that the vernacular architectural design prototypes and strategies proposed based on climate adaptability analysis represent just one of many design approaches. As a critical component, this method helps incorporate excellent traditional elements into the contemporary transformation of vernacular architecture (especially during the early design stages), while forming a scientifically sound and climate-adaptive design. However, if it only focuses on climate adaptation and neglects other elements (such as social, aesthetic, and humanistic needs), it will evidently fall short of meeting the demands of high performance and comfort.

4.1. Hot Humid Climate—Haikou

Hot and humid climates, found mainly in low-latitude regions, receive high-angle solar radiation year-round and experience high humidity. Cloud cover and moisture reduce atmospheric clarity, limiting solar radiation reaching the surface and resulting in lower ground-level radiation compared to drier regions at the same latitude. At night, reduced atmospheric transparency hinders cooling, leading to small diurnal temperature variations. High nighttime temperatures fail to relieve daytime heat, causing consistently high temperatures with few periods of comfort.

During the day, both indoor and outdoor spaces are hot, emphasizing the need for shading. At night, ventilation is essential to mitigate continued discomfort. Excessive humidity in hot and humid climates presents a greater challenge than in hot and dry climates, making thermal comfort standards harder to meet. High humidity often causes stifling conditions, which can only be alleviated by strong ventilation, as evaporative cooling is ineffective.

Therefore, in hot and humid climates, shading is the most critical requirement, determining that the most important architectural feature is the provision of long-lasting shade structures. Equally important is natural ventilation, as illustrated in the vernacular thermodynamic prototype of Hainan’s courtyard-style dwellings (see Figure 13). Specific strategies include shading structures that block solar radiation, reducing the impact of solar radiation on the building’s interior as well as on public or private open spaces. Vernacular architecture can achieve this by using large overhanging roofs combined with highly reflective materials to prevent excessive absorption of solar radiation, thereby creating a favorable microclimate around the building. In addition to reflecting solar radiation, the role of thermal storage and thermal inertia of building materials is generally minimal, with the appropriate use of insulating materials to block heat flow. At the settlement level, spaces should be designed to facilitate ventilation, and streets and public spaces should be planned with vegetation that maximizes shading.

To maintain good natural ventilation, buildings typically require large openings, strategically positioned based on the prevailing wind direction and combined with protections such as grilles, louvers, and curtains to block solar radiation. The building layout should also promote cross-ventilation, avoiding wide and deep building forms. It is important to avoid east–west-oriented exterior walls from direct solar radiation and to utilize raised floors to enhance ground-level ventilation and dehumidification. If natural ventilation strategies are insufficient to meet comfort requirements, then mechanical ventilation with cooling and dehumidification may be necessary to provide maximum comfort.

4.2. Arid Hot Climate—Turpan

Arid and hot climates are typically found in low-latitude regions with high-angle solar radiation and low humidity, or in inland desert areas. Due to minimal cloud cover and moisture, these regions experience intense solar radiation and high daytime temperatures. However, the clear sky also allows for significant radiative cooling at night, resulting in rapid temperature drops and large diurnal temperature variations. Cities in China such as Urumqi, Hohhot, Kashgar, and Turpan exemplify this climate.

In Turpan, a typical arid and hot city, 20.2% of the year achieves thermal comfort without interventions. The seasonal climate variability requires different passive strategies for summer and winter. In winter, passive solar heating, conventional heating, and insulation are essential, while summer strategies focus on shading, evaporative cooling, natural ventilation, and thermal storage. The need for passive, ventilation, and thermal storage strategies in arid and hot climates exceeds 10%.

Therefore, design strategies for arid and hot climates need to consider heat insulation and cooling strategies for summer and insulation strategies for winter, as illustrated in the vernacular thermodynamic prototype of courtyard-style dwellings in Turpan (see Figure 14). Firstly, in summer, it is crucial to focus on protecting against solar radiation and insulating against heat. An inward, centralized layout can be used in the building space, with the main living spaces arranged around the atrium. The atrium should be designed with appropriate shape, scale, orientation, and shading structures to regulate solar radiation. Building materials should function as thermal storage, collecting heat during the day and releasing it at night through ventilation and radiative cooling. Therefore, materials need to have a low thermal conductivity and high thermal inertia, enhancing radiative heat exchange while providing insulation.

In summer, ventilation and evaporative cooling are necessary, but outdoor conditions often exceed the capacity of natural ventilation. From May to September, when daytime temperatures surpass 35 °C, ventilation can worsen comfort by bringing in hot air, often accompanied by wind and sand in desert areas. Therefore, in addition to nighttime thermal storage and ventilation, structures like wind towers, earth tunnels for heat exchange, and evaporative cooling systems are commonly used in vernacular buildings in arid and hot climates, providing significant benefits. These strategies can be enhanced with vegetation and water features for evaporative cooling and humidification.

In winter, smaller openings for absorbing direct solar radiation are important. In Turpan, about 30% of the year requires passive solar heating during winter.

Traditional dwellings in Turpan, Xinjiang, offer effective summer cooling solutions. These two-story buildings often incorporate semi-underground spaces and flexible courtyard layouts, creating natural cooling effects with water courtyards and grapevine shade. The thick adobe walls provide insulation and heat protection, while small windows minimize heat gain.

4.3. Temperate Climate—Shanghai

Temperate climates are primarily concentrated in mid-latitude regions (20° to 60°), where the maximum angle of solar radiation varies significantly throughout the year. In summer, the solar altitude angle is high, while in winter, it is low, leading to distinct seasonal differences. Summers range from warm to hot, and winters range from cool to cold, with significant monsoon influence. Rainfall is also subject to seasonal variations, typically with more rain in summer and less in winter. Due to the cold winters in temperate climates, insulation becomes a necessary condition. However, unlike in high-latitude cold climates, there is potential in temperate climates to mitigate cold conditions by capturing solar radiation. During hot summers, it is essential to focus on heat dissipation and insulation to protect buildings from excessive solar radiation, as well as to ensure ventilation to prevent overheating. Due to the diurnal temperature fluctuations, thermal inertia also plays a role in stabilizing the indoor temperature environment. Representative cities in China include Shanghai, Nanjing, and Nanchang.

Shanghai, as a typical city with a temperate climate, exhibits climate adaptability characteristics. During the transitional seasons—from February to May and from October to December—passive solar heating strategies can provide all or part of the heating requirements. From June to September, natural ventilation strategies are needed to achieve maximum thermal comfort, with mechanical ventilation and cooling required in July and August to address part of the thermal comfort needs. In January, with 100% reliance on conventional heating, radiators are necessary to ensure thermal comfort during the coldest period.

Therefore, in temperate climates, it is important to consider both insulation and heating in winter, as well as heat dissipation, insulation, and natural ventilation in summer. Additionally, solar gain and heating strategies during the transitional seasons must be addressed, as illustrated in the vernacular thermodynamic prototype of courtyard-style dwellings in Shanghai (see Figure 15).

Firstly, flexibility in responding to solar radiation is essential to ensure sufficient sunlight is captured during winter while avoiding excessive solar radiation in summer. Specific strategies include designing public spaces that provide ample sunlight in winter while protecting against summer sun and rain, such as atriums and verandas, which facilitate the capture or avoidance of solar radiation and evaporative cooling. Shading and rain protection structures should be in place to prevent sun and rain exposure on walls, doors, and windows. Adjustable louvers and shading structures that can be adapted to seasonal and diurnal changes should also be considered.

Secondly, ensuring adequate natural ventilation during Shanghai’s summer is crucial. The organization of building clusters should be staggered to ensure smooth airflow. The orientation and size of openings should take both the position of the sun and the prevailing summer wind direction into account. For example, larger openings in exterior walls should include shading considerations for outdoor windows. Building facades should be designed for sufficient ventilation, and systems that promote airflow from the roof to the ground floor will aid in summer heat dissipation. Cross-ventilation should be considered in the floor plan.

Finally, the building envelope should provide both thermal inertia (high thermal capacity) and insulation (low thermal conductivity) to stabilize indoor temperatures in summer and retain heat in winter. For adequate thermal comfort with ventilation, the ceiling and interior wall surface temperatures should not exceed outdoor temperatures, especially in the evening and at night. Insulating materials like wood, porous bricks, concrete, and hollow blocks, when used at sufficient thickness, ensure effective thermal resistance. In temperate climates, evaporative cooling from vegetation and water features can also help dissipate heat during summer.

4.4. Cold Climate—Harbin

Cold climates are primarily concentrated in high-latitude regions, where the angle of solar radiation incidence is generally low. Combined with the effects of thick atmospheric layers and cloud cover, this results in low levels of solar radiation. Additionally, in polar regions, cold climates experience very short daylight hours in winter, and even in summer, the annual temperature remains relatively low. Representative cities in China include Harbin, Changchun, and Shenyang.

Harbin, as a typical city with a cold climate, exhibits climate adaptability characteristics, where many months fall below the freezing point, resulting in extremely cold and uncomfortable conditions. This necessitates the adoption of insulation and heat absorption measures.

In cold climates, buildings must first consider insulation strategies, including the use of materials with low thermal conductivity (low overall U-value for the building), optimizing the window-to-wall ratio for both insulation and heat absorption, and implementing airtightness measures while optimizing for natural light. Next, heat absorption strategies need to be considered. Harbin has the potential for passive solar heating from March to October, which can improve building performance through heat absorption strategies. Due to the relatively cold climate, indirect heat absorption strategies will be more effective than direct absorption. This can be achieved through overall building layout, the use of sunspaces, and increasing the area of sun-facing windows to capture more solar radiation. Based on the above analysis, the most important aspects of the thermodynamic prototype for vernacular architecture in cold climates include focusing on insulation and cold protection in winter, wind-proofing, and utilizing natural ventilation and thermal inertia materials in summer to maintain thermal comfort and eliminate excess humidity. Therefore, the design principles should follow the use of high-performance (low thermal conductivity and high thermal mass) insulation materials for walls, small openings, compact building layouts, the use of courtyards for organizing lighting and ventilation, and the implementation of airtight interfaces, as illustrated in Figure 16, which depicts the thermodynamic prototype for vernacular courtyard dwellings in Harbin.

4.5. Summary of Design Strategy Application Methods in the Early Design Stage

This chapter presents thermodynamic prototypes and design strategies for vernacular architecture based on different climate classifications, applying climate adaptability analysis methods and thermodynamic design paths to case studies from four regions. These case studies are situated in hot-humid, arid-hot, temperate, and cold climates, offering insights into how courtyard-style vernacular dwellings respond to environmental characteristics through passive strategies, while also constructing prototype strategies. On the one hand, the chapter illustrates how passive design strategies are employed in these four common climate types to address local environmental challenges, forming prototypes for each climate. On the other hand, it also demonstrates the analytical process from prototype extraction to strategic design recommendations at the architectural meso-level.

The overall analysis process can be summarized as follows: Firstly, based on different climate classifications and climate adaptability analysis tailored to specific regions, the “thermodynamic prototype of vernacular architecture” is proposed as a design tool that addresses the energy needs and traditional cultural demands of different climates. This leads to the development of thermodynamic prototypes and energy strategies for vernacular architecture based on four climate classifications. Then, through the study of the atrium spatial prototype paradigm in traditional architecture, combined with both qualitative and quantitative analyses, the processes of energy capture, energy exchange, and energy gradients of light, heat, and wind within atrium spaces are detailed, followed by corresponding thermodynamic performance analysis and validation. Finally, effective thermodynamic design strategies for atrium spaces are proposed, aiming to derive guiding principles for modern architectural design from the passive strategy prototypes of vernacular architecture.

5. Conclusions

This article uses vernacular architecture as a starting point, attempting to address the role architects can play in creative architectural design amid contradictions between globalization and regionalism, tradition and modernity, and energy conservation and energy consumption. As discussions about energy issues and ecological sustainability continue within the architectural field, the creativity and autonomy of architects are increasingly diminished, leading to a collective silence and impotence in addressing energy conservation challenges and a reliance on energy efficiency standards. When “ecological anxiety” and “energy-saving standards” flood the design domain, combined with prefabrication, smart buildings, and digitalization, we ask the following question: if future designs merely aim to meet singular criteria for energy efficiency and comfort—piling on technology and assembling metrics, while neglecting other considerations such as regionality, tradition, and humanistic needs—will future buildings become mere technical presentations that all look the same? If so, this is clearly both dangerous and tragic.

Thermodynamic architecture does not adhere to specific energy efficiency metrics; its conceptual scope, application stages, and impact value differ significantly from current energy-saving standards and green rating systems. Firstly, thermodynamic architecture does not refer to any specific technology, nor is it similar to today’s parametricism or regionalism, which are architectural design concepts with clear technological and formal indicators. It can be both traditional and avant-garde, drawing inspiration from deep research into physical systems in physics, encouraging designers to autonomously seek design solutions from logical formula parameters and reflect on architectural autonomy in the context of 21st-century sustainability. Secondly, a narrow pursuit of energy efficiency may not be truly reasonable from a global sustainability perspective. The early involvement of thermodynamic design methods focuses on climate adaptability and energy conservation issues, allowing architectural design discussions to address energy topics from the outset, thereby overcoming architects’ silence on these matters. Finally, the thermodynamic prototype of vernacular architecture is not limited to specific forms of “what it is”; rather, it provides architects with effective new approaches to answering the “how” in relation to regional and sustainable energy issues, offering significant practical value.

The establishment of thermodynamic design methods for vernacular architecture aims to propose a new architectural perspective that combines the study of energy concepts and thermodynamic knowledge. It focuses on the energy properties of the external environment in vernacular architecture, the influence and shaping of traditional architectural forms and spaces, and the relationship between energy changes at the architectural interface and building materials. The goal is to explore the systematic impact of energy as a guiding thread on the form, materials, and function of vernacular architecture, while also developing a new architectural aesthetic system that integrates traditional spatial prototypes and reflects thermodynamics, environmental protection, and energy efficiency. This approach seeks to re-establish architectural development on a foundation of respecting the environment and protecting nature, bringing together environmental and climatic factors to provide new perspectives and references for the theory and practice of energy and thermodynamic architecture. Ultimately, this will enable the study of ecological and green buildings to truly achieve a unified approach to ecological energy-saving technology and architectural innovation, exploring natural energy as a key influencing factor in the design of traditional and modern vernacular architecture that meets the needs of both ecological economy and comfort while preserving valuable traditions. This will form a theoretically significant and methodologically guided direction for architecture in the contemporary era.