Research on the Influence of the Parameters of the “AO-Shaped” Skywell of Traditional Huizhou Residential Houses on the Indoor Wind Environment

Abstract

This study was conducted in the context of China’s latest “double carbon” policy. The objective of this study was twofold: firstly, to examine the characteristics of traditional Chinese residential skywell; and secondly, to investigate and develop climate-adaptive technologies for these structures. To this end, a study was conducted on the Huizhou skywell architecture in China. Firstly, we obtained a large amount of basic data, such as traditional buildings and skywell parameters in Huizhou through field research and on-site mapping. Second, we combined a large number of parameters and typical cases to analyze the data and determine a more scientifically typical model of Huizhou architecture and experimental coverage of skywell data. Different shapes and sizes of skywell were formed by changing the combination of skywell length and width, and the indoor wind environments of these skywell dwelling models were simulated one by one using PHOENIX (v2016) software. Finally, the data obtained from these simulations are analyzed using the variable control method, and the simulated indoor wind environments of skywells under different scale combinations in terms of skywell length, width, and length–width coupling effects are summarized and compared. The following conclusions were drawn: (1) The length of the skywell has a certain effect on all indoor wind environments, and the variation in indoor wind speed is smallest when the length of the skywell is 7.5 m. When selecting the design size of the skywell, the length of the skywell can be increased accordingly. (2) The width of the skywell for the indoor wind environment is divided into two cases, when the length of the skywell is less than 3.75 m, increasing the width of the skywell will make the indoor wind environment more unstable. However, when the length of the skywell is greater than 3.75 m, the width of the skywell is positively related to the comfort of the indoor wind environment. (3) The area of the skywell should not be too large, usually between 11.25 m² and 18.75 m². A slender skywell is more likely to provide a comfortable indoor wind environment. (4) After extensive evaluation, we found that the comfort of the indoor wind environment is high when the width of the skywell is 2 m. The optimum dimensions for the ventilation performance of the skywell are 7.5 m in length and 2 m in width.

1. Introduction

1.1. Huizhou Architecture Skywell Structure

The courtyard is an important element of traditional Chinese architecture and is widely used in different regions, such as the “siheyuan” in Beijing, the “four waters returning to the hall” in Huizhou, and the “one seal” in Yunnan [1]. The skywell in Huizhou is an iconic part of Huizhou’s architecture. It was created under the unique geographical and humanistic conditions of the region and contains rich cultural connotations [2]. The mountainous terrain of Huizhou limited the availability of flat land for construction. Upon migrating south to this region, the Central Plains clans found insufficient space to replicate the expansive courtyard buildings that were prevalent at the time. As a solution, they adapted by reducing the scale of traditional courtyards and enclosing them with sloping roofs, forming a skywell—a distinctive architectural response to spatial constraints. The roofs surrounding the skywell slope inward toward the courtyard, channeling rainwater along the eaves and creating a dynamic interplay between the skywell and the interior space. This architectural feature, deeply embedded in Huizhou’s cultural symbolism, later evolved into the distinctive layout known as “Four Waters Return to the Hall” [3]. The skywell in traditional Huizhou houses is a space surrounded by houses or walls, open to the sky and connected to the ground, shaped like a deep well.

The Huizhou skywell, as the transitional space between the interior and exterior of traditional Huizhou houses, fulfills multiple roles. Characterized by high perimeter walls, deep layouts, and small windows positioned at higher levels on the tall exterior walls (primarily for outward viewing), these houses feature functional rooms with windows opening toward the skywell. Consequently, the indoor lighting of these inward-oriented buildings is primarily dependent on the skywell. Typically positioned at the center of the residential hall along the east–west horizontal axis of the building, the skywell occupies a relatively compact footprint. The surrounding houses’ eaves provide additional sun-shading effects. Furthermore, the skywell plays a central role in regulating the indoor and outdoor climate of traditional Huizhou houses. Historically, local able-bodied men would leave for business endeavors, while women and children remained at home. To safeguard against fire, theft, wild animals, and humidity, Huizhou houses were predominantly constructed with elevated walls and deep layouts, featuring small windows positioned at higher levels. Driven by these security and environmental concerns, this specific configuration resulted in minimal exterior openings. Compared with other types of traditional skywell buildings, which can rely more readily on doors, windows, open corridors, etc., for environmental exchange, the Huizhou skywell presents a unique case due to its greater reliance on the skywell itself for ventilation and lighting [4]. To support the ventilation of buildings, the passage of wind between the doors and windows of Huizhou traditional houses is not obvious. This makes the demand for the use of skywell to promote the function of internal and external ventilation of the building even more important, and the skywell plays a crucial role in regulating the indoor and outdoor climate. When outdoor temperatures rise, the skywell space—connected to the exterior—heats rapidly, creating lower air pressure compared to the roof-covered interior spaces. This pressure differential drives warm air upward through the skywell while drawing cooler indoor air outward, establishing convective airflow. The skywell forms a secure, private yet permeable transitional space between ground and sky, functioning as a communal area for family activities; a system for water collection and drainage; and a spatial element that facilitates family gatherings and aesthetic enhancement [5].

Over time, the ideological and cultural connotations embedded in the skywell have gradually emerged. The skywell contains the sentiments of local Huizhou merchants who put Confucian ideology and culture into practice, focusing on the functionality and practicality of the house as merchants do, and valuing the elegant taste of the living environment as literati do [6]. In addition, the skywell represents the Cheng-Zhu rationale of feudal rites: “Everything must have a reason” [7]. The architectural space of skywell connects the sky and the earth, organically combining nature, architecture, and people. The architecture of Huizhou residential buildings in the form of skywell structure not only saves construction land, but also strengthens the unity of the architectural structure around the skywell, so that the communication of people inside the building also becomes more, and achieves the true “unity of heaven and man” [8].

1.2. Layout of Traditional Architecture in Huizhou

Huizhou is located in a hilly area at the junction of Anhui and Jiangxi provinces, where the four seasons are distinct, the summer temperature is very high, and the rainfall is high, and it belongs to the hot summer and cold winter area in China’s building thermal design subzone. Therefore, buildings are required to be well ventilated for summer conditions and well insulated for winter conditions [9]. Most of the traditional houses in Huizhou are square buildings with wooden frames surrounded by closed brick walls, with inward-facing houses around the skywell as the basic unit. In order to save land, the distance between houses is very small, resulting in many narrow alleys only a few meters wide in the village. Architectural form, many villages in Huizhou, although through hundreds of years of development, the single building, regardless of the spatial form or facade treatment, has obvious homogeneity [10] and always maintains a unique “Huizhou” style. The layout of this kind of “Huizhou” type of single house usually presents a square shape, or a courtyard that is similar to a square shape. The building itself incorporates several distinctive features, including its primary construction from wood and its division into multiple courtyards through the inclusion of a central patio, thereby achieving a harmonious integration of multi-courtyard architectural forms. With a square plan and a typical center axis symmetrical layout. The layout of the building according to the location of the layout and the number of skywells can be summarized into the following four types: AO-shaped, HUI-shaped, H-shaped, and RI-shaped (

Table 1. The layout of the floor plan in traditional Huizhou architecture.

Case	AO-Shaped Three-in-One	HUI-Shaped Four-in-One	H-Shaped	RI-Shaped
Perspective view
Roof plan
Example	WangXueFa LuGuoZhong	ChengShouMing WuPengYing	ZhangMeiLan	ShuHanShu
Features	It is the most typical and simple residential layout representative of Huizhou. Usually, this type of house has one bright room and two dark rooms, and is usually two-storey. The door of the house opens to a skywell, followed by a hall, which is flanked by compartments, and the staircase is often located on the side or at the back of the skywell.	The layout of the house is in the form of a skywell. Compared to the Ao-shaped, the skywell is located in the middle of the house, with the addition of a doorway and rooms on both sides, which allows for more people to live in the house.	Combined with two triple skywells, each end of the dwelling has a skywell, and there are two halls, with rooms on both sides of the halls, which is a very long time ago when this type of multi-storey dwelling appeared.	This is a layout derived from a combination of the basic types of dwellings. The architectural pattern of the three-entry house is usually less frequent, and is often made up of a combination of a triplex and a quadrangle.

) [11,12]. It is easy to see that no matter what kind of layout, the pattern of houses arranged around the skywell is always AO-shaped as the basic combination unit of the three types of compounds, and the other three types can be combined by the AO-shaped compound. The AO-shaped skywell has the cleanest floor plan, with one side of the skywell often leaning against a side wall. The rest of the space surrounds the skywell, forming a living room with light on the first floor. The courtyard usually consists of three rooms surrounding a central hall, with the skywell connecting the main door and the entrances. The reason why the appearance of Huizhou traditional houses is neat and clear, the overall form is complete and orderly, and its layout is symmetrically arranged with the central axis, which is precisely the influence of the skywell on the layout of the houses. Among them, the AO-shaped skywell is the origin of all skywell types. This is also the reason why we chose the AO-shaped skywell as the research object. The Huizhou traditional houses with the AO-shaped as the “prototype” have a very unified style in terms of both exterior appearance and interior layout, and all follow a common order. This order also forms the basis of this experiment. we will find the most representative “prototype” of Huizhou architecture through a large amount of research data, and then carry out the experiment.

1.3. Proportion of Skywells in Traditional Huizhou Architectural

The skywell space of Huizhou traditional houses is actually a grey space between indoor and outdoor [13], shaped like a vertical well and connected to a semi-open hall at the bottom. For the skywell space, the building is expressed through the enclosing relationship of the surface. A thorough analysis of the skywell space reveals the necessity of three interfaces to enclose a skywell space: the bottom interface, the side interface, and the top interface [14]. The distinct characteristics of each element are intertwined, culminating in the determination of the skywell space’s sense of enclosure and scale [15]. The bottom interface of the skywell constitutes the pivotal interface that defines the skywell space, and it is also the prerequisite element for enclosing the skywell space. Due to the visual law of the human eye, people’s downward vision is usually larger than their upward vision. This results in a deeper spatial feeling for the bottom interface, which is also the key part of creating the skywel space. When rainwater cascades through the apertures, the bottom interface and the top interface establish a “symbiotic relationship” [16]. The side interface (the walls) of the Huizhou residential skywell functions as the enclosing interface of the skywell. Side interface virtual and real are interdependent, blurring the indoor and outdoor intermediary space and forming landscape penetration. The degree of closure of the skywell space, the scale of proportion, the interface characteristics, and the transition relationship can be visually reflected in the cross-section drawings. The top interface of the Huizhou skywell offers a prime illustration of the characteristics inherent to Huizhou traditional houses, with the opening at the top of the house serving as the most intuitive perception of the exterior of the skywell for most individuals.

Meanwhile, as a three-dimensional space, the skywell’s length-to-width-to-height ratios are key characteristics of a traditional Huizhou skywell. The folk geographical classic “Liqi Tushuo” records: “Skywell primarily serve functions such as drainage and ventilation. A large skywell facilitates airflow, while a small one may hinder it. The size of the skywell should be proportionate to the overall house layout”. Based on this principle, the text provides a standard form for the skywell: “The skywell should neither be perfectly square nor excessively elongated but rather resemble a single oar”. This so-called single-oar shape is akin to the oar used in rowing, where the ratio of the length to the width of the oar blade is approximately 5:1. Thus, the skywell is designed to be long and narrow, with its length-to-width ratio mirroring that of a single oar. The focus of this study lies specifically in the scale of the skywell enclosure defined by the top interface. In this paper, the focus of the study is the opening of the skywell’s top interface. A series of variations in the size ratio of this rectangular opening have been systematically analyzed, and the enclosure scale of the skywell’s top interface opening has been explored through simulation. In this article, the enclosure scale of the opening at the top of the skywell encompasses both the “length” and “width” of the rectangular opening, as well as the varying areas resulting from different combinations of these dimensions. To comprehensively examine the scales of skywell in traditional buildings in Yixian County, Anhui Province, the author has documented the skywell scales of three representative residences located in three villages within the Yixian area.

The skywell of traditional Huizhou residences is typically a long and narrow rectangle, commonly referred to as “one-line sky” residences. This characteristic is also reflected in the aspect ratios of the skywell. Most Huizhou residential buildings consist of two stories, with only a few being single-story structures. The skywell areas are generally not large, though there are occasional exceptions with larger-scale skywells. Among the four villages studied in this research, the skywells in Biyang Town exhibit similar shapes and share certain similarities in floor plans (

Table 2. Some representative skywell dimensions of residential buildings in Biyang Town.

Example	Length (m)	Width (m)	Height (m)	L/W
Cheng Xing Yuan Residential	4.46	1.85	7.14	2.41
Cheng Xiao Hu Residential	4.14	1.8	6.53	1.4
Shao Feng Ying Residential	4.87	1.66	7.6	2.93
Wang Xue Fa Residential	5.51	2.03	6.29	2.71
Zhu Hua Song Residential	6.04	2.05	8.05	2.12
Li Hua Ping Residential	5.1	1.76	6.6	2.90
Wang Long Shen Residential	5.5	1.6	6.7	3.44
Chen Xue Hua Residential	3.5	1.6	7	2.19
Cheng He Ping Residential	5.6	2.1	6.9	2.67

). The length of the skywell is predominantly between 5 and 6 m, while the width is almost always between 1 and 2 m. The skywells are characterized as long, narrow, and tall. In contrast, the skywells in Hong Town are mostly between 4 and 5 m in length but feature a wider span (

Table 3. Some representative skywell dimensions of residential buildings in Hong Town.

Example	Length (m)	Width (m)	Height (m)	L/W
Shu Zai Hao Residential	3.8	3.4	5.3	1.12
Shu Teng Fen Residential	6.3	4.5	5.1	2.3
Wu Rong Fa Residential	4.4	2.6	5.9	1.69
Li Feng Ming Residential	4	2.2	5.1	1.82
Li She Chang Residential	5.3	2.4	5.5	2.21
Li Wei Xiang Residential	4.9	2.3	5.2	2.13
Wang Xin Hao Residential	5	4.7	5.7	1.06
Xu Xin E Residential	5.1	2.4	5.1	2.13

). Their floor plans tend to be closer to a square shape, resulting in larger openings and improved lighting conditions. The aspect ratios of the skywell in Xidi Town (

Table 4. Some representative skywell dimensions of residential buildings in Ke Town.

Example	Length (m)	Width (m)	Height (m)	L/W
Ke Shi Temple	5.1	4.2	4.28	1.21
Ke Si Nv Residential	4.5	3.7	4.7	1.22
Ke Xiao Wu Residential	4.1	4.05	5.6	1.01
Ke Yang Chun Residential	2.8	2.4	4.8	1.17
Sun Xiang Xin Residential	5.5	3.7	4.9	1.49
Deng Chun Lai Residential	4.9	3	4.4	1.63
Ke Jin Ai Residential	5.6	4.3	5.8	1.3

) and Ke Town (

Table 5. Some representative skywell dimensions of residential buildings in XiDi Town.

Example	Length (m)	Width (m)	Height (m)	L/W
Fang Rong Feng Residential	4	3.9	5.6	1.03
Hu Jian Qiang Residential	4.5	3.8	5.4	1.18
Wang Guo Qiang Residential	6.1	3	7	2.03
Jiang Ju Lan Residential	3.9	2	5.1	1.95
Ye Shi Residential	4.2	3	6.2	1.4

) are the smallest among the studied locations. Some of these skywells have nearly equal width and length, forming square—shaped skywells.

1.4. Research Basis

In recent years, extensive research has been carried out on traditional regional residential buildings in China. Current studies on regional traditional dwellings predominantly focus on the extraction and preservation of architectural cultural symbols, structural forms, and historical contexts, often overlooking the research and protection value of traditional regional buildings concerning climate adaptability. The implementation of China’s “double-carbon” policy has put the climate resilience of regional buildings in the spotlight. The term “double-carbon” is short for “peak carbon dioxide emissions” and “carbon neutrality”. The skywell, as a distinctive spatial form in traditional Chinese residences, serves multiple functions such as ventilation and lighting and embodies rich constructional wisdom. This provides significant research value for exploring the climate adaptability of traditional residential buildings. Currently, research on the climate adaptability of traditional residential buildings across different regions and types is gaining significant attention. The academic community has conducted multi-dimensional studies on the dynamic interaction between traditional architectural forms and wind environments, gradually uncovering construction wisdom tailored to regional climate characteristics. By taking typical cases such as the ancient city of Xiong ya in Qingdao [17], the Qian hu Miao Village in Guizhou [4], minority villages in island areas [18], traditional residences in northeastern Hubei [19], and traditional residential courtyards in the Qin ling Mountains [20] as research subjects, scholars have systematically analyzed the adaptive strategies employed by traditional buildings to address climate challenges, with a focus on revealing the ecological construction logic embedded within these designs.

The wind environment of buildings has consistently been a critical research focus within the field of architectural climate adaptability. Scholars from various countries have investigated the interaction between different building aspects and their wind environments. For example, Heiselberg et al. [21] conducted a study summarizing the results of a series of laboratory measurements on two distinct types of windows to analyze the characteristics of indoor airflow. The findings demonstrated that modifying the opening direction of windows could alter the flow direction of incoming air. Based on these insights, a semi-empirical flow model was developed to further investigate indoor thermal comfort. Hassan et al. [22] integrated CFD technology with smoke tunnel visualization tracking to analyze the effects of factors such as the size, location of building openings, and prevailing wind direction on natural ventilation and indoor thermal comfort in buildings. To visualize the flow field, a smoke tunnel testing facility was constructed at the Residential and Building Research Center to evaluate several idealized building models [22]. Youngryel Ryua et al. [23] elucidated the characteristics of the “daechung” courtyard wind in Korea and its impact on indoor thermal comfort through field measurements. This courtyard design has enabled traditional Korean residences to achieve enhanced ventilation performance [23]. Cheng Lei [24] conducted a simulation study using numerical simulation software to investigate the natural ventilation conditions of a riverside building in Chongqing under varying wind directions. Simulation results indicate that good ventilation quality can be achieved by implementing measures such as adjusting the position and size of air vents [24]. Z L et al. [25] investigated the local traditional dwellings in Xinye Village, a region with hot summers and cold winters in China, to evaluate the effectiveness of climate-responsive strategies and conducted a qualitative analysis. They assessed the indoor thermal environment of a typical residence in the village during both summer and winter. The study revealed that traditional local dwellings can enhance the indoor thermal environment and achieve natural ventilation by incorporating skywells and internal balconies as buffer spaces [25].

Currently, many scholars focus their research on the special space of building skywells, primarily emphasizing thermal comfort, natural ventilation, and form analysis [15,26,27,28,29]. Skywell houses in regional traditional architecture remain a critical research area. Shi Feng et al. [30] carried out field measurements and simulations on the “multi-skywell” dwellings in Fuzhou, investigating the influence of skywell geometry on the building’s wind environment and quantitatively summarizing the relationship between skywell geometric characteristics and the building’s wind environment [30].

Yan Jun and Fu Liwei [31] performed a simulation analysis of the wind environment of traditional large houses in northeastern Hunan under varying seasonal conditions. The results demonstrated that the orientation and layout theory of the ideal settlement pattern possesses certain scientific connotations [31]. Liu Xiangmei et al. [32] utilized CFD simulation software to model the wind environment and investigated the influence of skywell scale on airflow velocity within skywell spaces by altering the length, width, and proportions of the skywell. They assessed the simulation outcomes based on two indicators: the average wind speed across each space and the percentage of areas meeting comfort-related wind speed requirements. Through quantitative analysis, they determined the most favorable skywell scale for natural ventilation, providing a design basis aligned with climatic adaptability [32]. In studying the form of traditional Beijing quadrangle skywells, Nong Limei et al. [33] conducted numerical simulations of skywell parameters and combined these with simulations of different parameterized skywell models to identify optimal skywell form parameters for the wind environment. Additionally, they explored the microclimate comfort and ecological efficiency of the residential environment in traditional mountain quadrangle courtyards in Cundiaba [33]. Liu Sheng et al. [34] validated the simulation accuracy through field measurements of the wind environment and subsequently conducted a comparative analysis of the wind environment for underground houses in a natural ventilation state using numerical simulation software. They explored the relationship between the natural ventilation effect and the geometric shape of the skywell, as well as the ventilation openings in three types of typical underground houses, quantitatively summarizing the geometric characteristics of the skywell [34]. Regarding the climate adaptability of traditional Huizhou residential buildings, many scholars have carried out research. Huand and Yu [35] conducted on-site measurements in typical traditional Huizhou residences to evaluate their building performance. They ultimately concluded that due to the advantages of natural ventilation and shading, the thermal comfort inside Huizhou residences was satisfactory during summer. However, in winter, poor air tightness led to suboptimal performance. Through the research of Huang and Zhang [36], it has been demonstrated that traditional Huizhou residences outperform modern residences in terms of insulation and ventilation during summer. The roof structure and hollow brick wall construction of traditional Huizhou residences play a significant role in enhancing summer insulation [36]. Huanhuan Fang et al. [37] investigated the influence of skywell shapes in traditional Huizhou residences on the outdoor wind environment. They compared the effects of three different skywell shapes on the wind environment. By integrating on-site measurements with simulation assessments, they discovered that the HUI-shaped skywell provided the most favorable wind environment within the skywell. Additionally, the size ratio of the skywell and the building’s opening degree also impacted the wind environment. Adjusting these factors could lead to an improved wind environment [37].

This research is a simulation experiment conducted using PHOENICS (v2019) software, focusing on exploring the relationship between key elements of skywell forms in traditional Huizhou residences and the wind environment, while proposing an optimization strategy for the typical model and skywell size of such residences. By employing CFD software to simulate skywell residence models under various combinations of key skywell elements, an effort is made to summarize the relationship between these elements and the indoor wind environment. The research findings provide a more scientifically grounded theoretical basis for the preservation and skywell renovation of traditional Huizhou residences, and to some extent, systematically summarize the morphological characteristics and data prototypes of traditional Huizhou skywell residences. Through our analysis of existing studies, we found that most studies on the wind environment adaptation of traditional houses have gaps in their simulations. These studies often have a problem of typicality. Previous studies have primarily selected typical buildings in villages for simulation analysis.

Research results based on specific experimental samples cannot avoid differences in results caused by variability among buildings, and these results cannot represent traditional houses in the entire region. To avoid this variability and optimize the experimental results, this experiment offers a novel research pathway for the quantitative study of traditional skywell residences.

This research is grounded in traditional Chinese villages, contributing to the exploration, protection, and inheritance of construction techniques and design methods of traditional residences. It investigates the protection strategies and modernization renovation concepts for traditional residences in the era of big data, providing a scientific basis for these efforts.

2. Method

2.1. Research Location

We conducted a field visit and research on the traditional dwellings in Yi County. Located in the north of Huangshan City, Anhui Province, Yi County spans between 117°38′30″ and 118°6′ east longitude, and 29°47′ and 30°11′30″ north latitude. Established during the Qin Dynasty, the county covers a total area of 857 square kilometers. According to China’s administrative division statistics, Yi County features a north subtropical humid monsoon climate, characterized by distinct seasons, a mild climate, long winters and summers, and relatively short springs and autumns. As a renowned historical and cultural city of China, Yi County boasts 1590 well-preserved ancient buildings from the Ming and Qing Dynasties, as well as the World Cultural Heritage Sites of Xidi and Hongcun. Based on an overall understanding of Huizhou’s traditional dwellings and considering the actual conditions, the authors selected Biyang Town, Hong Town, Xidi Town, and Ke Town as the primary villages for this study in Figure 1. These villages, situated in the southern and northeastern parts of Yi County, contain a significant number of traditional Huizhou dwellings.

2.2. Sample Selection

The field research encompassed various districts under the jurisdiction of Yixian County, Huangshan City, including streets and residences showcasing the charm of Huizhou architecture in Hongcun Town, Xidi Village, Biyang Town, and Kecun Town. Most of these buildings were constructed during the Ming and Qing Dynasties and serve as exemplary cases for studying traditional Huizhou residences. The research primarily concentrated on key protected buildings within the area.

We conducted extensive on-site visits and surveys across numerous traditional villages in Yixian County, collecting data on 495 well-preserved ancient buildings. Specifically, there were 318 households in and around Biyang Town (140 within the town and 178 outside), 120 households in Hongcun Town, 34 in Kecun Town, 17 in Xidi Village, and 6 in Meixi Township. Due to the nature and construction periods of the surveyed buildings, not all possessed skywell architectural elements. After screening, among the 495 buildings, 299 featured skywell spaces, of which 239 were “AO-shaped” skywells, accounting for 80%. Consequently, this paper focuses on the “AO-shaped” traditional Huizhou architectural unit as the research basis. We statistically analyzed the skywell data of these 239 buildings (some buildings contained multiple stairwells) and classified the selected buildings according to their preservation integrity and typicality into comprehensive surveys and brief surveys.

The authors use the housing data of all building units with skywell spaces as the data source for constructing typical skywell buildings in Yi County and adopt the comprehensively surveyed buildings as a reference for determining the orientation and wind direction of the typical skywell building models.

2.3. Research Model and Parameter Selection

Regarding the existing technologies for evaluating indoor wind environments, computer simulation has been extensively applied. In prior studies, the use of computer programs for modeling and simulation calculations has proven to save time and costs associated with on-site measurements and scale model applications. Additionally, computer simulation offers superior visualization capabilities. The construction of our model is grounded in preserving traditional architectural forms while incorporating a substantial number of actual survey samples. Furthermore, the building structure has been appropriately simplified to enhance computer modeling efficiency, minimize simulation errors, and reduce computational expenses.

2.3.1. Model Establishment

In the selection of the model for traditional Huizhou dwellings, we focused on the typical AO-shaped Huizhou dwelling as the primary research object. Based on relevant literature, it is evident that the AO-shaped floor plan is the most prevalent, widely utilized, and representative form in traditional Huizhou architecture. This layout features the skywell as its core, integrating the skywell, hall, and wing rooms into a harmonious arrangement known as “skywell wing rooms flanking the main hall”. Additionally, other skywell floor plans are derived by combining the AO-shaped layout through methods such as splicing and rotation. According to extensive survey data and our field research, the AO-shaped skywell dwelling constitutes the majority of surveyed cases in Yi County, accounting for 80% of all recorded skywells.

Since this experiment is based on a typical model, to restore the original form of Huizhou traditional dwellings as accurately as possible, we believe that extensive use of surveying data is necessary to summarize the key elements of the most representative building units and skywell forms, which will serve as the foundational model for our experiment. This approach aims to comprehensively reflect the construction techniques and design philosophies of Huizhou traditional dwellings. In this study, the generation of the three-dimensional model is divided into four steps: First, extract the survey plans of various layouts. Analysis reveals that the skywell space in most Huizhou traditional dwellings can be simplified into a core square area formed by the skywell and the hall. Second, determine the plan form by standardizing the simplified plans into a uniform format and statistically analyzing all detailed house data. Given the variations in internal layouts of traditional dwellings, CAD-drawn images are used as the benchmark for statistical analysis to ensure accuracy. Third, classify all statistical data, calculate average values, and utilize these averages for three-dimensional modeling in SketchUp (v2025). Finally, based on a few comprehensively surveyed representative buildings, determine the orientation and wind direction alignment for the basic model, thereby finalizing the fundamental three-dimensional model (Figure 2).

This model depicts a two-story building with dimensions of 9.4 m in length, 7.4 m in width, and 6.8 m in height. A skywell is centrally located on the longer side of the building, measuring 5 m in length, 2.4 m in width, and 6 m in depth.

2.3.2. Skywell Parameter Settings

We adjusted and integrated the two parameters of the skywell’s length and width to generate a skywell with varying sizes and shapes. By modifying only the skywell parameters while maintaining other building parameters constant, we performed experimental comparisons and analyses of the building’s wind environment under different conditions. This process aimed to investigate the influence of skywell parameters on the indoor wind environment and to systematically summarize the relationship between the key elements of the skywell shape in traditional Huizhou residences and the indoor wind environment. When determining the specific experimental dimensions, to ensure a more scientific selection, we aggregated all skywell data measured across various towns in Yi County and conducted a distribution analysis of all skywell dimensions. This analysis enabled us to partially summarize the measurement rules of Huizhou-style residences. The specific distribution of skywell planar data is presented in the accompanying Figure 3.

We conducted a comprehensive measurement and statistical analysis of a total of 255 skywell samples. Among these, the maximum length recorded was 10.94 m, while the minimum length was 1.5 m. A frequency distribution analysis using intervals of 2 m revealed that 137 samples were concentrated within the range of 3.5 m to 5.5 m. Notably, over 90% of the skywell lengths fell between 2.5 m and 7.5 m, with the modal length being approximately 5 m.

In terms of width, the maximum measured value was 6.3 m, whereas the minimum was 0.9 m. A frequency distribution analysis employing intervals of 1.1 m indicated that 145 samples were primarily concentrated within the range of 2 m to 3.1 m. Furthermore, more than 85% of the skywell widths were found to lie between 1 m and 3 m, with the most representative width approximately 2.5 m.

In the parameter setting for the present study, we synthesized insights from the existing literature and conducted a thorough analysis of mapping data. Our objective was to ensure that the dimensions of the experimental setup accurately reflect the typical scale of Huizhou-style skywell houses while maintaining uniform intervals and consistency with the actual dimensions observed in local samples.

Recognizing that the simulation necessitated four sets of width parameters and four sets of length parameters, establishing an appropriate range for these parameter values emerged as a critical step in the experimental design. Our analysis of large-scale real-world data revealed that, among 220 skywell samples, the lengths predominantly ranged from 3.5 m to 7.5 m. Similarly, an examination of 217 skywell samples indicated that their widths were primarily distributed between 0.9 m and 3.1 m.

Consequently, we determined that the experimental framework should prioritize two sets of the most representative parameters: one corresponding to skywell length and one to skywell width, strictly adhering to the identified intervals. Ultimately, the interval for skywell length was established at 1.25 m, while the interval for skywell width was set at 0.5 m (Figure 4).

The specific parameter settings are as follows: Based on the typical model derived from the analysis, four sets of dimensions are selected for both the length and width of the skywell. The width dimensions are set to 1.5 m (W1), 2 m (W2), 2.5 m (W3), and 3 m (W4). The length dimensions are set to 3.75 m (L1), 5 m (L2), 6.25 m (L3), and 7.5 m (L4). By systematically combining the length and width dimensions, a total of 16 distinct skywell configurations are generated. These configurations are utilized to simulate skywells with varying size ratios and areas, as illustrated in the accompanying

Table 6. Dimensions of 16 types of skywell working conditions.

Number	Length (m)	Width (m)	Area of the Skywell (m2)	Number	Length (m)	Width (m)	Area of the Skywell (m2)
L1W1	3.75	1.5	5.625	L3W1	6.25	1.5	9.375
L1W2	3.75	2	7.5	L3W2	6.25	2	12.5
L1W3	3.75	2.5	9.375	L3W3	6.25	2.5	15.625
L1W4	3.75	3	11.25	L3W4	6.25	3	18.75
L2W1	5	1.5	7.5	L4W1	7.5	1.5	11.25
L2W2	5	2	10	L4W2	7.5	2	15
L2W3	5	2.5	12.5	L4W3	7.5	2.5	18.75
L2W4	5	3	15	L4W4	7.5	3	22.5

.

In the numerical simulation of the indoor wind environment of traditional Huizhou residences, we identified key locations within the skywell and hall to establish wind speed measurement points, as illustrated in the accompanying figure. The measurement points were positioned at a height of 1.5 m above the ground, in accordance with the “Green Building Evaluation Standard” (GB/T 50378-2019) [38]. This height corresponds to the level of the human head and neck, where sensitivity to wind comfort is heightened.

The layout of the measurement points is categorized into three distinct groups (Figure 5).

The first group consists of measurement points a, b, c, d, e, f, g, and h, situated at a height of 1.5 m in the corners of the skywell and hall. These points, located along the edges of the spaces, are susceptible to the effects of spatial boundaries and thus provide insights into the wind speed conditions at these limits.

The second group comprises measurement points i and j, positioned at the geometric centers of the skywell and hall, respectively. These points reflect the wind speed conditions in the areas of highest activity within these spaces.

The third group includes measurement points a′, b′, c′, d′, e′, f′, g′, and h′, located at the midpoints along the line connecting the geometric center to the corner points of the skywell and hall, also at a height of 1.5 m. These points are less influenced by wall boundaries and more accurately represent the fundamental state of the wind environment within the spaces.

By conducting numerical simulations on models of traditional Huizhou residences with varying skywell configurations, and by comprehensively analyzing the results from these three types of wind speed measurement points, we aim to provide a holistic and objective assessment of how key elements of skywell design impact the indoor wind environment of the building.

2.4. Numerical Simulation

In building ventilation simulation research, computational fluid dynamics (CFD) software is typically utilized for modeling purposes. This study employs PHOENICS software for simulations, which has been validated by numerous scholars for its accuracy in modeling wind environments. Phoenics utilizes the standard k–ε turbulence model, characterized by relatively low computational cost, minimal fluctuations in numerical simulation, high precision, and ease of grid adaptation.

The determination of the computational domain and the quality of grid generation play critical roles in the stability of computations and the accuracy of results during the simulation process. This paper extensively references the findings from the Wind Engineering Research Group of the Architectural Institute of Japan (AIJ) in the “Green Building Performance Simulation Optimization Method” to establish the simulation boundaries and parameters.

The specific settings for the calculations are as follows: The wind direction is set to northeast (NE), with a dominant summer wind speed of 1.9 m/s. The computational domain is defined as a cylinder with a radius of 5H and a height of 3H, where H represents the building height. The simulation utilizes a grid comprising 160 × 160 × 56 computational cells. The calculation mode is set to KEMODEL, with 2000 iterations and a step size of 1, as illustrated in the accompanying Figure 6.

2.5. Wind Environment Assessment Standards

In terms of wind environment assessment, existing evaluation standards still exhibit limitations, such as insufficient differentiation in wind speed criteria. This study takes the traditional architecture of Yi County as the research object, referring to the “Green Building Evaluation Standard” (GB/T 50378-2019) and integrating the internationally standardized thermal comfort evaluation index PMV-PPD certified by the International Organization for Standardization (ISO), along with relevant studies [39,40].

In an indoor environment, when the wind speed is below 0.25 m/s, people are unlikely to perceive air flow. When the wind speed ranges between 0.25 m/s and 0.5 m/s, individuals generally experience comfort without their daily activities or mood being affected by the wind. Based on this, this paper adopts a wind speed range of 0.25 m/s to 0.5 m/s as the appropriate standard, categorizing wind speed zones into: Static Wind Zone (wind speed < 0.25 m/s), Moderate Wind Zone (wind speed between 0.25 m/s and 0.5 m/s), and Strong Wind Zone (wind speed > 0.5 m/s).

By combining domestic and international wind environment evaluation standards, this study references research on climate adaptability and wind environment simulation of buildings in hot summer and cold winter regions. The adopted wind environment simulation evaluation indicators include Wind Speed Ratio, Moderate Wind Zone Rate per Unit Area of Skywell, Percentage of Wind Area, and Uneven Factor of Wind Speed.

The Wind Speed Ratio is defined as the ratio of the wind speed at a pedestrian height of 1.5 m in the wind field to the average wind speed at the same height under undisturbed conditions. This metric reflects the extent of wind speed variation caused by different skywell parameters. The calculation formula Ri = Vi/V0, where Ri represents the Wind Speed Ratio at point i, Vi denotes the wind speed at pedestrian height at point i within the area, and V0 corresponds to the average wind speed at pedestrian height under undisturbed conditions. Based on this formula, the suitable indoor wind speed standard ranges from 0.25 m/s to 0.5 m/s, with the average summer wind speed being 1.9 m/s. Consequently, a Wind Speed Ratio between 0.13 and 0.26 indicates that the wind speed at that point is relatively appropriate. Based on the formula in the previous text, the standard for the appropriate indoor wind speed is 0.25 m/s to 0.5 m/s, and the average wind speed in summer is 1.9 m/s. Therefore, a Wind Speed Ratio between 0.13 and 0.26 indicates that the wind speed at this point is appropriate.

The Uneven Factor of Wind Speed refers to the variance of wind speeds at various measurement points within a region, that is, the average of the squared differences between the wind speed at each measurement point and the average wind speed of all measurement points, which is used to reflect the uniformity of wind speed both in the overall area and within each sub-region.

The “Percentage of Wind Area” is categorized into three components (

Table 7. The wind zone classification standard adopted by this paper.

Percentage of Wind Area	Wind Velocity (1.5H) (1.5H Stands for 1.5 m Pedestrians Height)	Human Comfortableness
Strong Wind Zone	V > 0.5 m/s	The perception of human comfort decreases as air movement becomes more disruptive.
Moderate Wind Zone	0.25 m/s ≤ V ≤ 0.5 m/s	Individuals feel comfortable with normal daily activities remaining unaffected when exposed to moderate air flow.
Static Wind Zone	V < 0.25 m/s	Airflow at low velocities often goes unnoticed by the human body.

): the proportion of Static Wind Zone, Moderate Wind Zone, and Strong Wind Zone. The proportion of Static Wind Zone refers to the percentage of regions where the wind speed is below 0.25 m/s within the defined range. A higher proportion of still wind area indicates lower ventilation efficiency and slower air circulation in the region. The proportion of Moderate Wind Zone represents the percentage of regions with wind speeds ranging from 0.25 m/s to 0.5 m/s. A larger proportion of moderate wind area suggests a more comfortable wind environment within the region. The proportion of the Strong Wind Zone denotes the ratio of areas where the wind speed exceeds 0.5 m/s to the total simulated area. A greater proportion of strong wind areas implies excessively high wind speeds that may disrupt indoor daily activities and cause discomfort to occupants.

The Moderate Wind Zone Rate per Unit Area of Skywell refers to the ratio of the area of the combined wind generated by a certain geometric parameter of the skywell to the area of the skywell itself. It can reflect the efficiency of the combined wind area generated per unit area by skywells with different geometric parameters. The higher the Moderate Wind Zone Rate per Unit Area of Skywell, the higher the efficiency of generating a comfortable wind zone by the skywell, and the more comfortable the environment is.

3. Results and Discussion

To more intuitively compare and analyze the impact of various parameters of traditional Anhui-style building skywells on the indoor wind environment, we present the parameters of 16 skywell groups and their simulation results in tabular form (

Table 8. Numerical simulation results of the wind environment in the L1-length skywell opening.

Number	Skywell Length (m)	Skywell Width (m)	Skywell Area (m2)	Wind Speed Distribution Diagram
L1W1	3.75 m	1.5	5.625
L1W2	3.75 m	2	7.5
L1W3	3.75 m	2.5	9.375
L1W4	3.75 m	3	11.25

,

Table 9. Distribution of wind speed in the L1-length skywell.

Number	Uneven Factor of Wind Speed	Moderate Wind Zone Rate per Unit Area of Skywell	Area of Moderate Wind Zone	Area of Static Wind Zone	Area of Strong Wind Zone
L1W1	0.1983	5.7042	32.086	48.8260	21.0081
L1W2	0.2012	3.8219	28.664	58.823	12.5135
L1W3	0.2194	2.8243	26.478	57.075	16.447
L1W4	0.2063	2.6109	29.373	58.26	12.3668

,

Table 10. Numerical simulation results of the wind environment in the L2-length skywell opening.

Number	Skywell Length (m)	Skywell Width (m)	Skywell Area (m2)	Wind Speed Distribution Diagram
L2W1	5	1.5	7.5
L2W2	5	2	10
L2W3	5	2.5	12.5
L2W4	5	3	15

,

Table 11. Distribution of wind speed in the L2-length skywell.

Number	Uneven Factor of Wind Speed	Moderate Wind Zone Rate per Unit Area of Skywell	Area of Moderate Wind Zone	Area of Static Wind Zone	Area of Strong Wind Zone
L2W1	0.217	3.7191	27.893	58.698	13.4086
L2W2	0.1999	3.639	36.39	49.53	14.0796
L2W3	0.1977	2.4796	30.995	55.136	13.8695
L2W4	0.195	1.6492	24.738	63.906	11.3564

,

Table 12. Numerical simulation results of the wind environment in the L3-length skywell opening.

Number	Skywell Length (m)	Skywell Width (m)	Skywell Area (m2)	Wind Speed Distribution Diagram
L3W1	6.25	1.5	9.375
L3W2	6.25	2	12.5
L3W3	6.25	2.5	15.625
L3W4	6.25	3	18.75

,

Table 13. Distribution of wind speed in the L3-length skywell.

Number	Uneven Factor of Wind Speed	Moderate Wind Zone Rate per Unit Area of Skywell	Area of Moderate Wind Zone	Area of Static Wind Zone	Area of Strong Wind Zone
L3W1	0.2065	2.8468	26.689	58.928	14.3825
L3W2	0.1984	3.4757	43.446	40.225	16.3290
L3W3	0.1949	2.2405	35.008	50.601	14.3916
L3W4	0.1916	1.5563	29.18	57.56	13.2598

,

Table 14. Numerical simulation results of the wind environment in the L4-length skywell opening.

Number	Skywell Length (m)	Skywell Width (m)	Skywell Area (m2)	Wind Speed Distribution Diagram
L4W1	7.5	1.5	11.25
L4W2	7.5	2	15
L4W3	7.5	2.5	18.75
L4W4	7.5	3	22.5

and

Table 15. Distribution of wind speed in the L4-length skywell.

Number	Uneven Factor of Wind Speed	Moderate Wind Zone Rate per Unit Area of Skywell	Area of Moderate Wind Zone	Area of Static Wind Zone	Area of Strong Wind Zone
L4W1	0.2026	3.202	36.023	48.979	14.9974
L4W2	0.195	3.3843	50.764	32.137	17.0992
L4W3	0.2017	1.4956	28.043	58.516	13.4413
L4W4	0.1812	1.2499	28.123	58.287	13.59

). Since the simulation experiment employs the control variable method, with all dimensions of the typical residential model (e.g., depth, width, and height) kept constant while only one skywell parameter is varied, the simulation results can be combined in different ways to investigate the relationships between skywell length, width, area, and the indoor wind environment.

3.1. The Influence of Skywell Size on the Indoor Wind Environment of Buildings

In this comparison, we split the simulation results from 16 models into two scenarios, and you can see the results in the figure. Since the skywell sizes in the simulation were evenly spaced, we could figure out how the length and width of the skywell affect the indoor wind environment by comparing the data. We used simulations from selected classic models as a way to measure things more precisely, which allowed us to model skywells in different sizes. While looking at how skywells impact the indoor wind environment, we also tried to find a skywell size that works well in general and creates a comfortable wind flow.

1.

The Impact of Building Skywell Length on the Indoor Wind Environment.

The 16 datasets were categorized into four model samples based on identical skywell opening widths. Subsequently, the simulation data of these four models were analyzed and compared in terms of three key aspects in Figure 7: Uneven Factor of Wind Speed, Moderate Wind Zone Rate per Unit Area of Skywell, and the Percentage of Wind Area. By combining the analysis of the Unevenness Factor of Overall Wind Speed with the Unevenness Factor of Skywell Wind Speed for each group, it was observed that when the width of the skywell remains consistent across groups, there is a discernible pattern in how the Unevenness Factor of Overall Wind Speed varies with changes in skywell length. Specifically, when the skywell width is fixed at W1, the Unevenness Factor of Overall Wind Speed initially increases and then decreases as the skywell length L increases, exhibiting a parabolic trend. At a skywell length of L2, the Unevenness Factor of Overall Wind Speed reaches its peak, indicating the most uneven airflow distribution under this condition. Conversely, when the skywell length exceeds L2, the Unevenness Factor of Overall Wind Speed demonstrates a negative correlation with skywell length. However, when the skywell width exceeds W1, the Unevenness Factor of Overall Wind Speed exhibits a negative correlation with skywell length; as the skywell length increases, the Unevenness Factor of Overall Wind Speed decreases, achieving optimal performance at a skywell length of L4.

The relationship between the skywell length and the percentage of the wind area exhibits a certain degree of regularity. Overall, the proportion of the moderate wind area within the simulation region tends to increase with the elongation of the skywell. However, this trend undergoes slight modifications when the skywell width reaches or exceeds W3. Specifically, when the skywell width equals W3, the proportion of the moderate wind area varies in a parabolic manner relative to the skywell length, initially increasing and subsequently decreasing. The maximum proportion of the moderate wind area occurs when the skywell length is L3. When the skywell width surpasses W3, changes in the skywell length result in the indoor moderate wind area proportion first declining, then rising, and eventually stabilizing. At this stage, the influence of the skywell length on the moderate wind area becomes relatively minor. Given that the proportion of the strong wind area remains relatively small across all groups, the proportion of the static wind area demonstrates an inverse relationship with that of the moderate wind area. Consequently, the variation trend of the static wind area proportion with respect to skywell length is opposite to that observed for the moderate wind area.

The results of the Moderate Wind Zone Rate per Unit Area of Skywell were analyzed based on the aforementioned grouping. As illustrated in the figure, there exists a significant negative correlation between the Moderate Wind Zone Rate per Unit Area of Skywell and the length of the skywell. In all four comparison groups, an increase in skywell length corresponds to a gradual decrease in the Moderate Wind Zone Rate per Unit Area of Skywell. This analysis indicates that longer skywells result in reduced efficiency for generating a comfortable wind zone. Consequently, when designing the length of skywell in traditional Huizhou residences, it is advisable to appropriately shorten them while still meeting other design requirements. From this analysis, it can be concluded that factors such as indoor wind speed uniformity, comfort within the wind environment, and efficiency in creating a comfortable wind zone within traditional Huizhou residences are influenced by the length of the skywell.

Overall, the uniformity of internal air flow distribution within traditional Huizhou residences diminishes as the length of the skywell increases. At its maximum length, designated as L4, the overall wind speed non-uniformity coefficient for these residences is at its lowest point, indicating a more uniform air flow distribution and stable variations in overall wind speed. Furthermore, the indoor wind environment comfort in traditional Huizhou residences exhibits a positive correlation with skywell length; thus, appropriately increasing this length can indeed create a gentler and more comfortable interior wind environment. This finding aligns with the traditional “one-line sky” design characteristic of the Huizhou skywell. Extensive data suggests that builders of traditional Huizhou residences often opt for long and narrow skywells. However, an analysis of changes in Moderate Wind Zone Rate per Unit Area associated with these structures reveals that indiscriminately extending skywell lengths does not enhance efficiency in generating comfortable wind speed zones. Therefore, while it is essential to meet lighting and ventilation requirements for the skywell and balance other performance indicators, one should avoid arbitrary increases in its length. Excessively large skywell dimensions may lead to disproportionately expansive areas that compromise the effectiveness of creating optimal wind zones. Consequently, it is advisable to maintain the length of the skywell below L4 whenever possible.

2.

The Impact of Building Skywell Width on the Indoor Wind Environment.

By categorizing the 16 sets of data into four groups based on identical skywell lengths, we can derive four distinct sets of simulation samples. In this comprehensive analysis, we also compared and evaluated the simulation data from these four model groups in terms of the Uneven Factor of Wind Speed, Moderate Wind Zone Rate per Unit Area of Skywell, and the Percentage of Wind Area.

From the Unevenness Factor of Overall Wind Speed variation in the figure, it can be seen that when the skywell length remains constant in each group, as the skywell width increases, the Unevenness Factor of Overall Wind Speed shows a negative correlation with the skywell width. When the skywell width is W4, the Unevenness Factor of Overall Wind Speed is the smallest. As the skywell width increases, the Unevenness Factor of Overall Wind Speed also decreases. The variation trend of the Unevenness Factor of Skywell Wind Speed is consistent with that of the Unevenness Factor of Overall Wind Speed, both showing a negative correlation with the skywell width.

The influence of the skywell width and the proportion of the moderate wind area is illustrated in Figure 8. When the length of the skywell remains constant, a discernible pattern emerges between its width and the proportion of moderate wind area. Specifically, when the length is L1, the proportion of moderate wind area exhibits a “U” shaped trend relative to skywell width, initially decreasing before subsequently increasing. The maximum proportion of moderate wind area occurs at a width of W1. Conversely, when the length exceeds L1, this relationship transforms into a “parabolic” trend; here, as skywell width increases, there is an initial rise followed by a decline in moderate wind area proportion. The peak for this scenario occurs at a width of W2. It is noteworthy that throughout these observations, the proportion of strong wind areas remained relatively small and showed minimal variation across different conditions. Consequently, there exists a clear inverse relationship between static wind area proportions and those of moderate wind areas, exhibiting an overall opposing trend. As such, an increase in moderate wind area corresponds with a decrease in static wind area and vice versa.

The Moderate Wind Zone Rate per Unit Area of the skywell for these 16 groups has been organized according to variations in width, as illustrated in the accompanying figure. It is evident that there exists a general negative correlation between the Moderate Wind Zone Rate per Unit Area of the skywell and its width. When the length of the skywell is L1 and its width is W1, the Moderate Wind Zone Rate per Unit Area reaches its maximum value. As the length of the skywell exceeds L1, a “parabolic” relationship emerges between the Moderate Wind Zone Rate per Unit Area and width; initially increasing before subsequently decreasing, with a peak at W2.

Analysis indicates that the width of the skywell significantly influences the internal wind environment within traditional Huizhou dwellings. An increase in skywell width contributes to a more uniform wind speed inside these structures. Upon reaching a width of W2, both the proportion of moderate wind area and Moderate Wind Zone Rate per Unit Area attain their highest values, signifying optimal efficiency for moderate wind generation per unit area of skywell.

3.2. The Synergistic Effects of the Length and Width Dimensions of Skywells on the Indoor Wind Environment in Buildings

According to Table 6, the dimensions of the skywell—specifically its length and width—exhibit variability under different working conditions, leading to distinct skywell areas. Due to the uniform intervals present in the size data set utilized in the simulation, certain working conditions yield identical skywell areas despite differing shapes. In this comparative analysis, we categorize the experiments into two cases based on the varying areas generated by combinations of skywell length and width. This approach aims to investigate the influence of skywell area on the indoor wind environment within buildings.

1.

The Influence of Skywell Size on Indoor Wind Environment.

During the field research phase, we observed that even among local residential buildings in Huizhou with similar floor areas, the sizes of their skywells varied significantly. In some instances, larger residential buildings were equipped with smaller skywells, while smaller buildings featured larger skywells. Skywells of different dimensions exert varying influences on the indoor wind environment of traditional Huizhou residences. This section aims to investigate the relationship between skywell area and the indoor wind environment within these traditional homes and to explore how variations in skywell size affect this environment. To facilitate our analysis, we organized 16 groups of models according to their skywell sizes in ascending order. According to the results shown in Figure 9, the following can be indicated:

The area of the skywell significantly influences the Moderate Wind Zone Rate per Unit Area associated with it. Generally, there is a negative correlation between the area of the skywell and its Moderate Wind Zone Rate per Unit Area. As the area of the skywell increases, there is a gradual decrease in the overall trend of this rate. Under working condition W1L1, where the area of the skywell is at its minimum, the Moderate Wind Zone Rate per Unit Area reaches its maximum value of 5.7%. Conversely, under working condition L4W4, where the area of the skywell is at its maximum, this rate declines to its lowest point at 1.25%. Additionally, as the area of the skywell expands, there are corresponding changes in the Unevenness Factor of Overall Wind Speed within the house. The overall trend exhibits an initial increase followed by a subsequent decrease, resulting in a “U”-shaped pattern. Specifically, under working condition L1W3, this factor peaks at 0.219. In contrast, under working condition L4W4, it attains its minimum value at 0.1811.

When the simulation results of the wind zone area ratios for different models are organized according to the size of the skywell, from smallest to largest, it becomes evident that there is no significant correlation between the wind zone area ratio and the dimensions of the skywell. The data pertaining to wind zone areas exhibits considerable fluctuations as the area increases. Specifically, with an increase in skywell size, there are instances where it leads to rapid increases or decreases in wind zone area. As previously mentioned, due to the relatively small proportion of strong wind zones within each group, a contrasting trend emerges between overall wind zone areas and static wind zones. Notably, under working condition L4W2, the moderate wind zone area ratio peaks at 50.76%, while concurrently, the static wind zone ratio reaches its minimum at 32.14%. From this analysis, it can be inferred that larger skywell areas correspond with reduced efficiency in generating comfortable wind speed zones. Although under the working condition L4W4—wherein the Unevenness Factor of Overall Wind Speed is minimized and airflow distribution is most balanced—a larger skywell does not necessarily yield a more extensive moderate wind zone. Consequently, when determining appropriate sizes for skywells in traditional Huizhou residences—while ensuring compliance with requirements for lighting, ventilation, and design—it may be advantageous to minimize skywell dimensions in order to select a more efficient configuration that fosters a comfortable indoor environment while effectively addressing winter cold protection and heat retention needs.

2.

The impact of skywell on the indoor wind environment within a consistent area.

As illustrated in

Table 16. The wind environmental conditions within a skywell of equivalent area.

Group	1		2		3		4		5		6
Number	L1W2	L2W1	L1W3	L3W1	L1W34	L4W1	L2W3	L3W2	L2W4	L4W2	L3W4	L4W3
Area of Skywell	7.5	7.5	9.375	9.375	11.25	11.25	12.5	12.5	15	15	18.75	18.75
The Percentage of Moderate Wind Zones	28.7	27.89	26.48	26.69	29.37	36.02	30.99	43.45	24.73	50.76	29.18	28.04
The Moderate Wind Zone Rate per Unit Area of the Skywell	3.822	3.719	2.82	2.85	2.611	3.202	2.48	3.48	1.649	3.384	1.56	1.50
The Unevenness Factor of Overall Wind Speed	0.201	0.217	0.219	0.206	0.206	0.203	0.198	0.1984	0.1949	0.195	0.19	0.20

, due to the uniform interval setting of the experimental dimensions, there remain several working conditions with identical skywell areas within this simulation. By grouping together skywells of the same area, we obtained six distinct groups of simulation samples characterized by equivalent skywell areas. We subsequently combined and analyzed the simulation data from these six groups to investigate the variations in indoor wind environment when the skywell area is consistent, thereby inferring the factors associated with skywells that influence indoor wind dynamics. The areas of these six groups of skywells, arranged from smallest to largest, are 7.5 m², 9.375 m², 11.25 m², 12.5 m², 15 m², and 18.75 m², respectively; they are designated as Group 1 through to Group 6. The analysis of these six data sets can be categorized into three scenarios.

According to the table’s findings, when considering relatively small skywell areas—specifically those less than 11.25 m²—the simulation data for Group 1 and Group 2 exhibit minimal differences. Under conditions where the area remains constant, even though combinations of lengths and widths for different-sized skywells vary significantly, discrepancies in metrics such as Moderate Wind Zone Rate per Unit Area of each skywell, proportionate moderate wind zone area coverage, and Overall Wind Speed Unevenness Factor are not substantial; consequently, ventilation efficiency remains nearly identical across these configurations.

When the skywell area is greater than 11.25 m² and less than 18.75 m², significant variations and certain patterns are observed in the three datasets of Groups 3, 4, and 5. For a skywell area of 11.25 m², Group 3 includes two datasets: L1W4 and L4W1. The proportion of moderate wind area for L1W4 is 29.37%, while that for L4W1 is 36.02%. This indicates that the moderate wind area proportion for L4W1 is notably higher than for L1W4. Additionally, the Moderate Wind Zone Rate per Unit Area for L1W4 is 2.6109, compared to 3.202 for L4W1, showing a significantly higher rate for L4W1. The Unevenness Factor of Overall Wind Speed for L1W4 is 0.2063, whereas it is slightly lower at 0.2027 for L4W1, indicating only a minor difference between the two configurations.

In Group 4, the two datasets are L2W3 and L3W2. The proportion of moderate wind area for L2W3 is 30.99%, while that for L3W2 is 43.446%, demonstrating a considerably higher proportion for L3W2. The Moderate Wind Zone Rate per Unit Area for L2W3 is 2.4796%, compared to 3.4757% for L3W2, further confirming the higher efficiency of L3W2. The Unevenness Factor of Overall Wind Speed for L2W3 is 0.1977, while it is slightly higher at 0.1984 for L3W2, but the difference remains negligible.

For Group 5, the two datasets are L2W4 and L4W2. The proportion of moderate wind area for L2W4 is 24.73%, while that for L4W2 is 50.7637%, indicating a substantially higher proportion for L4W2. The Moderate Wind Zone Rate per Unit Area for L2W4 is 1.6492%, compared to 3.3843% for L4W2, highlighting the superior performance of L4W2. The Unevenness Factor of Overall Wind Speed for L2W4 is 0.19495, while it is slightly higher at 0.195 for L4W2—there is only a marginal difference.

It can be concluded that among these three groups of data, under identical skywell areas, the combination of skywell length and width significantly influences the simulation results. Although the differences in the Unevenness Factor of Overall Wind Speed are minimal, configurations with greater disparities between skywell length and width tend to exhibit larger proportions of moderate wind areas and higher Moderate Wind Zone Rates per Unit Area.

When the area of the skywell reaches 18.75 m², the data from Group 6 reverts to its initial condition, and the simulation results for both groups of skywells exhibit minimal differences. Under conditions where both areas are maintained at 18.75 m², metrics such as the Moderate Wind Zone Rate per Unit Area of the skywell, the percentage of wind zone area, and the Unevenness Factor of Overall Wind Speed for L3W4 and L4W3 show negligible variation and are nearly equivalent. This observation suggests that when the area of a skywell is either excessively large or small, variations in its length-to-width configuration do not significantly influence indoor wind conditions. However, within a specific range—when the area falls between 11.25 m² and 18.75 m²—the dimensions’ configuration does impact indoor wind comfort in traditional Huizhou dwellings as well as efficiency in generating comfortable wind zones. From this analysis, it can be inferred that during the design process for traditional Huizhou dwellings, maintaining a larger disparity between width and length within this specified range is advisable for optimal performance. Specifically, selecting dimensions with greater lengths relative to widths will enhance indoor air quality by creating a more comfortable wind environment. Thus, it is recommended that when determining skywell dimensions under these circumstances, one should favor longer lengths paired with narrower widths to achieve an increased length-to-width ratio.

3.3. Comprehensive Ventilation Performance

In the preceding text, we conducted a comprehensive analysis of the simulation data from this study, focusing on three key aspects: the length of the skywell, its width, and its area. Our analysis involved comparing the numerical simulation results of wind environments in skywells with varying geometric parameters within traditional Huizhou residential buildings. This comparison was based on several indicators, including the Unevenness Factor of Overall Wind Speed, the proportion of areas experiencing different wind speeds, and the Moderate Wind Zone Rate per Unit Area within the skywell. Our findings indicate that skywells with distinct geometric parameters create spaces of varying shapes and sizes. These variations significantly influence factors such as wind speed uniformity and efficiency in generating comfortable indoor wind zones. However, it is important to note that these numerical values only assess specific aspects of wind environment evaluation criteria.

Therefore, to achieve a more comprehensive comparison of ventilation performance, this study will evaluate various wind environment indicators for different-sized skywells based on the results obtained from wind environment numerical simulations. To analyze the overall impact of skywells with varying geometric parameter combinations on the indoor wind quality of traditional Huizhou residences, we will rank and score 16 sets of numerical simulation results across five key indicators: the proportion of moderate wind area, the proportion of static wind area, the proportion of strong wind area, the Unevenness Factor of Overall Wind Speed, and the Moderate Wind Zone Rate per Unit Area of each skywell. The scoring system ranges from 1 to 16.

Among these indicators, both the proportion of moderate wind area and the Moderate Wind Zone Rate per Unit Area are positively correlated; thus, higher simulation values correspond to greater comfort levels in indoor air quality and result in higher scores. Conversely, for the proportion of static wind area, strong wind area proportions, and the Unevenness Factor of Overall Wind Speed, higher values indicate lower comfort levels within indoor environments, leading to reduced scores. Based on this evaluation framework, we will aggregate scores across all five data items; details regarding comprehensive scoring outcomes are presented in Figure 10.

To provide a more intuitive analysis of the comprehensive score situation, a color scale chart representing the comprehensive scores was generated, with darker colors indicating higher scores. The chart reveals that the color associated with row W2 is generally darker and exhibits a clear increasing trend. This indicates that regardless of whether the skywell length is L1 to L4, when the skywell width is set at W2, the simulation data consistently achieves relatively high scores. Furthermore, as the skywell length increases while maintaining a width of W2, there is a gradual darkening in color corresponding to an increase in the comprehensive score. Notably, when the skywell length reaches L4, it attains the highest score within this group.

In summary, among 16 groups of skywells analyzed, those with dimensions L4W2 demonstrate superior comprehensive ventilation performance and are capable of creating a comfortable indoor wind environment for traditional Huizhou residences.

Therefore, when selecting an appropriate width for the skywell, opting for a width of W2 will yield better indoor wind conditions, thus highlighting its significant impact on ventilation performance. It is recommended that traditional Huizhou residences consider utilizing a skywell dimensioned at L4W2 to optimize their ventilation efficacy.

4. Conclusions

This study employed computational fluid dynamics (CFD) simulations to systematically investigate the influence of key skywell geometric parameters—specifically length, width, and their combinations—on the indoor wind environment and associated comfort metrics in traditional Huizhou residences. The primary findings and their implications are summarized as follows:

• Influence of Skywell Length: Skywell length significantly impacts indoor airflow patterns. Analysis reveals a strong correlation between increased length and enhanced airflow distribution uniformity. Longer skywells (e.g., L4 = 7.5 m) promote more stable wind environments throughout the residential space, evidenced by a marked reduction in the fluctuation of Wind Speed Ratios across measurement points. Consequently, maximizing skywell length is generally recommended to improve wind environment stability and comfort, provided width constraints are considered.
• The effect of skywell width is contingent upon its length. For shorter skywells (e.g., L1 = 3.75 m), increasing width detrimentally affects stability, leading to greater flow irregularity and a significant reduction in the area experiencing comfortable wind speeds. Conversely, for longer skywells (≥L2), increasing width contributes positively, enhancing overall ventilation efficiency and spatial coverage of comfortable conditions. This suggests that width optimization must be context-dependent, considering the chosen length.
• Impact of Length–Width Combination and Area Constraint: Analysis of combined dimensions highlights that excessively large skywell areas (>~18.75 m² in this study) can be counterproductive for optimizing both wind environment and thermal performance. While larger areas might offer potential ventilation benefits, they also significantly increase heat loss during winter, a critical concern in Huizhou’s climate. Furthermore, our results indicate that combinations featuring greater length relative to width (higher aspect ratio) generally yield superior airflow organization and stability. This aerodynamic advantage helps explain the prevalence of narrower skywells observed in surviving historical Huizhou dwellings.
• Synthesized Design Recommendation: Integrating the findings across all evaluation parameters—Moderate Wind Zone Rate per Unit Area, Uneven Factor of Wind speed, Percentage of Wind Zone, velocity ratios, and ventilation efficiency—the simulation results demonstrate that a skywell configuration of 7.5 m length (L4) and 2.0 m width (W2) achieves optimal performance for the studied Huizhou residence typology. This specific combination (Area = 15 m², Aspect Ratio = 3.75):
  • Leverages the stability benefits of maximum practical length (L4).
  • Utilizes a width (W2) that effectively supports ventilation efficiency within a longer skywell structure (as per Point 2).
  • Maintains an area within the practical range (11.25–18.75 m²) that balances wind environment optimization with mitigating excessive winter heat loss (Point 3).
  • Produces the most uniform airflow, minimal wind speed fluctuation, and the largest proportion of space within comfortable wind speed ranges compared to other simulated configurations.

Therefore, for new designs or retrofits aiming to enhance the indoor wind environment comfort in Huizhou-style residences, prioritizing a skywell dimension of 7.5 m (length) by 2.0 m (width) is supported by this study analysis. Future work could explore the sensitivity of these findings to different building orientations, surrounding urban contexts, and seasonal variations.