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Article

Renovation Methods for Atrium-Style Educational Buildings Based on Thermal Environment Testing in Cold Regions of China

by
Kunming Li
1,2,
Xiao Liu
3,4,*,
Jian Ma
1,
Zhongxun Li
3 and
Hua Zhang
1
1
Department of Architecture, Henan University of Technology, Zhengzhou 450001, China
2
Henan Key Laboratory of Grain and Oil Storage Facility & Safety, HAUT, Zhengzhou 450001, China
3
State Key Laboratory of Subtropical Building and Urban Science, School of Architecture, South China University of Technology, Guangzhou 510640, China
4
Department of Architecture, College of Design and Engineering, National University of Singapore, Singapore 119077, Singapore
*
Author to whom correspondence should be addressed.
Buildings 2025, 15(12), 2077; https://doi.org/10.3390/buildings15122077
Submission received: 27 April 2025 / Revised: 9 June 2025 / Accepted: 14 June 2025 / Published: 17 June 2025
(This article belongs to the Special Issue Building Resilient Cities: Architecture and Urban Planning for Combating Extreme Hot and Cold Weather)
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Abstract

:
While cold regions in China experience harsh winters, their summers also present significant overheating challenges in atrium-style buildings due to excessive solar gain. This study investigates the thermal environment of a non-ventilated atrium educational building located in a cold region of China, with tests conducted throughout the four seasons. The findings indicate that the atrium temperature is 1.7 °C, 1.1 °C, and 1.7 °C lower than that of the inner corridor during spring, autumn, and winter, respectively, but 0.6 °C higher in summer. From 7:00 a.m. to 10:00 p.m. on summer days, north-facing rooms with horizontal shading are 0.5 °C warmer than those facing south. A retrofit strategy that combines ventilated atrium shading with north-facing vertical shading is proposed, leading to a 0.7 °C reduction in atrium temperature and a 9.4% decrease in summer air conditioning energy consumption. Additionally, this study develops a retrofit framework for existing buildings, encompassing scope definition, diagnostics, strategy formulation, and evaluation to support high-quality renovations.

1. Introduction

Atrium spaces have become a prominent architectural feature in contemporary buildings globally, offering benefits such as enhanced natural lighting, improved ventilation, and aesthetically pleasing environments [1,2]. However, due to their expansive volumes, multiple openings, and diverse heat sources, atriums often exhibit complex airflow patterns, resulting in pronounced temperature stratification and uneven thermal distribution [3,4,5]. To meet occupant comfort requirements, mechanical systems such as air conditioning and central heating are typically employed. Nevertheless, the substantial energy demands associated with maintaining year-round thermal comfort in atriums remain a critical challenge, as these structures are inherently prone to low energy efficiency [6]. Consequently, a comprehensive analysis of atrium thermal environments is imperative to develop effective design strategies for optimizing thermal performance.
Numerous field studies have examined the influence of design strategies on atrium thermal performance. For instance, Hu [7] investigated an architectural department atrium in a hot-summer/cold-winter region of China. The study revealed that, owing to the atrium’s extensive planar dimensions and height, only its upper space effectively retained heat during winter. Furthermore, thermal comfort could be improved through roof retrofitting and internal layout optimization. Similarly, Abdullah et al. [8] evaluated a three-story hotel atrium in a tropical climate, comparing the cooling efficiency of blinds and water spray systems. Sokkar and Alibaba [9] demonstrated that double-skin skylights could achieve 77% annual thermal comfort by modulating the opening ratio based on weather conditions, with minimal impact from glass material selection. Moosavi et al. [10] assessed passive and hybrid cooling strategies (thermal stack flue, cross ventilation, and water walls) in a Malaysian low-energy office building, highlighting cross ventilation as particularly effective. Additionally, scaled-model experiments have been employed to study atrium thermal dynamics [11,12,13]. Collectively, these findings indicate that optimized atrium design not only enhances thermal comfort but also reduces energy demand and operational carbon emissions.
Field measurements provide the most accurate representation of real-world built environment performance [14,15]. In addition, on-site measurements can provide a reliable verification basis for numerical models. Based on validated numerical models, researchers have extensively investigated the impact of various design parameters on atrium thermal environments, including opening configurations [11,16,17,18,19], atrium geometry [20,21], and roof design [22]. For instance, Lin and Linden [23], Holford and Hunt [16], and WANG and HUANG [24] experimentally assessed how opening size, location, and operational conditions influence thermal performance. Other studies have evaluated implementation strategies such as solar-assisted natural ventilation [25,26], nighttime ventilation [27,28], and wind-induced airflow [29,30,31]. Chu et al. [32] further simulated the effects of different air-supply angles, velocities, temperatures, and outlet heights on the atrium thermal and wind environments during winter. Despite advances in computational fluid dynamics (CFD) simulation of atria over recent decades, most studies rely on simplified models for parametric analysis [33,34], likely due to experimental validation challenges and the high computational cost of coupled radiation–ventilation simulations [33,34].
Modern atrium design is employed in a variety of buildings across different climate zones, with various forms and design factors tailored to specific climate conditions. In universities, atriums have emerged as an effective solution to address issues such as insufficient day lighting and poor ventilation in classrooms. As a result, they have become a common feature of architectural space in university buildings. However, the increasing use of large glazed surfaces (e.g., glass curtain walls) has introduced overheating risks, particularly in Chinese university buildings with suboptimal designs [8]. This issue is pronounced in cold climates, where atriums are typically low-rise, well-insulated structures with glass roofs to maximize solar heat gain in winter. While effective for cold-season heating, such designs often lead to summer overheating due to excessive solar radiation [35].
In summary, this paper, with a focus on atrium-style educational buildings in universities in China’s cold regions, reveals the long-term thermal environment characteristics of these buildings through a thermal environment test in four seasons, proposes an energy efficiency renovation strategy based on inspection and diagnosis, and finally conducts a quantitative evaluation on the renovation plan using computer simulation. The proposed methodology offers a systematic approach for retrofitting similar buildings, providing theoretical and practical insights for sustainable atrium design.

2. Study Method

2.1. Study Location

China’s building thermal design standards classify the country into five distinct climate zones, primarily based on the average temperatures of the coldest (January) and hottest (July) months. Cold regions, as defined by this classification, exhibit pronounced seasonal variability characterized by cold and dry winters, hot and humid summers, short springs and autumns, and large annual temperature differences. This study focuses on Zhengzhou, a representative cold-region city (geographic location shown in Figure 1). The city experiences an annual mean daily temperature range of 1.5 °C (January) to 27.0 °C (July), reflecting the climatic extremes typical of this zone.

2.2. Study Object

The subject of this investigation is a six-story atrium-style educational building located at a university in Zhengzhou (Figure 2). The building has a total of 6 floors, with the first floor being 4.2 m high and the remaining floors being 3.8 m high, resulting in a total height of 23.2 m. This six-floor building features a traffic circulation organized via inner corridors in both north and south wings. To improve the indoor ventilation and day lighting of the classrooms for the architecture majors in the south wing, an atrium is designed through the second to the sixth floors, completely enclosed by a skylight roof made of transparent tempered glass. The building is equipped with facade sunshades (see Figure 2). Horizontal sunshades extending 0.9 m outwardly are installed on each floor of the south, west, and north facades, along with fences in various areas to provide shading and light blocking. For the facades facing the courtyard, only horizontal sunshades are provided (see Figure 2 for the north facade of the south wing).

2.3. Thermal Environment Test

Seasonal field measurements were conducted in the atrium building during representative days to minimize anthropogenic interference. All measurements were performed on sunny days during winter/summer vacations or weekends, with specific test dates detailed in Table 1. The locations of measurement points and photographic documentation of the field tests are presented in Figure 3. To analyze the thermal environment characteristics of the vertical and horizontal spaces in the atrium area, the horizontal measurement points were finalized to be: measurement point 2 on the third floor of the atrium, and the south-facing measurement point 1 and north-facing measurement point 3 in the classrooms on both sides. The vertical spatial measurement points included measurement point 7 on the second floor and measurement point 8 on the fifth floor of the atrium. In addition, the horizontal spatial measurement points included corridor measurement point 5 on the fifth floor of the north wing, south-facing measurement point 4, and north-facing measurement point 6 for rooms on both sides. A small weather station was also set up on the roof to record the annual meteorological parameters.
For typical day tests, a HOBO temperature and humidity data logger (model: U23-001; accuracy: ±0.2 °C; origin: Bourne, MA, USA) with a radiation shield was provided at each measurement point. It was fixed on a tripod, about 1.1 m above the ground. The range and accuracy of all testing instruments complied with the relevant provisions of ISO 7726 [36]. For example, the accuracy of all temperature probes was ±0.2 °C. The logging interval was set to 1 min.

3. Test Results

3.1. Temperature Distribution in Vertical Spaces of the Atrium in Four Seasons

The average hourly air temperature in the vertical spaces of the atrium during the main service period, from 7:00 to 20:00 on typical days in each season, is shown in Figure 4, while the daytime temperature values and differences across various vertical spaces are detailed in Table 2. As shown in Figure 4, the air temperature in the vertical spaces of the enclosed atrium on typical days in different seasons was distinctively stratified. It increased along with the rise in floor height, with the lowest temperature on the second floor and the highest on the fifth floor. Table 2 shows that the temperature differences between the fifth and the second floors and that between the fifth and the third floors were the largest (3.5 °C and 2.5 °C) in autumn, followed by spring (3.3 °C and 2.4 °C), winter (2.6 °C and 1.9 °C), and summer (2.2 °C and 1.2 °C). It also showed that the temperature difference between the third and second floors remained constant at about 1 °C on typical days in all four seasons. Seasonal variations in vertical temperature gradients were observed, with the maximum values occurring in autumn (0.31 °C/m) and spring (0.29 °C/m), a moderate value in winter (0.23 °C/m), and the minimum in summer (0.19 °C/m).

3.2. Temperature Distribution in Horizontal Spaces of the Atrium in Four Seasons

The thermal environment of the enclosed atrium at the horizontal level presents a stepped pattern, as shown in Figure 5. In spring, autumn, and winter, the daytime air temperature in the atrium area at the horizontal level was highest on the south side of the third floor, followed by the third floor itself, and lowest on the north side of the third floor. However, the trend reversed in summer: from 7:00 to 11:00 in the morning, the temperature on the north side of the third floor was the highest, followed by the third floor itself, and lowest on the south side of the third floor. At other times, the temperature was highest on the third floor, while it remained similar on its north and south sides. According to the statistics in Table 3, the temperature difference between the south-facing rooms and the north-facing rooms on the third floor was the largest (about 3.0 °C) in winter, followed by spring and autumn (about 1.7 °C) and summer (−0.2 °C), indicating that the temperature on the north side was greater than on the south side in summer. The temperature difference between the atrium area and the south-facing rooms varied significantly as the seasons changed throughout the year, with a fluctuation range of −2.6 °C to 0.3 °C; the temperature difference between the atrium area and the north-facing rooms was small, ranging from 0.1 °C to 0.7 °C.

3.3. Comparison of Temperature in the Atrium and the Corridor Spaces in Four Seasons

The average hourly air temperature at the horizontal level of the atrium and the corridor during the main service period from 7:00 to 20:00 is shown in Figure 6. The average temperature values and differences of various rooms are shown in Table 4. For the corridor area in autumn and winter, the temperature in the south-facing rooms beside the inner corridor > the temperature in the inner corridor > the temperature in the north-facing rooms beside the inner corridor, and the temperature difference was more significant in winter. In spring and summer, the temperature changes in the corridor were more complex. For example, most of the time in spring, the temperature in the south-facing rooms > the temperature in the north-facing rooms > the temperature in the inner corridor, and only in the morning (7:00 to 11:00) and evening (19:00 to 20:00), the temperature in the north-facing rooms was lower than in the inner corridor; in summer, the temperature in the north-facing rooms was the lowest throughout the whole day, the temperature in the south-facing rooms was lower than in the inner corridor during the periods from 7:00 to 12:00 and from 17:00 to 20:00, and the temperature in the south-facing rooms was higher than in the inner corridor from 12:00 to 17:00. As shown in Figure 6, the temperature in the atrium space was lower than in the corridor space in spring, autumn, and winter. The statistics in Table 4 indicate that the temperature values were 1.7 °C lower in spring, 1.1 °C lower in autumn, and 1.7 °C lower in winter, respectively, and the temperature in the atrium space was 0.6 °C higher than in the corridor in summer.

4. Analysis of Renovation Strategy Based on Thermal Environment Testing

4.1. Renovation Strategy

Field measurements revealed two primary thermal performance issues in the atrium building: (1) the atrium’s enclosed design, with a transparent tempered glass roof, led to excessive solar heat gain in summer, making it hotter than the inner corridor; and (2) The north-facing classrooms with horizontal sunshades had excessively high temperature in the morning in summer. Since the building was built in 2012 and the energy efficiency design of its walls, roof, exterior windows, and other envelops meets the requirements of China’s Design Standard for Energy Efficiency of Public Buildings [37], the renovation strategy focuses on solving the problems found in the thermal environment test.
To address these problems, this paper mainly elaborates on renovating the ventilation and shading design for the atrium, as well as the shading design for the north-facing exterior windows. In the principle of preserving the original appearance of the building, the renovation plan aims for performance improvement and building energy efficiency with minimum intervention (see Figure 7 for the integrated renovation plan). Key modifications include: (1) redesigning the atrium skylight with a 1.2 m overhang and perimeter side windows (45% openable area), supplemented by intelligently controlled internal sunshades; and (2) installing vertical sunshades (0.9 m projection) on north-facing windows to mitigate solar heat gain. These measures aim to improve thermal comfort while maintaining energy efficiency.

4.2. Model Verification and Quantitative Analysis of the Renovation Design for Thermal Environment Improvement in Summer

Following the establishment of the retrofit strategy based on thermal environment testing, a comparative analysis was conducted on the thermal environment and energy consumption before and after the renovation via computer simulation. The simulation process is shown in Figure 8. The simulation used the Honeybee plugin based on the Rhino+Grasshopper platform, which can directly interface with the EnergyPlus/OpenStudio engine for building energy and thermal performance simulation. EnergyPlus 9.6/OpenStudio 3.3.0 software, developed by the U.S. Department of Energy (DOE), is a globally validated and widely adopted simulation tool. The core algorithm of EnergyPlus is based on a non-steady-state heat balance method, solving coupled equations for envelope heat conduction, surface heat exchange, and indoor air energy conservation at each timestep [38,39].
By discretizing energy conservation equations, the software integrates radiation, convection, and conduction heat transfer mechanisms. For convective heat transfer, multiple indoor and outdoor models are built-in, including natural convection models based on temperature difference and surface orientation, and forced convection models considering wind speed, supporting adaptive selection of heat transfer coefficients. The heat conduction section mainly provides the conduction transfer function method (CTF) and finite difference method (FD), which are respectively suitable for conventional and high-precision modeling requirements. In terms of radiative heat transfer, long wave is calculated using the gray body theory and viewing angle factor method for surface exchange, while short wave is simulated using solar ray tracing and the distribution coefficient method to investigate the effects of sunlight. These processes are iteratively coupled at each timestep to accurately capture the dynamic variations in building thermal performance.
The 3D building model and envelope thermal properties (e.g., U-values of walls, windows, and roofs) were configured using field survey data and design documents (see Table 5). Operational parameters for annual simulations, including HVAC schedules, occupancy patterns, and density, were configured in accordance with China’s Standard for Green Performance Calculation of Civil Buildings for educational buildings, with specific parameters provided in Table 6. The HVAC system was modeled using EnergyPlus’s Ideal Loads Air System, while natural ventilation was activated only when outdoor temperatures ranged between 18 °C and 26 °C, with windows remaining closed outside this range and no mechanical ventilation implemented. To focus on the impact of passive retrofit strategies on indoor thermal conditions and cooling loads, internal heat gains were limited to occupant metabolic heat, excluding lighting, equipment, and infiltration effects. Meteorological data were obtained from an on-site weather station installed on the rooftop.
It should be noted that EnergyPlus typically employs the well-mixed air assumption within thermal zones, which enhances computational efficiency but may introduce certain inaccuracies when simulating large spaces such as atriums, primarily due to unaccounted thermal stratification effects caused by natural convection. While coupled CFD approaches could provide more refined simulations of airflow patterns and thermal distribution, their substantial computational costs render them unsuitable for the current research focus. Consequently, this study adopts an alternative methodology where each atrium zone is modeled as an independent thermal zone, incorporating the AirflowNetwork module to simulate buoyancy-driven vertical air currents. This approach enables partial representation of natural ventilation dynamics while maintaining reasonable computational efficiency. Although the fundamental well-mixed air assumption persists, the implemented methodology demonstrates sufficient accuracy and practical utility for the specific analytical objectives of this investigation.
The comparison between the measured and simulated results of the selected rooms in the natural ventilation condition on the third floor of the atrium area on typical summer days is shown in Figure 9, which indicates that the simulated values can reflect the variation of the measured temperature in different rooms. For example, most of the time in summer, the temperature in the atrium is the highest, and in the morning, due to the solar radiation, the temperature in the north-facing rooms is higher than in the south-facing rooms. It is worth noting that compared with the measured data, the simulation results show larger thermal amplitude changes, with more pronounced extreme values in the morning and noon. This difference may stem from model simplification, including: (1) idealized boundary conditions that ignore microscale thermal buffering effects, and (2) assumptions about uniform material properties that underestimate real-world thermal inertia. Quantitative validation confirms satisfactory model performance, with a root mean square error (RMSE) of 0.47 and a consistency index (d) of 0.90, demonstrating the simulation’s capacity to capture essential thermal environment dynamics. These findings substantiate the model’s utility for evaluating retrofit strategies in atrium buildings, despite its conservative treatment of extreme temperature events.
The changes in average hourly air temperature values in the atrium area and the north-facing and south-facing classrooms before and after renovation throughout the summer (from June to August) are shown in Figure 10. The comparative analysis shows that the thermal environment in the atrium area and the rooms on both sides have been improved through minor renovation. For example, throughout the summer on the third floor, the average temperature decreases by 0.7 °C in the atrium area, by 0.4 °C in the north-facing rooms, and by 0.8 °C in the south-facing ones. Among them, the atrium area and the south-facing rooms show more significant improvement effects. Through comparative energy consumption analysis, the simulation results demonstrate that the annual cooling energy consumption of the south wing atrium building decreased from 93.92 kWh/m2 to 85.12 kWh/m2 after implementing the proposed renovation measures, representing a significant 9.4% reduction in summer cooling energy demand. This improvement is primarily attributed to the enhanced shading system and optimized ventilation strategy, which effectively mitigated the previously observed overheating issues while maintaining the building’s architectural integrity.

4.3. Renovation Design and Application Process for Existing Buildings Based on Thermal Environment Testing

Following the case study on an atrium-style educational building renovation design based on thermal environment testing, this paper summarizes the general process of renovation design for existing buildings based on thermal environment testing, as shown in Figure 11, which is divided into four stages: (1) defining the renovation object and main scope; (2) conducting test and diagnosis, including preparation (collecting data, designing measurement points, and determining test date), implementation (collecting and collating data), and analysis and summary (clarifying the characteristics of thermal environment creation, identifying the key influencing factors for its advantages and disadvantages, and providing feedback for design); (3) establishing renovation design strategies; and (4) simulating quantitative evaluation: using relevant software to quantitatively evaluate the effectiveness of the physical indicators of the design results.
The testing and diagnosis in the renovation design process for existing buildings include long-term testing and typical day testing, depending on specific project circumstances. Moreover, testing and diagnosis can be organically combined with methods such as actual measurement, expert validation, computer simulation, and machine learning to improve efficiency and shorten the renovation timelines. The proposed renovation design process aims to provide staged guidance for building renovations, and by emphasizing the importance of testing and diagnosis, to implement more effective renovations with limited resources and ultimately achieve high-quality development of buildings.

5. Analysis and Discussion

5.1. Temperature Distribution in the Vertical Atrium Spaces in Four Seasons

The vertical temperature in the non-ventilated atrium area with a transparent glass roof varies significantly in spring, autumn, and winter, and slightly in summer. The trajectory of solar movement and the heat storage capacity of the building are the main reasons for such variation. As shown in Figure 12, the solar altitude angle is low in spring, autumn, and winter, and the sun only shines on the upper part of the atrium. In addition, it is difficult to achieve airflow because the top of the atrium is enclosed, resulting in a large temperature difference between the top and bottom of the atrium in spring, autumn, and winter. As the solar altitude angle increases in summer and the sunshine reaches the lower part of the atrium, the temperature at the bottom rises due to solar radiation. Moreover, heat is also building up during this period, thus resulting in a narrower vertical temperature difference. The relevance between the temperature difference in the atrium and the solar radiation in the typical day test in summer has also been verified in the atrium test conducted by WEN [40]. As revealed by his study in Jinan, China, the indoor temperature in the atrium is mainly related to the solar radiation and the convective heat exchange between the inner surface of the atrium and the air, where the direct solar radiation is the main cause of the temperature difference.
Numerous studies have examined the thermal stratification of atrium space, which is influenced by factors such as outdoor weather conditions and various operational strategies (Table 7). Our study, conducted in Zhengzhou, China—situated between the BSk and Cwa climate zones—represents a region characterized by hot, humid summers and cold, dry winters. We found that the vertical temperature gradient in the atrium reached 0.23 °C/m in winter, exceeding the 0.19 °C/m observed in summer. The more pronounced stratification in winter is attributed to stronger solar radiation, which enhances heat accumulation on the roof and sunlit surfaces within the atrium. These findings are consistent with studies by Huang in Shanghai, China [41], while contrasting with the studies in Ottawa, Canada [42] and Xi’an, China [6], which show that the vertical temperature gradient in winter is less than the vertical temperature gradient in summer. Furthermore, our results showed that the stratification during the transition season is more pronounced. While differences in building design and climate zones across these studies preclude direct comparisons, these findings provide valuable references.

5.2. Comparison of Temperature Between Horizontal Atrium and Corridor Spaces in Four Seasons

It is speculated that the reason for the temperature difference between the atrium and the corridor area in four seasons is related to the atrium design. For instance, as the non-ventilated atrium with a glass roof receives more solar radiation in summer, its indoor temperature will rise more significantly than in the inner corridor space; as a result, the temperature on the third floor of the atrium is higher than on the fifth floor of the inner corridor space in summer. On typical summer days, the atrium temperature was 0.6 °C higher than the corridor (Table 4). This phenomenon aligns with the study by Abdullah et al. [8], which highlighted that excessive solar gain in enclosed atriums exacerbates summer overheating. During the transitional season and cold season, the atrium’s temperature was 1.1–1.7 °C lower than the corridor (Table 4). The low solar altitude angle limits radiation penetration, while the atrium’s high window-to-wall ratio facilitates greater heat loss, reducing its thermal efficiency. Similar observations were reported by Lu et al. [3] in cold regions, where atriums with poor insulation exhibited higher heat exchange rates. The seasonal temperature variation in the atrium space and the inner corridor space further verifies that in atrium buildings; ventilation and daylighting are the advantages for atrium space. However, unreasonable ventilation and daylighting design may bring negative effects, such as the neglect of shading in summer, which may lead to an increase in temperature in the atrium space and subsequent inflation of energy consumption for building operation.
In the test, it was found that from 7:00 to 11:00 in summer mornings, north-facing rooms were 0.5 °C warmer than south-facing rooms (Figure 5). This anomaly is attributed to direct morning solar radiation penetrating horizontal shading devices, as noted by He [44]. Such high temperature caused by the solar radiation in the north-facing rooms in the early morning proves the necessity of vertical shading for north-facing exterior windows. The retrofit strategy of adding vertical shading to north-facing windows (Section 4.1) effectively mitigated this issue, reducing temperatures by 0.4 °C (Figure 10).
The inner corridor’s stable temperature contrasts with the fluctuating conditions in perimeter rooms due to their direct exposure to external heat exchange (Figure 6). For instance, in spring, north-facing rooms were warmer than the corridor during peak hours (11:00–19:00). In spring, as the interior of the building continuously warms up, the temperature difference between indoors and outdoors decreases. The inner corridor, which has minimal exposure to the outside, tends to maintain a more stable and elevated temperature. The rooms on the north and south sides, however, are separated from the outdoors by exterior walls and windows, resulting in a higher heat exchange efficiency compared to the corridor. This means that during the daytime, when outdoor temperatures rise, these rooms experience a significant heating effect. Consequently, at times when outdoor temperatures are lower, the temperatures in the north and south rooms can be lower than those of the inner corridor; and during periods of higher outdoor temperatures, the south-facing room typically experiences higher temperatures than the corridor.

6. Conclusions

In pursuing China’s “carbon peaking and carbon neutrality” goals, it is of great significance to promote energy efficiency renovation of existing buildings [45,46]. The energy efficiency renovation of existing buildings based on thermal environment testing and diagnosis can achieve more effective results with limited resources while ensuring indoor thermal comfort. This paper presents research on renovation strategies based on the typical day testing and long-term testing for atrium-style buildings in cold regions of China, and arrives at the following conclusions:
  • The temperature values in vertical spaces of an enclosed atrium increase with the rise in floor height and exhibit distinctive stratification on typical days in different seasons. The temperature difference between the fifth and the second floors is 3.5 °C in autumn, which is the greatest, followed by 3.3 °C in spring, 2.6 °C in winter, and 2.2 °C in summer. The temperature difference between the third and the second floors remains constant at about 1 °C on typical days throughout the year.
  • The thermal environment in horizontal spaces of an enclosed atrium exhibits a stepped pattern. In spring, autumn, and winter, the daytime air temperature in the atrium area at the horizontal level is highest on the south side of the third floor, followed by the third floor itself, and lowest on the north side of the third floor. However, the trend reverses in summer: from 7:00 to 11:00 in the morning, the temperature on the north side of the third floor is the highest, followed by the third floor itself, and lowest on the south side of the third floor. At other times, the temperature is highest on the third floor of the atrium, while it remains similar on its north and south sides.
  • The non-ventilated atrium with a glass roof receives more solar radiation in summer and has a higher overall temperature rise than the inner corridor space. On typical days in summer, the temperature in the atrium area is 0.6 °C higher than in the inner corridor area; in spring, autumn, and winter, the temperature in the atrium space is lower than in the corridor space by 1.7 °C, 1.1 °C, and 1.7 °C, respectively.
  • Based on the problems found in the thermal environment test, a design proposal for ventilation and shading renovation of the atrium and vertical shading renovation of the north facade was provided. After renovation, the temperature of the third floor of the atrium area in summer drops by 0.7 °C, and the energy consumption of the atrium building is cut by 9.4%.
This study demonstrates that thermal environment testing is indispensable for diagnosing building performance and guiding targeted retrofits. Our four-season field measurements (Section 2.3) revealed critical issues, including summer overheating in the atrium (+0.6 °C vs. corridors) and morning solar gain in north-facing rooms (+0.5 °C vs. south-facing), which would remain undetected through simulation alone. This data-driven approach ensures that renovations address actual thermal pathologies rather than assumed deficiencies, maximizing energy savings while preserving occupant comfort.
In this paper, it is concluded that the process of renovation design for existing buildings based on thermal environment diagnosis should be divided into four stages: defining the renovation object and scope, conducting thermal environment testing, proposing renovation strategies, and evaluating these strategies, which provides a methodological reference for the regeneration and renovation of existing buildings. The characteristics of the thermal environment in windowless atrium-style educational buildings revealed in this paper also offer theoretical guidance for promoting the green renovation of similar buildings.

Author Contributions

Conceptualization, K.L., X.L., J.M. and H.Z.; methodology, K.L., X.L., J.M. and H.Z.; software, K.L., X.L., J.M. and Z.L.; formal analysis, K.L. and J.M.; investigation, K.L., X.L. and J.M.; resources, K.L., X.L. and J.M.; data curation, K.L., J.M. and H.Z.; writing—original draft preparation, K.L., X.L. and J.M.; writing—review and editing, K.L., X.L., J.M., Z.L. and H.Z.; visualization, K.L., J.M., H.Z. and Z.L.; project administration, X.L.; funding acquisition, X.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2024A1515012129); the Science and Technology Research Project of Henan Province (Grant No. 252102110346); The Open Project of Henan Key Laboratory of Grain and Oil Storage Facility and Safety (Grant No. 2023KF-B06); the Fundamental Research Funds for the Central Universities (Grant No. 2024ZYGXZR048); the State Key Laboratory of Subtropical Building and Urban Science, South China University of Technology (Grant No. 2024ZB06); Guangzhou Basic and Applied Basic Research Foundation (Grant No. 2024A04J9930). It is also partly supported by the China Scholarship Council (CSC) scholarship under the CSC Grant No. 202406150137. Special thanks to the cultivation program for young backbone teachers at Henan University of Technology.

Data Availability Statement

Data will be made available upon request.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Climate zoning for thermal design of buildings in China and location of Zhengzhou.
Figure 1. Climate zoning for thermal design of buildings in China and location of Zhengzhou.
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Figure 2. Layout of an atrium-style educational building.
Figure 2. Layout of an atrium-style educational building.
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Figure 3. Measurement points and photos of the loggers.
Figure 3. Measurement points and photos of the loggers.
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Figure 4. Average hourly air temperature in vertical spaces of the atrium during the main daytime service period on typical days in four seasons.
Figure 4. Average hourly air temperature in vertical spaces of the atrium during the main daytime service period on typical days in four seasons.
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Figure 5. Average hourly air temperature in horizontal spaces of the atrium during the main daytime service period on typical days in four seasons.
Figure 5. Average hourly air temperature in horizontal spaces of the atrium during the main daytime service period on typical days in four seasons.
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Figure 6. Average hourly air temperature in the horizontal spaces of the atrium and the corridor during the main daytime service period on typical days in four seasons.
Figure 6. Average hourly air temperature in the horizontal spaces of the atrium and the corridor during the main daytime service period on typical days in four seasons.
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Figure 7. Integrated renovation plan for atrium ventilation and shading.
Figure 7. Integrated renovation plan for atrium ventilation and shading.
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Figure 8. Simulation process.
Figure 8. Simulation process.
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Figure 9. Comparative analysis of simulated and actual measurement results of the atrium.
Figure 9. Comparative analysis of simulated and actual measurement results of the atrium.
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Figure 10. Comparison of average daytime temperature before and after renovation in summer (from June to August).
Figure 10. Comparison of average daytime temperature before and after renovation in summer (from June to August).
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Figure 11. General process of renovation design for existing buildings based on thermal environment Ttsting.
Figure 11. General process of renovation design for existing buildings based on thermal environment Ttsting.
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Figure 12. Relevance between solar altitude angle and atrium space in different seasons.
Figure 12. Relevance between solar altitude angle and atrium space in different seasons.
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Table 1. Test schedule.
Table 1. Test schedule.
YearSeasonDates of Typical Day TestsTime of Typical Day Tests
2023Spring15 April and 16 April7:00–20:00
Summer16 July, 17 July, and 18 July
Autumn15 October and 16 October
2024Winter14 February and 15 February
Table 2. Average daily temperature values and differences in various vertical spaces of the atrium.
Table 2. Average daily temperature values and differences in various vertical spaces of the atrium.
Spring (°C)Summer (°C)Autumn (°C)Winter (°C)
5F24.532.824.212.9
3F22.131.621.711.0
2F21.230.620.710.3
Difference between 5F and 2F3.32.23.52.6
Difference between 5F and 3F2.41.22.51.9
Difference between 3F and 2F0.91.01.00.7
Table 3. Average daily temperature values and differences in horizontal spaces of the atrium.
Table 3. Average daily temperature values and differences in horizontal spaces of the atrium.
Spring (°C)Summer (°C)Autumn (°C)Winter (°C)
North side of 3F22.231.521.010.6
3F22.731.621.711.0
South side of 3F23.931.322.713.6
Difference between the south and north sides1.7−0.21.73.0
Difference between the atrium and its south side−1.20.3−1.0−2.6
Difference between the atrium and its north side0.50.10.70.4
Table 4. Average daily temperature values and differences in the horizontal spaces of the atrium and the corridor.
Table 4. Average daily temperature values and differences in the horizontal spaces of the atrium and the corridor.
Spring (°C)Summer (°C)Autumn (°C)Winter (°C)
North side of 3F of the atrium22.231.521.010.6
3F of the atrium22.731.621.711.0
South side of 3F of the atrium23.931.322.713.6
North side of 5F of the corridor23.930.421.711.5
5F of the corridor24.231.422.812.8
South side of 5F of the corridor24.830.824.416.3
Difference between south and north wings−1.70.6−1.1−1.7
Table 5. Thermal parameters of envelope.
Table 5. Thermal parameters of envelope.
AttributesConstruction/MaterialsU-Value (W/(m2K))
Exterior wall20 mm cement mortar + 50 mm insulation layer + 200 mm concrete + 20 mm cement mortar0.61
Interior wall20 mm cement mortar + 200 mm concrete block + 20 mm cement mortar1.30
Floor20 mm acoustic tile + 100 mm concrete + 20 mm cement mortar1.74
Exterior floor50 mm insulation layer + 200 mm concrete0.65
Roof60 mm insulation layer + 100 mm concrete + 20 mm cement mortar0.49
GlazingSkylight: (SHGC:0.74)3.5
Window: (SHGC:0.78)6.0
Table 6. Simulation parameter setting.
Table 6. Simulation parameter setting.
ParametersNumerical ValueUnite (of Measure)
Occupant activity level120W
Floor space per capita6m2
Cooling setpoint26°C
Heating setpoint18°C
Window opening threshold18–26°C
Table 7. Experimental results of the vertical temperature gradient studies in the non-air-conditioned atrium.
Table 7. Experimental results of the vertical temperature gradient studies in the non-air-conditioned atrium.
LocationAtrium Height (m)Vertical Temperature Gradient Results (°C/m)Refs.
Harbin, China (Dwa)22.85Summer: 0.2Lu et al., 2019 [3]
Tianjin, China (Dwa)18.3Winter: 0.45Xu et al., 2023 [35]
Nanjing, China (Cfa)10Summer: 0.15–1.2
Winter: 0.03–0.08		Dai et al., 2022 [43]
Shanghai, China (Cfa)31.3Summen: 0.62
Winter: 0.77
Transition season: 0.1		Huang et al., 2006 [41]
Ottawa, Canada (Dfb)21Vertical temperature gradient in winter <
Vertical temperature gradient in summer		A. Laouadi and M.R. Atif, 1998 [42]
Xi’an, China (between the BSk and Cwa)49.3Summen: 0.095
Winter: 0.046		Su et al., 2025 [6]
Zhengzhou (between the BSk and Cwa)16.8Summen: 0.19
Winter: 0.23
Transition season: 0.29–0.31		This study
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Li, K.; Liu, X.; Ma, J.; Li, Z.; Zhang, H. Renovation Methods for Atrium-Style Educational Buildings Based on Thermal Environment Testing in Cold Regions of China. Buildings 2025, 15, 2077. https://doi.org/10.3390/buildings15122077

AMA Style

Li K, Liu X, Ma J, Li Z, Zhang H. Renovation Methods for Atrium-Style Educational Buildings Based on Thermal Environment Testing in Cold Regions of China. Buildings. 2025; 15(12):2077. https://doi.org/10.3390/buildings15122077

Chicago/Turabian Style

Li, Kunming, Xiao Liu, Jian Ma, Zhongxun Li, and Hua Zhang. 2025. "Renovation Methods for Atrium-Style Educational Buildings Based on Thermal Environment Testing in Cold Regions of China" Buildings 15, no. 12: 2077. https://doi.org/10.3390/buildings15122077

APA Style

Li, K., Liu, X., Ma, J., Li, Z., & Zhang, H. (2025). Renovation Methods for Atrium-Style Educational Buildings Based on Thermal Environment Testing in Cold Regions of China. Buildings, 15(12), 2077. https://doi.org/10.3390/buildings15122077

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