Energy-Saving Renovation of Existing Buildings: Balancing Thermal Performance and Visual Performance—A Case Study of a University Sports Training Annex in Guangzhou

Abstract

Energy conservation renovation of existing buildings is a crucial aspect of sustainable energy development. This study examines the annex of a university sports training building in Guangzhou, highlighting the conflict between maintaining landscape visibility and mitigating excessive solar radiation and thermal conditions following renovation without external shading. Specifically, the analysis focuses on scenarios where the building’s primary orientation aligns with the region’s unfavorable solar orientation. To address this challenge, five facade optimization strategies are proposed, four of which incorporate external shading solutions: horizontal shading, vertical baffle shading, inclined baffle shading, and a comprehensive shading system. Performance simulations were conducted using Ladybug and Honeybee tools within the Grasshopper platform to evaluate the multi-objective optimization of the building’s thermal and visual performance under energy conservation constraints. The findings demonstrate that an integrated shading system significantly influences both building energy consumption and thermal performance. Notably, the 46° inclined baffle shading scheme proves particularly effective in the Guangzhou context, successfully reducing solar radiation, improving indoor lighting quality, and lowering energy consumption, while minimizing visual obstruction. These results provide valuable insights for developing energy-efficient renovation strategies for similar buildings in the region.

1. Introduction

Global climate change poses one of the most pressing environmental crises and one of the most complex multidimensional challenges of the 21st century. To address this global challenge, the international community has established landmark agreements such as the Kyoto Protocol and the Paris Agreement. Major economies, including the European Union, the United States, and the United Kingdom, have committed to achieving carbon neutrality by 2050 [1]. Similarly, China has actively engaged in climate governance. In 2020, China announced its ambitious goals to peak carbon dioxide emissions by 2030 and achieve carbon neutrality by 2060 [2]. Against the backdrop of global decarbonization efforts, building energy efficiency has emerged as a critical lever for advancing energy conservation and emission reduction strategies. This urgency is driven by the fact that buildings account for approximately 40% of global energy consumption [3,4], positioning building energy conservation as a cornerstone of sustainable development. The imperative for action grows stronger with accelerating urbanization, particularly in the context of energy retrofits for public buildings. According to 2021 operational statistics, buildings accounted for 21.9% of the nation’s total energy consumption, with public buildings contributing disproportionately (42%) to this operational consumption [5]. Given their significant energy demand and potential for improvement, public buildings represent a key focus area for energy conservation initiatives.

Renovating existing buildings offers a significant potential to reduce energy consumption and greenhouse gas emissions, thereby fostering the sustainability of the built environment [6]. Among various strategies, optimizing the building envelope and façade design represents a promising approach to achieving a balance between design functionality and energy efficiency [7]. For instance, Y.C. Duan et al. [8] conducted research on residential buildings in cold regions of China and demonstrated that optimizing building geometry and envelope design could reduce energy consumption, enhance thermal comfort, and improve daylight performance. Similarly, Vidhya Maney Surendran et al. [9] implemented measures such as roof reflectivity and high-performance windows in school buildings in India’s hot and humid climate, achieving notable energy savings and improved thermal comfort. Furthermore, Walaa S.E. Ismaeel and Ahmed Gouda Mohamed employed structural equation modeling (SEM) to quantify the interrelationship between materials, energy consumption, and indoor environmental quality during renovation processes, offering a methodological framework for multi-objective decision-making [10]. Collectively, these studies underscore the significant role of building envelope optimization in reducing energy consumption, while emphasizing the importance of tailored strategies that account for local climatic conditions and specific building characteristics.

The integration of shading devices is a key façade optimization strategy and an essential energy-saving measure, capable of reducing the peak cooling load outside the building [11]. In public building renovations, creating flexible large indoor spaces to meet functional requirements often necessitates the use of large-area glass curtain wall systems. These systems serve as a critical interface element for spatial organization, enhancing façade transparency and simplicity while providing users with desirable landscape views. However, this approach conflicts with the building’s light and heat performance and energy consumption. While glass curtain walls introduce abundant natural light, large-area glazing significantly increases solar heat gain, thereby raising the cooling load and energy consumption of the building envelope [12]. Façade shading devices can effectively mitigate this issue, but optimizing their shading ratio requires balancing the indoor lighting environment and thermal equilibrium—two aspects that are often contradictory [13]. For instance, shading devices such as blinds can reduce excessive solar gain and glare caused by extensive glazing [14,15], but excessive shading may compromise indoor illuminance and obstruct landscape views. Therefore, research on building energy-saving renovations should not only focus on energy conservation but also comprehensively consider factors such as thermal and visual performance for multi-objective optimization [6,16].

Shading design plays a crucial role in achieving multi-objective optimization in building performance. Francesco De Luca et al. [17] demonstrated that external static sunshades can significantly enhance visual comfort and energy efficiency in the climate of Tallinn, while effectively balancing daylighting and visual requirements. Yanjin Wang et al. [18] optimized a composite external shading system (combining the optimized integrated external shading with the perforated shading panel) for classrooms in Nanchang, China, to balance energy efficiency, lighting quality, and visual comfort. Building envelopes, in particular, play a significant role in optimizing light and thermal environments while achieving energy savings [19,20]. Sun Zhenyu [21] advanced the concept of landscape orientation in his research, analyzing the inherent conflict between landscape orientation and indoor light and thermal performance at the Bailuyuan Water Ecological Center. Through architectural form and envelope optimization, he successfully achieved a harmonious balance between light and thermal performance and the surrounding landscape environment. In summary, optimizing building envelopes [22,23] and façades [24,25] is essential for resolving the conflict between light and thermal performance and landscape views, while advancing energy conservation in buildings.

To date, numerous scholars have explored multi-objective optimization strategies for building energy-saving renovations [26,27,28]. However, comprehensive studies simultaneously addressing landscape views, thermal performance, daylight conditions, and building energy consumption remain relatively scarce. Thus, this paper selects the annex building of a university sports training center in Guangzhou, a city in China’s hot summer and warm winter climate zone (hereafter referred to as the “sports training annex building”), as a case study. Through on-site investigations and analyses of the current contradictions in building performance, the paper proposes five renovation strategies. It employs numerical simulations to evaluate and compare the thermal and daylight performance, as well as energy consumption, of the proposed renovation schemes. The optimal scheme is then selected based on its balance with landscape views, with the objective of providing new insights into energy-saving renovation approaches for existing public buildings in the hot summer and warm winter zones.

The remainder of this article is structured as follows: Section 2 details the research methodology. Section 3 evaluates the performance of the five optimization strategies through various simulation results and identifies the optimal approach. Section 4 highlights the differences between this study and existing research, discusses the study’s limitations, and explores potential directions for future research. Section 5 concludes with a summary of the research findings.

2. Methodology

2.1. Climate Condition in Guangzhou

Guangzhou City is situated in southern China, with geographical coordinates ranging from 22.51° N to 23.55° N in latitude and 112.94° E to 113.95° E in longitude. The city exhibits a subtropical monsoon climate, characterized by an annual average temperature of 21.7 °C to 23.1 °C. Solar radiation in Guangzhou is predominantly concentrated on the west and south sides, as illustrated in Figure 1. According to the Köppen climate classification system [29], it falls into the hot and humid climate zone. According to the American Society of Heating, Refrigerating and Air-Conditioning Engineers’ standard “ANSI/ASHRAE Standard 169-2020” [30], its climate zone is 2A (warm and humid). In China’s “Standard for Building Climate Zoning” [31], Guangzhou City is located in the hot summer and warm winter zone (the fourth building climate zone). This area has a long summer and no heating in winter. Therefore, reducing the energy consumption for cooling in summer is the focus of energy conservation efforts, and its effectiveness depends on the shading and insulation performance of the transparent envelope structure [32].

2.2. Research Cases and Current Status

Given the regional characteristics of intense solar radiation, ventilation patterns, and lighting requirements typical of hot summers and warm winters [33], south-east or south-oriented buildings are considered optimal. Conversely, west-facing buildings are least favorable due to their prolonged exposure to intense afternoon solar radiation. As a result, few buildings in this region adopt a westward orientation. However, buildings with unusual orientations may also exist due to site constraints, such as land shape or desired views. In such cases, the absence of appropriate green building design strategies can lead to increased building energy consumption.

This study selects a case where the landscape orientation is aligned with an unfavorable regional orientation for analysis. The case involves the annex building of a university sports training center, located on the northern side of the campus. The main building and the annex are arranged perpendicularly. A portion of the annex is adjacent to a lake, making it a waterside structure.

The sports training annex building is a two-story structure with dimensions of 47.19 m in length, 10.8 m in width, and a total height of 7.8 m, with each floor elevated at 3.9 m. The primary structural system is a frame construction, featuring a substantial glass curtain wall on its west-facing elevation. Exterior wall surfaces are finished with white and red real stone paint. The west and southwest elevations provide views of Zhishan Lake on campus, constituting the principal landscape vista. The west side includes a lakeside platform equipped with benches and shade structures, while the east side is adjacent to a small plaza near the Guangzhou Higher Education Mega Center’s Middle Ring Road West. The building’s location and existing conditions are illustrated in Figure 2.

2.3. Current Contradictions

The sports training annex building has an elongated and narrow footprint, with its primary façade-oriented westward. Originally designed as a golf club, it is classified under sports facilities. The building is characterized by an open and transparent spatial layout, with minimal partition walls, primarily confined to the restrooms on the southern side. A large glass canopy extends along the western façade. On the first floor, the western side is fully open, while the eastern side is equipped with guardrails. The second floor features guardrails along both the eastern and western elevations. The floor plan is shown in Figure 3.

The sports training annex building has been converted into a multi-functional facility integrating leisure, communication, and catering functions. The renovation preserves the original architectural layout and maintains its open, transparent interior spaces. The previous restrooms have been reconfigured into private rooms and rest areas. The updated floor plan is shown in Figure 4. Hereafter, this renovation approach is referred to as the original renovation scheme.

The original renovation scheme incorporated an exterior wall system featuring fire rescue windows on the eastern elevation and expansive glass curtain walls on the western elevation. This design strategy achieved a visually permeable facade while preserving visual connectivity to the surrounding landscape, thereby enhancing interior spatial quality through controlled transparency. However, post-renovation evaluation revealed an inherent conflict between daylight optimization and thermal performance in the building’s operational phase.

(1) The contradiction between the landscape view and the thermal performance of buildings. In the hot summer and warm winter zone, the west side of buildings is prone to the influence of the afternoon sun, causing the indoor temperature to be too high. Therefore, buildings in this area usually avoid large windows on the west side. However, in the original renovation scheme, the west and southwest sides were the main landscape views, and the large canopy on the west facade was removed. Only small canopies were installed above the three entrances. Furthermore, the west side lacked tall trees or external shading devices to effectively shield against solar radiation. Consequently, the seating areas on the west side were subjected to excessive solar radiation, causing indoor temperatures to become excessively high during the summer. This necessitated prolonged air-conditioning operation and lower set temperatures, ultimately increasing the building’s cooling energy consumption.

(2) The contradiction between the landscape view and the building’s light performance. While the extensive glazing on the west facade offers enhanced visual access to the surrounding landscape, it also introduces significant glare issues caused by intense natural daylight, resulting in visual discomfort for occupants seated on the west side. Although the original renovation scheme included interior blinds to control indoor light levels and thermal comfort, this approach significantly detracted from the desired visual connection with the exterior.

In summary, although the original renovation of the sports training annex building successfully transformed its functionality, it did not adequately address the significant light-heat imbalance on the west facade. Balancing landscape visibility with thermal performance on the west side presents challenges, resulting in higher energy demands for cooling and visual discomfort for users during the summer. To resolve these issues, the following sections will present additional renovation strategies designed to reconcile the light and heat imbalance on the west side.

2.4. Renovation of the Exterior Envelope Structure

In the original renovation scheme, the design of the peripheral protective structure was implemented. The structural changes before and after the renovation as shown in Figure 5.

(1) The exterior wall renovation. The original renovation scheme included the addition of exterior walls on both the east and west facades. These walls were primarily constructed using aerated autoclaved concrete blocks. To improve the building’s thermal insulation performance, a 15-mm-thick layer of glass microsphere thermal insulation mortar was applied to the inner side of the exterior walls, serving as an insulation layer. The west-facing glass curtain wall was composed of 6 mm high-transparency low-E glass, 12 mm of air space, and 6 mm transparent glass, designed to minimize solar radiation while maintaining energy efficiency.

(2) Roof renovation. In the renovation design, the original aged waterproof membrane was removed and replaced, and a 40-mm-thick B1-grade extruded polystyrene foam insulation board was added to reduce the heat gain caused by solar radiation on the roof, thereby minimizing its influence on the indoor temperature.

The renovation design of the building envelope, aimed at transforming the building’s functionality, introduces new spatial experiences and improves safety within the structure. However, it also creates the thermal and visual comfort issues discussed earlier within the interior space.

2.5. Facade Renovation

In the hot summer and warm winter zone, shading and thermal insulation are critical components of building energy conservation strategies. The original renovation scheme only installed three canopies above the first-floor west entrance without implementing comprehensive external shading measures. Therefore, based on this scheme, this study proposes four distinct external shading methods for the building’s west façade, as shown in Figure 6. Aluminum alloy coated with fluorocarbon paint exhibits excellent weather resistance, moisture resistance, and UV resistance, making it highly suitable for long-term use in high-temperature and high-humidity environments without requiring special maintenance [34,35]. As a result, this material is selected for the external shading panels in the renovation schemes.

2.6. Analysis Tools and Evaluation Indicators

This study employs the Ladybug and Honeybee analysis tools within the Grasshopper platform of Rhino 7 to perform building performance simulation analyses. By utilizing the EPWmap component of Ladybug Tools 1.7.0, the EPW file for Guangzhou 592870 was retrieved from the CSWD (China Sustainable Weather Data) database. This dataset serves as the meteorological input for simulating and evaluating the energy-saving retrofitting strategies proposed for the sports training annex building. The integration of these tools enables a comprehensive assessment of the building’s thermal and energy performance under local climatic conditions, providing critical insights for optimizing the renovation design.

The evaluation of the landscape view considers the visual range of indoor occupants. A seat position is defined as 0.6 m away from the west façade, with the eye height of a seated occupant set at 1.1 m. The view range is analyzed in both vertical and horizontal directions, with a larger range indicating better visual access.

The thermal performance evaluation is based on the solar radiation intensity of the west façade’s envelope structure. Junyu Wang et al. [36] demonstrated that the solar radiation heat gain of the envelope structure is positively correlated with the heat gain entering the room. Therefore, this study uses the solar radiation heat gain of the envelope structure as the evaluation index for this simulation and calculates the cumulative solar radiation for each month throughout the year. A lower cumulative value indicates better performance.

The thermal and lighting performance of the building is evaluated to assess the impact of façade retrofitting on the indoor light environment. In this study, indoor natural daylight illuminance is selected as the primary metric for evaluating light performance. According to the “Standard for daylighting design of buildings” [37], Guangzhou is categorized into light climate zone IV, where buildings with side lighting are required to meet an indoor natural illuminance standard value of 300 lx. However, considering the need for self-study in the indoor environment, the standard value is set at 450 lx for teaching buildings. Additionally, two light environment evaluation indicators are introduced: Useful Daylight Illuminance (UDI) and Daylight Autonomy (DA). UDI refers to the ratio of the effective natural illuminance time on the working plane throughout the year [38], while DA represents the probability that the test point exceeds the minimum indoor illuminance requirement throughout the year [39]. Higher values for these indicators indicate better performance.

The energy consumption evaluation is based on the annual cooling energy use and lighting energy consumption, which serve as the key performance indicators. The resulting energy consumption values are employed to compare the energy-saving effects of different renovation schemes, with lower values indicating better performance.

3. Transformation Strategies and Simulation Analysis

3.1. Simulation Settings

3.1.1. Landscape View Simulation Settings

By generating sectional views of the renovation schemes, variations in the visual field at a given location under different design options can be systematically compared. Subsequently, the renovation proposals are modeled utilizing Rhino7 software and rendered through D5 renderer (Version 2.10.1.1003) to produce perspective simulations. With an eye height of 1.1 m and a southwest-oriented viewpoint, this approach effectively demonstrates the sunshade’s blocking effect on the surrounding landscape in both vertical and horizontal orientations.

3.1.2. Thermal Performance Simulation Settings

In Rhino software, the main building and the annex building of the physical training center were modeled. The main building was only considered for its shading effect on the annex building, while the latter served as the basis for simulation operations. Ladybug tools were utilized to compute the annual solar radiation metrics for each of the five design schemes, as shown in Figure 7.

3.1.3. Optical Performance Simulation Settings

a. Computational grid settings: To investigate the effects of facade optimization on indoor lighting performance, simulations of the indoor light environment were conducted for different design schemes. In the Honeybee computational model, a working plane at a height of 0.75 m above the floor was established, with a computational grid resolution of 0.5 m.

b. Sky environment setting: Given the significant differences in light environment impacts under various sky conditions in Honeybee, the overcast sky with minimal natural light availability is selected as the sky environment to represent the most unfavorable scenario.

c. Calculation time setting: The solar altitude angle fluctuates throughout the year and during different times of the day, significantly influencing the natural lighting within a room. Consequently, for the purpose of illuminance calculation, specific times—namely 9 a.m., 12 p.m., and 5 p.m.—which correspond to periods of heightened human activity, are selected for analysis. These times are evaluated on both the summer solstice, when the solar altitude angle is at its peak, and the winter solstice, when it reaches its lowest point. The data collected are then input into Honeybee PIT Grid for illuminance simulation calculations, as shown in Figure 8.

d. Numerical range setting: The UDI daylight limit was established based on visual requirements. When natural daylight illuminance exceeds 2000 lx, it is classified as glare. Generally, the effective illuminance range is set between 100 and 2000 lx to ensure effectiveness [38]. To meet functional requirements, the useful illuminance range in this study was defined as 450–2000 lx. This range was input into HB Annual Daylight for the simulation calculations of UDI and DA, as shown in Figure 9.

3.1.4. Simulation Settings for Refrigeration Energy Consumption and Lighting Energy Consumption

a. Enclosure structure parameter setting: In Honeybee, the building block and doors and windows of the sports training annex building were established. The exterior wall and roof structure were input to calculate the heat transfer coefficient, as shown in Figure 10. The heat transfer coefficient and solar heat gain coefficient of the west facade curtain wall glass were queried and input into the required parameters for the walls, roof, and glass, as shown in Figure 11.

b. Schedule setting: Then, based on the parameters in the “General Code for Building Energy Efficiency and Renewable Energy Utilization” [40], the daily schedule for building occupants, equipment, fresh air, and lighting was established. This daily schedule was then input into the weekly schedule and subsequently into the seasonal schedule. Winter and summer vacation periods were subtracted from the schedule, with the winter vacation set from 15 January to 1 March and the summer vacation from 15 July to 25 August, as shown in Figure 12.

c. Settings for the activation conditions of cooling and lighting: When the air temperature reaches 26 °C or higher, the air-conditioning system is activated for cooling, as shown in Figure 13. When indoor illuminance falls below 450 lx, the lighting system is activated, as shown in Figure 14. All these operational parameters are input into the HB Model, and Honeybee is utilized to call EnergyPlus and OpenStudio to perform energy consumption simulations on the training building annex model.

3.2. Simulation Results

3.2.1. Landscape View Simulation Results

The influence of different renovation schemes on the landscape view in the vertical direction is shown in Figure 15 and

Table 1. The vertical landscape viewing angle of the renovation schemes.

Renovation Schemes		Landscape Viewing Angle (°)	Above the Horizontal Line (°)	Below the Horizontal Line (°)
Basic scheme	1F	118	70	48
	2F	118	70	48
Scheme 1	1F	101	53	48
	2F	82	53	29
Scheme 2	1F	92	44	48
	2F	68	44	24
Scheme 3	1F	88	40	48
	2F	88	40	48
Scheme 4	1F	101	53	48
	2F	82	53	29

.

In the vertical direction, the Basic scheme provides an unobstructed landscape view, with both the first and second-floor views spanning 118°, resulting in an excellent viewing experience. In the facade renovation schemes, the addition of shading introduces partial obstruction of the landscape views. Among these, Scheme 2 exhibits the greatest obstruction, with the first-floor view retaining only 78.0% and the second-floor retaining 57.6% of the Basic scheme’s view range. Scheme 3 follows with the second-highest obstruction, maintaining a viewing angle of 74.6% on both floors compared to the Basic scheme. Specifically, the upper portion retains 57.1% of the original view, while the lower portion remains unaffected. Scheme 1 and Scheme 4 demonstrate the least obstruction, with identical view retention rates of 85.6% on the first floor and 69.5% on the second floor compared to the Basic scheme.

In the horizontal direction, Scheme 4 introduces vertical shading, resulting in greater obstruction of the landscape view compared to the other schemes. The remaining schemes maintain the same horizontal landscape view.

Basic scheme and Scheme 1 share identical landscape view performance, fully presenting the southwest view. Scheme 2 and Scheme 3 incorporate shading that partially obscures the sky view, though the view below the shading remains unaffected. In contrast, Scheme 4 features vertical shading that markedly disrupts the landscape view. The perspective simulation results are demonstrated in

Table 2. Indoor view simulation diagram of the renovation schemes.

Renovation Schemes	View
	1F	2F
Basic scheme
Scheme 1
Scheme 2
Scheme 3
Scheme 4

.

In summary, among all the renovation schemes, the Basic scheme provides the optimal landscape view, while Scheme 4 yields the least favorable results in terms of landscape views.

3.2.2. Thermal Performance Simulation Results

The simulation results for monthly solar radiation on the west facade throughout the year are presented in Figure 16 and

Table 3. Annual solar radiation and shading rate of the west facade of the renovation schemes.

Renovation Schemes	Annual Solar Radiation on the West Facade/(kW·h/m2)	Obscuration Amount/(kW·h/m2)	Occlusion Rate (%)
Basic scheme	213,813.4
Scheme 1	165,112.6	48,700.8	22.8
Scheme 2	120,498.5	93,314.9	43.6
Scheme 3	141,370.4	72,443.0	33.9
Scheme 4	142,239.6	71,573.8	33.5

. The basic scheme experiences relatively high solar radiation on its west facade year-round, whereas all facade renovation schemes reduce this radiation. Among the schemes, Scheme 2 demonstrates the most significant shading effect, with the west facade receiving 120,498.5 kW·h/m2 of solar radiation annually—a reduction of 43.6% compared to the Basic scheme. Scheme 3 follows with the second-best shading performance, achieving a 33.9% reduction. Scheme 1 exhibits the least shading effect, reducing radiation by 22.8%. Notably, when vertical shading boards are added in Scheme 4, the shading rate increases by 10.7% compared to Scheme 1.

3.2.3. Optical Performance Simulation Results

The illuminance simulation results, as shown in

Table 4. Illumination simulation of the renovation schemes.

Renovation Schemes	Summer Solstice Day			Winter Solstice Day			Legend
	9:00	12:00	17:00	9:00	12:00	17:00
Basic scheme
Scheme 1
Scheme 2
Scheme 3
Scheme 4

, reveal uneven illuminance distribution across all five schemes. The east and west sides of the building exhibit the highest illuminance levels, while the middle area shows a relatively uniform distribution, and the south restroom has the lowest illuminance. In the Basic scheme, the west side experiences relatively high illuminance at 12:00 p.m. on the summer solstice day, with 21.6% of the area exceeding 2000 lx, resulting in glare issues. By the winter solstice day at the same time, the glare on the west side is reduced, with only 14.4% of the area exceeding 2000 lx. Among the facade renovation schemes, all demonstrate a reduction in west-side glare. Scheme 1 shows a relatively low reduction, with 15.4% of the west side exceeding 2000 lx at 12:00 p.m. on the summer solstice day. Scheme 2, however, demonstrates the most effective reduction, with only 8.1% of the west side exceeding 2000 lx at the same time. Scheme 4 shows an improvement over Scheme 1, with 12.4% of the west side exceeding 2000 lx.

The average illuminance results, as shown in Figure 17, indicate that the illuminance levels on the summer solstice day are higher than those on the winter solstice day across all five schemes. For the Basic scheme, the average indoor illuminance at the three time points on the summer solstice exceeds 450 lx, satisfying the code requirements. However, on the winter solstice day, only the 12:00 p.m. time point meets the code requirements, while the average illuminance at 9:00 a.m. and 5:00 p.m. falls short of the standard. Among the facade renovation schemes, Scheme 1 exhibits the highest average illuminance at the corresponding time points. Compared to the Basic scheme, Scheme 1 shows a reduction of 9.9% and 20.9% in average illuminance on the summer and winter solstices for the first and second floors, respectively. Scheme 4 follows with the second-highest average illuminance. Due to the vertical shading, Scheme 4 experiences a reduction of 6.9% and 7.8% in average illuminance on the summer and winter solstices day for the first and second floors, respectively, compared to Scheme 1. Scheme 2 has the most significant impact on natural lighting, with average illuminance levels decreasing by 27.6% and 37.6% on the summer and winter solstices day for the first and second floors, respectively, compared to Basic scheme.

The values of Daylight Autonomy (DA) and Useful Daylight Illuminance (UDI) percentage are shown in

Table 5. Renovation schemes DA and UDI_450–2000 value.

Renovation Schemes		DA (%)	UDI450–2000 (%)
Basic scheme	1F	88.8	41.5
	2F	89.0	40.5
Scheme 1	1F	88.7	43.1
	2F	87.7	46.9
Scheme 2	1F	86.6	49.0
	2F	84.3	52.2
Scheme 3	1F	85.7	50.0
	2F	85.4	50.1
Scheme 4	1F	87.9	46.0
	2F	86.6	50.1

. All five schemes achieve indoor DA values exceeding 80%, while the UDI values exhibit significant variation. The basic scheme has the smallest UDI_450–2000 value, at 41.5% on the first floor and 40.5% on the second floor. Scheme 2 and Scheme 3 demonstrate relatively high UDI450–2000 values, with Scheme 3 achieving approximately 50% on both floors and Scheme 2 reaching 49% on the first floor and 52.2% on the second floor. Based on the illuminance simulation results, the Basic scheme has a higher probability of west-side illuminance exceeding 2000 lx, leading to potential glare issues and a lower UDI_450–2000 value. In contrast, the facade renovation schemes reduce illuminance levels while mitigating glare through external shading, enhancing the proportion of effective daylight illuminance and improving overall indoor light performance throughout the year.

3.2.4. Cooling Energy Consumption and Lighting Energy Consumption Simulation Results

The simulation results are shown in

Table 6. Annual energy consumption performance of the renovation schemes.

Renovation Schemes	Refrigeration Energy Consumption/(kW·h)	Energy Consumption for Lighting/(kW·h)	Total Energy Consumption/(kW·h)	Energy Consumption Proportion of the West Facade (%)	Relative Energy-Saving Rate (%)
Basic scheme	67,309.2	10,299.4	77,608.6	25.5
Scheme 1	64,990.4	10,303.3	75,293.7	24.1	3.0
Scheme 2	61,644.4	10,408.5	72,052.9	19.4	7.2
Scheme 3	62,150.0	10,369.9	72,546.9	19.2	6.5
Scheme 4	63,743.7	10,318.6	74,062.3	22.4	4.6

and Figure 18.

According to the cooling energy consumption results, the Basic scheme has the highest energy consumption, while all facade renovation schemes exhibit reduced consumption. Among the renovation schemes, Scheme 2 demonstrates the most significant reduction, with a decrease of 5664.8 kW·h compared to the Basic scheme, representing an 8.4% reduction. Scheme 3 follows with the second-highest reduction, saving 5159.2 kW·h compared to the Basic scheme, a 7.7% decrease. Scheme 1 shows the smallest energy-saving effect, with a reduction of 2318.8 kW·h, corresponding to a 3.4% decrease compared to the Basic scheme.

According to the results of lighting energy consumption, the Basic scheme has the lowest lighting energy consumption. The lighting energy consumption of the facade renovation schemes all slightly increased. Among them, Scheme 2 has the highest lighting energy consumption, which is 109.1 kW·h higher than that of the Basic scheme, with an increase of 1.1%. The lighting energy consumption of Scheme 3 is slightly lower than that of Scheme 2, which is 70.5 kW·h higher than that of the Basic scheme, with an increase of 0.7%. The lighting energy consumption of Scheme 1 is the lowest among the external shading schemes, which is only 3.9 kW·h higher than that of the Basic scheme, with an increase of 0.04%.

Based on the total energy consumption analysis, the facade renovation schemes achieve substantial cooling energy savings, despite minor increases in lighting energy consumption, resulting in a net decrease in total energy consumption. Compared to the Basic scheme, Scheme 2 demonstrates the most significant improvement, with a total energy consumption reduction of 5555.7 kW·h, achieving a relative energy-saving rate of 7.2%. Scheme 3 follows with the second-best performance, achieving a relative energy-saving rate of 6.5%. In contrast, Scheme 1 has the lowest relative energy-saving rate at 3%, indicating the least improvement in total energy consumption.

According to the energy consumption proportion of the west facade, the Basic scheme has the highest energy consumption proportion of the west facade, accounting for 25.5% of the total energy consumption. Among the facade renovation schemes, the energy consumption proportion of the west facade has decreased. Among them, Scheme 3 has the lowest energy consumption proportion of the west facade, at 19.2%; Scheme 2 follows, at 19.4%; and Scheme 1 has the highest proportion, at 24.1%.

3.3. Optimal Scheme Selection

The comprehensive analysis of landscape view performance, the building’s thermal and lighting performance, and energy consumption simulation results are used to evaluate the renovation schemes, as shown in

Table 7. Architectural landscape view, light and thermal performance, and energy consumption rating.

Renovation Schemes	Landscape View					Thermal Performance					Optical Performance					Refrigeration Energy Consumption					Energy Consumption for Lighting					Total Energy Consumption					Legend
Basic scheme	5					1					1					1					5					1					5 Best 4 Excellent 3 Good 2 Average 1 Worst
Scheme 1	4					2					2					2					4					2
Scheme 2	2					5					5					5					1					5
Scheme 3	3					4					4					4					2					4
Scheme 4	1					3					3					3					3					3

.

From the perspective of landscape views, the Basic scheme provides the optimal landscape view among the five renovation options, enhancing the viewing experience for indoor occupants. Scheme 1 ranks second, closely following the Basic scheme. Scheme 3 is in the middle range, while Scheme 4, which incorporates a comprehensive shading system, results in the most significant obstruction to the landscape view and the least favorable visual appeal.

Based on the thermal and light performance of the building, the ratings of these two indicators are consistent. Scheme 2 has the best performance, effectively reducing westward solar radiation to the greatest extent and minimizing indoor glare, thereby improving the building’s optical performance. Scheme 3 follows closely. In contrast, the Basic scheme has the lowest ratings across all three indicators.

In the renovation schemes, cooling and lighting energy consumption ratings are inversely related. The increase in lighting energy consumption is less significant than the decrease in cooling energy consumption. Consequently, the building’s total energy consumption aligns with the cooling energy consumption trends. Among the schemes, Scheme 2 achieves the lowest cooling energy consumption and total energy consumption, despite having the highest lighting energy consumption. Scheme 3 follows with the second-lowest total energy consumption. In contrast, the Basic scheme has the highest total energy consumption.

Based on a multi-objective optimization analysis, Scheme 2 demonstrates the highest ratings for building thermal performance and cooling energy consumption. However, the use of vertical shading results in poor landscape views and increased lighting energy consumption, failing to optimally balance these conflicting requirements. In contrast, Scheme 3, which employs 46° inclined shading, achieves slightly lower ratings in thermal performance and cooling energy consumption but offers better landscape views and lower lighting energy consumption compared to Scheme 2. It effectively balances landscape views and thermal performance while maintaining energy efficiency, making it the preferred renovation scheme for this study.

4. Discussion

This study selected a case study to analyze the scenario where a building’s primary orientation aligns with the unfavorable orientation of its location. The research demonstrates that optimizing the building envelope and adding external shading devices to the facade can achieve a balance between landscape views and thermal and light performance while reducing building energy consumption. Despite achieving the expected results, this research has certain limitations.

The applicability and limitations in different climate zones. The energy-saving effects of passive shading and high-performance insulation vary in different climates [41], while this study focuses on buildings in hot and humid climates and has not yet covered multiple climate types. Optimization strategies must account for these regional differences in climate conditions. In future research, optimization strategies should be tailored to specific climate conditions by integrating regional characteristics and empirical data.

The material selection is limited. S. Summa et al. [42] conducted experiments to investigate the thermal performance, environmental impact, and cost-effectiveness of sustainable prefabricated facade modules made from various materials, addressing the construction industry’s demand for efficient shading and energy-saving solutions. In addition to traditional materials like concrete, wood, steel, and aluminum, innovative solutions such as solar sails and photovoltaic panels can also serve as shading components [43]. Nevertheless, in this study, only fluorocarbon-coated aluminum alloy was utilized as the shading material. Future research could expand this approach by simulating and analyzing multiple materials to evaluate their respective impacts on energy-saving performance.

Considering thermal comfort and return on investment, many current multi-objective optimization studies on building energy efficiency renovations incorporate thermal comfort as a key target [8,16,44]. Building energy efficiency renovations aim not only to conserve energy but also to enhance the indoor environment’s comfort for users. Therefore, in future research, incorporating targets like thermal comfort and return on investment could provide deeper insights, enhancing the study’s applicability and promotion potential.

5. Conclusions

This study investigates the renovation of the annex building of a university sports training facility in Guangzhou, systematically examining the existing contradictions in the original renovation scheme concerning landscape view, light and thermal performance, and energy consumption. Additionally, it evaluates the design of the building envelope structure. Building on the Basic scheme without external shading, four distinct facade renovation strategies are proposed. Through comprehensive simulation analyses utilizing Ladybug and Honeybee tools, the following conclusions are reached:

In existing public buildings in the Guangzhou area, where the building’s primary orientation aligns with the region’s unfavorable solar exposure, the implementation of a 46° inclined baffle shading system has proven effective in reducing cooling energy consumption while preserving approximately 70% of the landscape view. This system achieves a relative energy-saving efficiency of 6.5% and reduces the west facade’s energy consumption proportion from 25.5% (without external shading) to 19.2%. Additionally, the 46° inclined baffle shading system demonstrates a shading efficiency of 33.6%, effectively mitigating excessive solar radiation. It also reduces glare within the building and improves the proportion of effective daylight illuminance, thereby enhancing indoor light quality.

Inclined baffle shading presents a sustainable energy-saving solution that effectively balances landscape views with building thermal and light performance. The analysis demonstrates that external shading systems offer an effective and practical approach to building energy conservation. Well-designed shading systems can enhance thermal performance while achieving substantial energy savings. This study not only proposes a specific energy-saving renovation scheme for the annex of a university sports training building in Guangzhou but also offers actionable insights into optimizing energy efficiency for existing public buildings in hot and humid climates where conflicts arise between landscape views and thermal performance. Furthermore, the findings provide a comprehensive framework for addressing similar challenges in architectural energy conservation across various climates.