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Article

Evaluating the Cooling Effects and Building Energy-Saving Potential of Vegetation and Albedo: A Case Study of Gyeonggi-Do, South Korea

by
Yuedong Wang
1,
Yuhan Zhang
2,
Younkeun Song
2,
Junga Lee
3,
Guanlin Li
4,
Zipeng Song
5,
Zhicheng Zhou
1,
Junxue Zhang
6,
Jiacong Xu
1,
Jingang Li
7,* and
Yingnan Li
1,8,9,*
1
Department of Environmental Design, Jiangsu University, Zhenjiang 212013, China
2
Department of Environmental Design, Graduate School of Environmental Studies, Seoul National University, Seoul 08826, Republic of Korea
3
Division of Environmental Science and Ecological Engineering, Korea University, Seoul 02841, Republic of Korea
4
School of Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, China
5
Interdisciplinary Program in Landscape Architecture, Graduate School of Environmental Studies, Seoul National University, Seoul 08826, Republic of Korea
6
School of Civil Engineering and Architecture, Jiangsu University of Science and Technology, Zhenjiang 212100, China
7
School of Architecture and Urban Planning, Jilin Jianzhu University, Changchun 130119, China
8
OJeong Resilience Institute, Korea University, Seoul 02841, Republic of Korea
9
Department of Landscape Architecture, School of Architecture, Southeast University, Nanjing 210096, China
*
Authors to whom correspondence should be addressed.
Buildings 2025, 15(4), 597; https://doi.org/10.3390/buildings15040597
Submission received: 17 December 2024 / Revised: 13 January 2025 / Accepted: 24 January 2025 / Published: 14 February 2025
(This article belongs to the Special Issue Advanced Studies on Housing Energy Efficiency, Net Zero Developments and Real Estate Values)
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Abstract

Numerous studies have explored the cooling and energy-saving effects of vegetation and reflective materials under extreme heat conditions in urban residential areas. However, few have explored the synergistic effects of vegetation and albedo, particularly in low-rise, high-density residential areas. Therefore, this study selected six typical low-rise, high-density residential areas in Gyeonggi-do, South Korea, based on the neighborhood characteristics. This study investigated the cooling effects and energy-saving potential of vegetation and cooling materials through the development of five simulation scenarios. These included original conditions, the application of highly reflective cooling materials, increased vegetation cover, the removal of vegetation cover, and a comprehensive strategy combining cooling materials with enhanced vegetation. These scenarios were analyzed using ENVI-met and DesignBuilder to evaluate their impact on the microclimate and building energy consumption. The results reveal the following: (1) Cooling materials can lower air temperatures by 1.9 °C, saving 10.37% in energy consumption during the summer, demonstrating a greater efficiency in reducing air temperature and energy use. (2) Vegetation slightly reduces daytime air temperatures but hampers nighttime cooling in dense low-rise areas, increasing energy demand. Shrubs or grass are preferable to tall trees. (3) Cooling materials had a stronger correlation with energy consumption reduction compared to vegetation. Hence, combining cooling materials with strategically placed vegetation and controlling vegetation size maximized cooling and energy-saving benefits. This study provides valuable insights for urban planners and designers, offering guidance for improving urban microclimates, reducing building energy use, and achieving carbon neutrality goals.

1. Introduction

Urbanization has improved urban life but has also brought a series of problems, such as a significant increase in urban populations, a sharp rise in energy consumption, and an increase in global temperature [1,2,3,4]. Since 2007, the urban population has exceeded that of rural areas, marking a key shift in global demographic trends [5]. By 2050, it is projected that 68% of the global population will reside in urban areas, significantly increasing energy demand [6,7,8]. Urban environments are typically warmer than rural ones due to concentrated energy use and human activities [9,10]. Within this urban context, the building sector plays a major role, accounting for 40% of global energy consumption and 28% of total greenhouse gas emissions [11,12]. Reducing the environmental impact of cities and the energy use of urban buildings has become an urgent priority.
Urban development alters local climate patterns and surface properties, thereby affecting thermal environments and energy consumption trends, particularly in low-rise building areas [13]. However, thermal environmental issues are especially pronounced in high-density low-rise residential areas [14]. These areas are typically composed of aging neighborhoods in need of revitalization, characterized by tightly spaced buildings and limited open spaces. Due to the lack of space, planting a wide variety of vegetation is often unfeasible, and much of the terrain is covered by heat-absorbing surfaces such as asphalt and brick [15]. The compact layout of these structures not only impedes airflow but also reduces wind speed, exacerbating thermal discomfort [16]. Additionally, the low-rise buildings in these areas are more vulnerable to direct sunlight, offering little shade, which creates a less favorable thermal environment for pedestrians, especially in outdoor areas [17,18]. The scarcity of open areas further complicates efforts to establish significant vegetation cover, a critical factor in reducing urban heat [19]. Therefore, enhancing the environment in these high-density, low-rise residential areas is of paramount importance.
Since the 1960s, South Korea has experienced a period of rapid urbanization and population growth [20]. To alleviate the issues of population density and housing shortages in Seoul and the Gyeonggi-do region, the South Korean government has developed satellite cities in these areas [21]. During the construction of various residential types, low-rise residences emerged as a cost-effective solution to meet the residential needs of families [22]. According to Seoul’s building regulations, specifically “Energy-Saving Design Standards for Buildings”, low-rise residential areas are categorized into detached residences, multi-household residences, and townhouses [23]. Notably, 76% of detached residences, one of the main building types in South Korea, are over 20 years old [22]. However, due to inadequate policies and lax regulations, these areas suffer from poor infrastructure—characterized by a high building density, outdated facilities, and limited vegetation—and often undergo uncoordinated modifications, leading to increased energy consumption in these buildings. In urban environments, high temperatures drive energy demand for cooling, while low temperatures increase the need for heating—especially in regions like South Korea that experience four distinct seasons [24,25,26]. By 2016, South Korea’s annual greenhouse gas emissions reached 700 million tons. As of 2019, the total energy consumption in South Korea was 231,235 GWh, with the building sector accounting for approximately 19.9% (45,952 GWh) of this figure. Residential buildings, including detached, multi-family, and other types, made up 58.3% of building energy consumption [27]. Detached residences, in particular, contribute significantly to urban energy consumption, largely due to poor insulation in older buildings [28,29]. The energy consumption of these residences averages 358 kWh/m2, far exceeding the benchmark of 120–150 kWh/m2 established by Korea’s National Building Energy Policy [30,31]. The South Korean government aims to cut greenhouse gas emissions to 536 million tons by 2030 with the target of a 32.5% reduction. To meet this goal, enhancing urban energy efficiency in high-density, low-rise residential areas will be essential for reaching carbon neutrality.
The primary objective of this study is to evaluate the cooling effects and energy-saving potential of vegetation and albedo in low-rise residential areas within Gyeonggi Province, South Korea. To achieve this, Gwacheon-si and Uiwang-si, two satellite cities in Gyeonggi Province, were selected as the primary study sites. The ENVI-met model was employed to simulate the microclimatic impacts of vegetation and high-albedo surfaces, while DesignBuilder software 6.1 was utilized to assess building energy consumption under various scenarios. By integrating insights from multi-objective optimization and comprehensive quantitative analysis, this study proposes an optimized strategy for enhancing cooling efficiency and reducing energy consumption in urban residential areas. Grounded in empirical data from the selected sites, these findings aim to contribute to sustainable urban development and the advancement of carbon neutrality initiatives.

2. Literature Review

2.1. Impact of Cooling Materials on Microclimate and Building Energy Efficiency

Cooling materials significantly influence the energy equilibrium of their surroundings, primarily through their surface properties that enhance solar reflectivity. This characteristic, known as albedo, is quantified by higher values that indicate greater reflectivity. When applied to urban surfaces, high-albedo materials are effective in reducing outdoor air temperatures, thereby improving thermal comfort [9]. Wang (2016) conducted research on strategies to reduce energy consumption in various urban neighborhoods and highlighted the significant influence of urban typology and green spaces on solar irradiance accumulation. His simulation-based study demonstrated that the use of cooling pavements and roofs, incorporating high-albedo materials, led to surface temperature reductions of up to 7.9 °C and 11.3 °C, respectively [32]. In another study, Evola et al. (2017) observed an increase in pavement reflectivity from 0.2 to 0.83, resulting in an average cooling effect of one degree Celsius in the study area [33]. Similarly, Litardo et al. (2020) investigated a type of concrete with enhanced cooling properties due to its high albedo, achieving a surface temperature reduction of six degrees Celsius [34]. Such decreases in surface temperature also can alter the microclimate around buildings, which in turn affects their energy consumption. Miller et al. (2015) analyzed that modifying roofing materials in high-density, low-rise residential areas could reduce cooling loads by 5% to 35% [35]. Ankita et al. (2020) found that the use of cooling materials can reduce cooling energy by 19.2% [36].

2.2. Greening Strategies for Microclimate and Building Energy Reduction

Previous studies have indicated that greening strategies, including vertical greening, rooftop greening, and ground-level greening, significantly influence building microclimates and energy consumption [37,38]. For example, Bounoua et al. (2015) found that vegetation provided notable cooling effects, with a two degrees Celsius temperature reduction compared to asphalt and concrete surfaces [39]. Further research by Mir and Sahar demonstrated that 50% tree coverage effectively enhanced thermal performance in both high- and low-density areas, especially in hot and arid climates, while also mitigating the urban heat island effect [40]. To better understand the impact of urban vegetation coverage on air temperature and building energy consumption, more extensive studies have been conducted. Hwang (2016) noted that vegetation’s cooling efficiency is influenced by factors such as size, spatial pattern, and canopy type, which in turn affect energy-saving performance [41]. Morakinyo et al. (2018) found that in high-density urban areas (20–220 m), with approximately 30% green coverage, summer daytime energy savings could reach 1900 kWh or greater [41]. However, due to the complexity of vegetation types and dimensions, vegetation can sometimes negatively impact air temperature and building energy consumption. Ge (2024) highlighted that evergreen vegetation could increase air temperature at the block scale and raise building energy consumption by up to 7.16% [42].

2.3. The Impact of Block Morphology on Microclimate and Building Energy Consumption

Block morphology, including street orientation, building height, and urban density, plays a critical role in shaping the microclimate and influencing building energy consumption in urban areas [18,43]. Various studies have highlighted the significance of these factors in determining thermal comfort, urban heat island effects and energy demand. Deng et al. (2020) noted that variations in street orientation significantly affect the microclimate around buildings. North–south-oriented streets provide higher levels of thermal comfort due to reduced solar radiation exposure, but they increase the cooling energy demand of buildings compared to east–west-oriented streets [44,45,46]. Additionally, Fahed’s research suggests that more compact urban morphologies are associated with higher building energy consumption. Conversely, Adnane’s findings (2021) indicate that buildings situated on wider streets consume more energy in the summer due to the aspect ratio of street canyons [47,48]. The impact of building height on the effect of street orientation varies: in streets bordered by buildings less than five m tall, orientation has a negligible impact on the thermal environment. However, for buildings over 20 m, the shading provided by these taller structures significantly enhances thermal conditions. High-rise buildings generate extensive shaded areas, which lower both surface and air temperatures. However, in urban canyons, sunlight reflections can intensify the urban heat island effect. Hu et al. (2023) achieved a cooling load reduction of 31% and reduced energy consumption by 29% through simulation optimization [49]. Similarly, Spanos argues that strategic block orientation and landscape coverage can reduce a building’s energy demand by 20%, primarily by regulating the penetration of daylight into indoor spaces [50]. In summary, block morphology significantly affects both microclimate regulation and energy consumption. By strategically considering factors such as street orientation, building height, and vegetation coverage, urban planners can optimize urban design to enhance thermal comfort and reduce energy demand.
Although previous studies have explored the potential of cooling materials and greening strategies, most research has focused on high-rise, high-density urban areas, while overlooking the challenges faced by low-rise, high-density environments [13,34]. These residential areas are characterized by a high building density, limited vegetation, aging infrastructure, and narrow streets, which exacerbate urban heat island effects and increase energy demand. Moreover, findings on the cooling effects of vegetation have been inconsistent across different building heights and densities [28]. To address these gaps, this study examines the application and combined effects of cooling materials and greening strategies in low-rise, high-density residential areas, offering practical insights for improving urban microclimates and enhancing energy efficiency.

3. Methods

3.1. Study Site

Figure 1 illustrates the location of Gyeonggi Province in the northwestern part of South Korea, situated between 126° and 127° east longitude and 36° and 38° north latitude. Covering an area of 10,171 square kilometers—about 10% of South Korea’s total land area—Gyeonggi Province has experienced rapid population growth due to the country’s modernization and urbanization. Its population surged from 641,411 in 1970 to 13,717,827 in 2022 “www.kosis.kr (accessed on 4 February 2024)”. The province has a continental climate with four distinct seasons: cold, dry winters; hot, humid summers; and brief spring and autumn periods. Statistically, the average annual temperature ranges between 10 °C and 16 °C. Figure 2 illustrates the average monthly temperatures during the hottest months, typically July and August, which range between 23 °C and 27 °C, with extremely high temperatures reaching 37.1 °C “www.weather.go.kr (accessed on 23 December 2023)”. The prolonged high temperatures during the summer significantly increase urban energy demand.
Urban development in Gyeonggi Province has led to significant changes in its urban surfaces. As satellite cities of Seoul, the urban renewal of Gyeonggi Province plays a key role in supporting the sustainable development of the capital [51]. To assess the feasibility of strategies aimed at improving the urban thermal environment and reducing energy consumption, Gwacheon and Uiwang—two cities in Gyeonggi Province—were selected for this study. Gwacheon, located between Cheonggye Mountain and Gwanak Mountain, serves as an important connection between Seoul and Gyeonggi Province. Similarly, Uiwang is located south of Gwacheon and is an important industrial and transportation base. Sezer, N et al. (2023) found that the thermal environment in low-rise high-density residential areas is more complex and has a significant impact on building energy demand [52]. Therefore, this study focuses on the low-rise, high-density residential areas in both Uiwang and Gwacheon in Gyeonggi Province.
Furthermore, such residential areas, commonly represented by detached residential areas in South Korea, are characterized by aging infrastructure, narrow streets, and poor thermal environments, which exacerbate urban heat challenges. These low-rise, high-density residential areas, often constructed two or three decades ago, lack sufficient vegetation and open spaces, resulting in a pronounced urban heat island effect. And street orientations significantly influence thermal environments by affecting sunlight exposure, ventilation, and heat dissipation. Therefore, we have selected six low-rise, high-density residential areas, representing three typical street orientations, as our research sites: Burim, Byeoryang, Munwon, Cheonggye, Sam, and Gocheon. Detailed characteristics, including administrative level, location of each selected area, orientation, and site size, are listed in Table 1.

3.2. Setting Up Scenarios and Modelling Simulations

Figure 3 illustrates the research process, which involves field investigation, microclimate measurement and validation, and then establishment and simulation of microclimate and building energy consumption models for different scenarios.

3.2.1. Simulation Model in ENVI-Met

This study used numerical model ENVI-met (V5.6) to simulate the thermal environment of urban streets. ENVI-met was developed in 1998 by Professor Michael Bruse from the Department of Geography at the Johannes Gutenberg University Mainz, Germany [53,54,55]. It is a three-dimensional microclimate simulation tool based on fluid mechanics and thermodynamics theories. The software simulates the physical processes of heat, energy, and material exchange between buildings, the ground, vegetation, and the atmosphere in small-scale urban environments. ENVI-met is widely recognized for its relevance and applicability in urban microclimate research across various regions [56,57,58].
In this study, ENVI-met 5.6 was employed for microclimate simulation to evaluate urban heat island mitigation strategies in several high-density, low-rise building areas in Gyeonggi-do, South Korea. Table 2 illustrates the environmental model constructed in ENVI-met based on field surveys and satellite imagery. To maintain model resolution and simulation accuracy, selected building areas were modeled based on on-site measurements, remote sensing data, and LiDAR urban data. Google Earth imagery was utilized to assist in creating and editing grids for ground elevations, building orientations, and vegetation distribution. Six urban environmental models were established in ENVI-met to simulate experimental environments under various influencing factor scenarios. The spatial dimensions of all simulated areas were set to 300 m in width, 300 m in length, and 30 m in height. All models were simulated using a 150 × 150 × 30 (xyz) grid with grid spacings of dx = 2 m, dy = 2 m, and dz = 2 m. Considering different street orientations, three block orientations were defined at 30-degree intervals: 30 degrees northeast, 30 degrees northwest, and due north. Regional input files were rotated clockwise at different angles to align the grid with the main direction of the blocks.

3.2.2. Building Energy Calculation in Designbuilder

Designbuilder is a widespread and accepted tool in the building energy analysis community around the world [59]. Designbuilder is a console-based program that reads input and writes output to text files. It includes a number of utilities, such as IDF-Editor for creating input files using a simple spreadsheet-like interface, EP-Launch for managing input and output files and performing batch simulations, and EP-Compare for graphically comparing the results of two or more simulations. Several comprehensive graphical interfaces for Designbuilder are also available.
To evaluate the energy-saving effects of residential energy conservation strategies, we employed both ENVI-met and DesignBuilder. ENVI-met generates data on reduced ambient temperatures, which are then converted into an EPW file for input into DesignBuilder. DesignBuilder models how changes influence a building’s environmental performance, such as ventilation, HVAC systems, and energy consumption over time. The procedure for calculating energy savings from these strategies is detailed. To create the most up-to-date weather files in the DesignBuilder format, meteorological data were extracted from the Leonardo plug-in for ENVI-met results and exported as Excel files, covering temperature, humidity, wind speed, direction, and solar radiation. Additional weather data, including solar radiation and precipitation, were adjusted and merged with the exported data using information from weather.go.kr. Ultimately, a new EPW file was generated through the Element tool.

3.2.3. Simulation Scenario Design

In this study, we systematically investigate the cooling effects and energy-saving potential of vegetation and cooling materials through the design and analysis of various simulation scenarios. Subsequently, five distinct design scenarios have been developed. The first scenario represents the existing condition of the site, serving as a reference point. The second scenario involves the substitution of low-reflectance materials with high-reflectance cooling materials. Specifically, surfaces including rooftops and pedestrian walkways are replaced with high-albedo materials such as granite (with an albedo of 0.60) and bright asphalt (with an albedo of 0.50), thereby increasing the pavements’ reflectivity to 0.5 and the buildings’ reflectivity to 0.6, as indicated in Table 3. The third scenario focuses on enhancing vegetation coverage by planting trees, shrubs, and grasses along streets with different aspect ratios and implementing green roofs and vertical greening to minimize heat transfer through the building envelope. The fourth scenario explores the removal of vegetation from the streets, and the vegetation mainly consists of grass due to the scarcity of large vegetation. The fifth scenario combines the application of cooling materials with increased vegetation coverage, integrating these strategies to optimize the thermal environment. Therefore, for the convenience of research and reference, these design scenarios are numerically labeled in accordance with the study sites, as shown in Table 4.
Figure 4 presents a selection of building models created in DesignBuilder for the purpose of energy consumption simulation. Table 5 presents the relevant parameter settings used in the building energy consumption simulation process. Field surveys and digital modelling were conducted for the baseline scenario of 30 July 2022, along with four other scenarios, to assess microclimate and energy consumption. Given the hot summer climate of Gyeonggi-do, cooling load was identified as the primary energy load in this study. During the simulations, the air conditioning set temperature for buildings in summer was maintained at 24 °C. To model energy consumption, this study selected twenty typical residential buildings and calculated their average energy consumption. These buildings are detached residences, with heights ranging from 6 to 12 m, most of which are 2 to 3 stories. Each building includes essential living units, encompassing several bedrooms, a living room, kitchen, bathrooms, and toilets.

4. Results

4.1. Data Validation of the Model

To evaluate and validate the model, it was necessary to compare the air temperature and relative humidity data derived from the model with the actual ground-level measurements. The study sites were characterized by a dense, urban environment with a high concentration of low-rise buildings and concrete pavements. The initial model was created to accurately represent these features and was used for validation purposes. Various meteorological parameters were used to analyze the microclimate of each sample site and compare the measured values with those obtained from the model.
Figure 5 shows the validation of the accuracy of the ENVI-met model results. In this study, a linear regression analysis was employed, and the model’s performance was assessed using the coefficient of determination (R2), p-values, and the root mean square error (RMSE). R2 measures how well the model explains the variance in the observed data, with values closer to one indicating a better fit. The results show that the R2 values across the six scenarios ranged from 0.9506 to 0.9735, signifying a very high degree of agreement with the observed data. The RMSE reflects the average deviation between simulated and observed values; lower RMSE values indicate higher model accuracy. In this study, the RMSE ranged from 0.25 to 0.34, further confirming the reliability and precision of the ENVI-met model. These results demonstrate that the model effectively reproduces the microclimatic characteristics of the study area, validating the reliability and applicability of the simulation results.

4.2. Effect of Different Scenarios on Microclimate

Figure 6 shows the air temperature distribution for each scenario extracted from the model. Six time points were selected for analysis, spaced at three-hour intervals: 6:00 (morning), 9:00 (morning), 12:00 (noon), 15:00 (afternoon), 18:00 (evening), and 21:00 (night). As can be seen from the box plots, of the five scenario types, Scenario R exhibits the most significant daytime cooling effect, with the average temperature in the study area dropping by 1.9 °C. The BY box plot has the most prominent distribution of data, presenting the greatest cooling effect, with the temperature dropping by 2.4 °C. This highlights the effectiveness of reflective surfaces in mitigating daytime heat. In addition, the box plots for scenario R at 21:00 were lower than all the others, suggesting that the nighttime cooling trend in the area around the building is intensified due to the reflective properties of these surfaces. In contrast, Scenario N, which removed vegetation cover, showed a marked increase in daytime air temperature, with an average increase of 0.29 °C. Scenario MU-N-T experienced the largest temperature increase, with a rise of 0.51 °C. This is primarily attributed to the absence of trees and shrubs, leading to reduced shading and increased solar radiation absorption. Scenarios V and C demonstrated similar patterns. As the vegetation cover increased, the cooling effect became less pronounced, particularly in Scenario BY-V-W, which exhibited the smallest cooling effect at 15:00, with a temperature reduction of just 0.11 °C. This suggests a diminishing return in cooling efficiency with increased vegetation coverage under certain conditions.
Figure 7 illustrates the air temperature differences between Scenario O and other scenarios at 12:00, 15:00, 18:00, and 21:00. The size of the circles in Figure 7 corresponds to the magnitude of the temperature differences, with larger circles indicating more significant variations. The results demonstrate that the daily maximum air temperature for all scenarios occurred at 15:00. Furthermore, Scenario N exhibited the most pronounced nighttime cooling effect, with Scenario SA-N-N achieving a temperature reduction of 1.54 °C. However, Scenarios V and C displayed less effective nighttime cooling compared to their daytime performance. Notably, nighttime temperatures in Scenario C were consistently higher than those in Scenario V at various locations. This indicates that in dense low-rise building areas, reducing vegetation can enhance ventilation between streets, thereby improving cooling effects, whereas excessively high vegetation coverage can reduce heat dissipation.

4.3. Effect of Different Scenarios on Building Energy Consumption

Figure 8 illustrates the distribution of building energy consumption simulations across different scenarios, and the violin plot depicts the concentration trend and distribution of energy consumption in detail. Scenarios R and C demonstrate a superior energy-saving performance, evident from their lower median energy consumption values. However, Scenario R also exhibits greater variability, as indicated by the broader and more uneven distribution across the plot, suggesting that the energy-saving effects in this scenario are less consistent across different cases. Conversely, Scenario C presents a more concentrated distribution, with a narrower range of values, reflecting greater stability in energy savings. Notably, certain data points within Scenario V indicate lower energy consumption than those observed in Scenarios O and N, which could be attributed to the influence of specific vegetation configurations contributing to localized cooling effects.
In this research, the use of cooling materials in Scenario R led to a notable reduction in energy consumption. Specifically, this scenario achieved a decrease of 38.51 kWh in daily cooling demand during the summer, translating to an energy savings of around 10.99%. This substantial reduction underscores the potential of cooling material technology in enhancing building energy efficiency. Following Scenario R, Scenario C, which combined the use of cooling materials with increased vegetation cover, demonstrated notable energy-saving effects. Compared to Scenario O, this integrated approach resulted in a reduction of 24.50 kWh in building energy demand, equivalent to an energy savings of 6.99%. Among these, Scenario SA-C-N showed the best energy-saving effect, reaching 29.87 kWh, surpassing the energy-saving effect of Scenario CH-R-W. This indicates that the combined approach of using cooling materials and increasing vegetation cover can effectively enhance energy savings in buildings during the summer. However, in Scenarios V and N, the simulation results showed an increase in building energy consumption, rising by 9.21 kWh and 4.30 kWh, respectively. Among these, Scenarios CH-V-W and MU-N-T performed worse, with energy consumption increasing by 21.13 kWh and 24.43 kWh, respectively. This outcome can be attributed to the removal of vegetation cover in densely populated low-rise residential areas, leading to insufficient shading and enhanced solar radiation during the day, thereby increasing building energy consumption.

4.4. Analysis of Elements Affecting Building Energy Consumption

Figure 9 shows the Pearson correlation coefficients between various urban form factors and the average daily building energy consumption. The results reveal that the primary determinant of building energy consumption is the use of cooling materials, with the green ratio. A strong negative correlation between cooling materials and energy consumption suggests that their application can substantially reduce energy usage, likely by lowering the demand for artificial cooling [60]. Similarly, the green ratio shows a notable negative correlation with energy consumption, suggesting that greater vegetation can reduce cooling demand, thereby lowering energy usage. Furthermore, a weak positive correlation is observed between the green ratio and the use of cooling materials, implying that areas with more greenery may also incorporate cooling materials more often to enhance energy savings [61]. Therefore, the strategic use of cooling materials, along with the optimized green ratio, can significantly decrease building energy consumption, providing a basis for achieving energy-saving and emission-reduction goals. These findings offer valuable insights into energy-efficient urban design and building layout strategies.

5. Discussion

5.1. Discussion on Microclimate and Building Energy Performance

This study describes the high potential of cool materials in reducing the ambient temperature and cooling energy demand of the building stock in high-density and low-rise residential areas. Increasing the reflection of the cooling material can reduce the air temperature in the building area by 1.9 °C, resulting in energy savings of 11% during the summer. During the daytime, highly reflective surfaces lead to a visible decrease in air temperature and building energy consumption, while at night, the influence is minimal. These results tie in well with previous studies. Jandaghian et al. (2020) found that by increasing the albedo of urban surfaces (walls, roofs, and sidewalks), the daily average urban surface temperature and absolute humidity can be reduced by 3.3 °C and 0.6 g/kg, respectively, and the cooling energy demand can be reduced by nearly 10% [62]. However, previous studies have found that excessively high road reflectivity can cause discomfort to residents [63,64].
In these areas, increasing vegetation cover in high-density, low-rise residential zones is not an effective method for reducing building energy consumption. Most previous studies have indicated that different building types require varying levels of vegetation cover to achieve optimal results [65,66]. Agnoli’s study has shown that three-dimensional greenery can reduce wall temperatures by one to three degrees Celsius and that energy consumption through air infiltration accounts for 40% of the total energy consumption of residential buildings [36,42]. However, this study reveals that in high-density, low-rise residential areas, trees can hinder natural ventilation in urban canyons due to the narrow spacing between buildings [67,68]. Air temperature affects the temperature of a building’s walls, which affects the indoor temperature and the building’s energy demand. This results in a weak cooling effect and even raises temperatures in some special areas. And due to the thermal energy storage of trees at night, it will lead to greater building energy consumption: 2.03 kWh per day. The findings of this study are consistent with those of a similar study conducted in Manchester. In that study, field meteorological measurements were taken using sensors placed around buildings, which revealed that the ground, building facades, and roofs absorb significant amounts of long-wave radiation. As a result, areas with unobstructed views of the sky—where there are no trees or other barriers to block the view—tend to experience higher air temperatures. In some cases, trees do reduce the air temperature slightly because the large gaps between trees absorb long-wave radiation from the ground, raising the temperature of the area [60,69].
This study investigates energy consumption in residential areas with three different street orientations, recognizing street orientation as another crucial parameter affecting urban building energy consumption, as highlighted by previous research. Past studies have noted that different street orientations significantly impact the microclimate around buildings. Streets oriented north–south, due to their shorter period of exposure to solar radiation, offer the highest level of thermal comfort; compared to east–west-oriented streets, they increase the energy demand for cooling [44,45,46]. For residential areas oriented at 30° and 60°, direct afternoon sunlight entering through the main building facade leads to higher indoor temperatures and increased cooling demand, as shown in Figure 10. However, this study concludes that in densely populated low-rise residential areas, increasing or decreasing vegetation has a poor effect on reducing building energy consumption. Therefore, in street blocks oriented at 30° and 60°, enhancing shading facilities rather than altering vegetation is a more effective method to reduce building energy consumption.

5.2. Strategies for Urban Energy Savings

Low-rise, high-density residential areas, characterized by a blend of internal and open spaces, often grapple with several urban design challenges. These factors collectively contribute to a unique urban landscape, necessitating tailored solutions.
In such environments, strategically using cooling materials and incorporating vegetation have become effective methods for reducing building energy consumption [70,71]. (1) Replacing traditional building surfaces and sidewalks with materials that have cooling properties can significantly lower the air temperature in the area, thereby reducing energy demand during the summer [60,72]. (2) However, previous studies have shown that dense buildings may hinder natural ventilation [73]. To optimize the cooling effect of vegetation, it is best to control the number and size of trees in high-density residential areas [61]. (3) In addition, retractable shading devices can be installed in certain areas of the street, not only providing shade in the summer, but also adjusting the coverage in the winter to allow sunlight to reach the street. This approach not only helps to reduce temperature, but also breaks up the persistent urban heat island, thereby alleviating thermal conditions and reducing overall energy consumption [74]. (4) Addressing the unique thermal demands of streets with different orientations is equally important. For instance, in areas oriented slightly north of east, direct afternoon sunlight can significantly increase indoor temperatures, which can be mitigated by installing external shading devices on the western side of buildings. Conversely, in areas oriented slightly north of west, it is advisable to manage vegetation and shading structures on the southern side of buildings to ensure adequate sunlight [75,76]. These strategies highlight the necessity of integrating built and natural environments in urban planning to create energy-efficient, thermally comfortable spaces.

5.3. Limitations and Further Study

This study has several limitations. First, the experiments focused on a typical meteorological day in summer, which restricts the generalizability of the findings. Future studies should include data from winter and other seasons. Second, previous research has indicated that increasing surface material reflectivity may reduce thermal comfort and increase heating energy consumption during winter [77,78,79]. Therefore, future research should investigate the effects of materials with varying levels of reflectivity on thermal comfort and energy consumption under different temperatures and climates. Third, this study was limited by the small number of sampling points and did not include comparisons of similar building types in different climate zones [80]. Future research should aim to expand the sample size and conduct comparative analyses of buildings with similar characteristics across different climate zones to provide a more comprehensive understanding of the relationship between microclimates and building energy consumption. Fourth, although the ENVI-met model’s air temperature simulations have been validated, it has inherent limitations in simulating the impact of building waste heat on the thermal environment and in accurately capturing wind direction changes, which may lead to deviations from real-world conditions [81,82]. Therefore, future studies should integrate multiple simulation software tools to enhance the accuracy of microclimate modeling. Lastly, higher surface reflectivity, while beneficial for reducing air temperatures and energy consumption, may increase the physiological equivalent temperature (PET) in street canyons, leading to decreased thermal comfort for pedestrians. Future research should explore the impact of high-reflectivity materials on PETs and outdoor thermal comfort, as well as develop strategies to balance cooling effects and human comfort in dense urban environments.

6. Conclusions

The potential of cooling materials and vegetation to substantially decrease summer air temperatures and curtail building energy consumption within dense, low-rise residential areas, particularly in urban settings, remains largely uncharted. Consequently, this study undertakes simulations of urban heat environments and energy consumption to meticulously explore the cooling and energy-saving impacts of cooling materials and vegetation in typical dense, low- rise residential areas located in Gyeonggi Province during the summer season. By delving into these aspects, we aim to fill the existing knowledge gaps and offer valuable insights for urban planning and energy-efficient design in such areas.
The main findings of the study are as follows:
(1)
Adding vegetation can slightly reduce the daytime temperature between buildings, but it will affect the nighttime cooling effect. Removing vegetation can reduce the nighttime space temperature, but it may lead to higher daytime temperatures. Therefore, in dense low-rise residential areas, the size of vegetation should be controlled, excessive planting should be avoided during the renovation process, and shrubs or grasses should be selected instead of trees;
(2)
Increasing the coverage of cooling materials and vegetation can significantly reduce air temperatures and building energy consumption in dense low-rise residential areas, with more pronounced effects during the daytime. However, in narrow streets, the reduced heat dissipation from vegetation transpiration at night makes the cooling effect less effective during the nighttime. Therefore, cooling materials should be prioritized in built-up areas of dense low-rise buildings;
(3)
The strategic use of cooling materials significantly reduces building energy consumption in high-density low-rise residential areas, showing a more substantial impact compared to vegetation alone. Cooling materials have a strong negative correlation with energy consumption, making them highly effective in minimizing artificial cooling demands. Vegetation, while complementary, plays a secondary role and should be used as an auxiliary cooling method. Combining cooling materials with carefully planned vegetation placement can maximize energy-saving benefits.
This study makes a significant contribution by elucidating the mitigating effects of urban forms on summer energy demand in such residential buildings. Research that quantifies the environmental impacts and models the energy consumption in residential buildings is instrumental in enabling cities and states to respond to climate change with practical, actionable strategies. By exploring the nuanced relationship between urban forms, microclimates, and energy consumption, this study provides valuable guidance for urban planners and policymakers.

Author Contributions

Conceptualization, Y.W., Y.L., Y.S., J.L. (Junga Lee) and J.Z.; methodology, Y.W. and Y.L.; software, Z.Z.; validation, Y.W., Y.Z., J.L. (Jingang Li) and Z.S.; investigation, Y.W. and Y.Z.; writing—original draft preparation, Y.W., Z.Z. and Z.S.; writing—review and editing, Y.W., Y.Z., Z.Z. and Z.S.; visualization, Y.S., J.L., J.X., G.L. and J.L. (Jingang Li); supervision, Y.L., Y.S., J.L. (Junga Lee) and G.L.; project administration, Y.L. and J.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported by the Project of the Philosophy and Social Science Research of Universities in Jiangsu Province (2020SJA2045), the Jiangsu University Senior Talent Fund (19JDG004), the Talent Project of the “Double-Entrepreneurial Plan” in Jiangsu Province, and the National Research Foundation of Korea.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author(s).

Conflicts of Interest

The authors declare no conflict of interest.

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Buildings 15 00597 g001
Figure 1. Site location and on-site measurement: (a) the location of Gyeonggi-do, Gwacheon-si, and Uiwang-si; (b,c) study sites in Gwacheon-si and Uiwang-si; (d) site condition and on-site meteorological measurement.
Figure 1. Site location and on-site measurement: (a) the location of Gyeonggi-do, Gwacheon-si, and Uiwang-si; (b,c) study sites in Gwacheon-si and Uiwang-si; (d) site condition and on-site meteorological measurement.
Buildings 15 00597 g001
Buildings 15 00597 g002
Figure 2. Monthly temperature and precipitation in Gyeonggi Province for 2020–2022.
Figure 2. Monthly temperature and precipitation in Gyeonggi Province for 2020–2022.
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Buildings 15 00597 g003
Figure 3. Research framework.
Figure 3. Research framework.
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Buildings 15 00597 g004
Figure 4. Designed models in Designbuilder, (A–D) represent the four building models established in DesignBuilder based on field measurements.
Figure 4. Designed models in Designbuilder, (A–D) represent the four building models established in DesignBuilder based on field measurements.
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Buildings 15 00597 g005
Figure 5. Data validation of measured and simulated average air temperature.
Figure 5. Data validation of measured and simulated average air temperature.
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Buildings 15 00597 g006
Figure 6. Temperature distribution at different points within the simulated plots at 6:00, 9:00, 12:00, 15:00, 18:00, and 21:00 on the simulated dates for scenarios BU–GO separately.
Figure 6. Temperature distribution at different points within the simulated plots at 6:00, 9:00, 12:00, 15:00, 18:00, and 21:00 on the simulated dates for scenarios BU–GO separately.
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Buildings 15 00597 g007
Figure 7. Temperature difference between the other scenarios and scenario O at 12:00, 15:00, 18:00, and 21:00.
Figure 7. Temperature difference between the other scenarios and scenario O at 12:00, 15:00, 18:00, and 21:00.
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Buildings 15 00597 g008
Figure 8. Distribution of daily energy consumption in different modelling buildings for scenarios BU–GO.
Figure 8. Distribution of daily energy consumption in different modelling buildings for scenarios BU–GO.
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Buildings 15 00597 g009
Figure 9. Correlation between urban form factors and the daily average of building energy consumption.
Figure 9. Correlation between urban form factors and the daily average of building energy consumption.
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Figure 10. Distribution of building energy consumption based on street orientations of 0°, 30°, and 60°.
Figure 10. Distribution of building energy consumption based on street orientations of 0°, 30°, and 60°.
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Table 1. Data resources of study areas.
Table 1. Data resources of study areas.
ToponymBurimByeoryangMunwon
Administrative levelDong
FigureBuildings 15 00597 i001Buildings 15 00597 i002Buildings 15 00597 i003
Administrative regionGwacheon-si
OrientationBuildings 15 00597 i004Buildings 15 00597 i005Buildings 15 00597 i006
Size300 M × 300 M
ToponymCheonggyeSamGocheon
Administrative levelDong
FigureBuildings 15 00597 i007Buildings 15 00597 i008Buildings 15 00597 i009
Administrative regionUiwang-si
OrientationBuildings 15 00597 i010Buildings 15 00597 i011Buildings 15 00597 i011
Size300 M × 300 M
(Note: Buildings 15 00597 i010 means between west of north 35° and 25°; Buildings 15 00597 i011 means between west of north 5° and east of north 5°; Buildings 15 00597 i011 means between east of north 35° and 25°).
Table 2. Models of the study sites in ENVI-Met.
Table 2. Models of the study sites in ENVI-Met.
ToponymBurimByeoryangMunwon
ModelBuildings 15 00597 i012Buildings 15 00597 i013Buildings 15 00597 i014
ToponymCheonggyeSamGocheon
ModelBuildings 15 00597 i015Buildings 15 00597 i016Buildings 15 00597 i017
Table 3. Pavement characteristics.
Table 3. Pavement characteristics.
Surface TypeMaterial TypeAlbedo
RoadBright asphalt/Permeable brick0.5/0.3
PedestriansGranite0.6
RoofGranite/Concrete0.6/0.25
Table 4. Designed scenarios.
Table 4. Designed scenarios.
I: Study sitesBU Burim; BY Byeoryang; MU Munwon;
CH Cheonggye; SA Sam; GO Gocheon.
II: Designed scenariosO the original site;
R high-reflectance cooling materials;
V high vegetation coverage;
N no vegetation coverage;
C combination of high-reflectance cooling materials and high vegetation coverage.
III: OrientationT  Buildings 15 00597 i018;  W  Buildings 15 00597 i019;  N  Buildings 15 00597 i011.
ORVNC
BurimBU-O-TBU-R-TBU-V-TBU-N-TBU-C-T
ByeoryangBY-O-WBY-R-WBY-V-WBY-N-WBY-C-W
MunwonMU-O-TMU-R-TMU-V-TMU-N-TMU-C-T
CheonggyeCH-O-WCH-R-WCH-V-WCH-N-WCH-C-W
SamSA-O-NSA-R-NSA-V-NSA-N-NSA-C-N
GocheonGO-O-NGO-R-NGO-V-NGO-N-NGO-C-N
(Note: Buildings 15 00597 i010 means between west of north 35° and 25°; Buildings 15 00597 i011 means between west of north 5° and east of north 5°; Buildings 15 00597 i011 means between east of north 35° and 25°).
Table 5. Model specifications.
Table 5. Model specifications.
HVAC templateRadiator heating, boiler HW, nat vent
Activity templateResidential spaces’ activity template
Construction templateBest practice, medium weight
Infiltration rate1.5 m3/m2
Lighting templateBest practice
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Wang, Y.; Zhang, Y.; Song, Y.; Lee, J.; Li, G.; Song, Z.; Zhou, Z.; Zhang, J.; Xu, J.; Li, J.; et al. Evaluating the Cooling Effects and Building Energy-Saving Potential of Vegetation and Albedo: A Case Study of Gyeonggi-Do, South Korea. Buildings 2025, 15, 597. https://doi.org/10.3390/buildings15040597

AMA Style

Wang Y, Zhang Y, Song Y, Lee J, Li G, Song Z, Zhou Z, Zhang J, Xu J, Li J, et al. Evaluating the Cooling Effects and Building Energy-Saving Potential of Vegetation and Albedo: A Case Study of Gyeonggi-Do, South Korea. Buildings. 2025; 15(4):597. https://doi.org/10.3390/buildings15040597

Chicago/Turabian Style

Wang, Yuedong, Yuhan Zhang, Younkeun Song, Junga Lee, Guanlin Li, Zipeng Song, Zhicheng Zhou, Junxue Zhang, Jiacong Xu, Jingang Li, and et al. 2025. "Evaluating the Cooling Effects and Building Energy-Saving Potential of Vegetation and Albedo: A Case Study of Gyeonggi-Do, South Korea" Buildings 15, no. 4: 597. https://doi.org/10.3390/buildings15040597

APA Style

Wang, Y., Zhang, Y., Song, Y., Lee, J., Li, G., Song, Z., Zhou, Z., Zhang, J., Xu, J., Li, J., & Li, Y. (2025). Evaluating the Cooling Effects and Building Energy-Saving Potential of Vegetation and Albedo: A Case Study of Gyeonggi-Do, South Korea. Buildings, 15(4), 597. https://doi.org/10.3390/buildings15040597

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