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Article

Simulation-Integrated Climate-Adaptive Pedestrian Design Explorations for Summer Thermal Comfort: The Case of Culturally Diversified Green Way Project in Seoul, South Korea

by
Gawon Bae
1,
Eujin Julia Kim
2 and
Kwangmin Ham
2,*
1
Eospace, Chungmin-ro, Songpa-gu, Seoul 05552, Republic of Korea
2
Department of Environmental Landscape Architecture, Gangneung-Wonju National University, Gangneung 25457, Republic of Korea
*
Author to whom correspondence should be addressed.
Sustainability 2025, 17(21), 9910; https://doi.org/10.3390/su17219910 (registering DOI)
Submission received: 4 August 2025 / Revised: 21 October 2025 / Accepted: 27 October 2025 / Published: 6 November 2025
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Review Reports Versions Notes

Abstract

This study investigates the effectiveness of climate-adaptive pedestrian design through greening strategies by integrating microclimate simulations in central Seoul. Utilizing ENVI-met 5.0, five pedestrian street typologies along the “Cultural Complex Axis” in central Seoul were analyzed for their thermal environments before and after greening interventions. Results indicate that pedestrian greening improves thermal comfort across all sites, though cooling effects vary significantly with site-specific urban morphology and microclimatic factors such as wind flow. Notably, Hyehwa-ro exhibited the greatest reduction in Physiological Equivalent Temperature (PET) despite a modest increase in greenery, underscoring that cooling efficiency depends on more than vegetation quantity alone. Conversely, Jangchungdan-ro, with greater green coverage, observed diminished thermal improvements, which were mainly attributed to reduced wind velocity. The findings emphasize the need for context-sensitive, tailored greening approaches that particularly emphasize securing wind corridors and avoiding dense planting in narrow urban canyons to maximize cooling impacts. This study contributes by providing insights into both the research process and its outcomes through the exploration of thermal comfort simulations applied to a practical pedestrian renovation case.

1. Introduction

According to the “Climate Change Analysis Report of South Korea over 109 Years (1912–2020)”, the average temperature in South Korea has steadily increased by 0.2 °C every decade over the past 109 years. As a result, the average temperature rose from 12 °C during the 1910s (1912–2010) to 13.9 °C in the 2010s (2011–2020), an increase of approximately 1.9 °C. Compared to the global average temperature increase of 1.09 °C from the pre-industrial period (1850–1900) to the 2010s, it is evident that the temperature rise in South Korea exceeds the global average. Seoul, a densely populated city in South Korea, recorded an average temperature of 13.0 °C in the last decade (2011–2020), which is a rise of 2.3 °C compared to the previous decade (1911–1920). This increase is higher than both the global average rise of 1.09 °C and South Korea’s average increase of 1.9 °C. Moreover, the frequency of extreme climate events such as heatwaves and tropical nights has also been increasing recently; in 2005, there were 6 days of heatwaves and 11 tropical nights, while in 2018, these numbers surged to 35 days and 29 nights, respectively.
To address these climate changes, the city of Seoul has established a comprehensive plan for “Green Transportation Zone within the Four Great Gates of Seoul”. This plan includes various initiatives aimed at reducing greenhouse gas emissions, such as restrictions on vehicle idling, emissions testing, support for eco-friendly vehicles, the Eco-Mileage program, and the operation of green transportation zones. The Green Transportation Zone encompasses the area within the Hanyang Fortress, including the four gates of Sujkungmun, Donuimun, Sungnyemun, and Heunginjimun. The plan aims to create a “people-first, safe, and pleasant urban environment” without the use of private vehicles. By 2030, Seoul intends to reduce private vehicle traffic by 30% compared to 2017 and to more than double the space allocated for green transportation options, including walking, cycling, and public transit. Furthermore, there is a robust enforcement of restrictions on the operation of vehicles classified as grade 5 in terms of emissions, showcasing proactive efforts to mitigate climate change.
This study examines the effectiveness of climate-adaptive pedestrian design through greening strategies by integrating microclimate simulations in central Seoul. Using ENVI-met 5.0 version, five pedestrian street typologies along one of the major axes in the city downtown were analyzed to assess thermal conditions before and after greening interventions. This research contributes to the design of pedestrian streets in dense urban areas by testing a range of practical, scalable greening strategies—such as road reduce, incentive-based public open spaces, rooftop and wall greening, and the integration of existing waterways—within real-world renovation contexts. Through iterative design and simulation processes, the study offers a framework for balancing greenery with wind flow, providing actionable insights for improving outdoor thermal comfort in compact city environments. By incorporating microclimate simulations into the early stages of urban design, this research underscores the potential for more informed and spatially responsive planning decisions.

2. Literature Review

2.1. Climate-Adaptive Urban Regeneration

Given the spatial constraints inherent in densely populated cities, well-connected green infrastructure (GI) and the regeneration of existing urban grey spaces with nature-based solutions (NBS) become critical [1]. Numerous studies have emphasized the significance of NBS and GI in reducing heatwave mortality, enhancing human thermal comfort, and mitigating climate change effects in urban areas [2,3,4]. The declining urban regeneration sites have been recognized as highly vulnerable to climate change [5,6,7,8]. To address this, research focusing on urban regeneration aimed at supporting safer and more climate-friendly mobility is needed [9]. In this context, Valente et al. (2021) proposed a process of evaluating and designing the regeneration of surrounding urban corridors as a green infrastructure network [10], while Nardino et al. (2021) conducted modeling research for urban services and regeneration by conducting microclimate classification [11].
Street trees are a notable component of urban green spaces, and are often viewed as valuable natural resources that enhance the liveability of cities [12,13,14,15]. In this regard, numerous analyses have been conducted on the impact of urban form and structure, such as changes in tree and building heights [16,17], variations in types of roadside greenery [18], and aspect ratios of street canyons [19], in relation to reducing fine dust along roadsides.
Based on the literature review, we focused on applying scientific knowledge to dense urban pedestrian design by integrating thermal comfort simulations. While numerous studies have been conducted through scientific experiments, there is still a lack of research that simulates the application of green space design in complex regeneration projects, where existing conditions are often highly complicated to deal with [20]. In this study, we explored a simulation-integrated pedestrian renovation design process and highlighted its potential as well as its limitations.

2.2. Adaptive Design Parameters for Pedestrian Thermal Comfort in Urban Microclimates

Pedestrian-level microclimates within urban environments are strongly influenced by both urban morphology and landscape context. Key urban design parameters affecting outdoor thermal comfort are generally categorized into two groups: urban geometry and urban landscape elements. Urban geometry—defined by the spatial arrangement of streets, open spaces, and building massing—modulates microclimatic conditions by altering patterns of solar access, shading, and heat retention. In contrast, non-geometrical landscape elements such as vegetation and water features significantly impact surface temperatures and humidity through evapotranspiration and shading [21].
Among these factors, solar radiation is widely recognized as the most influential determinant of thermal conditions at street level. Numerous studies have analyzed the impact of urban geometry, particularly street canyon orientation and aspect ratio (height-to-width ratio), on thermal comfort across diverse climatic zones [22,23,24,25,26]. The role of aspect ratio is also significant, as higher ratios enhance shading during the day, reducing surface and air temperatures [27]. This pattern correlates with the sky view factor (SVF), a metric representing the portion of visible sky from ground level, which has been used to quantify solar and radiative exposure [28,29].
Wind flow is another critical variable in the thermal comfort equation. Urban geometry dictates wind patterns, with street canyon orientation relative to prevailing winds (parallel, perpendicular, or oblique) influencing wind speed at the pedestrian level [30]. Furthermore, studies have shown a positive relationship between SVF and wind speed—open urban forms allow higher wind penetration, while compact forms suppress it [31,32]. However, compactness may offer thermal benefits via increased shading, which can outweigh the negative impact of reduced airflow.
Urban landscape elements, such as vegetation and water bodies, also play a substantial role in moderating urban thermal environments. Trees reduce incoming solar radiation and can alter local wind flow [33]. Tree shading and evapotranspiration significantly reduce both air and surface temperatures in summer, particularly in E–W streets with low aspect ratios—typically the most heat-exposed configurations [34]. Additional landscape-based cooling strategies include green roofs, which have shown localized cooling effects at the pedestrian level in buildings under 10 m tall [35] and high-albedo materials, pervious pavements, and open water features, all of which enhance thermal comfort by reducing surface heat absorption and promoting evaporative cooling [23].
In summary, literature underscores the critical influence of both urban geometry and landscape elements on pedestrian-level thermal comfort in urban environments. While urban form determines patterns of solar exposure, shading, and wind flow, landscape features like vegetation and water bodies offer substantial cooling effects through shading and evapotranspiration, highlighting the need for an integrated approach in climate-responsive urban design.

3. Methodology

3.1. Study Area

Toward achieving a climate-adaptive, carbon-neutral city regeneration, the Seoul city government is transforming the traditional city center, defined by the old city wall boundary, into a “greened, ecological downtown.” (2040 Seoul City Basic Planning Report, https://urban.seoul.go.kr/view/html/PMNU3030000001, accessed on 24 March 2022). This government plan emphasizes green transportation and urban public area design, specifically aiming to reduce vehicular roads and traffic while expanding green and pedestrian spaces. Within this ecological downtown plan, four major routes have been designated along the heavily trafficked roads running north-south through Seoul’s city center. These routes have been themed according to their surrounding land uses, historical assets, and landmark buildings; the “National Central Axis” centered on Gwanghwamun to City Hall, the “Historical and Cultural Tourism Axis” centered on Insadong to Myeongdong, the “North-South Green Axis” centered on the Sewoon District, and the “Complex Cultural Axis” centered on the Dongdaemun Design Plaza (DDP), along with a “Global Industrial Axis” that runs east-west, making a total of 4 + 1 axes (Figure 1).
Among these four routes, the Gwanghwamun Square, as part of the National Central Axis, is undergoing extensive reconstruction, which includes widening the road on the east side to 7 to 9 lanes and removing the lanes on the west side to significantly enhance the square. The percentage of impervious surfaces is 16% for the National Central Axis, 20% for the Historical and Cultural Tourism Axis, 14% for the North-South Green Axis, and 50% for the Complex Cultural Axis. Based on an analysis of existing conditions (i.e., road lanes, green space, surrounding building heights, building functions, and impervious pavement percentage), we have selected the Complex Cultural Axis as our target area for transformation and experiment, as it has not yet begun development, has a relatively low green coverage, and a high percentage of impervious surfaces (Figure 1), suggesting significant potential for thermal condition improvements through diverse greening strategies. Additionally, a large portion of this area is designated as a redevelopment district, increasing the likelihood of significant changes in adjacent private lands, such as the addition of green spaces in front of buildings. The Complex Cultural Axis spans a total of 4 km, connecting Hyehwa-ro, Daehak-ro, Yulgok-ro, and Jangchungdan-ro. Contrary to its theme, there are no representative areas that showcase cultural characteristics, and while there are generally connected street trees, they consist mostly of a single tree species. However, there are usable public spaces and greenery available, with roads varying from 2 to 10 lanes. Depending on the designated land use, there are both low-rise and high-rise buildings, enabling a comprehensive investigation of various urban built form factors, and with its designation as a redevelopment area, plans have been established for changes in building forms or conversion into parks.

3.2. Research Flow

Based on a comprehensive literature review of thermal comfort factors ([21,22,23,24,25,26,27,28,29,30,31,32,33,34,35]), we identified key variables relevant to the urban pedestrian context. These variables include road width, surrounding building heights and density, adjacent green and open spaces, and street trees. We selected five different pedestrian sections along an axis, each characterized by distinct conditions regarding the studied parameters, potential design strategies focused on greening interventions, and themed open space programs based on adjacent land uses. Initially, we simulated the microclimate of the precondition of each section and evaluated the outdoor thermal comfort (OTC). Using the preliminary simulation results as a reference (see Appendix A), we developed specific site designs incorporating strategies such as road narrowing, greening interventions for surrounding buildings, expansion of green and open spaces, and the addition and rearrangement of street trees. The detailed greening designs for each section are described in the results section. We then simulated the post-design conditions of the sites, evaluated the OTC, and adjusted the site designs accordingly (Figure 2).

3.3. ENVI-Met Modeling for OTC Simulation

Figure 3 illustrates the three-dimensional modeling of the five pedestrian redesign plans, showcasing both the before and after conditions. It also includes an enlarged example of one section where various interventions were applied, such as road reduction, greening space expansion, the addition and rearrangement of street trees and plantings, and the implementation of green walls and roofs. To simulate existing vegetation, including major street trees (Platanus occidentalis L., Ginko biloba L., Zelkova serrata, Pinus densiflora) and shrubs (Euonymus alatus, Euonymus japonica), we conducted field measurements and collected data on their heights, crown dimensions, leaf types, and arrangements. Due to the limitations of the vegetation modeling library (Albero) in ENVI-met, based on existing trees, we adjusted tree sizes and forms using coding procedures in the L-system rules within the Albero tree settings.
For the thermal comfort simulation, we utilized the ENVI-met 4.3.4 program. ENVI-met is a three-dimensional microclimate CFD-based model widely employed in microclimate simulation studies. Notably, over half of the vegetation thermal effect simulations have used ENVI-met, unlike other models, it excels in simulating surface–plant–air interactions (i.e., evapotranspiration), offering detailed vegetation representation with high resolution [36]. The accuracy of ENVI-met simulations has been validated under various conditions, and most research conducted in different urban contexts shows high agreement between simulation results and field measurements [37,38,39,40].
Table 1 shows the local climate data of the studied area found from a meteorological observatory, located at Seoul City University, 90 Jeonnong-dong, Dongdaemun-gu, Seoul, Republic of Korea, which is approximately 3.7 km distant from the study site. According to the collected data, July was identified as the hottest month of 2021, with an average air temperature of 28.1 °C. Over the past three years, the average temperatures recorded for July were 28.1 °C in 2021, 24.1 °C in 2020, and 25.9 °C in 2022. During this period, the average relative humidity fluctuated between 69% and 77%, while the average air velocity measured at 10 m above ground ranged from 1.8 to 2.4 m/s. For this research, the meteorological conditions observed during the hottest days, specifically 23–24 July 2021, were analyzed. For local climate data input, hourly data of air temperature, humidity, and wind velocity were utilized.
For built forms, most building materials were set as lightweight concrete. For roads and streets, asphalt and granite stone paving was used. For landscape elements, tree type, height, and density were described in Figure 3.

3.4. Thermal Comfort Evaluation

Several thermal comfort indices have been developed to quantify thermal stress. Initially tailored for specific climates, universal indices like the Standard Effective Temperature (SET), Physiological Equivalent Temperature (PET), and Universal Thermal Climate Index (UTCI) have emerged [41]. These indices generally utilize a two-node model to assess thermal comfort based on heat science principles. In contrast, the Predicted Mean Vote (PMV) employs a one-node model derived from thermal sensation data from over 1300 subjects (Fanger 1970) [42]. The Wet Bulb Globe Temperature (WBGT), designed for the U.S. Army, relies solely on environmental variables. While PMV and SET are suited for indoor settings, PET is primarily for outdoor use, allowing users to compare their thermal experiences in different environments [43,44]. UTCI combines advanced thermophysiological models and clothing considerations [45,46]. For our study, we chose PET due to its widespread applicability, proven accuracy, and positive correlations with field data, enhancing reliability [41,47]. Additionally, PET’s expression in degrees Celsius makes it accessible for urban planners and policymakers [48].

4. Results and Discussion

4.1. Precondition Simulation for Five Street Types

Before proceeding with the full design, buildings and trees that reflect the actual conditions for each street type at the target site were modeled and analyzed using ENVI-met, a microclimate simulation program. The simulation was conducted for a 24-h period on 23 July 2021, when a heat wave was recorded. The cell size used was 4 m × 4 m × 4 m (x, y, z), with a target area of 100 m × 200 m. Results were extracted for the period between 15:00 and 16:00, which was the hottest hour of the day.
  • First Street Type: Hyehwa-ro
Hyehwa-ro features a two-lane road with low-rise buildings ranging from 3 to 20 m in height on both sides. Surrounding facilities include theaters, workshops, and café streets. The pavement composition consists of 20.9% asphalt, 67.9% concrete, 4.8% granite, 5.3% macadam, and 0.8% trees, with ginkgo and hybrid poplar planted. As a result of the simulation, wind flows between the buildings, but is blocked by trees and structures, resulting in an uncomfortable thermal sensation of 44.56 to 57.40 °C in pedestrian areas, making it the least pleasant among the five street types.
Sustainability 17 09910 i001
  • Second Street Type: Daehak-ro
This street features a six-lane road with low to mid-rise buildings ranging from 15 to 45 m. It is densely surrounded by educational facilities such as Seoul National University’s Yeongon Campus, an elementary school, a girls’ middle school, and Seoul Open University. The pavement composition is 28.5% asphalt, 58.0% concrete, 18.6% granite, 12.7% blocks, 0.7% trees, and 0.2% ground cover. Ginkgo trees are predominant, with zelkova and ground cover found in Marronnier Park. As a result of the simulation, the wind flows along the six-lane road, and cool air spreads from the flower beds next to the school, with thermal comfort recorded at 43.19 to 54.33 °C.
Sustainability 17 09910 i002
  • Third Street Type: Heunginjimun
This street has a seven-lane road with low-rise buildings from 3 to 25 m on the left and Heunginjimun Park on the right. The pavement composition includes 25.9% asphalt, 36.6% concrete, 18.6% granite, 6.7% trees, 2.3% shrubs, and 9.9% ground cover. As a result of the simulation, the cool breeze from Heunginjimun Park flows along the road, resulting in a thermal comfort level of 43.10 to 52.67 °C, making it the coolest of the five street types.
Sustainability 17 09910 i003
  • Fourth Street Type: Yulgok-ro (DDP)
This street features a ten-lane road with high-rise shopping malls ranging from 45 to 60 m on the left, and Dongdaemun Design Plaza, a 9-m height building, on the right. The pavement composition consists of 37.0% asphalt, 16.5% concrete, 45.4% granite, and 1.1% trees along the road. As a result of the simulation, hot air from the wide asphalt road is blocked and circulated by the high-rise buildings. Consequently, thermal comfort ranges from 43.29 to 51.01 °C.
Sustainability 17 09910 i004
  • Fifth Street Type: Jangchungdan-ro
This street features a six-lane road with low to mid-rise buildings ranging from 3 to 30 m on both sides. To the left is the Namsoyeonggil Plaza, comprised of grass and trees. The area is famous for its many restaurants, attracting office workers who take lunch breaks in the plaza. The pavement composition is 37.5% asphalt, 51.4% concrete, 6.4% granite, 1.6% trees, and 3.2% ground cover. As a result of the simulation, wind flows along the road and between the buildings. Although it was expected that the temperature would be lower in the plaza, thermal comfort was generally recorded between 45.36 and 53.84 °C, making it the second hottest of the five street types.
Sustainability 17 09910 i005
This analysis highlights considerations for design, such as the strategic placement of trees that do not obstruct wind, the selection of appropriate tree species, the utilization of cooling green spaces, the reduction of hot asphalt roads, and the expansion of pedestrian paths and greenery to facilitate cooler breezes, thereby lowering temperatures and enhancing thermal comfort. Notably, Heunginjimun Gate street demonstrated improved temperature and thermal comfort due to the presence of multi-layered vegetation in addition to the park. This will be considered in the design. Based on the analysis of the results, it is advisable to utilize the values from 1 to 2 pm, as this is when the boundary between the hot and cool areas is most clearly defined (Figure 4).

4.2. Design Application and Thermal Comfort Comparison Before and After Pedestrian Design

Considering the precondition simulation results and utilizing the space gained through vehicular road reduce the most, design schemes of each street have been developed in line with the existing designation of “Cultural Complex Axis.” This design commonly incorporates linear green spaces and bicycle paths that connect the whole axis, with each themed street featuring a distinct green space and programs. This approach aims at not only providing diverse experiences but also helping lower temperatures, creating a more pleasant walking environment.

4.2.1. Hyehwa-Ro

Figure 5a presents the PET and air temperature maps before and after the design application in the Hyehwa-ro area (right). The figure also includes the average PET values, the percentage distribution of PET-classified pixels, and the changes in green area ratio following the design application (left). Hyehwa-ro has been transformed into an art street connecting theaters, workshops, and cafés, enhancing artistic experiences through performances and workshops. The proposal narrows the road from 7 m to 5.5 m, creating a planting zone for low-growing ground cover and plane trees. The section is particularly characterized by a dense concentration of low-rise buildings. Additionally, street trees such as ginkgo, hybrid poplar, and pine are planted at narrow intervals, resulting in poor airflow between the buildings and the trees. To address this issue, low-growing ground cover and herbaceous plants were primarily planted, while trees were spaced at a minimum of 5 m apart to avoid obstructing the lateral alleys and allowing wind to flow through. The design also incorporated extensive rooftop and wall greening. The simulation results indicate that with a 1.1% increase in the green ratio, the average PET value decreased by 2.1 °C, dropping from 49.3 °C to 47.2 °C. Notably, the area with PET values below 48 °C saw a significant increase of 67.9%, rising from 14.5% to 82.4% following the implementation of pedestrian greening strategies.

4.2.2. Daehak-Ro

Figure 5b presents the PET and air temperature maps before and after the design application in the Daehak-ro area (right). The figure also includes the average PET values, the percentage distribution of PET-classified pixels, and the changes in green area ratio following the design application (left). Daehak-ro has been planned as a learning street, centered around educational themes, featuring institutions such as Seoul National University’s College of Medicine and its affiliated elementary and girls’ middle schools, as well as Marronnier urban park. The design proposal reduces the road width from 20–24 m to 15–18 m and secures planting space by reducing the area of buildings within the redevelopment zone by 10% considering the Floor Area Ratio (FAR) incentive regulation. Additionally, the green space of the existing resting facilities is expanded, and planting areas were added on both sides centered around a bicycle path. A small stream near the school was preserved, and air ventilation was maximized around the stream, while additional trees, shrubs, and ground cover were planted in a manner that does not obstruct ventilation. The simulation results indicate that with a 3.4% increase in the green ratio, the average PET value decreased by 0.2 °C, dropping from 47.7 °C to 47.5 °C. Notably, the area with PET values below 48 °C shows a slight increase of 5.4%, rising from 60.2% to 65.6% following the implementation of pedestrian greening strategies.

4.2.3. Yulgok-Ro—Heunginjimun

Figure 5c presents the PET and air temperature maps before and after the design application in the Yulgok-ro Heunginjimun area (right). The figure also includes the average PET values, the percentage distribution of PET-classified pixels, and the changes in green area ratio following the design application (left). Yulgok-ro, which features Heunginjimun Park, has been planned to preserve the existing greenery while also incorporating a Jongno 4 and 5 redevelopment zone designated for future park connection. Since Heunginjimun Park is a sloped linear park, the design connects it to the adjacent walkway. The first level will function like a plaza, while the second to fourth levels will utilize a variety of trees and shrubs, such as pine, arrowwood, and hostas, to reflect the unique character of Heungin Street. Additionally, the previously narrow walkway, which was further constricted by the addition of a bicycle lane, has been improved through a road reduce that created an extra 4 m of space for smoother pedestrian movement. To harmonize with the current appearance of Heunginjimun Park, a traditional-style marstone pavement and a pine tree-centric park layout were designed. The simulation results indicate that with a 19.5% increase in the green ratio, the average PET value decreased by 1.1 °C, dropping from 47.1 °C to 46.0 °C. Notably, the area with PET values below 46 °C shows a slight increase of 29.8%, rising from 3.6% to 33.4% following the implementation of pedestrian greening strategies.

4.2.4. Yulgok-Ro—DDP

Figure 5d presents the PET and air temperature maps before and after the design application in the Yulgok-ro DDP area (right). The figure also includes the average PET values, the percentage distribution of PET-classified pixels, and the changes in green area ratio following the design application (left). The DDP (Dongdaemun Design Plaza) on Yulgok Road has been transformed by burying the wide ten-lane road underground and utilizing the grassy plaza and public spaces in front of the shopping mall. The green space has been significantly expanded, and the newly freed space has been converted to be used for events such as flea markets hosted by nearby fashion malls, Fashion Week at DDP, and the Night Market. Additionally, emergency and bus lanes have been maintained on both sides of the grassy plaza to ensure accessibility for emergencies and public transportation. The public space in front of the shopping mall will feature bike paths running through a forest and several small gardens. Climbing plants will be planted on the walls of the high-rise shopping mall. The simulation results indicate that with a 37.0% increase in the green ratio, the average PET value decreased by 1.3 °C, dropping from 47.5 °C to 46.2 °C. Notably, the area with PET values below 48 °C shows a slight increase of 20.7%, rising from 73.5% to 94.2% following the implementation of pedestrian greening strategies.

4.2.5. Jangchungdan—Ro

Figure 5e presents the PET and air temperature maps before and after the design application in the Jangchungdan-ro area (right). The figure also includes the average PET values, the percentage distribution of PET-classified pixels, and the changes in green area ratio following the design application (left). Jangchungdan Road is planned as a food-themed street, taking advantage of its fame as a popular eating alley where office workers often enjoy coffee and stroll through Namsoyeonggil Park after lunch and dinner. The design proposal reduces the road width from 6–10 lanes to 4–8 lanes and expands the existing greenery in Namsoyoung-gil Park, and includes the installation of a green median along the road. In the park, a grassy plaza is created, and tall plane trees are additionally planted to provide shade and facilitate wind flow. The simulation results indicate that with a 22.0% increase in the green ratio, the average PET value decreased by 0.4 °C, dropping from 48.9 °C to 48.5 °C. Notably, the area with PET values below 48 °C shows a slight increase of 14.6%, rising from 2.2% to 16.8% following the implementation of pedestrian greening strategies.

4.3. Temporal Thermal Comfort Comparison Before and After Pedestrian Design

To more accurately assess the cooling effectiveness of various pedestrian greening conditions, we calculated the differences in Physiological Equivalent Temperature (PET) between the post-design and pre-design scenarios during daytime hours. Figure 6 illustrates the PET differences across five pedestrian types before and after the greening interventions over time.
Overall, the cooling effect increased gradually until around noon and then declined in the late afternoon. The magnitude of cooling varied significantly across locations, with the most noticeable variation observed on Hyehwa-ro Street. There, PET reductions ranged from 1.0 °C to 4.4 °C, with the greatest cooling effect occurring at 5 pm. In contrast, Daehak-ro exhibited the smallest change, with cooling magnitudes ranging from −0.05 °C to 0.22 °C. All streets, except Daehak-ro at 4 pm, demonstrated improved thermal comfort levels, with PET reductions ranging from 0 °C to 4.4 °C.
Following the previous analysis, PET values during daytime hours were extracted from the models of the five pedestrian types of pre- and post-design application to evaluate the cooling impact of pedestrian greening. Figure 7 presents boxplot comparisons of pre- and post-design for each of the five pedestrian types. Based on the first-phase precondition simulation results, we decided to use the values from 1:00 to 2:00 pm, as the boundary between hot and cool areas is most clearly defined during this period.
Based on the results, the locations can be broadly categorized into three groups. The first group includes only Hyehwa-ro, which exhibited the most significant differences in PET values before and after the greening intervention. The second group comprises Heunginjimun and Yulgok-ro, where PET reductions were moderate but still clearly noticeable. The third group includes Daehak-ro and Jangchungdan-ro, where the differences in PET values were minimal and largely negligible.

4.4. Overall Comparison and the Influence of Landscape Parameters

To examine the relationship between PET and greening ratio changes, Figure 8 simultaneously presents the average PET values at 1 pm and the corresponding changes in greening ratios before and after the pedestrian greening interventions. Overall, the results suggest that increases in greening ratio do not consistently correspond to proportional decreases in PET. This highlights the importance of incorporating simulation in the early design stage and adjusting design strategies according to the site’s microclimatic conditions in order to maximize the cooling effect.
For example, although Hyehwa-ro experienced the smallest increase in greening ratio, it exhibited the greatest reduction in PET. Conversely, Jangchungdan-ro showed the second-largest increase in greening ratio, yet the associated cooling effect, as indicated by PET, was comparatively minimal.
Overall, for most streets, an increase in green ratio was associated with a decrease in the thermal comfort index, demonstrating the cooling effect of greening across various urban street conditions. However, the magnitude of cooling did not increase proportionally with the extent of greening.
Notably, a significantly greater cooling effect was observed on Hyehwa-ro—a street characterized by shallow width, higher density, and lower building heights—where trees were proven to weaken the existing wind corridor in precondition simulation. Figure 9 illustrates that, in most street segments, the presence of trees reduces wind velocity. Consequently, achieving a balance between incorporating greenery and maintaining adequate wind flow became a key consideration in multiple design iterations. For Hyehwa-ro Street, the greening was carefully implemented without reducing wind velocity. Despite having the smallest increase in green area, this location exhibited a distinctively high cooling efficiency. Conversely, Jangchungdan-ro, which shares similar spatial characteristics with Hyehwa-ro, showed the lowest cooling efficiency. In this case, even a slight reduction in wind velocity from an initially high level appeared to diminish the cooling effect. These findings highlight the critical role of maintaining and managing wind flow in densely built, narrow urban environments to maximize the benefits of greening strategies.
This study provides insights into pedestrian streets, showing that the amount of added greenery often corresponded to the reduction in road space, resulting in relatively similar levels of thermal comfort improvement across sites. However, the key differentiator was how the design interacted with existing wind flow. The study revealed that preserving and enhancing natural airflow had a greater impact on thermal comfort than simply increasing vegetation.
This research contributes by testing a range of practical design strategies—such as the use of road-reduced area, incentive-based public open spaces, feasible rooftop and wall greening, and the integration of existing waterways—within real-world pedestrian renovation contexts. Through multiple rounds of simulation and design iteration, the findings emphasize that maintaining unobstructed wind flow is crucial for achieving meaningful improvements in outdoor thermal comfort in dense urban environments.
Since this study aims to explore the application of simulation across the entire design process, it has limitations in fully revealing all the scientific and technical factors that influence thermal comfort. In particular, aspects such as building density, height, and overall urban morphology are critical variables that require further investigation beyond the current scope.
Although solar exposure related to sky view factor (SVF) conditions was different in streets, in general, the introduction of trees produced relatively similar cooling effects across pedestrian spaces through shading and evapotranspiration. Among these, wind flow may have emerged as the decisive factor, particularly how existing building-induced wind corridors were preserved or obstructed by plantings, and how flows generated by such river corridors with planting additions could be maximized. Therefore, in the pedestrian conditions where building contexts are nearly fixed factors and road reduce patterns among streets are similar, the role of wind flow becomes particularly critical.
Further investigation may be required to account for the solar radiation changes related to building and tree shadows across an expanded temporal scale, as well as plant evapotranspiration with wind dynamics. In addition, the limitations of ENVI-met in simulating wind flow were recognized, highlighting the need for complementary studies employing computational fluid dynamics (CFD) models to better explain wind dynamics.

5. Conclusions

This study explored the effectiveness of climate-adaptive pedestrian design with greening strategies through the integration of microclimate simulations in central Seoul. Using ENVI-met, five different pedestrian street types along the “Cultural Complex Axis” were analyzed in terms of their pre- and post-intervention thermal environments.
Simulation results showed that pedestrian greening generally improved thermal comfort across all five sites, though the magnitude of cooling varied considerably depending on site-specific characteristics. Hyehwa-ro, despite the smallest increase in green ratio, achieved the most significant PET reduction, highlighting that cooling efficiency is not solely dependent on the quantity of greenery but also on urban form and microclimatic conditions such as wind flow, as revealed in precedent studies ([30,31,32]). In contrast, Jangchungdan-ro—with a much higher increase in green coverage—yielded a comparatively modest thermal improvement, largely attributed to a slight decrease in wind velocity. Although SVF and solar exposure varied according to streets, tree planting seems to produce broadly similar cooling through shading and evapotranspiration, making wind corridors the decisive influence. Preserving or enhancing flows, particularly those linked to building form or river corridors, proved essential. Future work should address shadow–wind interactions over longer time spans and incorporate CFD to complement ENVI-met’s limits in wind simulation. In addition, the simple forcing based on relatively basic weather data inputs used in this study has limitations in capturing the varied local microclimates across the large study site, implying further investigation is needed to improve representativeness by introducing multi-sensor field observations [49]. While much research emphasizes the evaluation of pedestrian thermal comfort [50,51,52], there are few studies integrating simulation and design process based on practical urban design cases. This study underscores the importance of a context-sensitive approach to pedestrian climate-adaptive design by introducing simulation in the early stage. Specifically, maintaining effective wind corridors and avoiding overly dense vegetation in narrow, high-density areas are crucial for maximizing the cooling benefits of urban greening. Moreover, greening strategies should be tailored to local urban morphology rather than relying on a one-size-fits-all increase in vegetation.
This study supports previous research demonstrating the greening intervention cooling effect [53]. In this study, greening interventions resulted in a PET reduction of 0–4.4 °C. While this cooling effect is somewhat lower than the findings of a recent pedestrian greening simulation study in Glasgow—where the addition of street trees reduced thermal sensation from “hot” to “slightly warm” or “warm” (approximately 5–10 °C)—the decrease observed here remains meaningful. Given the varied street conditions analyzed, a reduction of even one PET class represents a significant improvement in outdoor thermal comfort. It also supports urban wind corridor formation importance under various pedestrian conditions [54,55], and further connects the discussion by exploring the impact of greening strategies at a practical urban landscape design scale.
Despite its contributions, the study recognizes limitations related to several confounding variables, including the combined effects of greening with specific building forms and densities, as well as the types of greening, such as vertical greenery require further detailed investigation. A more sensitive, controlled study is needed to isolate and quantify these factors, helping to clarify design priorities for pedestrian environments.
This study demonstrates the potential of utilizing a simulation-integrated process to enhance the effectiveness of pedestrian renovation design and serves as a baseline dataset, laying the groundwork for subsequent experimental research aimed at optimizing climate-adaptive pedestrian greening strategies.

Author Contributions

Conceptualization, E.J.K. and K.H.; methodology, G.B. and E.J.K.; software, G.B.; validation, E.J.K. and K.H.; data curation, G.B.; writing—original draft preparation, G.B. and E.J.K.; writing—review and editing, E.J.K. and K.H. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (grant number: RS-2025-00555206).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The datasets generated or analyzed in the current study are available from the corresponding author upon reasonable request.

Conflicts of Interest

Gawon Bae was employed by Eospace. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Appendix A. Example of Preliminary Simulation Result of PET (Based on a Wider Range of Legend Class)

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Figure 1. Four themed way developments in the central district, Seoul, South Korea.
Figure 1. Four themed way developments in the central district, Seoul, South Korea.
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Figure 2. OTC simulation-integrated pedestrian design procedure.
Figure 2. OTC simulation-integrated pedestrian design procedure.
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Figure 3. Three-dimensional site and vegetation modeling in ENVI-met.
Figure 3. Three-dimensional site and vegetation modeling in ENVI-met.
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Figure 4. PET, air temperature, and wind velocity of the current site condition (initial simulation at 3 pm).
Figure 4. PET, air temperature, and wind velocity of the current site condition (initial simulation at 3 pm).
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Figure 5. (a) PET comparison of Hyehwa Road sections (top: before, bottom: after) (1 pm). (b) PET comparison of Daehak Road sections (top: before, bottom: after) (1 pm). (c) PET comparison of Yulgok Road—Heunginjimun sections (top: before, bottom: after) (1 pm). (d) PET comparison of Yulgok Road—DDP sections (top: before, bottom: after) (1 pm). (e) PET comparison of Jangchungdan Road sections (top: before, bottom: after) (1 pm).
Figure 5. (a) PET comparison of Hyehwa Road sections (top: before, bottom: after) (1 pm). (b) PET comparison of Daehak Road sections (top: before, bottom: after) (1 pm). (c) PET comparison of Yulgok Road—Heunginjimun sections (top: before, bottom: after) (1 pm). (d) PET comparison of Yulgok Road—DDP sections (top: before, bottom: after) (1 pm). (e) PET comparison of Jangchungdan Road sections (top: before, bottom: after) (1 pm).
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Figure 6. Averaged PET difference before–after the greening design of five streets from 7 am to 6 pm.
Figure 6. Averaged PET difference before–after the greening design of five streets from 7 am to 6 pm.
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Figure 7. Box plots of 1 pm PET before and after pedestrian design for five themed streets.
Figure 7. Box plots of 1 pm PET before and after pedestrian design for five themed streets.
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Figure 8. Five pedestrian comparisons of green space ratio and 1 pm average PET changes before–after the greening design.
Figure 8. Five pedestrian comparisons of green space ratio and 1 pm average PET changes before–after the greening design.
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Figure 9. 1 pm average wind velocity comparisons before–after the greening design.
Figure 9. 1 pm average wind velocity comparisons before–after the greening design.
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Table 1. Initial atmospheric input and simulation configuration settings.
Table 1. Initial atmospheric input and simulation configuration settings.
Location and dateLocationSeoul, Republic of Korea (37° N, 126° W)
Simulation Day (DD.MM.YYYY)23 July 2021~24 July 2021
Simulation start time (HH:MM:SS)00:00:00 (48 h)
Meteorological
condition		Wind speed at 10 m above ground (m/s)1.7 m/s
Wind direction (°, clockwise from 0°: N)140
Roughness length (m)0.01
Atmospheric temperature (°C)26.90 (min), 36.30 (max)
Relative humidity (%)38.00 (min), 75.00 (max)
Built formsStreet/road paving materialAsphalt, brick (road)
granite pavement, concrete (pedestrian)
loamy soil (park trail)
Building materialConcrete
Landscape elementsTree type, height, densityAs described in Figure 3
Green space/water spaceGrass/Deep water
Simulation settingsOutput interval main files (min)60
Boundary ConditionSimple Forcing
Grid size (m)4 × 44
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Bae, G.; Kim, E.J.; Ham, K. Simulation-Integrated Climate-Adaptive Pedestrian Design Explorations for Summer Thermal Comfort: The Case of Culturally Diversified Green Way Project in Seoul, South Korea. Sustainability 2025, 17, 9910. https://doi.org/10.3390/su17219910

AMA Style

Bae G, Kim EJ, Ham K. Simulation-Integrated Climate-Adaptive Pedestrian Design Explorations for Summer Thermal Comfort: The Case of Culturally Diversified Green Way Project in Seoul, South Korea. Sustainability. 2025; 17(21):9910. https://doi.org/10.3390/su17219910

Chicago/Turabian Style

Bae, Gawon, Eujin Julia Kim, and Kwangmin Ham. 2025. "Simulation-Integrated Climate-Adaptive Pedestrian Design Explorations for Summer Thermal Comfort: The Case of Culturally Diversified Green Way Project in Seoul, South Korea" Sustainability 17, no. 21: 9910. https://doi.org/10.3390/su17219910

APA Style

Bae, G., Kim, E. J., & Ham, K. (2025). Simulation-Integrated Climate-Adaptive Pedestrian Design Explorations for Summer Thermal Comfort: The Case of Culturally Diversified Green Way Project in Seoul, South Korea. Sustainability, 17(21), 9910. https://doi.org/10.3390/su17219910

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