The Role of Urban Greenery in Enhancing Thermal Comfort: Systematic Review Insights

Abstract

As cities grapple with rising temperatures, the integration of urban greenery has gained recognition as a viable solution to mitigate these effects and enhance outdoor thermal conditions. This paper identifies widely used and emerging numerical models, highlights research gaps, and addresses key insights from the selected literature. Grounded in a PRISMA-based review, it offers insights to optimize strategies for mitigating urban heat islands and enhancing livability. The study explores synergies and trade-offs between green infrastructure and the built environment, aiming to provide insights into optimizing these elements for sustainable urban development. In this research, a mixed-methods approach was adopted by combining a systematic review and a bibliometric review using the PRISMA 2020 and VOSviewer 1.6.19 of 48 relevant studies. The PRISMA process led to the selection of the papers used for both the qualitative synthesis and bibliometric analysis. The results indicate a significant increase in research output in the last decades with a marked focus on green roofs, urban parks, and vertical greening systems. Our findings provide an elaborate conceptual framework that maps the interrelation between the research topics. Also, the study highlights existing research gaps in numerical modeling software for evaluating the cooling potential of urban greenery and its impact on thermal comfort across diverse urban contexts. The study recommends developing standardized frameworks and metrics for evaluating thermal comfort in urban areas, as well as suggesting that advancing numerical modeling software is essential to accurately simulate the complex interactions between urban greenery, microclimates, and urban forms.

1. Introduction and Background

The increasing levels of global urbanization and the consequent urban heat island effect have prompted researchers to investigate the potential of urban greenery in mitigating outdoor thermal conditions [1]. Urban greenery refers to the vegetation in urban areas, including parks, gardens, street trees, green roofs, and green walls, which contribute to environmental quality and enhance the urban landscape [2]. Urban greenery requires abundant water supply; hence, the environmental impact of water scarcity directly impacts urban greenery [3]. Thermal comfort refers to a state of mind in which an individual feels content with the surrounding thermal conditions [4]. Green infrastructure refers to an interconnected network of natural and semi-natural spaces strategically designed and managed to deliver ecosystem services, support biodiversity, and enhance human well-being. It includes a cohesive ecological system of parks, forests, community gardens, green roofs, street trees, and other features that operate across various scales, from small corridors to expansive landscapes [5,6]. These elements provide multifunctional benefits such as water purification, air quality improvement, recreational opportunities, and climate regulation [7]. In urban contexts, green infrastructure integrates features like green roofs, bioswales, permeable pavements, and urban wetlands, offering health-supporting ecosystem services while minimizing land consumption [8]. Designing urban green spaces that can effectively mitigate the urban heat island effect and enhance thermal comfort for city dwellers is a key focus of landscape researchers and urban planners [9,10,11]. Studies have shown that the presence of urban greenery, such as parks, trees, and other vegetation, can significantly lower air temperatures and create a more comfortable outdoor environment [12,13]. Thermal comfort in urban environments is a crucial aspect of sustainable city planning and design, as it directly impacts the well-being and quality of life for city residents [10]. Recent studies have highlighted the significant role of urban greenery in enhancing thermal comfort, with factors such as street design, vegetation, and height-to-width (H/W) ratios playing a crucial part [9,11,14].

As urban areas around the globe grapple with the impacts of rapid urbanization and climate change, the importance of achieving thermal comfort within urban environments has emerged as a pressing concern [15,16]. Thermal comfort, which refers to the state of mind in which individuals feel neither too hot nor too cold, is increasingly influenced by urban heat islands (UHIs)—a phenomenon where urban areas experience higher temperatures than their rural counterparts [17,18]. Research worldwide has demonstrated that urban greenery, encompassing vegetation and natural elements (water bodies, soil, rocks) in cities, can significantly mitigate the adverse effects of UHIs by lowering surface and air temperatures, improving air quality, and enhancing the overall quality of urban life [19,20,21]. In global contexts, countries like Singapore, the U.S., and China have pioneered initiatives to integrate greenery into their urban landscapes. For instance, Singapore’s “City in a Garden” initiative, which aims to transform the city into a green metropolis by emphasizing vertical gardens, rooftop greenery, and extensive urban parks, is one such strategy to enhance thermal comfort [22]. Similarly, studies in European cities highlight the role of tree canopies in reducing ambient temperatures and the cooling effects of urban parks [23,24]. These initiatives underscore the global recognition of urban greenery as a cost-effective and sustainable means of improving thermal environments in cities. In the Indian context, urban greenery is gaining traction as a critical component of urban sustainability, particularly considering rising temperatures and escalating urban heat stress [25]. Indian cities such as Delhi, Mumbai, and Bengaluru face extreme UHI effects, with summer temperatures often exceeding 45 °C, causing significant discomfort and health risks for urban residents [26]. Also, there is limited exploration of the long-term performance and maintenance impacts of green roofs and walls, and there is a lack of comparative analysis with other sustainable building practices [27,28]. Recent initiatives, such as Hyderabad’s Haritha Haram afforestation program, aim to address these gaps by enhancing green cover and reducing heat stress [29]. Furthermore, research from Saudi Arabia highlights that due to the region’s climatic conditions, green walls and roofs demand substantial irrigation to sustain their effectiveness throughout their lifespan. Despite numerous efforts to implement green infrastructure [30,31,32,33], there is a need for more accurate quantification (highlighted studies in Section 3.5) of the benefits of greenery concerning thermal comfort, especially on a global scale. The previous literature in this area, involving urban greenery, thermal comfort, green infrastructure, and the built environment, explores these themes individually. For example, studies by Tzoulas et al. (2007) and Jim and Chen (2006) have highlighted the environmental and health benefits of urban greenery, emphasizing its role in mitigating urban heat island effects and enhancing community well-being [34,35]. In parallel, research on thermal comfort, exemplified by the work of Oke (1988) and Santamouris (2013), has concentrated on how urban design, material properties, and building configurations influence microclimates and human thermal sensation [36,37]. Meanwhile, investigations into green infrastructure, such as those by Benedict and McMahon (2006), have primarily addressed its effectiveness in stormwater management, ecological resilience, and sustainable urban planning [38]. Similarly, the built environment has been examined mainly through the lens of energy efficiency, spatial design, and socio-economic impacts, as discussed by Newman and Kenworthy (1999) [39]. Although each of these bodies of work offers important insights, the integrated examination of their interrelationships remains underexplored. This gap underscores the need for a more holistic approach that investigates how the synergies and trade-offs among urban greenery, thermal comfort, green infrastructure, and the built environment can collectively contribute to urban sustainability. While urban greenery is known to improve thermal environments, challenges arise when balancing it with the needs of green infrastructure and the built environment [40].

The pyramid chart shown in Figure 1 represents the hierarchy of research topics in the study of urban greenery and thermal comfort. It is organized into three levels, showcasing the thematic depth and focus of the research field. At the base level, the broad categories of urban planning and Built Environment serve as foundational elements [41]. These themes highlight the overarching framework within which urban greenery and thermal comfort are studied, emphasizing the role of spatial planning and architectural design in shaping sustainable urban environments. The middle level introduces more targeted areas, such as Urban Heat Island and Green Infrastructure. These themes capture the specific challenges and solutions within urban environments, where the heat island effect exacerbates thermal discomfort, and green infrastructure emerges as a mitigating strategy. At the top level, the most specific focus is on Urban Greenery and Thermal Comfort, which represent the primary concerns of the study.

This level examines how vegetation in urban areas directly impacts thermal comfort by reducing temperatures, enhancing livability, and promoting environmental sustainability. This hierarchical structure underscores the interconnections and progression from broad urban themes to a specific research focus. Simulation software plays a critical role in advancing urban greenery and thermal comfort research by enabling precise modelling of microclimatic conditions and predicting the impact of green infrastructure [42,43,44,45]. Tools such as ENVI-met 5.7, DesignBuilder 7.0.2.006, MUKLIMO_3, and UMEP 2.0.35 (Urban Multi-scale Environmental Predictor) have emerged as leading options, each with distinct advantages and challenges. ENVI-met is a CFD (computational fluid dynamics) model that offers detailed insights into vegetation–microclimate interactions, but it demands high computational resources and has uncertainties in measuring shaded/unshaded areas. DesignBuilder v7.3 integrates energy and green system modelling for building-scale applications, yet it lacks broader urban analysis capabilities. MUKLIMO_3 effectively evaluates urban heat islands using local climate zone classifications, but it operates at a coarser resolution. UMEP integrates socioeconomic and physical constraints, providing high-resolution greening scenarios, although it requires broader validation across climates. Identification of the right tool is essential for tailoring strategies to specific urban contexts, while deeper analyses comparing thermal performance, scalability, and cost-effectiveness can guide holistic urban planning and policy-making efforts.

This literature review aims to identify both widely used and emerging software, highlight research gaps, and address key insights from the selected literature using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2020 [46]. The study explores the synergies and trade-offs between urban greenery, thermal comfort, green infrastructure, and the built environment, aiming to provide insights into optimizing these elements for sustainable urban development.

2. Materials and Methods

In this research, a mixed-methods approach was adopted by combining a systematic review—using the PRISMA 2020 framework—with bibliometric analysis, facilitated by VOS viewer version 1.6.19 [46,47,48,49]. The PRISMA process led to the selection of the papers used for both qualitative synthesis and bibliometric analysis. The mixed-methods approach has been instrumental in achieving the objectives of this study [50]. Expanding upon previous discussions, this study integrates the structured qualitative depth of a systematic review with the quantitative insights of bibliometric analysis to explore the synergies and trade-offs between urban greenery, green infrastructure, and the built environment. The research protocol for the study is shown in Figure 2 with regard to how the study is progressing. The study follows the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines and checklist [51].

2.1. The PRISMA Framework

The PRISMA framework was employed to systematically collect, screen, and analyze articles from the Web of Science (WOS) database. This method ensures transparency and reproducibility, which are vital for academic rigor [52,53]. There were four phases in the literature collection procedure. A web search was done on 24 November 2024 as the initial step. Using the basic search in search mode, the search terms ((“Thermal Comfort” OR “Built environment”) AND (“urban greenery” OR “green roof*” OR “green facade*” OR “urban green space*” OR “vertical green system”)) and then search method topic was selected. The Web of Science core collection database provided 795 journal articles using this search. The systematic review followed the PRISMA framework shown in Figure 3, encompassing four key phases to ensure a transparent and rigorous methodology. The process began with the identification stage, in which 795 records were retrieved from the WoS database using a comprehensive search. This broad search aimed to capture diverse and relevant studies within the research scope. During this phase, studies from 2015–2024 were considered, following which 152 articles were excluded because they were not in English, were review papers, or were categorized as early access articles. This resulted in 643 records proceeding to the next phase.

The screening stage involved a thorough assessment of the remaining records. Duplicate and irrelevant records were removed, and studies were evaluated based on their titles and abstracts. A total of 591 records were excluded at this stage due to their lack of alignment with the research focus, particularly the absence of a connection between thermal comfort and urban greenery. This refined the dataset to 52 records for further evaluation.

In the eligibility stage, the full texts of the 52 remaining records were reviewed against predefined criteria, including their relevance to the research themes of thermal comfort, green infrastructure, and urban greenery. Four records were excluded because they were conference proceedings deemed ineligible for detailed analysis.

Finally, the inclusion stage resulted in 48 studies being selected for detailed analysis that were from the last ten years, i.e., 2015–2024. These studies formed the foundation of the systematic review and provided critical insights into key themes, methodologies, and research gaps. By employing the PRISMA framework, the review ensured a structured and reliable process, yielding a robust dataset that highlights the methods adopted and research gaps in the field. This approach not only synthesizes existing knowledge but also paves the way for future research by systematically identifying synergies and challenges in the domain of urban greenery and thermal comfort. In the Supplementary Materials Section of this study, a comprehensive list of all 48 studies included in the systematic review is presented, along with their respective citation details. Each study is systematically documented, noting information such as the authors, year of publication, title, and the number of citations, thereby providing a transparent overview of the research corpus. These studies were meticulously selected through the PRISMA framework, ensuring relevance to the themes of thermal comfort and urban greenery.

2.2. Bibliometric Analysis

In this study, “VOSviewer” was employed to create visual bibliometric maps that illustrate the co-occurrence of keywords, bibliographic coupling, and co-citation patterns in the literature related to thermal comfort and urban greenery. The bibliographic data was collected from the WOS Core Collection database using a targeted search query, with 48 studies being selected for detailed analysis. This dataset was analyzed in VOSviewer to generate graphical representations, including keyword co-occurrence maps, country networks, and top citated papers. The keyword co-occurrence map highlighted frequently used terms such as thermal comfort, urban greenery, and green infrastructure, with node sizes representing frequency and connections indicating co-occurrence. The analysis also identified thematic clusters that revealed synergies between urban greenery, green infrastructure, and built environments, while the country network mapped the geographical distribution of influential research. This comprehensive visualization provided deeper insights into key trends, thematic relationships, and research gaps, offering a foundation for identifying major themes and advancing knowledge in the field.

3. Results and Analysis

3.1. Publication Trends

The research on thermal comfort has shown a moderate increase in publications between 2015 and 2024, as shown in Figure 4. A key factor influencing the growth of research in this field was the COVID-19 pandemic (2020–2022), which had a profound impact on thermal comfort studies. The pandemic led to increased attention on indoor environmental quality, natural ventilation, and the role of urban greenery in mitigating heat stress in both indoor and outdoor environments [54].

The analysis of publication trends reveals a significant increase in the number of publications over the past three years, reflecting growing research interest and advancements in the field. Applying a linear-exponential regression model to the 2015–2019 dataset (excluding 2024 due to incomplete coverage) resulted in a moderate fit with an R² value of 0.63. While this suggests a tendency toward exponential growth, the moderate fit indicates that additional influencing factors may be at play, preventing a purely exponential trajectory. Given the limitations of an exponential assumption over a relatively short timeframe, a longer observation period would be required to establish whether exponential growth is sustained. The overall trend highlights the growing interest and research activity in the field, with a particularly significant increase in publications from 2022 onwards.

3.2. Analysis of Co-Occurring Keywords in Research on “Thermal Comfort”

The co-occurring keyword analysis identified 347 results, highlighting the most frequently occurring keywords in thermal comfort and related research. Among these, the top co-occurring keywords are built environment, urban green space, ecosystem services, health, parks, and urban heat island. These keywords reflect key themes in the literature, emphasizing the interconnectedness of thermal comfort with broader environmental and urban factors. Figure 5 illustrates the co-occurrence network of often utilized keywords related to thermal comfort using VOS viewer network visualization. There is a total of 19 clusters formed using cluster analysis. The largest cluster contains 29 items, such as urban green space, health, built environment, thermal comfort, and impact. The second largest cluster contains 28 items, such as heat island, urban climate, air temperature, ecosystem services, etc. A co-occurrence keyword cluster map (Figure 5) is a powerful tool used in data analysis to visualize the relationships between keywords based on their co-occurrence patterns in a dataset [55]. This visualization technique helps in identifying the most significant keywords and understanding the underlying thematic structure within a dataset [56].

3.3. Top Cited Research Articles

Table 1. Top cited documents in the WoS database.

No.	Country	Key Finding	Citation	References
1	United States	The study reveals that urban green spaces are vital for enhancing public health, as they offer opportunities for physical activity, improve mental well-being, and contribute to a healthier urban environment. However, it also uncovers a troubling disparity: many low-income neighborhoods and communities of color face significant barriers to accessing these essential green areas. This lack of access not only limits the health benefits that green spaces provide but also perpetuates existing public health challenges within these marginalized communities.	2452	[57]
2	Global	The study highlights the significant cooling effects of urban greening, such as parks and trees, which can lower local temperatures by an average of 1 °C compared to non-green areas, particularly important during heat waves. Larger green spaces tend to provide greater cooling benefits, and their effects can extend beyond immediate boundaries, benefiting surrounding areas. Different types of vegetation contribute variably to cooling, with tree canopies offering essential shade and shorter vegetation providing evaporative cooling. The research emphasizes the need for further studies to rigorously assess these effects and their implications for public health, advocating for the integration of green spaces in urban planning to enhance resilience against rising temperatures and heat-related health issues.	1688	[58]
3	Global	The paper by M. Santamouris highlights the significant potential of cool and green roofs in mitigating urban heat islands and improving thermal comfort in cities. It emphasizes that increasing the albedo of roofs can lead to measurable reductions in ambient temperatures, with cool roofs generally outperforming green roofs in energy conservation and thermal comfort. However, the effectiveness of these technologies varies based on regional characteristics and specific building contexts.	1144	[59]
4	Victoria, Australia	The key finding of the paper is that implementing urban green infrastructure (UGI) can significantly mitigate high temperatures in urban areas, particularly in the city of Port Phillip, Australia. The study developed a prioritization framework that integrates high-resolution thermal remote sensing data with socio-economic indicators to identify neighborhoods most vulnerable to heat exposure. This approach allows local governments to strategically allocate resources and implement UGI solutions, such as tree planting and water-sensitive designs, to enhance thermal comfort and improve community resilience against extreme heat events.	699	[60]
5	Hong Kong	The study reveals that achieving a tree coverage of over one-third of the total land area can lead to a cooling effect of approximately 1 K, which is crucial for enhancing outdoor comfort and reducing energy consumption in buildings. However, it also notes that simply planting trees or grass in high-rise areas may not effectively cool the pedestrian environment, highlighting the importance of strategic placement and the need for comprehensive greening guidelines to maximize benefits for urban inhabitants.	636	[61]
6	Global	The review highlights that urban green spaces significantly contribute to improved health outcomes, including enhanced mental well-being, reduced cardiovascular issues, and increased physical activity. It emphasizes the positive associations between proximity to green spaces and various health benefits, such as lower stress levels and improved mood. However, the authors note limitations in the generalizability of findings, as most studies were conducted in the global North and primarily focused on adult populations. There is a call for more research in diverse urban settings, particularly in the global South and among vulnerable populations, to better understand the complex interplay between urban nature and health.	620	[62]
7	Global	The key finding of the paper is that incorporating vegetation into urban building envelopes, such as green roofs and walls, significantly mitigates urban heat, particularly in hot and arid climates like Riyadh. The research demonstrates that air temperatures can decrease substantially—up to 26.0 °C at roof level and 11.3 °C within urban canyons—due to the cooling effects of vegetation. This highlights the importance of integrating green infrastructure into urban design to combat the heat island effect, improve thermal comfort, and enhance the overall livability of cities.	618	[63]
8	Global	The key finding of this paper is that the effectiveness of green infrastructure in improving air quality varies significantly based on urban morphology and vegetation characteristics. In street canyon environments, high-level vegetation, such as trees, can negatively impact air quality by obstructing airflow, while low-level, dense vegetation like hedges tends to enhance air quality by reducing pollutant exposure. Conversely, in open road conditions, specific configurations of vegetation can lead to pollutant reductions. The review emphasizes the need for tailored recommendations for the design and implementation of green infrastructure to optimize its air pollution abatement potential in different urban contexts.	571	[64]
9	Hokkaido, Japan	Key findings indicate that the cooling load in cities can be substantially higher than in rural areas, leading to increased energy demands for air conditioning and associated CO2 emissions. The research underscores the importance of urban planning strategies, such as incorporating green spaces, optimizing building materials, and enhancing albedo, to mitigate UHI effects, reduce energy consumption, and promote environmental sustainability in urban settings.	430	[65]
10	Global	The findings suggest that exposure to these natural environments can positively influence well-being, although the evidence is still emerging and requires further research to establish more robust causal relationships. The review emphasizes the importance of integrating outdoor blue spaces into urban planning as a strategy to improve public health, while also acknowledging the need for standardized methodologies and consideration of cultural differences in future studies.	408	[66]

Notes: Papers which conducted studies on more than three countries have been classified as ‘Global’.

presents an analysis of the top 10 most cited papers related to urban greenery and thermal comfort. Each study identifies key findings in their study areas, providing valuable insights into the role of green infrastructure in enhancing built environment and health outcomes across various global contexts.

These studies emphasize the multifaceted role of urban green infrastructure in addressing urban heat, improving health, and promoting sustainability across diverse cities globally. Each study underscores the importance of strategic urban planning and further research to optimize the health and environmental benefits of green spaces.

3.4. Analysis of Country Distribution in Research on “Thermal Comfort”

Based on the WoS search results, Figure 6 shows the country distribution tree map. The WoS country tree map data chart highlights the distribution of research contributions from various countries in the field of urban green spaces, thermal comfort, and related studies. The People’s Republic of China leads with the highest contribution, representing 33.33% of the total publications, followed by the United States at 16.67%. Italy contributes 10.42%, while countries such as the Czech Republic, England, Ireland, and Singapore each account for 8.33% of the publications. Other notable contributors include Australia, Canada, Greece, and Japan, each with 6.25%.

This chart reveals a global interest in the field, with strong contributions from both developed and emerging economies, underscoring the universal importance of addressing urban heat, environmental sustainability, and public health through research and green infrastructure.

3.5. Emerging Softwares, Research Gaps, and Key Insights from the Literature

In this section, the studies explored in various countries highlight significant research gaps in understanding urban greenery’s impact on thermal comfort, green infrastructure and the built environment. For instance, in Hungary, there are research gaps related to quantifying vegetation’s cooling potential under heatwave conditions, using models like MUKLIMO_3 to simulate thermal perceptions through the Klima-Michel model [67]. Similarly, studies in the USA and China identify gaps in addressing humid heat stress and evaluate the adaptability of urban green infrastructure under climate change challenges, employing Earth System Models and urban-specific humid heat measures. ENVI-met emerges as a critical tool across multiple studies for simulating urban greenery’s microclimatic effects [68,69]. To synthesize the diverse literature on urban greenery’s impact on thermal comfort, we reorganized the studies into five primary thematic areas: (i) simulation and modeling approaches, (ii) empirical field measurements, (iii) urban design and morphological influences, (iv) advanced analytical methods, and (v) long-term, multi-scale evaluations. This thematic condensation not only streamlines the discussion but also highlights key insights, such as the critical role of urban geometry and the need for long-term validation, while identifying common research gaps that future studies should address. Key insights emphasize the localized cooling effects of dense urban vegetation, the necessity for context-specific greening strategies, and challenges such as water limitations and airflow interference by dense tree canopies. These findings stress the importance of integrating socio-environmental constraints into urban planning for effective climate regulation and human thermal comfort.

3.5.1. Simulation and Modeling Approaches

Recent studies have explored the cooling effects of urban greenery and green infrastructure (GI) on urban thermal comfort using tools like ENVI-met, PALM, and 3D-USM, as shown in

Table 2. Simulation and modeling approaches from the literature.

Ref	Year	Country	Climate Zone	Software/Tool Used	Key Insight	Research Gap
[70]	2023	Hong Kong	Cfa	ENVI-met v5.7	Systematic quantification of cooling effects of seven green infrastructure (GI) strategies; introduced cooling indicators (CI, CA, CD).	Limited exploration of cooling effects across various combinations of GI typologies.
[71]	2024	China	Cfa	ENVI-met v5.7	Urban form factors (street orientation, building height, spatial layout) significantly influence GCIE; building shadows are a major cooling factor.	Limited exploration of underlying mechanisms; lack of comprehensive analysis of cooling distance.
[72]	2023	South Korea	Dwa	3D-USM	Demonstrates that street orientation significantly impacts pedestrian thermal comfort.	Lacks field validation of the 3D-USM model and does not incorporate other heat transfer processes or anthropogenic heat effects.
[80]	2020	Hong Kong	Cfa	ENVI-met v5.7	Urban density affects the cooling benefits of greenery; identifies non-linear relationships between greenery coverage and cooling efficiency (optimal ~20–30%).	Limited exploration of long-term effects and insufficient data on optimal greenery coverage across diverse urban contexts.
[73]	2023	Czech Republic	Cfb	PALM modeling system v6.0	Urban greenery can significantly reduce thermal exposure, with trees lowering UTCI by up to 10 °C.	Limited focus on long-term effects and need for real-time validation of models in diverse urban settings.
[74]	2024	UK	Cfb	ENVI-met v5.7	Urban green systems, such as trees and living facades, can mitigate UHI and improve pedestrian thermal comfort.	Lacks consideration of psychological aspects, nighttime UHI effects, and air pollution impacts.
[75]	2022	Italy	Cfa	Rhinoceros 8, EnergyPlus v24.2.0	Develops a digital twin model to assess pedestrian-level thermal comfort and the feasibility of a green pedestrian network.	Lacks extensive validation across different urban contexts and does not address long-term impacts of greenery on microclimates.
[77]	2020	Hong Kong	Cfa	ENVI-met v5.7	Ozone pollution significantly reduces the cooling performance of urban trees, underscoring the need for tailored greening strategies.	Lacks comprehensive analysis of species-specific responses to ozone and impacts on LAI and cooling performance.
[76]	2020	Slovenia	Cfb	ENVI-met v5.7	Identifies optimal greening models that enhance shading and reduce temperatures in parking areas.	Limited exploration of long-term impacts of greening strategies on UHI and user behavior.
[81]	2022	Hong Kong	Cfa	UGBE model, UrBEC model	The UGBE model effectively simulates the cooling performance of urban greenery; limited cooling effects are observed in high-density areas.	Lacks a first-principles model to predict dynamic interactions among greenery, buildings, and anthropogenic activities at street scale.
[82]	2024	Czech Republic	Cfb	PALM model system v6.0	Trees significantly reduce UTCI during heatwaves (average reduction ~3.5 °C); spatial effectiveness is influenced by tree positioning relative to buildings.	Limited validation of radiative models in urban contexts and lack of application in diverse climatic zones beyond Europe.
[78]	2023	USA	Cfa	Mobile weather station, COMFA, GWR models	Green infrastructure positively impacts outdoor thermal comfort; significant micro-scale variations in thermal comfort exist within small areas.	Limited micro-scale analysis of the cooling effect of blue spaces; need for broader data collection across various distances from water bodies.
[79]	2025	China	Cfa	ENVI-met v5.7	Demonstrates that combining vegetation with fountains can significantly reduce urban heat, enhancing pedestrian comfort in urban streets.	Lack of field tests to validate the cooling effects of fountains; heavy reliance on simulation data without real-world calibration.
[68]	2017	Global	Csa	ENVI-met v5.7, WRF v 4.6.1	Provides an extensive analysis of the cooling potential of various mitigation technologies, showing an average peak temperature drop of 2 K and ambient reduction of 0.74 K.	Lacks comprehensive experimental validation for some mitigation techniques and has limited real-scale data.
[69]	2023	Hong Kong	Cfa	ENVI-met v5.7	Emphasizes the significance of accurate LAD in tree modeling for microclimatic sensitivity; proposes a systematic workflow for developing a vegetation model library.	The vegetation model library is in its preliminary stage and lacks comprehensive substrate property data.

. Research in Hong Kong and China highlighted the role of GI typologies and urban form factors but lacked comprehensive analysis across diverse contexts [70,71]. South Korea and the Czech Republic demonstrated significant cooling from street orientation and urban greenery efforts, though real-world validation remains limited [72,73]. Studies in the UK, Italy, and Slovenia emphasized the benefits of green systems on pedestrian comfort but noted gaps in long-term impact assessments [74,75,76]. Pollutant interactions and micro-scale variations, particularly in Hong Kong and the USA, revealed the need for tailored greening strategies and broader data collection [77,78]. The global carbon impact estimation (GCIE) is a metric used to assess the total carbon footprint of a system, considering emissions from material extraction, production, operation, and disposal. The localized air distribution (LAD) refers to the distribution of air within a specific zone or space, optimizing ventilation efficiency and thermal comfort. While integrating vegetation with features like fountains showed promise in China, many studies still rely heavily on simulations without field calibration [79].

3.5.2. Empirical Field Measurements

Recent studies emphasize the critical role of urban greenery and green infrastructure in enhancing thermal comfort across various climatic regions while also identifying gaps in their integration with the built environment, as shown in

Table 3. Empirical field measurements summary.

Ref	Year	Country	Climate Zone	Software/Tool Used	Key Insight	Research Gap
[83]	2016	Australia	Csa	i-Tree Canopy v7.1	Highlights the importance of urban greenery for heat resilience; identifies critical thermal conditions affecting public space activities.	Limited number of public spaces analyzed; lacks broader geographic applicability.
[84]	2018	Sweden	Cfb	i-Tree model v6.0.38	Links urban green structure components to ecosystem services, emphasizing perceived well-being and functional traits in urban planning.	Limited application of the framework in contexts beyond Gothenburg; lack of long-term monitoring data.
[85]	2018	Serbia	Cfa	Comparative analysis, Field measurements, Temperature measurement	Urban greenery significantly reduces air temperatures compared to paved surfaces; shaded and high-albedo materials mitigate UHI.	Limited exploration of material properties beyond thermal characteristics; lack of long-term data on cooling strategies.
[54]	2021	Malaysia	Af	Pyranometer, Graphtec Data Logger GL220	Vegetated areas exhibit lower temperatures compared to built environments; urban greenery and high albedo materials improve thermal comfort.	Limited exploration of long-term effects of urban design on thermal comfort; lack of comparative studies in tropical regions.
[86]	2016	Singapore	Af	i-Tree Canopy tool	Site-specific characteristics (e.g., canopy structure) significantly influence micro-scale climate variations; balance between shade and windbreaks is critical.	Lacks comprehensive analysis of temporal variations in thermal comfort (e.g., pre-noon vs. post-noon) and nocturnal conditions.
[87]	2019	Singapore	Af	Rayman Model	Calibrated PET for neutral, acceptable, and preferred thermal comfort in an equatorial park; shows significant acclimatization differences between locals and non-locals.	Limited exploration of psychological factors influencing thermal comfort; lack of direct validation of temperature thresholds.

. In Australia and Sweden, the i-Tree Canopy and i-Tree model highlighted how urban greenery contributes to heat resilience and ecosystem services, though broader geographic applicability and long-term monitoring remain limited [83,84]. Research in Serbia and Malaysia has demonstrated that urban greenery and high-albedo materials significantly reduce air temperatures compared to paved surfaces in the built environment, enhancing thermal comfort and mitigating the urban heat island effect. However, long-term impacts and material properties beyond thermal characteristics require further exploration [54,85].

3.5.3. Urban Design and Morphological Influences

In Hong Kong, studies have demonstrated that strategic tree planting, larger crown species, and roadside greenery can significantly reduce air temperatures and improve pedestrian comfort, yet gaps persist in evaluating diverse species, long-term ecological impacts, and real-world applications [88,89,90,91]. Indian and Sri Lankan studies have highlighted the benefits of green roofs and walls in lowering urban temperatures, but further research is needed on their long-term performance and comparative cost-effectiveness with other sustainable practices [28,92]. Additionally, studies in Greece and Southern China have stressed the role of flexible shading and radiative cooling from trees in optimizing thermal comfort, though comprehensive economic evaluations and comparisons with alternative shading materials are lacking [93,94]. Physiologically equivalent temperature (PET) is an index used to assess human thermal comfort by considering meteorological factors such as air temperature, humidity, wind speed, and radiation, along with human physiological responses. The sky view factor (SVF) is a dimensionless parameter that quantifies the proportion of the sky visible from a specific point, influencing urban microclimates, solar exposure, and thermal comfort. These findings (shown in

Table 4. Urban design and morphological influences summary.

Ref	Year	Country	Climate Zone	Software/Tool Used	Key Insight	Research Gap
[95]	2022	Iran	Bsk	ENVI-met v5.7	Highlights the importance of neighborhood design and greenery in mitigating UHI and enhancing thermal comfort.	Limited exploration of socio-economic factors; lack of long-term field studies for validation.
[96]	2019	Iran	Bsk	ENVI-met v5.7	Shows a significant positive relationship between SVF and PET; indicates that greenery arrangement and building heights impact thermal comfort differently based on street orientation.	Lacks comprehensive exploration of long-term effects and seasonal variations.
[97]	2023	Italy	Cfa	ENVI-met v5.7	Urban textures and tree species diversity are critical for monitoring thermal conditions; urban vegetation can influence microclimates effectively.	Limited exploration of a wider range of urban textures and tree species; need for real-time on-site monitoring.
[88]	2016	Hong Kong	Cfa	ENVI-met v5.7	Demonstrates that strategic tree planting can significantly reduce air temperatures and mitigate UHI effects in urban centers.	Limited evaluation to a single tree model; lacks systematic assessment of diverse tree species and their ecological functions.
[89]	2022	Hong Kong	Cfa	City energy and mass balance	Reveals that tree species with larger crowns and higher LAI provide better cooling and humidification; sparse planting patterns enhance shading and evapotranspiration.	Does not extensively address long-term ecological impacts or the socio-economic factors influencing tree selection and maintenance.
[98]	2023	Hong Kong	Cfa	ENVI-met v5.7	Shows that higher tree view factors can significantly improve pedestrian thermal comfort; recommends integration of individual-based comfort metrics in design.	Lacks comprehensive evaluation of different tree species’ morphologies and their specific cooling effects on pedestrian comfort.
[28]	2023	India	Aw	DesignBuilder v7.3	Green buildings with green roofs/walls exhibit lower air temperatures, radiant temperatures, and solar heat gain compared to conventional buildings.	Limited exploration of long-term performance and maintenance impacts; lack of comparative analysis with other sustainable practices.
[90]	2017	Hong Kong	Cfa	ENVI-met v5.7	Roadside trees can significantly reduce mean radiant temperatures and PET in high-density areas, particularly under low SVF conditions.	Lacks comprehensive evaluation of long-term effects of tree planting on microclimate and seasonal variations.
[20]	2024	Italy	Csa	i-Tree Eco v6.0.38	Indicates that cutting down large trees for smaller ones can result in loss of ecosystem benefits and a decrease in urban quality of life.	Limited application of i-Tree Eco in Europe; need for updated meteorological and pollutant data.
[93]	2023	Southern China	Cfa	ENVI-met v5.7, BioMet	Emphasizes the need for flexible shading solutions that adapt to varying weather conditions.	Lacks comparison with other shading materials (e.g., umbrellas, textiles).
[92]	2018	Sri Lanka	Af	ENVI-met v5.7	Demonstrates that various green strategies (trees, green roofs, green walls) effectively reduce temperatures and mitigate UHI in Colombo.	Limited economic analysis of green infrastructure options; further studies needed to assess cost-effectiveness.
[99]	2018	Japan	Cfa	ArcGIS 10.2	Identifies high-risk heat stress locations along a marathon route; proposes mitigation strategies such as route adjustments and increased shading.	Limited exploration of long-term climate adaptation strategies and detailed physiological responses of users to heat stress.
[94]	2021	Greece	Csa	ENVI-met v5.7, EnergyPlus v 24.2.0	Demonstrates that the cooling potential of trees—mainly via radiative shading—reduces solar heat gains on building façades; tree species and planting patterns are crucial.	Does not explore long-term effects of tree growth and seasonal changes; lacks sensitivity analysis for optimal insulation levels.
[100]	2023	Italy	Csa	SOLWEIG, UMEP v4.0	Proposes a spatially explicit method to identify greening scenarios that maximize cooling benefits; emphasizes the importance of land tenure and cover in planning.	Lacks comprehensive economic valuation of greening scenarios and their long-term benefits.
[91]	2022	Hong Kong	Cfa	ENVI-met v5.7	Shows that building setbacks combined with roadside tree planting can create a comfortable thermal environment; a 3-m setback with trees can mimic a 6-m setback.	Lack of comprehensive evidence evaluating individual design elements or their integration in real-world settings.

) call for more holistic approaches that integrate urban greenery and green infrastructure into sustainable urban design while addressing long-term, socioeconomic, and ecological considerations in the built environment context.

3.5.4. Advanced Analytical Methods

The emerging technologies presented in

Table 5. Advanced analytical methods summary.

Ref	Year	Country	Climate Zone	Software/Tool Used	Key Insight	Research Gap
[101]	2022	Japan	Cfa	COMFA, AI algorithm-driven Google Street View Images Analysis	Demonstrates that urban geometry (SVF, FAR) influences thermal comfort; spatial clusters of high thermal stress do not always align with urban greenery.	Findings may not be applicable to other climate zones; lacks detailed exploration of physical street design elements.
[102]	2023	Taiwan	Cwa	SPSS Statistics 22.0, DeepLab V3	Shows strong correlations between deep learning and manual classifications for urban feature extraction; SVF and GVI are critical for outdoor thermal comfort.	Limited validation across diverse contexts; insufficient exploration of seasonal variations and additional view factors (BVF, TVF).
[103]	2022	China	Cwa	Fully Convolutional Neural Network (FCN-8s) for image segmentation	Indicates that urban greenery significantly improves outdoor thermal comfort; different greenery measures have varying impacts on microclimate regulation.	Limited longitudinal studies and lack of diverse geographical representation beyond cold regions.
[104]	2022	Czech Republic	Cfb	eCognition (Trimble), SAGA GIS, MODTRAN 5.3	Developed a novel photographic approach to assess long-term thermal perception and comfort using surveys combined with Google Street View images.	Limited exploration of cultural differences in thermal perception; lack of cross-validation with in-situ measurements.
[105]	2022	USA	Bwh	Gaussian Process Regression (GPR)	Demonstrates the use of machine learning for optimizing urban design, highlighting the potential of multi-objective approaches in urban planning.	Limited consideration of additional environmental metrics beyond heat and carbon emissions; potential oversimplification of urban dynamics.

, such as AI and machine learning, are increasingly used to assess the interplay between urban greenery, thermal comfort, and green infrastructure within the built environment. In Japan and Taiwan, studies employing AI-driven tools like COMFA and DeepLab V3 revealed the influence of urban geometry (e.g., SVF, FAR) on thermal comfort, though they highlighted gaps in validating these findings across diverse climates and street designs [101,102]. Floor area ratio (FAR) is the ratio of a building’s total floor area to the size of the plot of land on which it is built, used to regulate urban density and land use. Some abbreviations used in Table 5 include the green view index (GVI) for visible green vegetation, building volume fraction (BVF) for built-up volume in urban space, and tree volume fraction (TVF) for tree canopy coverage, all of which influence environmental and thermal conditions. Research in China using Fully Convolutional Neural Networks (FCN-8s) has demonstrated that various urban greenery strategies significantly improve outdoor thermal comfort, yet longitudinal studies and broader geographical representation are needed [103]. A novel photographic method in the Czech Republic combined Google Street View imagery with GIS tools to assess long-term thermal perception, though cultural differences in thermal comfort remain underexplored [104]. In the USA, Gaussian Process Regression (GPR) showcased the potential of machine learning to optimize urban design by integrating multiple objectives in urban planning, but further research is required to incorporate broader environmental metrics beyond heat and carbon emissions [105].

3.5.5. Long-Term, Multi-Scale Evaluations

Global analyses reveal increased research on greenery’s cooling effects, though empirical validation across diverse climates remains limited [106]. In South Korea and Egypt, tools like COMFA and ENVI-met show significant improvements in thermal comfort and energy efficiency, yet long-term and seasonal impacts need further study [107,108]. Research in the Czech Republic and Hungary demonstrates that urban green spaces reduce thermal exposure, though the socioeconomic impact and applications in medium-sized cities are underexplored [67,109]. A summary of long-term, multi-scale evaluations is provided in

Table 6. Long-term, multi-scale evaluations summary.

Ref	Year	Country	Climate Zone	Software/Tool Used	Key Insight	Research Gap
[106]	2024	Global	–	R (bibliometrix package v4.3.2, tidyverse v2.0.0)	Reveals a significant increase in publications on urban greenery’s cooling effect since 2008; identifies key themes and future research directions.	Lacks in-depth empirical studies directly measuring cooling effects across diverse urban settings and climates.
[107]	2024	South Korea	Dwa	COMFA energy budget model, Urban IoT sensor network (S-DoT)	Indicates that green infrastructure significantly mitigates outdoor thermal comfort-related UHI; greater cooling effects observed in areas with high vegetation cover.	Lacks comprehensive analysis of the long-term effects of green infrastructure on outdoor thermal comfort across seasons.
[110]	2015	Global	–	Literature review	Highlights that urban warming significantly impacts energy consumption, health, and environmental quality; effective mitigation includes expanding green spaces and reflective materials.	Lack of quantitative data on the effectiveness of specific mitigation techniques under varying climatic conditions.
[109]	2022	Czech Republic	Cfb	PALM-4U v23.10	Shows that urban greenery—particularly broad-leaved and coniferous trees—can significantly reduce thermal exposure and improve pedestrian comfort during heat waves.	Limited exploration of long-term effects and socio-economic implications of urban greenery.
[111]	2023	Global	–	Community Earth System Model (CESM) v 2.1.5	Highlights the significant role of humidity in urban heat exposure; emphasizes the need for urban adaptation strategies to mitigate heat stress.	Limited focus on specific urban case studies; lacks detailed local adaptation strategies.
[108]	2017	Egypt	Bwh	ENVI-met v5.7, DesignBuilder v7.3	Demonstrates that urban greenery significantly impacts microclimatic conditions and energy consumption; coupled outdoor-indoor simulations assess these effects.	Limited exploration of long-term impacts of green adaptation strategies beyond 2080; lack of comprehensive field validation.
[67]	2024	Hungary	Cfb	MUKLIMO_3, Klima-Michel	Urban green spaces significantly reduce UHI effects and improve thermal comfort during heatwaves.	Limited research on perceived temperature patterns in specific urban districts; need for broader application to other medium-sized cities.

.

3.6. Study on Software Used for Thermal Comfort Simulation

The analysis of software tools shown in

Table 7. Different software used for thermal comfort simulation.

S. No.	Software	Parameters to Consider	Parameter Type	References
1	EnergyPlus v5.7	Air Temperature (Ta)	Input	[115,116,117,118,119,120,121,122,123,124]
		Relative Humidity	Input
		Wind Speed	Input
		Inflow Direction	Input
		Solar Radiation	Input
		Geographical Location	Input
		Roughness Length	Input
2	DesignBuilder v7.3	Building dimensions	Input	[125,126,127,128,129,130,131,132,133,134,135,136,137,138]
		Orientation and location	Input
		Construction materials (U-value, thermal mass)	Input
		Weather data (air temperature, humidity, wind speed, solar radiation)	Input
		Shading (nearby buildings, vegetation)	Input
		Terrain properties (roughness length)	Input
3	TRNSYS v18	Air Temperature (Ta)	Input	[43,139,140,141,142,143,144,145,146,147,148,149,150,151]
		Relative Humidity	Input
		Wind Speed	Input
		Inflow Direction	Input
		Solar Radiation	Input
		Geographical Location	Input
		Roughness Length	Input
		Initial Temperature	Input
		Atmosphere	Input
		Vegetation Information	Input
		Surface Information	Input
4	Ecotect	Material properties for embodied energy and lifecycle assessment	Input	[44,152,153,154,155,156,157,158,159,160,161,162]
		Environmental impact analysis (e.g., carbon footprint)	Output
		Energy consumption, CO2 emissions, EUI (Energy Use Intensity), Indoor air quality (CO2 levels, fresh air supply)	Output
5	e-QUEST v 3.65	Electricity Usage (lighting, plug loads, HVAC energy consumption)	Output	[42,163,164,165,166,167,168,169,170,171,172,173]
		Insulation (wall, roof, floor, and window insulation properties)	Input
		Weather Data (air temperature, humidity, wind speed, solar radiation)	Input
6	CBE	Comfort Index (e.g., PMV, PPD)	Output	[174,175,176,177,178,179,180,181,182,183,184,185,186,187]
		Energy Performance Metrics (EUI, total energy consumption)	Output
		Air Quality Indicators (CO2 levels, ventilation effectiveness)	Output
		Heating and Cooling Loads (peak and annual loads)	Output

demonstrates their diverse capabilities in assessing building energy performance and environmental impacts. Table 7 presents a comparative overview of the parameters considered in various Building Energy Simulation (BES) tools, distinguishing their distinct scopes. These parameters primarily serve as input variables that influence simulation results, although some tools also generate specific output parameters. EnergyPlus focuses on simulating indoor thermal dynamics and airflow utilizing inputs such as air temperature, humidity, and solar radiation. DesignBuilder extends this by integrating building-specific attributes like materials, shading, and weather data for energy efficiency optimization. TRNSYS includes vegetation and surface interactions, allowing for environmental impact assessments in built environments. Ecotect, in contrast, specializes in lifecycle and material property assessments, emphasizing environmental effects such as carbon footprint. Although BES tools mainly model indoor environments, they also provide insights into outdoor thermal comfort by analyzing interactions between buildings and microclimates. This is particularly relevant for studying urban heat islands, the cooling impact of vegetation, and urban planning decisions that mitigate outdoor thermal discomfort [112]. These tools simulate building–envelope interactions with the surrounding outdoor environment, which is essential for assessing the impact of buildings on the local microclimate [113]. By incorporating outdoor factors such as solar radiation, wind speed, shading, and air temperature, these tools help evaluate how buildings influence outdoor thermal conditions, especially in urban areas with significant greenery [114]. This capability is particularly relevant when studying urban heat islands, the cooling effects of vegetation, and how urban planning decisions can mitigate thermal discomfort in outdoor spaces.

The three primary climatic scales are microscale, local scale, and mesoscale. According to traditional research [188], the horizontal range for the microscale spans from 0.001 m to 1000 m, the local scale covers distances between 100 m and 50,000 m, and the mesoscale extends from 10,000 m to 200,000 m. Variations in the horizontal scale are present in the recent literature [13]. The details of the numerical modeling techniques employed and their capabilities, examples, advantages, limitations, software platforms, and scale are shown in

Table 8. Numerical modeling techniques and their capabilities, examples, advantages, limitations, software platforms, and scale.

Numerical Modelling Technique	Capabilities	Examples	Advantages	Limitations	Software Platform	Typical Scale
Computational Fluid Dynamics (CFD) Models	Simulates airflow, heat transfer, and vegetation impact on microclimates.	Simulating street canyon cooling effects; analyzing tree wind-shielding effects.	High spatial resolution; detailed analysis of small-scale phenomena.	Computationally expensive; requires detailed input data. Have difficulties in simulating static cloud and wind conditions.	ANSYS Fluent, OpenFOAM, ENVI-met v. 5.7	Microscale and Local Scale
Atmospheric Models	Simulates regional and climate weather forecasts, including different greening scenarios	Evaluating city-wide temperature reductions from urban greenery.	Captures neighborhood or city-wide impacts; links greenery to climate patterns.	Computationally expensive; coarser spatial resolution compared to CFD.	WRF (with urban canopy models)	Mesoscale
Energy Balance Models	Quantifies contributions of greenery to shading, evapotranspiration, and soil heat flux.	Modeling urban park evapotranspiration; assessing green roof cooling effects.	Simple and efficient for urban-scale simulations.	Simplifies complex processes; limited spatial detail.	TEB (Town Energy Balance model), Rayman, I-Tree Eco, SOLWEIG (Solar and LongWave Environmental Irradiance Geometry)	Local scale
Building Energy Models (BEMs)	Models shading and insulation effects of greenery on building energy performance.	Quantifying energy savings from shaded buildings; simulating green wall impacts.	Focuses on building-scale effects; links greenery to energy savings.	Limited to individual buildings or clusters.	EnergyPlus, TRNSYS	Microscale
Remote Sensing and GIS-Based Models	Analyzes spatial distribution of greenery and associated temperature changes.	Mapping urban greenery and temperature relationships using satellite data.	Large-scale analysis with real-world data.	Relies on indirect measurements; limited temporal resolution.	ArcGIS, QGIS, Google Earth Engine, SkyHelios	Mesoscale
Hybrid Models	Integrates micro- and macro-scale phenomena for comprehensive understanding.	Combining CFD with GIS for large-scale urban cooling analyses.	Balances detail and scale; integrates diverse datasets.	Requires expertise and high computational power.	ENVI-met + GIS, CFD + Energy Balance Models	Local scale and Microscale

.

4. Discussion

The interrelation between the four key components— built environment, urban greenery, green infrastructure, and thermal comfort —is deeply interconnected and forms the foundation for sustainable urban development. The built environment, encompassing buildings, streets, and urban spaces, serves as the foundational framework that integrates various elements. However, dense urbanization often exacerbates challenges like the urban heat island (UHI) effect, necessitating interventions to enhance environmental quality [189,190]. Urban Greenery, such as trees, parks, green roofs, and vertical gardens, acts as a natural cooling system, reducing ambient temperatures through shading, evapotranspiration, and carbon sequestration [191,192]. By incorporating green infrastructure, which includes engineered solutions like permeable pavements, rain gardens, and urban wetlands, cities can enhance stormwater management, reduce surface heat, and provide multifunctional spaces [193]. This infrastructure supports urban greenery by ensuring optimal conditions for its growth and sustenance. The studies analyzed offer diverse insights into urban greenery’s role in mitigating heat and improving urban thermal comfort. Research in Iran [135] emphasizes the influence of the sky view factor (SVF) on street-level thermal comfort, revealing that east–west oriented streets are more affected by SVF than north–south ones. Despite the precision of thermal comfort scenarios generated using ENVI-met, the study is limited by its reliance on localized climate data. Similarly, a study in the USA [78,105] employs Gaussian Process Regression to optimize urban heat and carbon dynamics. This machine learning approach enhances the accuracy of mitigation strategies but requires extensive training data, with notable trade-offs between improving various environmental indicators.

In China, ENVI-met modelling is used to refine vegetation-related microclimatic parameters, with a focus on leaf area density (LAD) as a critical factor for accurate simulation. While this improves modeling clarity, the computational complexity restricts usability for general practitioners [71,103]. Conversely, Hungarian research [67] employs the MUKLIMO_3 microclimate model to examine the impact of green spaces during heatwaves, finding that dense greenery can reduce perceived temperatures by up to 3 °C. However, the cooling effects are highly localized, confined to modified areas and their immediate surroundings.

The conceptual framework shown in Figure 7 illustrates the synergies and trade-offs between the built environment, urban greenery, green infrastructure, and thermal comfort categories in urban settings. Green infrastructure (GI), such as green roofs and walls, when strategically integrated into the built environment, enhances thermal comfort by improving insulation, air quality, and microclimates while reducing heat load [70]. However, a lack of integration leads to design inefficiencies, reduced thermal benefits, and poor performance in high-density areas due to suboptimal planning and maintenance [79]. Similarly, urban greenery, through shading and evapotranspiration, contributes significantly to cooling, but its effectiveness varies depending on the urban design, density, and climate [85]. A synergistic approach combines GI with urban greenery to optimize microclimates, enhance biodiversity, and amplify cooling effects. However, a trade-off emerges as urban greenery competes for space and resources with other GI elements and requires higher maintenance. Additionally, while high-albedo building materials can enhance greenery’s cooling benefits, urban geometry and high density may restrict airflow and sunlight, counteracting the greenery’s effectiveness [88,94,98]. This framework underscores the need for integrated urban planning to balance synergies and trade-offs, ensuring that urban greenery and green infrastructure work collectively to maximize thermal comfort in the built environment.

These interventions work synergistically to mitigate urban heat, enhance shade, and improve air quality, thereby optimizing thermal comfort for urban residents. The arrows in the framework signify the flow and interaction of these components, emphasizing that the inclusion of greenery and green infrastructure not only modifies the thermal properties of the built environment but also fosters sustainable urban development.

5. Conclusions

This study systematically reviewed the interrelation between thermal comfort and urban greenery using a combination of bibliometric and systematic analyses. The findings reveal a steady increase in the number of research studies on thermal comfort over time, underscoring its growing significance in urban and environmental studies. A notable trend is the geographic focus, with most of the published research centered on China, Hong Kong, Singapore, Japan, and Italy, reflecting their proactive efforts in urban heat management and sustainable urban planning. The systematic review highlights diverse data sources, a research gap analysis, and key insight findings from selected research studies and numerical modeling simulation or analytical tools that were employed in urban greenery studies. Advanced software and simulation tools like ENVI-met, EnergyPlus, DesignBuilder, CFD (Computational fluid dynamics) simulation have been widely used to model thermal comfort dynamics and predict the cooling effects of urban greenery.

These findings demonstrate the evolving nature of research in this field and emphasize the need for global and context-specific studies to address urban greenery challenges comprehensively. The frontier research directions in the field of “urban greenery” encompass a blend of traditional studies and cutting-edge technological advancements. A significant focus is on improving thermal comfort in small-scale housing, particularly in China, by examining climate zones, thermal comfort approaches, and influencing factors such as wind speed, humidity, and building construction.

In this paper, several recommendations are proposed to enhance the understanding and application of thermal comfort and urban greenery within the built environment. First, the integration of green infrastructures such as green roofs, vertical green systems, and urban green spaces—should be prioritized in urban planning and design to optimize thermal comfort. Policymakers and urban planners are encouraged to adopt nature-based solutions to mitigate urban heat islands and improve microclimate conditions. Additionally, the study emphasizes the importance of diversifying geographic research to include underrepresented regions beyond countries like China, where most studies are currently concentrated. This would provide a broader understanding of the relationship between thermal comfort and urban greenery in varied climatic, cultural, and urban contexts. The use of advanced simulation tools and software for predictive modeling is also recommended to assess the cooling benefits of urban greenery at various scales. This can support evidence-based decision-making for future urban development. Furthermore, the paper highlights the need for cross-disciplinary collaborations between architects, urban planners, environmental scientists, and policymakers to implement holistic strategies for sustainable urban growth. Public awareness campaigns on the benefits of urban greenery and thermal comfort should also be promoted to ensure community participation and acceptance of green infrastructure initiatives. These recommendations aim to bridge research gaps and support the practical implementation of sustainable urban strategies.