A Systematic Review of Vertical Greenery: Environmental Impacts, Architectural Innovations, and Future Directions

Abstract

Vertical greenery is increasingly applied in modern cities for environmental improvement and landscape enhancement. Given the insufficient coverage of recent developments in research and practice by prior reviews, this paper conducts a systematic review based on literature from Web of Science and global patent databases following PRISMA guidelines, with CiteSpace used for bibliometric analysis. This study summarizes the theoretical achievements of vertical greenery in ecological environment, building energy efficiency and technical materials. It also analyzes practical innovations via patent mining—a new supplement compared with traditional reviews. The environmental impacts of both outdoor and indoor vertical greenery are elaborated on: outdoor systems improve urban microclimate, noise control and air quality; indoor systems enhance indoor comfort, air purification and people’s mental status. Current innovations are categorized into structure and equipment, intelligent management, and social–cultural values. The outcomes of this work offer practical guidance for the design, construction and maintenance of vertical greenery in real projects. This paper also identifies future research priorities for the long-term development of vertical greenery.

1. Introduction

Vertical greenery is a sustainable urban green infrastructure that covers vertical surfaces of buildings or artificial structures with growing vegetation, which turns previously unused vertical space into ecologically functional vertical green space [1]. It not only requires minimal land area, yields rapid results, and provides high greening coverage, but it also enhances the esthetic appeal of buildings, making the environment cleaner, more beautiful, and livelier. In an era of increasingly limited urban land, vertical greenery has become a particularly important solution for increasing green coverage and improving residential environments [2].

Vertical greenery has an important environmental impact in urban contexts, such as carbon absorption and oxygen production [3], dust retention [4], noise reduction [5], improving the urban ecological environment [6], adjusting microclimate temperatures and humidity, and mitigating the urban heat island effect [7,8]. Urban ecological governance is a crucial aspect of urban development, with the scale and quality of greening being fundamental elements in shaping the ecological environment. However, due to the urbanization process in recent years, population growth, and the formation of densely populated living environments, the proportion and scale of green spaces in urban construction sites have been limited, making it difficult for greening to fulfill its potential ecological benefits. Recently, vertical greenery has attracted increasing attention for its ability to significantly expand green areas with minimal land use and has been applied in many engineering practices.

For urban environments, vertical greenery can alleviate the urban heat island effect, reduce urban particulate pollution, and improve air quality. It can also enhance the urban ecological environment, achieve a balance between humans and nature, increase biodiversity, and provide habitats for animals [9]. For the buildings to which it is attached, vertical greenery softens the appearance, presenting a favorable ecological visual effect. Plants on building facades can block solar radiation, thus protecting the exterior of the building and extending its lifespan [9]. At the same time, plant transpiration helps cool the building during the summer, reducing energy consumption [10,11]. Indoor vertical greenery also offers environmental benefits. It typically appears in modular structures, beautifying indoor spaces while alleviating fatigue and improving work efficiency [12]. It also purifies indoor air quality, effectively reducing CO₂ and organic compound levels [13], thus providing a healthier indoor environment for people working and living indoors for extended periods.

Vertical greenery is mainly divided into two categories: “Green facades” and “Living walls” (Figure 1). “Green facades” refers to greenery integrated into the building facade, while “Living walls,” also known as “bio-walls,” refers to plants growing directly on the walls, independent of the natural ground. In Germany, these systems are officially referred to as “bodengebundene Begrünung” and “fassadengebundene Begrünung,” which can be translated as “ground-based greening” and “wall-based greening” [1]. “Ground-based greening” involves plant growth naturally supported by the ground, vertically oriented, while “wall-based greening” entails plants being directly planted on the wall, not connected to the natural ground. Some scholars also recognize other types of vertical greenery, such as David Fuller’s “Brown wall systems,” which differ from the two categories mentioned above. Fuller’s classification includes green walls formed by climbing plants growing from seeds in cracks or crevices on walls [2].

While research on vertical greenery has largely focused on thermal performance [14], other key variables, such as light, sound, and wind, remain underexplored. Notably, the sound insulation potential of green walls has rarely been investigated [15].

This paper reviews academic articles on vertical greenery from Web of Science since 2000, summarizing the current research trends, methods, and recent findings, with the aim of providing a reference for future research and innovation in design practices. Specifically, the research focuses on two objectives:

• Summarizing and analyzing the various impacts of vertical greenery on the urban built environment, covering not only thermal environments but also sound, wind, building energy consumption, air quality, ecological environments, and psychological effects.
• Reviewing and analyzing classic cases and patent innovations, categorizing the development of vertical greenery into structure and equipment, control and management, and social and cultural values, and summarizing current trends and future directions.

2. Methods

To fulfill the research objectives, a comprehensive review of relevant literature and patent databases was conducted. This study strictly follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (illustrated in Figure 2). The PRISMA 2020 Checklist can be found in Supplemental Materials (Table S1).

The research on the impact of vertical greenery on urban built environment is based on literature from the Web of Science Core Collection, with the search query being TS = (green façade OR green wall OR living wall OR vertical greenery system) AND TS = (heating energy OR cooling energy OR building energy OR urban heat island OR UHI OR air quality OR human psychology OR acoustics). The timespan was set from 2000 to 2025, and the document types were limited to research articles and reviews, yielding an initial total of 2522 records. All records were imported into reference management software, and 1390 duplicates were automatically identified and removed by matching fields such as the title, author, and DOI, leaving 1132 records for the initial screening phase.

In the initial screening phase, relevance was assessed according to predefined inclusion and exclusion criteria. The inclusion criteria were as follows: studies had to address the impact of vertical greenery systems (green façades or living walls) on indoor or outdoor physical environmental parameters or on human psychology, and had to be peer-reviewed English-language papers. Exclusion criteria included: (1) incomplete research such as conference abstracts and editorial letters; (2) studies focusing exclusively on green roofs without addressing vertical wall greening; (3) studies falling purely within plant physiology or horticulture without discussing building environmental effects; and (4) literature for which titles and abstracts were inaccessible. Following our pre-defined inclusion/exclusion criteria, this screening round filtered out 858 ineligible records, retaining 274 records for full-text assessment in the subsequent manual screening step.

In the full-text assessment phase, the research team obtained the full texts of all retained records and evaluated each one in detail. Studies lacking adequate relevance to vertical greenery were further excluded. To improve the reliability of manual screening, all retained records were subjected to independent full-text assessment by two authors, and inter-rater reliability was verified via the Cohen’s kappa test. Any disagreements were first settled through discussion to reach a consensus. If negotiation failed to resolve discrepancies, a third reviewer with relevant research expertise was invited to make the final judgment. Cohen’s kappa coefficient was adopted to measure inter-rater reliability. A coefficient of 0.76 demonstrated substantial agreement between the two raters. Ultimately, 71 high-quality research articles were included in the qualitative or quantitative synthesis, forming the core evidence base for the discussion of built environment impacts in this paper.

The literature was divided into two main categories: “outdoor vertical greenery” and “indoor vertical greenery”. Within the outdoor vertical greenery category, research was further classified based on the impacts on thermal environment, acoustic environment, wind environment, building energy consumption, and the effects on air quality and ecological environment. The indoor vertical greenery section was further divided into impacts on thermal comfort and human comfort, sound environment, air quality, and effects on human psychology and health. The review also included the research methods, experimental setups, and simulation software used, along with the research conclusions. Finally, based on bibliometric and content analysis, current research trends, hot topics, and gaps in vertical greenery studies were summarized. A meta-analysis was conducted with reference to the Köppen climate classification system (Appendix A

Table A1. The Köppen climate classification used in the text.

Code	Ecological Climate Type
Af	Equatorial, fully humid
Am	Equatorial, monsoonal
Aw	Equatorial, winter dry
BWh	Arid, desert, hot arid
BWk	Arid, desert, cold arid
BSk	Arid, steppe, cold arid
BSh	Arid, steppe, hot arid
Cfa	Warm temperate, fully humid, hot summer
Cfb	Warm temperate, fully humid, warm summer
Csa	Warm temperate, summer dry, hot summer
Csb	Warm temperate, summer dry, warm summer
Cwa	Warm temperate, winter dry, hot summer
Dfa	Snow, fully humid, hot summer
Dfb	Snow, fully humid, warm summer
Dwa	Snow, winter dry, hot summer

).

To track the frontiers of vertical greenery practice and innovation, a systematic search and screening of patents and built cases was conducted in parallel (illustrated in Figure 2). Search sources included patent databases such as Google Patents, Espacenet, USPTO, and WIPO, as well as architectural and landscape design websites including Archdaily, Dezeen, Designboom, Archinect, Gooood, Arch2o and Afasia archzine. The search used the keywords “(green facades) OR (green wall) OR (living wall) OR (vertical greenery system)”, supplemented by patent citations retrieved from Web of Science, and yielded an initial pool of over 10,000 results. An initial relevance screening was then performed based on titles and abstracts. Inclusion criteria focused on vertical greenery inventions and projects that were integrated with building walls, involved indoor or outdoor applications, exhibited structural system innovations, or possessed clear socio-cultural value. Exclusion criteria included: (1) items relating solely to general agricultural apparatus; (2) standalone irrigation components; (3) cultivation techniques not associated with the building envelope; and (4) entries that were purely product promotions without technical details. After initial screening, 200 patents and 200 practical cases were retained for secondary manual screening. The manual screening process involved reviewing patent specifications, construction drawings, on-site photos and legal claims to assess their relevance to vertical greenery research and applications. A total of 25 patents and 15 projects were ultimately selected for detailed classified analysis and technical trend exploration. Again, Cohen’s kappa coefficient was calculated for the full-text screening stage to quantify inter-rater reliability, yielding a kappa value of 0.71, which indicates substantial consistency between the two raters’ judgements.

3. Results and Analysis

3.1. Literature Search Results

After conducting a literature search on Web of Science, a total of 2522 articles related to the built environment were retrieved (as of 31 December 2025), among which the majority pertained to the influence of vertical greenery on the indoor and outdoor thermal environments of buildings and the urban heat island effect. In terms of the publication time of the literature, the included articles demonstrate a year-on-year ascending trend, with a relatively marked growth amplitude (Figure 3).

The research orientations are mainly distributed in construction building technology, civil engineering, energy fuels, environmental sciences, green sustainable science technology, environmental engineering, environmental studies, multidisciplinary materials science, thermodynamics, mechanics, mechanical engineering, chemical engineering, acoustics, applied physics, multidisciplinary chemistry, etc. (Figure 4).

Following the PRISMA workflow illustrated in Figure 2, 274 records were retained after identification and initial screening. Further manual relevance screening narrowed down the pool to 71 articles, which served as the valid dataset for subsequent bibliometric analysis. Using this dataset, we performed CiteSpace analysis, and the resulting keyword co-occurrence network is displayed in Figure 5. The most frequent keywords include performance, building, temperature, thermal performance, system, energy performance, impact, design, urban heat island and energy.

CiteSpace was used to generate a heat map illustrating authors’ countries of origin (Figure 6). The results show that the major contributing countries include China, the United States, Italy, the United Kingdom, Australia, India, Spain and Germany.

By using CiteSpace to perform Citation Bursts analysis (Figure 7), it was revealed that the term with the strongest strength was “green infrastructure”, with a duration from 2020 to 2021. Simultaneously, it could be noted that other top-ranked terms in terms of strength, such as “thermal comfort” and “comfort”, were also significantly related to thermal comfort, suggesting that in recent years, related articles have paid more attention to the thermal environment. By sorting the top 10 keywords with the strongest strength over time, it was found that researchers’ attention might have shifted from terms such as “environment”, “vegetation”, “climate”, “green roofs”, and “green infrastructure” during 2012–2020 to terms such as “living walls”, “design”, “green walls”, “thermal comfort”, and “model” during 2020–2025.

Based on the citation burst map presented in Figure 7, the research hotspots in vertical greenery can be summarized into two distinct phases. In the first phase (approximately 2012–2020), the burst keywords are predominantly macro-ecological and environmental themes such as “green infrastructure”, “green roofs”, “climate”, “environment”, and “vegetation”, indicating that early studies focused on the ecosystem services of vertical greenery, including climate mitigation, urban heat island regulation, and habitat provision. In the second phase (2020–2025), the hotspots shift rapidly toward more performance-oriented terms, namely “living walls”, “green walls”, “thermal comfort”, “design”, and “model”, reflecting a transition from proof-of-concept investigations to optimization-driven technical and design research, with particular emphasis on thermal comfort modeling, system integration, and parametric design. In terms of evolutionary trajectory, the strongest burst term is “green infrastructure”, which peaks during 2020–2021—a period bridging the two phases—suggesting that macro-ecological values remain foundational. Subsequently, the sustained bursts of “thermal comfort” and “model” signal a paradigm shift from an ecologically dominant discourse towards engineering-driven performance evaluation. Overall, the field of vertical greenery research has evolved from conceptual ecological arguments to quantitative, human-centric, and model-supported design optimization.

Table 1. Statistics on research topics and Köppen climate classification.

Climate	Thermal Environment	Acoustic Environment	Wind Environment	Energy Consumption	Air Quality	Health
Af	—	—	—	1	—	—
Aw	1	—	—	—	—	—
BWk	—	—	—	—	1	—
BSk	—	—	—	2	—	—
Cfa	4	1	—	2	2	2
Cfb	5	—	1	1	4	1
Csa	5	2	—	1	1	—
Cwa	3	—	—	1	2	1
Dfa	—	—	1	—	—	—
Dfb	1	—	—	—	1	1
Dwa	—	—	—	—	—	1

shows statistics on research topics and Köppen climate classification. The distribution pattern of relevant research reflects not only regional differences in practical environmental demands, but also the concentration of academic resources and long-standing research traditions. The most intensively investigated topic is the thermal environment in temperate climates (Group C), which are substantially higher than those of other topics and climate zones. Additionally, air quality constitutes a secondary research hotspot. In contrast, several topics remain understudied. Wind environment and energy consumption each have merely one publication across all climate types and have never been mainstream research focuses. Except for two publications in the Csa climate, acoustic environment only has one publication in other climate zones. Likewise, thermal environment yields just one publication in continental climates (Dfa, Dfb, Dwa), forming a stark contrast with Group C temperate climates.

Such distribution discrepancies can be explained by multiple factors. Group C temperate regions (e.g., Western Europe, East Asia and the west coast of North America) feature dense populations, developed economies and strong demands for thermal comfort in summer, driving sustained research attention to the thermal environment. In continental climates (Group D) with frigid winters, research interests tend to shift towards heating energy consumption and the health impacts of extreme low temperatures, resulting in limited studies on the thermal environment. The abundant literature on air quality in the tropical savanna, semi-arid and partial continental climate zones is probably linked to biomass burning, dust pollution and coal combustion in winter in these areas. The prominent research on human health in Cfb regions may be attributed to the high aging population and well-established research traditions of healthy buildings locally. The generally low publication volume regarding wind environment, energy consumption and acoustic environment suggests that these topics are mostly treated as secondary variables in existing studies.

3.2. Case and Patent Search Results

A total of over 200 vertical greenery projects were collected and sorted out from mainstream landscape design platforms including Archdaily, Dezeen, Designboom, Archinect, Gooood, Arch2o and Afasia archzine. Among them, 15 representative cases were selected for a comparative analysis in Section 4.2.1.

The initial search on Google Patents yielded over 10,000 results. Figure 8 reveals that vertical greenery-related patents were scarce from 2001 to 2010, yet their publications have risen year on year starting from 2005. The patent count hit a peak in 2020 and declined moderately in 2021–2022, reflecting a generally growing trend of relevant patents for innovative architectural designs. After initial filtering, 200 patents underwent manual review, and 25 representative patents were selected for detailed analysis in Section 4.2.2.

4. Discussion

4.1. The Impact of Vertical Greenery on the Built Environment

Vertical greenery exerts a vital influence on both the indoor and outdoor environments of buildings. In order to structure the subsequent review systematically, the research categories examined in this section were derived from a synthesis of bibliometric trends and thematic clustering observed in the retrieved literature. As illustrated in the co-occurrence network of keywords (Figure 5), terms such as “thermal performance,” “energy performance,” “urban heat island,” “air quality,” “acoustics,” and “comfort” appear with high frequency and strong centrality, indicating that these are the principal dimensions along which the environmental impacts of vertical greenery have been investigated. Furthermore, the citation burst analysis (Figure 7) reveals a temporal evolution of research foci—from early emphases on “green infrastructure” and “climate” toward more recent concerns with “living walls,” “thermal comfort,” and “model.” This shift underscores a growing recognition that vertical greenery’s effects extend beyond thermal regulation alone, encompassing a broader spectrum of microclimatic, energetic, and human-centric outcomes.

Consequently, the following subsections are organized to reflect these emergent thematic clusters:

In Section 4.1.1, this review first summarizes the common experimental methods and testing instruments adopted across various research themes, so as to systematically illustrate the general methodologies and tools repeatedly applied in Section 4.1.2 and Section 4.1.3.

In Section 4.1.2, the review addresses outdoor impacts, which constitute the majority of the extant literature, and are further subdivided into:

▪

Thermal environments, encompassing both surface temperature modulation and ambient microclimate cooling;

▪

Acoustic environments, focusing on noise attenuation mechanisms and frequency-dependent performance;

▪

Wind environments, where vegetation is conceptualized as a porous medium influencing airflow and ventilation;

▪

Building energy consumption, which integrates thermal and aerodynamic effects to assess net heating and cooling demand;

▪

Air quality and ecological value, including particulate matter capture, gaseous pollutant removal, and biodiversity support.

In Section 4.1.3, the review turns to indoor impacts, a comparatively nascent but rapidly expanding domain. Here, the analysis is structured around:

▪

Thermal environment and human comfort, examining how active and passive systems modify temperature, humidity, and occupant satisfaction;

▪

Acoustic environment, evaluating sound absorption contributions to interior acoustic quality;

▪

Air quality, with particular attention to CO₂, VOCs, and formaldehyde remediation;

▪

Psychological well-being and health, a category that has gained prominence in the post-2020 literature and addresses stress reduction, cognitive performance, and biophilic responses.

4.1.1. Research Methods and Equipment for Existing Studies

In studies exploring the impact of vertical greenery on indoor and outdoor thermal environments, the predominant research approaches include experimental measurement, software simulation, and a combination of both for validation. Empirical measurements frequently employ instruments such as air temperature and humidity meters, infrared thermometers, micro-weather stations, thermistors, heat flux meters, and solar radiation sensors. These tools are critical for quantifying surface temperature reductions, ambient cooling effects, and latent heat dissipation from plant transpiration. For simulation-based inquiries, software platforms such as TAS [16], EnergyPlus [17], and ENVI-met [18,19] are widely adopted. These tools allow researchers to model complex interactions—such as shading coefficients, leaf area density (LAD), and substrate moisture—under varying climatic scenarios without the constraints of physical prototypes.

Investigations into the acoustic environment rely predominantly on empirical measurement. The primary objective is to quantify sound absorption and scattering properties of both the vegetation layer and the substrate. Standard instrumentation includes integrated sound level meters, acoustic analyzers [20], alarm guns or loudspeakers [21] (as controlled noise sources), microphones [22], and impedance guns [23]. The choice of equipment is determined by the need to differentiate between high-frequency scattering by foliage and low-to-medium frequency absorption by the porous growing medium.

Research concerning the wind environment and its interaction with VGS often employs a combination of empirical measurement and Computational Fluid Dynamics (CFD) modeling. Empirical setups utilize humidity and temperature data loggers, thermocouples, solar radiation meters, and wind speed sensors to capture the microclimatic changes in the air cavity behind the greenery [24]. Simulation studies, often using software like ImageJ [25] for leaf area analysis or dedicated CFD platforms [18,25,26], model vegetation as a porous medium using equations such as Darcy–Forchheimer to predict airflow modification and its subsequent effect on building ventilation and thermal resistance.

For air quality assessments, the research methods vary slightly between outdoor and indoor contexts due to differing pollutant profiles. Outdoor studies often involve electron microscopes and image analysis software (e.g., ImageJ, INCA [9]) to quantify particulate matter (PM) deposition on leaf surfaces. Indoor air quality research, conversely, focuses on volatile organic compounds (VOCs) and CO₂ removal. This necessitates the use of indoor environmental monitoring instruments [27], PTFE tubes, adsorbent tubes, sampling pumps, flow meters, and photometers [28]. These tools facilitate the calculation of single-pass removal efficiency and clean air delivery rates in active biofiltration systems.

Finally, studies on human comfort and psychological well-being rely heavily on human-centric methodologies. Beyond the environmental sensors (temperature and humidity recorders [29,30], air velocity meters [30], button skin thermometers [31]) used to correlate physical conditions with subjective responses, research in this domain frequently employs questionnaires, scales (e.g., State-Trait Anxiety Inventory), and physiological monitoring (e.g., electroencephalography, skin conductance) [32]. More recently, virtual reality (VR) environments have been utilized to isolate the visual and psychological impacts of biophilic design from confounding environmental variables [33].

In summary, the methodological landscape of vertical greenery research is diverse and application-specific. While thermal performance studies dominate the field—reflected in the widespread use of energy simulation software—recent advancements have seen the integration of artificial intelligence (AI) and high-throughput remote sensing. For instance, Helman et al. [34] demonstrated the use of AI to interpret high-throughput camera data for continuous monitoring of plant health and the microclimate, signaling a shift toward more autonomous and data-driven research paradigms.

4.1.2. The Impact of Outdoor Vertical Greenery on the Built Environment

Impact of Thermal Environments

Vertical greenery regulates building surface temperature and urban microclimate mainly through two dominant mechanisms: foliage shading and plant transpiration, among which the shading effect plays a leading role [34]. Its cooling performance is significantly governed by leaf area density, vegetation coverage, substrate properties and building orientation, with obvious seasonal variations and climatic zone discrepancies (Table 2).

In summer, dense foliage provides prominent shading and greatly reduces solar heat gain of building envelopes. In winter, deciduous vegetation allows solar transmission for passive heating, while evergreen greenery may increase thermal resistance and heating load. In general, living walls outperform conventional green facades due to thicker substrates, independent air cavities and complete irrigation systems [35].

Across tropical, subtropical, temperate and Mediterranean climates, vertical greenery presents stable cooling benefits. The wall surface temperature can be reduced by up to 26 °C in subtropical regions [36], while a 10–21.6 °C reduction is commonly observed in temperate areas [33], with the Mean Radiant Temperature decreased by around 5 °C [37]. Vegetation coverage shows a positive correlation with cooling effect: each 10% coverage increase corresponds to a 0.6–0.9 °C surface temperature drop, reaching the optimal performance at 36.1% coverage [38].

Table 2. The impact of outdoor vertical greenery on thermal environments.

Location	Climate	Type	Season	Findings	Instrument/ Software	Reference
Nagoya, Japan	Cfa	Green facades	Summer	Per 10% increase in coverage, wall surface temperature ↓0.6–0.9 °C. Maximum reduction ↓10.2 °C at 36.1% coverage.	Infrared thermometer	[38]
Brighton, UK	Cfb	Green facades	Year-round	GF reduced solar radiation by 70% via multilayered foliage.	Thermistor Heat flux meter	[39]
Berlin, Germany	Cfb	Green facades	Summer	Exterior wall temperature ↓15.5 °C (80% shading). Irrigation demand: 2.5 L·d−1·m−2.	Pyrheliometer	[40]
La Rochelle, France	Cfb	Living wall	Summer & Winter	Summer: Façade temperature ↓15 °C; Heat gain ↓97%. Winter: Heat loss ↓30%; Heat gain ↓40% (insulation/shading effects).	Solar flux sensor	[41]
Hong Kong, China	Cwa	Green facades	Winter	Air cavity temperature ↑4–6 °C by passive indoor warming.	Portable transpiration measuring instrument	[42]
Baishizhou, Shenzhen	Cwa	Green facades	Summer	Outdoor air temperature ↓16.2 °C; Building surface temperature ↓37 °C.	Rhino7 grasshopper ENVI-met	[19]
Alaba, Spain	Cfb	Living wall	Summer & Winter	Summer: External wall temperature ↓10 °C; Solar absorptivity↓85%. Thermal resistance ↑49%.	Surface temperature sensors Heat flux sensor	[43]
Toronto, Canada,	Dfb	Green facades	Summer	Surface temperature ↓7.0 °C (enhanced efficacy on south-oriented façades).	HOBO Temperature Data Loggers Radiation Shield Weather Station	[44]
Seville, Spain	Csa	Living wall	Summer	MRT ↓5 °C UTCI ↓0.4–1.2 °C.	Thermo-Hygrometer Anemometer Testo 905 T2 Thermometer ENVI-met (version 5.1.1)	[37]
Turin, Italy	Cfa	Living wall	Year-round	Peak summer: MRT ↓1.6–2.27 °C. Winter: Air temperature ↓1.6 °C; UTCI improvement (↓0.55 °C thermal stress).	Landsat-9 satellite EnergyPlus ArcGIS Pro Anemometers, pyranometers	[45]

Note: ↑ indicates an increase, ↓ indicates a decline. MRT: Mean Radiant Temperature. UTCI: Universal Thermal Climate Index.

Table 2. The impact of outdoor vertical greenery on thermal environments.

Location	Climate	Type	Season	Findings	Instrument/ Software	Reference
Nagoya, Japan	Cfa	Green facades	Summer	Per 10% increase in coverage, wall surface temperature ↓0.6–0.9 °C. Maximum reduction ↓10.2 °C at 36.1% coverage.	Infrared thermometer	[38]
Brighton, UK	Cfb	Green facades	Year-round	GF reduced solar radiation by 70% via multilayered foliage.	Thermistor Heat flux meter	[39]
Berlin, Germany	Cfb	Green facades	Summer	Exterior wall temperature ↓15.5 °C (80% shading). Irrigation demand: 2.5 L·d−1·m−2.	Pyrheliometer	[40]
La Rochelle, France	Cfb	Living wall	Summer & Winter	Summer: Façade temperature ↓15 °C; Heat gain ↓97%. Winter: Heat loss ↓30%; Heat gain ↓40% (insulation/shading effects).	Solar flux sensor	[41]
Hong Kong, China	Cwa	Green facades	Winter	Air cavity temperature ↑4–6 °C by passive indoor warming.	Portable transpiration measuring instrument	[42]
Baishizhou, Shenzhen	Cwa	Green facades	Summer	Outdoor air temperature ↓16.2 °C; Building surface temperature ↓37 °C.	Rhino7 grasshopper ENVI-met	[19]
Alaba, Spain	Cfb	Living wall	Summer & Winter	Summer: External wall temperature ↓10 °C; Solar absorptivity↓85%. Thermal resistance ↑49%.	Surface temperature sensors Heat flux sensor	[43]
Toronto, Canada,	Dfb	Green facades	Summer	Surface temperature ↓7.0 °C (enhanced efficacy on south-oriented façades).	HOBO Temperature Data Loggers Radiation Shield Weather Station	[44]
Seville, Spain	Csa	Living wall	Summer	MRT ↓5 °C UTCI ↓0.4–1.2 °C.	Thermo-Hygrometer Anemometer Testo 905 T2 Thermometer ENVI-met (version 5.1.1)	[37]
Turin, Italy	Cfa	Living wall	Year-round	Peak summer: MRT ↓1.6–2.27 °C. Winter: Air temperature ↓1.6 °C; UTCI improvement (↓0.55 °C thermal stress).	Landsat-9 satellite EnergyPlus ArcGIS Pro Anemometers, pyranometers	[45]

Note: ↑ indicates an increase, ↓ indicates a decline. MRT: Mean Radiant Temperature. UTCI: Universal Thermal Climate Index.

Impact of Outdoor Vertical Greenery on Acoustic Environment

Vertical greenery mitigates urban traffic noise through the combined effect of plant scattering and substrate absorption (

Table 3. The impact of outdoor vertical greenery on acoustic environment.

Location	Climate	Type	Season	Findings	Instrument/ Software	Reference
Nanjing, China	Cfa	Green facades & living wall	Year-round	Noise reduction: GF: ↓12.4 dB (in 75–80 dB), ↓7.5 dB (in 50–55 dB), ↓5.7 dB (in 30–35 dB) LW: ↓15.6 dB (in 75–80 dB), ↓9.3 dB (in 50–55 dB), ↓7.0 dB (in 30–35 dB).	Loudspeaker Acoustic analyzer	[22]
Lelida, Spain	Csa	Living wall	Year-round	Thin vegetation (20–30 cm), sound insulation ↑1–3 dB.	Sound level meter Acoustic analyzer	[21]
Madrid, Spain	Csa	Green facades	Autumn	Sound absorption ↑4–20%; 80% from substrate, 5–20% from vegetation.	Impedance gun Pressure-particle velocity probe Loudspeaker Velo software	[23]

). High-frequency noise is mainly attenuated by foliage scattering, while medium- and low-frequency noise is dominated by porous substrate absorption [21]. Since urban background noise mainly falls within the medium–low range, vertical greenery possesses practical noise reduction potential [5].

Overall, living walls achieve better acoustic performance than green facades [22], with noise reduction ranging from 5.7 dB to 15.6 dB under different sound pressure levels. The substrate contributes 80–90% of total sound absorption, whereas vegetation only accounts for 5–20%. Even in defoliation seasons, green facades can still improve sound absorption by 15–20% [23], proving that substrate characteristic is the core factor determining acoustic performance.

Impact of Outdoor Vertical Greenery on Wind Environment

Vertical greenery can be regarded as a porous medium that reshapes the airflow field around buildings. Plant morphology and structural features directly determine wind resistance and attenuation magnitude [26]. The wind reduction effect varies significantly with building orientation: east- and west-facing green walls reduce wind speed by 42–43%, south-facing ones by about 18%, and north-facing ones show nearly no obvious change [24]. The Darcy–Forchheimer equation combined with CFD simulation provides an effective method to characterize airflow passing through different plant configurations [26]. Representative findings are presented in

Table 4. The impact of outdoor vertical greenery on wind environment.

Location	Climate	Type	Season	Findings	Instrument/ Software	Reference
Antwerp, Belgium	Cfb	Living wall	Year-round	Plant species variation complicates airflow calculation.	Darcy–Forchheimer equation CFD	[26]
Chicago, USA	Dfa	Green facades	Summer	Air velocity ↓0–43% vs. exposed facade (direction-dependent).	Humidity and temperature data logger Thermoelectric couple Meteorological microstation Pyrheliometer Wind speed sensor	[24]

.

Impact of Outdoor Vertical Greenery on Building Energy Consumption

The energy-saving performance of vertical greenery systems (VGS) varies greatly across climate zones (

Table 5. The impact of outdoor vertical greenery on building energy consumption.

Location	Climate	Type	Season	Findings	Instrument/ Software	Reference
Lelida, Spain	BSk	Green facades	Summer	Indoor temp and air conditioner energy ↓ (dependent on plants coverage & moisture).	Illuminometer Digital hygrograph Infrared thermometer	[46]
Hong Kong & Wuhan, China	Cwa & Cfa	Green facades	Summer	Summer: Passive benefit ↑. Winter: Heating demand ↑ (net reduction ↓3%).	EnergyPlus T-thermocouples	[36]
Ghent, Belgium	Cfb	Living wall	Summer & winter	Summer: Indoor temp ↓3.5 °C Winter: Indoor temp ↑1.4 °C Annual energy ↓6%.	Crodeon Reporter Temperature Sensors Weather Station	[48]
Turin, Italy	Cfa	Green facades & living wall	Year-round	Surface temp: GF ↓41% (summer)/26% (winter); LW ↓30% (summer)/18% (winter) Cooling energy: GF ↓15.2%; LW ↓8.5% Heating energy: GF ↑4.5%; LW ↑3.2%.	EnergyPlus Python	[47]
Catalonia, Spain	Csa	Green facades & living wall	Summer & Winter	Summer: Energy saving: LW 58.9%; GF 33.8% Winter: No extra consumption.	Pyranometer Temperature probes	[35]
Singapore	Af	Living wall	Summer	MRT ↓18 °C (74%); Cooling load ↓32%.	Thermal Analysis Software	[16]
Lelida, Spain	BSk	Green facades	Summer	Indoor temp and air conditioner energy ↓ (dependent on plants coverage & moisture).	Illuminometer Digital hygrograph Infrared thermometer	[49]

), whereas their summer cooling effectiveness has been widely verified. Under semi-arid climatic conditions, the energy-saving efficiency of green facades is dominated by vegetation coverage and substrate moisture content, which effectively reduces indoor temperature and air-conditioning consumption [46]. In humid subtropical and monsoon regions, green walls can reduce building exterior surface temperature by up to 26 °C and achieve a net cooling energy saving of 3% in summer; nevertheless, reduced solar heat gain raises heating demand in winter, which reflects the inherent seasonal energy trade-off of vertical greenery [36]. Further quantification from temperate-region experiments reveals that both green facades and living walls cut summer cooling loads by approximately 30%, yet their winter heating consumptions increase by 4.5% and 3.2% respectively, highlighting the necessity of climate-oriented vertical greenery design in temperate zones [47].

Compared with the above climate types, temperate oceanic climates present milder seasonal energy conflicts. Relevant measurements indicate that living walls attain an average summer energy saving of around 44%, in contrast to roughly 20% for green facades; in winter, living walls still deliver a modest energy saving of 3.6% and green facades save 0.8% correspondingly [41]. An additional case study finds that modular living walls decrease peak indoor temperature by 3.5 °C in summer and raise the minimum indoor temperature by 1.4 °C in winter, leading to an annual energy reduction of nearly 6% [48]. For Mediterranean hot–dry summer climates, neither greening type induces extra winter heating consumption; living walls achieve a prominent summer energy saving of nearly 59% versus 34% of green facades, owing to thicker substrate, active irrigation and thermal insulation air gaps behind the green system [35]. In cooling-dominated tropical rainforest climates, vertical greenery shows the most outstanding energy-saving potential: modular living walls reduce Mean Radiant Temperature (MRT) by approximately 74%, accompanied by a 32% drop in building cooling load [16].

In summary, vertical greenery yields remarkable energy savings universally in summer, while its winter energy performance is strongly governed by regional climate and greening configuration. Reasonable selection of greening forms and plant species based on local climate is therefore essential in practical engineering to optimize the annual energy efficiency of buildings.

Impact of Outdoor Vertical Greenery on Air Quality and Ecology

Outdoor vertical greenery serves as a critical strategy for urban ecological restoration [50], improving urban air quality through three core mechanisms: particulate matter dry deposition on foliage, gaseous pollutant absorption, and carbon sequestration, while enhancing urban biodiversity via habitat provision. Based on integrated evidence from field measurements and simulations across multiple climate zones, its ecological benefits show clear quantitative patterns and mechanisms, which are stable overall and significantly influenced by plant type, substrate structure, and system configuration (Table 6).

For particulate matter (PM) removal, vertical greenery achieves purification mainly through foliar adsorption, retention, and deposition, with particularly high efficiency in capturing fine particles (PM_2.5, PM_1.0). Plants with small, waxy, or hairy leaves exhibit stronger PM capture capacity [51]. Among different system forms, textile-substrate green walls show significantly higher PM removal rates than traditional planter-based modules, whereas moss substrates may cause particle resuspension under disturbance, resulting in weaker purification performance [25].

For gaseous pollutant remediation, plant photosynthesis and foliar uptake effectively remove CO₂, NO₂, O₃ and other pollutants from the urban atmosphere, with stable and quantifiable annual absorption per unit area [52]. Vertical greenery systems provide long-term carbon sinks, with cumulative carbon sequestration increasing continuously as plants grow, making them an effective approach for low-carbon urban development [53].

For biodiversity enhancement, vertical greenery offers habitats, shelters, and foraging spaces for urban birds and other animals. The ecological benefits are especially pronounced in winter, when bare building walls provide little protection. Compared with non-greened facades, vertical green walls support significantly higher bird activity and species richness, effectively alleviating habitat fragmentation in high-density cities [9].

Overall, outdoor vertical greenery delivers multiple synergistic benefits in air purification and ecological enhancement, simultaneously reducing dust and pollutants, sequestering carbon, and conserving biodiversity. It is high-performance urban green infrastructure that integrates environmental governance and ecological restoration.

Table 6. The impact of outdoor vertical greenery on air quality and ecological value.

Location	Climate	Type	Season	Findings	Instrument/ Software	Reference
Siena, Italy	Csa	Living wall	Year-round	CO2 capture: 0.44–3.18 kg CO2-eq/m2 (long-term accumulation).	STELLA (version 8.1.4)	[53]
Staffordshire, UK	Cfb	Green facades	Year-round	Avian activity ↑ vs. bare walls (winter habitat value ↑).	Binoculars SPSS	[9]
Antwerp, Belgium	Cfb	Living Wall	Summer	Planter-based LW: PM0.1 ↓2%; PM2.5 ↓4% Textile LW: PM0.1 ↓23%; PM2.5 ↓5% Moss substrate LW: PM0.1 ↑2%; PM2.5 ↑5%.	Scanning Mobility Particle Sizer Optical Particle Sizer Leaf Area Meter (Li-3100) Contact Angle Goniometer Molspin Pulse Magnetiser JR-6 Spinner	[25]
Cologne, Germany	Cfb	Green facades	Year-round	Annual absorption: ~5 kg NO2/ha, ~13 kg O3/ha, ~6000 kg CO2/ha., with species-dependent variation (max 0.20 µg O3/m2/s).	Mid-infrared direct laser absorption spectrometer Cavity-ring-down spectrometer Photosynthetic lamp Levenberg–Marquardt algorithm	[52]

Table 6. The impact of outdoor vertical greenery on air quality and ecological value.

Location	Climate	Type	Season	Findings	Instrument/ Software	Reference
Siena, Italy	Csa	Living wall	Year-round	CO2 capture: 0.44–3.18 kg CO2-eq/m2 (long-term accumulation).	STELLA (version 8.1.4)	[53]
Staffordshire, UK	Cfb	Green facades	Year-round	Avian activity ↑ vs. bare walls (winter habitat value ↑).	Binoculars SPSS	[9]
Antwerp, Belgium	Cfb	Living Wall	Summer	Planter-based LW: PM0.1 ↓2%; PM2.5 ↓4% Textile LW: PM0.1 ↓23%; PM2.5 ↓5% Moss substrate LW: PM0.1 ↑2%; PM2.5 ↑5%.	Scanning Mobility Particle Sizer Optical Particle Sizer Leaf Area Meter (Li-3100) Contact Angle Goniometer Molspin Pulse Magnetiser JR-6 Spinner	[25]
Cologne, Germany	Cfb	Green facades	Year-round	Annual absorption: ~5 kg NO2/ha, ~13 kg O3/ha, ~6000 kg CO2/ha., with species-dependent variation (max 0.20 µg O3/m2/s).	Mid-infrared direct laser absorption spectrometer Cavity-ring-down spectrometer Photosynthetic lamp Levenberg–Marquardt algorithm	[52]

4.1.3. The Impact of Indoor Vertical Greenery on the Built Environment

Impact of Indoor Vertical Greenery on Thermal Environment and Human Comfort

Conventional vertical green walls function as passive biofilters, yet they turn into active vertical green walls when coupled with indoor air-conditioning and ventilation systems. Powered airflow forces outdoor air to pass through the vegetation layer in active systems. By taking advantage of plants’ evaporative cooling performance and biological purification capacity, such systems cut down building ventilation and cooling energy consumption. Existing measurements (see Table 7) prove that active vertical greening can reduce indoor air temperature by 0.8–4.8 °C under subtropical Mediterranean climates [29]. Another study within the same climatic zone further indicates that lightweight walls combined with green facades reduce peak heat flux by 60%, far outperforming conventional masonry walls with merely 10–13% heat reduction [54]. Accordingly, active design remarkably improves the thermal regulation performance of green walls.

Active vertical greening presents superior performance in indoor cooling and humidity modulation compared with passive counterparts. Controlled experiments reveal that when planting substrates are fully saturated and moist, active green walls lower indoor temperature by 1–3 °C, while passive alternatives only achieve a temperature drop of 0.5–2 °C under identical working conditions [55]. In addition, vertical greenery effectively raises indoor relative humidity and facilitates the formation of a more stable indoor microclimate [56]. In terms of solar shading, plant leaf surface temperature stays below 35 °C under given solar irradiance, whereas traditional shading blinds exceed 55 °C, enabling green walls to optimize indoor working environments effectively [57]. Nevertheless, vertical greenery is subject to seasonal energy trade-offs: indoor temperature falls by roughly 0.6 °C in summer, yet plant coverage blocks solar heat gain in winter and triggers an approximately 4% rise in heating demand [58]. Such seasonal trade-offs have been verified by field tests in temperate and humid subtropical climate regions [59].

Vertical green walls positively regulate indoor thermal environments no matter if they are installed indoors or outdoors, and improved thermal conditions directly enhance occupants’ thermal comfort. Long-term monitoring demonstrates that green wall installation significantly upgrades indoor thermal comfort and air quality, alongside a roughly 20% reduction in total building energy use [30]. Questionnaire surveys further confirm that an appropriate indoor vegetation layout improves office workers’ thermal comfort satisfaction by 19–25% [60].

In summary, active living walls deliver better performance than passive systems in cooling, energy savings and thermal comfort enhancement, despite their inherent drawback of higher heating loads in winter. For practical engineering applications, active configurations are thus recommended. Tailoring design solutions to local climatic conditions helps balance seasonal energy use and maximizes overall benefits.

Table 7. Impact of indoor vertical greenery on thermal environment and human comfort.

Location	Climate	Type	Season	Findings	Instrument/ Software	Reference
Seville, Spain	Csa	Living wall	Summer	Temp ↓0.8–4.8 °C (distance-dependent).	Automatic temperature and humidity recorder	[29]
Sydney, Australia	Cfa	Living wall	Year-round	Active system: Temp ↓1–3 °C; Humidity ↑ Passive system: Temp ↓0.5–2 °C; Humidity ↑.	Infrared laser thermometer gas analyzer, test chamber	[55]
Delft, Netherlands	Cfb	Living wall	Year-round	Plant shading vs. blinds: Temp increase 50%.	Test chamber, Stec Simulink	[57]
Rehovot, Israel	Csa	Living wall	Long-term	VGS: Thermal comfort ↑. IAQ ↑; Energy consumption ↓20%.	Temperature, humidity, air velocity and other sensors	[30]
Changzhou, China	Cfa	Living wall	Spring and summer	Indoor temp ↓0.7 °C (seasonal average).	Multi-in-one IEQ monitoring device, outdoor weather station	[59]
Qingdao, China	Cwa	Living wall	Winter	ILW-SAC: Freshness sensation ↑1.32 Thermal comfort ↑1.10.	Indoor thermal environment tester Button skin thermometer Intelligent electric meter	[31]
Florence, Italy	Csa	Living wall	Summer and winter	Summer: Air temp ↓0.6 °C Winter: Heating demand ↑4%.	Thermometer Design builder Energy plus	[58]
Catania, Italy	Csa	Green façades	Summer	Peak temp ↓1.9 °C (lightweight wall) Other walls ↓1.0 °C.	TRNSYS Software Heat Flux Measurements Experimental Mock-ups	[54]
Chennai, India.	Aw	Green facades & living wall	Summer	Indoor air temperature ↓2.3 °C (day)/1.8 °C (night); Indoor relative humidity ↑73.2%.	Temperature and Humidity Sensors Weather Station	[56]

Note: IAQ: indoor air quality. ILW-SAC: indoor living wall-split air conditioners.

Table 7. Impact of indoor vertical greenery on thermal environment and human comfort.

Location	Climate	Type	Season	Findings	Instrument/ Software	Reference
Seville, Spain	Csa	Living wall	Summer	Temp ↓0.8–4.8 °C (distance-dependent).	Automatic temperature and humidity recorder	[29]
Sydney, Australia	Cfa	Living wall	Year-round	Active system: Temp ↓1–3 °C; Humidity ↑ Passive system: Temp ↓0.5–2 °C; Humidity ↑.	Infrared laser thermometer gas analyzer, test chamber	[55]
Delft, Netherlands	Cfb	Living wall	Year-round	Plant shading vs. blinds: Temp increase 50%.	Test chamber, Stec Simulink	[57]
Rehovot, Israel	Csa	Living wall	Long-term	VGS: Thermal comfort ↑. IAQ ↑; Energy consumption ↓20%.	Temperature, humidity, air velocity and other sensors	[30]
Changzhou, China	Cfa	Living wall	Spring and summer	Indoor temp ↓0.7 °C (seasonal average).	Multi-in-one IEQ monitoring device, outdoor weather station	[59]
Qingdao, China	Cwa	Living wall	Winter	ILW-SAC: Freshness sensation ↑1.32 Thermal comfort ↑1.10.	Indoor thermal environment tester Button skin thermometer Intelligent electric meter	[31]
Florence, Italy	Csa	Living wall	Summer and winter	Summer: Air temp ↓0.6 °C Winter: Heating demand ↑4%.	Thermometer Design builder Energy plus	[58]
Catania, Italy	Csa	Green façades	Summer	Peak temp ↓1.9 °C (lightweight wall) Other walls ↓1.0 °C.	TRNSYS Software Heat Flux Measurements Experimental Mock-ups	[54]
Chennai, India.	Aw	Green facades & living wall	Summer	Indoor air temperature ↓2.3 °C (day)/1.8 °C (night); Indoor relative humidity ↑73.2%.	Temperature and Humidity Sensors Weather Station	[56]

Note: IAQ: indoor air quality. ILW-SAC: indoor living wall-split air conditioners.

Impact of Indoor Vertical Greenery on Acoustic Environment

Although research on indoor acoustics remains limited, existing evidence consistently shows that vertical greenery enhances indoor acoustic comfort through foliage sound scattering and porous substrate sound absorption. Large-leaf plants provide stronger mid-to-high frequency absorption than small-leaf plants, and the overall sound absorption coefficient rises with increasing green coverage [49].

Compared with conventional interior finishes and furniture, vertical greenery exhibits superior sound absorption across all frequency bands [5], effectively reducing indoor reverberation time and improving speech intelligibility. It is suitable for spaces demanding high acoustic quality, such as open offices, classrooms, and libraries.

Impact of Indoor Vertical Greenery on Air Quality

Improvements in indoor air quality by vertical greenery are verified by many in situ monitoring and controlled experiments (see

Table 8. Impact of indoor vertical greenery on air quality.

Location	Climate	Type	Season	Findings	Instrument/ Software	Reference
Nanjing, China	Cfa	Living wall	Year-round	CO2 concentration ↓from 12 to 17% in corridors with vertical green walls.	CO2 steel cylinder Air quality monitor Photosynthetically active Radiometer Anemograph	[64]
Qingdao, China	Cwa	Living wall	Summer	In the uninhabited environment, CO2 levels ↓10%	Thermal environment tester Indoor environmental monitoring instrument Laboratory	[27]
Watford, UK	Cfb	Living wall	Year-round	VOCs ↓57% (activated carbon medium).	PTFE tube Adsorbent tube Sampling pump flowmeter	[28]
Chengdu, China	Cwa	Living wall	Year-round	Formaldehyde removal ↑ (flow rate- & species-dependent).	Formaldehyde generator flowmeter Axial flow ventilator Gas sampler Test chamber	[61]
Isfahan, Iran	BWk	Potted plant	Summer	Formaldehyde removal: 65–100%, (max 1.47 mg/m2·h at 14.6 mg/m3 input). Removal was higher in light than dark.	Photometer Air flow meter Test chamber	[63]
Moscow, Russia	Dfb	Green facades & living walls	Year-round	Biotecture with gerbera daisy: Trichloroethylene ↓ 2336 μg/m2; Benzene ↓ 6459 μg/m2. Combining gerbera daisy and bamboo palm: Formaldehyde ↓ below limits by 3.85 mg/m3.	Temperature Sensors Weather Station, Air Quality Monitors ENVI-met	[62]
Guangzhou, China	Cfa	Green facades & living walls	Year-round	CO2 removal ↑1176 mg/h; Fresh air demand ↓13.9–38.5%; Energy consumption ↓28.2%.	Temperature and Humidity Sensors Weather Station, Air Quality Monitors ENVI-met	[13]

Note: VOCs: volatile organic compounds.

), covering three aspects: gaseous pollutant removal, particulate matter interception, and CO₂ regulation. The purification efficiency is governed by plant species, substrate properties, airflow velocity, and lighting conditions. For VOCs and formaldehyde, active bio-filtration systems perform prominently, with single-pass removal efficiencies ranging from 38.15% to 94.42% [61]. Soilless substrates mixed with activated carbon achieve an average of 57% for VOCs such as methyl ethyl ketone [28]. Selected plant combinations (e.g., Gerbera jamesonii with Chrysalidocarpus lutescens) can reduce formaldehyde concentrations below regulatory limits, with unit removal capacities of 2336 μg/m² for trichloroethylene and 6459 μg/m² for benzene [62]. Under prolonged exposure, green plants remove 65–100% of airborne formaldehyde, with better performance under daylight [63]. For particulate matter, plant leaves effectively capture PM_2.5 and PM₁₀ via dry deposition, reducing indoor particle loading. For CO₂ regulation, plant photosynthesis reduces indoor CO₂ concentrations by 10–17% [64]. More specifically, living walls remove 1176 mg CO₂ per hour, reduce fresh air demand by 13.9–38.5%, and cut building energy consumption by 28.2% [13]. Nevertheless, sufficient attention should be paid to CO₂ accumulation caused by the respiration of vertical greenery plants at night. This potential drawback does not negate the application value of vertical greenery, but indicates that systematic consideration is required during design, operation and maintenance.

Impact of Indoor Greenery on Psychological Well-Being and Health

From a biophilic design perspective, a number of empirical studies confirm the positive effects of indoor vertical greenery on psychology and cognition (

Table 9. Effects of indoor greenery on psychological well-being and health.

Location	Climate	Type	Findings	Instrument/ Software	Reference
Qingdao, China	Cwa	Potted plant	Indoor plants can relieve anxiety caused by self-isolation.	Questionnaire	[65]
Oslo, Norway	Dfb	Potted plant	More plants in the field of vision are associated with higher productivity.	Questionnaire	[66]
Amsterdam, Netherlands	Cfb	Potted plant	Students are more active and attentive to learning in an indoor green environment	Questionnaire Scale	[12]
Seoul, Korea	Dwa	Potted plant	The visual stimulation of green leafy plants improves students’ concentration.	Anthropometer Body fat analyzer Wireless electroencephalogram Questionnaire	[32]
Boston, USA	Cfa	Living wall	Participants exposed to indoor greenery had better recovery responses after stressors.	Physiological index measuring instrument Rhino5 VR	[33]
Carolina, USA	Cfa	Living wall	Microalgae appearance had no direct effect on convergent or divergent diversity or mood. Encouraging designers to incorporate biophilic elements into their designs.	Brainstorming for sustainable design	[67]

). Indoor greenery significantly alleviates anxiety and stress, enhances positive emotions, reduces fatigue, and improves attention and work/study efficiency. During the COVID-19 pandemic, over 70% of respondents experienced anxiety, while interest in indoor plants rose by 33% and interaction frequency by 78%; about 61% reported relief from self-isolation anxiety [65]. Virtual reality (VR) studies confirm better stress recovery with indoor greenery [33], and plants in the field of view are correlated with improved task performance and reduced stress [66], including better student attention [32] and lower learning fatigue [12]. Microalgae facades do not hinder creativity but encourage biophilic design solutions [67]. However, a research gap remains: whether large-scale vertical greenery systems provide greater psychological benefits than a few potted plants requires further investigation.

Despite the aforementioned psychological and physiological benefits of indoor vertical greenery, its potential adverse impacts on residents’ health and environmental hygiene cannot be ignored. The persistently humid microclimate, especially under the common indoor conditions of poor ventilation and insufficient light, creates an ideal breeding environment for mold and fungi. Moreover, stagnant water in drainage trays, water-saturated growing substrates and damp plant canopies may facilitate mosquito reproduction. Such insects not only cause physical discomfort and psychological distress to occupants, but also potentially act as carriers of pathogens indoors.

4.2. Configurations and Innovations

4.2.1. Configurations

This section explores representative global vertical greenery projects that have been successfully implemented, demonstrating their efficacy in enhancing urban environments, improving building energy performance, and beautifying urban landscapes. These case studies illustrate the adaptability and feasibility of vertical greenery under various climatic conditions and urban settings, offering valuable insights for future projects.

After analyzing multiple case studies, vertical greenery typologies were categorized into four primary forms (summarized in Figure 9 and

Table 10. Summary of the classic cases of vertical greenery that have emerged worldwide in recent years.

Project Name	Location	Climate	Designer	Completion Year	Type
The Spiral (New York)	New York, USA	Cfa	BIG (Bjarke Ingels Group)	2023	Balcony Garden
Pixel Building	Melbourne, Australia	Cfb	Studio505	2010	Balcony Garden
Marco Polo Tower	Hamburg, Germany	Cfb	Behnisch Architekten	2010	Balcony Garden
CaixaForum Madrid	Madrid, Spain	Csa	Herzog & de Meuron	2008	Facade Integrated Garden
Bosco Verticale	Milan, Italy	Cfb	Stefano Boeri Architetti	2014	Facade Integrated Garden
One Central Park	Sydney, Australia	Cfa	Ateliers Jean Nouvel	2013	Facade Integrated Garden
EDITT Tower	Singapore	Af	TR Hamzah & Yeang	Uncompleted	Facade Integrated Garden
Quai Branly Museum	Paris, France	Cfb	Jean Nouvel	2006	Facade Integrated Garden
The Vertical Forest (Nanjing)	Nanjing, China	Cfa	Stefano Boeri Architetti	2018	Facade Integrated Garden
Oasia Hotel Downtown	Singapore	Af	WOHA Architects	2016	Facade Integrated Garden
PARKROYAL on Pickering	Singapore	Af	WOHA Architects	2013	Sky Garden
Sky Garden at 20 Fenchurch Street	London, UK	Cfb	Rafael Viñoly Architects	2014	Sky Garden
Gardens by the Bay	Singapore	Af	Grant Associates, Wilkinson Eyre	2012	Sky Garden
The Interlace	Singapore	Af	OMA/Buro Ole Scheeren	2013	Staggered Roof Garden
ACROS Fukuoka Prefectural Hall	Fukuoka, Japan	Cfa	Emilio Ambasz & Associates	1995	Staggered Roof Garden

):

Balcony Garden:

This typology utilizes the vertical space of balconies or terraces for greening. It expands the greenery coverage of buildings while adding depth and natural appeal to the visual design. Through climbing plants or potted setups on balcony railings and walls, this approach enhances exterior esthetics and boosts indoor living comfort.

Completed in 2023 and designed by BIG, The Spiral in New York extends nature from the ground level up to its 66-story tower through setback spiral balcony greening, forming a continuous vertical ecosystem within high-rise architecture. The Pixel Building in Melbourne, finished in 2010 and designed by Studio505, integrates balcony greenery onto its colorful zero-carbon building envelope, marking Australia’s first carbon-neutral office building. The Marco Polo Tower in Hamburg, completed in 2010 by Behnisch Architekten, features greenery arranged on rotating balconies of each floor. This design provides residents with private sky gardens and delivers shading effects for the lower floors.

Facade-Integrated:

Wall-mounted vertical greenery integrates green systems into building facades, such as modular growing systems, planting troughs, or vine trellises. These systems are closely attached to walls, providing structural support for plants while offering shading and insulation benefits. Additionally, they contribute to microclimatic improvements in the surrounding environment.

Completed in 2008 and designed by Herzog and de Meuron, CaixaForum Madrid features a 24 m high vertical garden created by Patrick Blanc. Covering a wall area of approximately 460 m², it accommodates more than 15,000 plants of over 250 species and has become a vital cultural landmark in Madrid. One Central Park in Sydney, completed in 2013 and designed by Ateliers Jean Nouvel, integrates vertical gardens designed by botanist Patrick Blanc with a daylight reflection system, realizing an ecological facade for large-scale mixed-use buildings. The Quai Branly Museum in Paris, finished in 2006 under the design of Jean Nouvel, possesses a green wall of around 800 m² and ranks among the most representative public building cases of vertical greenery in Paris. Oasia Hotel Downtown Singapore, completed in 2016 and designed by WOHA, incorporates multi-layered sky greenery into the tower wrapped with a red aluminum mesh facade, with its vegetation coverage reaching ten times the original site area.

Sky Garden:

This type utilizes indoor and outdoor spaces at different vertical levels of the building to accommodate greenery. It is particularly suitable for high-rise and super tall buildings, as the wind speed at high altitudes is much higher than on the ground floor, which can easily cause plant shedding and maintenance difficulties [68]. The multi-layered arrangement enriches plant distribution and creates diverse ecological habitats, creating a natural feeling in an artificial environment.

The Sky Garden at 20 Fenchurch Street in London, completed in 2014 and designed by Rafael Viñoly, is celebrated for its three-tier public sky gardens on the 36th to 38th floors, known as the “oasis in the sky” inside the Walkie Talkie Building. Singapore’s Gardens by the Bay, delivered in 2012 through the collaborative design of Grant Associates and Wilkinson Eyre, feature iconic Supertree vertical green structures, establishing themself as a distinctive urban landscape and eco-tourism landmark of Singapore.

Staggered Roof Garden:

This type extends roof greening across various heights and stepped roof platforms, maximizing spatial utility. Stepped roof greening is typically employed in high-rise buildings or large-scale rooftops, significantly enhancing ecological performance by regulating temperature, improving air quality, and boosting visual appeal.

Designed by OMA/Buro Ole Scheeren and completed in 2013, The Interlace in Singapore consists of 31 six-story residential blocks arranged in a staggered stacking layout. The complex forms eight large courtyards and staggered roof gardens, pioneering an innovative low-density high-rise residential typology. ACROS Fukuoka Prefectural Hall in Fukuoka, finished in 1995 and designed by Emilio Ambasz and Associates, adopts a terraced setback roof garden to create an accessible green hill in the city center. It is a classic pioneering precedent integrating early ecological architecture with vertical greenery.

In recent years, vertical greenery has developed rapidly, and some classic built-up cases have emerged in those four types. The main considerations for designing vertical greenery are also different.

In tropical regions, exemplified by Singapore’s PARKROYAL on Pickering, the primary purpose is combating intense heat and humidity; this necessitates the special consideration of selecting high-transpiration, humidity-tolerant species like ferns and banyans, yielding the outcome of effective microclimate cooling and enhanced local biodiversity. Conversely, temperate projects like Milan’s Bosco Verticale prioritize seasonal energy balance, demanding the special consideration of integrating deciduous trees to provide summer shade while permitting winter solar gain, achieving the outcome of year-round building envelope thermal regulation and reduced HVAC (Heating, Ventilation, and Air Conditioning) loads. Beyond climate adaptation, a core purpose across leading projects is ensuring operational efficiency and resilience. This drives extensive technological integration, such as the sophisticated rainwater harvesting in Singapore’s EDITT Tower (special consideration for water scarcity), which delivers a measurable outcome of about 40% potable water savings, alongside IoT monitoring systems optimizing plant health and maintenance. Crucially, these projects converge in delivering significant multifunctional ecological benefits as a core purpose: shared outcomes include substantial urban heat island mitigation (5–8 °C surface cooling), notable carbon sequestration (about 30 tons CO₂ annually absorbed by Bosco Verticale), and biodiversity enhancement, while construction considerations like Nanjing’s use of 2800 prefabricated modules demonstrate enhanced feasibility and speed.

Looking forward, the purpose shifts towards mainstream sustainability accessibility, propelled by emerging trends featuring AI-optimized planting (e.g., Melbourne’s Pixel Building), lightweight materials like 3D printing reducing costs (about 25%), and socially engaging edible gardens (e.g., NYC’s The Spiral), collectively advancing vertical greenery beyond iconic statements towards practical, scalable urban ecological infrastructure.

4.2.2. Patents and Innovations

Vertical greenery, as a green building technology, demonstrates broad development prospects and significant ecological benefits. Nevertheless, its high maintenance costs, technical challenges, sustainability issues, and social acceptance still constitute the main obstacles that need to be overcome in future development. With the continuous progress of technology and the growing social concern for environmental issues, vertical greenery is anticipated to gain wider application and improvement in the future. In addition to practical cases, patents related to vertical greenery are also increasing year by year. However, discussions on patents related to vertical greenery are relatively scarce. Therefore, this part mainly presents the innovations based on relevant patents (Figure 10 and

Table 11. Summary of typical vertical greenery patents.

Patent	Citation	Title of the Patent	Category	Publication Date
US20180255711A1	[69]	Green wall with overlapping hexagonal shaped modules on a vertical structure	Structure and equipment	13 September 2018
US9974243B2	[70]	Systems, methods, and devices for aeroponic plant growth	Structure and equipment	22 May 2018
US10681881B2	[71]	Apparatus and method for automated aeroponic systems for growing plants	Structure and equipment	16 June 2020
US9359759B2	[72]	Ecological construction systems for buildings with green walls	Structure and equipment	7 June 2016
US11291173B2	[73]	Growth device for crops, use of such a device, and a series of growth devices	Structure and equipment	5 April 2022
EP2734034B1	[74]	Vorrichtung zum züchten von pflanzen	Structure and equipment	27 June 2018
CN102177821A	[75]	Three-dimensional greening device combined with functional baffle and method	Structure and equipment	18 April 2012
CN212079128U	[76]	Double-layer window suitable for green building	Structure and equipment	4 December 2020
CN212414007U	[77]	Ecological garden landscape wall	Structure and equipment	29 January 2021
CN112177098A	[78]	Green building structure and construction method thereof	Structure and equipment	5 January 2021
CN205491894U	[79]	Climb a vegetables balcony and plant frame	Structure and equipment	24 August 2016
WO2019137063A	[80]	Solar-driven intelligent vertical greenery ecological sunshade device	Structure and equipment	18 July 2019
CN221615666U	[81]	Vertical greenery system for curved building facades	Structure and equipment	30 August 2024
CN109691327A	[82]	Prefabricated vertical greenery flexible modules, systems, and construction methods	Structure and equipment	30 April 2019
CN104871865A	[83]	A green wall system that can be quickly assembled and disassembled	Structure and equipment	12 June 2015
CN109041898A	[84]	A quickly detachable rainwater collection green wall	Structure and equipment	21 December 2018
US10271485B2	[85]	Method and apparatus for growing plants	Control and management	30 April 2019
KR102238511B1	[86]	Indoor wall greening maintenance system to reduce fine dust	Control and management	13 April 2021
KR102136364B1	[87]	Air Cleaning System and Method having Electrostatic Precipitator and Vegetation Filters	Control and management	21 July 2020
KR102268653B1	[88]	Wall planting structure with air purification	Control and management	23 June 2021
US20200163285A1	[89]	Sustainable tandem vertical farming system for urban shopping centers	Control and management	28 May 2020
US11771016B2	[90]	System and method for growing plants and monitoring growth of plants	Control and management	3 October 2023
WO2011148011A1	[91]	Green wall system	Control and management	1 December 2011
CN213030385U	[92]	Art pergola based on indoor decoration	Social and cultural values	23 April 2021
CN220586953U	[93]	Indoor view device	Social and cultural values	15 March 2024

).

Vertical greenery was initially envisioned as an energy-saving and environmentally friendly means of greening in confined spaces. Hence, new vertical greenery structures have been integrated with many new low-carbon and environmentally friendly technologies. The patents presented in this section can be categorized into three overarching domains: Structure and Equipment, Control and Management, and Social and Cultural Values, which was derived through a systematic content analysis of the retrieved patent records. Following the manual screening of over 200 relevant patents from Google Patents, Espacenet, and national repositories, each patent abstract, claims, and representative figures were examined to identify its principal inventive contribution and functional orientation. A bottom-up, inductive coding approach was employed, wherein recurring thematic elements were aggregated into higher-order categories. Patents that predominantly advanced physical components, such as modular containers, lightweight substrates, supporting frameworks, and soilless cultivation apparatuses were assigned to the Structure and Equipment cluster. Those whose novelty resided in the coordination of multiple components through computational or sensor-based regulation, including automated irrigation, environmental monitoring via the Internet of Things (IoT), and adaptive climate control, were grouped under Control and Management. Finally, innovations that explicitly foregrounded esthetic enhancement, community engagement, cultural expression, or user interaction with the greening system were classified within Social and Cultural Values.

It is important to acknowledge that this tripartite taxonomy is neither mutually exclusive nor prescriptive; many patents exhibit characteristics that span two or more categories. In such instances, classification was guided by the primary inventive step as articulated in the patent documentation and the predominant problem addressed. This approach aligns with established frameworks in technology classification studies [1], which recognize that innovation in complex systems frequently transcends rigid disciplinary boundaries. By elucidating the methodological underpinnings of this categorization, the subsequent analysis aims to provide a transparent and replicable synthesis of recent developmental trajectories in vertical greenery technologies.

When referring to relevant patents in the following text, the author used “patent number (publication number)” for reference to facilitate readers’ access to further relevant information. Additionally, for ease of reading, the images in this section may have been modified by the author.

Hardware Structure Innovations (Structure and Equipment)

With the continuous progress of technology, the techniques of vertical greenery structures are constantly undergoing innovation and development. Novel technologies, such as new plant growth substrates, automatic irrigation systems, and intelligent control, keep emerging to enhance the efficiency, sustainability, and maintainability of vertical greenery systems [1]. At present, technological innovation and research and development related to the hardware structure of vertical greenery can mainly be classified into three aspects:

(a)

Structural design innovation: encompassing modular design, lightweight design, and support-frame design, among others.

(b)

Plant selection and cultivation: including adaptive plant selection, soilless cultivation techniques, and so forth. In terms of adaptive plant selection, traditional vertical greenery systems typically employ climbing plants, but the future trend could be more diversified. People tend to select more attractive and diverse plants, including flowers, ornamental plants, and those with ecological value, to create more esthetically pleasing and eco-friendly vertical greenery landscapes. Regarding soilless cultivation techniques, aeroponics or hydroponics have matured increasingly, which can reduce pests and diseases or soil pollution, and enable precise nutrient adjustment for plants.

(c)

Other creative structures: often combined vertical greenery with other functions.

In terms of modular structure, in US9359759B2 [72] (Figure 11A), the inventor comprehensively contemplates previous similar vertical green wall systems and points out that previous vertical green walls often necessitated drilling and the use of nails, making the installation rather troublesome. Hence, the patent presents a new modular green wall, which could be installed via sliding rails, significantly enhancing the stability of the green wall structure and the convenience of installation. Usually, the integrated construction of the green wall makes it rather difficult to replace the plants within. Thus, the European patent EP2734034B1 [74] (Figure 11B) adopts an improved approach, facilitating the replacement of plants after planting. A modular planting structure named “the Tessellated Double Green Perforated Façade” is designed, comprehensively considering the advantages and disadvantages of previous planting structures in six aspects: noise abatement, stormwater use, potential, biodiversity, air pollution mitigation, environmental amenity, and esthetic value.

In terms of lightweight structural design, vertical greenery typically requires a steel frame for support, which may lead to excessive load on the wall surface. CN221615666U [81] (Figure 12A) introduces a vertical greenery system for building facades that utilizes a flexible composite planting mat instead of traditional rigid containers. The planting mat features fixed pockets designed with a larger upper portion and a smaller lower portion, filled with a lightweight substrate (such as a mixture of coconut coir and perlite), with a thickness of only 3–5 cm. The backing plate is made of PVC foam material, providing both waterproofing and flexibility, allowing it to conform to curved building facades. Its advantages include applicability to irregular wall surfaces, eliminating the need for steel frame support, resulting in a lightweight structure that reduces load by 60%. Based on this, CN109691327A [82] (Figure 12B) proposes a flexible composite structure wherein the planting trough consists of a flexible backing layer (waterproof layer), a three-layer recycled fiber planting mat, and a filament elastic top layer, utilizing stitch lines to delineate planting units and form stretchable planting bags. Module edges feature overlapping edges and mounting holes, allowing them to be stacked and fixed like tiles onto the framework, enabling seamless coverage of irregular wall surfaces while reducing the system’s weight to 3.5 kg/m². This addresses the issues of load and shape constraints for greening on irregular surfaces.

In terms of support frame design, to hold vertical greenery in place, it is often necessary to drill holes or use bolts, which wastes time and reduces work efficiency. CN104871865 [83] (Figure 13A) proposed a profile frame that can be quickly disassembled and assembled, the vertical column adopts the split profile design of the main column cover body, and the inner cavity is embedded with reinforced profile parts to enhance the shear resistance. The transverse tie rod is connected to the column by the snap-on method, without welding, and a single module can be disassembled and assembled within 5 min. It is used in temporary green walls and modular assembly landscapes of large-scale exhibitions. On this basis, CN109041898A [84] (Figure 13B) has put forward other innovations, which is a kind of rain collection green fence, with fixed bolts at both ends of the planting trough, which are directly connected with the screw holes of the fixing parts on the column, and can complete the disassembly and assembly of a single module within 10 min. And it integrates rainwater harvesting and automatic irrigation systems. A rain collection trough is set on the top to collect rainwater, and the internal water storage space is connected to the planting trough through a diversion funnel. The bottom is equipped with a water pump and water pipe, which automatically pumps water to replenish when there is a shortage of water, forming a closed-loop water supply. It is suitable for municipal roads, temporary exhibition areas and other scenarios. Its innovation realizes the rapid deployment of vertical greenery, which reduces the need for artificial irrigation of vertical greenery to a certain extent. Nevertheless, it cannot be applied to arid areas or seasons, and due to the limitation of the volume of the storage space, it collects less rainwater and cannot be completely separated from artificial irrigation.

In terms of cultivation techniques, traditional soil-based cultivation as a vertical greenery planting method has numerous drawbacks, such as heavy weight and insect control. Innovations in vertical greenery substrates are conducive to improving the survival rate of vertical greenery plants and their growth conditions. US10681881B2 [71] (Figure 14A) can serve as an example. This patent adopted vaporized planting methods, which could minimize the consumption of the substrate and facilitate the parametrization of substrate use.

The position where vertical greenery plants grow is not necessarily invariant. US10271485 [85] (Figure 14B) also proposed a structure where plants grow on a conveyor belt. Their positions change continuously along with the conveyor belt from seeding and taking root in germination.

Concerning plant selection, Warren et al. [67] utilized a green curtain wall in their experiment (Figure 15A), where the inventor implanted green algae into irregularly shaped containers made of glass, forming a green wall with green algae. Through a controlled experiment, they compared the differences in artistic work under the conditions of a green algae wall and a wall without green algae. Shushunova et al. [62] (Figure 15B) considered five different green systems and combinations of nine plants in their article. The experiment discovered that vertical walls using German daisies and bamboo palms could reduce more pollutants.

To address the problem of excessive water consumption by equipment due to climate conditions, US20180255711A1 [69] (Figure 16A) proposed a new architecture designed for tropical and subtropical countries and regions. Its relatively thicker walls can have a better heat reduction effect, by utilizing hexagonal-shaped modules for housing soil and vegetation. These hexagonal-shaped modules overlap with a vertical structure in such a manner that they provide shading underneath modules. Furthermore, these hexagonal-shaped modules are slant downward to aid in soil volume and thermal reduction as well as to keep roots cool and maximize water availability. US11291173 [73] (Figure 16B) proposed a structure that can provide sufficient water to plants for a longer time compared to the traditional living wall structure with a bottom water reservoir.

System Innovations (Control and Management)

System innovations can be broadly categorized into four aspects:

(a)

Environmental Control. In climate control systems, innovations are typically achieved through the integration of temperature, humidity, and lighting control systems to create optimal growing environments. For ventilation control systems, innovations generally involve designing structures that effectively guide and regulate airflow to enhance plant ventilation.

(b)

Irrigation System. Beyond structural innovations in planting containers such as planting bags or boxes, automatic irrigation systems can be integrated with sensors and controllers to achieve precise water and nutrient delivery. Nutrient solution circulation systems can be designed to efficiently recycle nutrient solutions, ensuring continuous nutrient supply for plants.

(c)

Intelligentization and Internet of Things (IoT). Innovations frequently combine sensor networks and intelligent management systems. The former involves deploying sensors to monitor plant growth environments, including moisture, temperature, and light intensity. The latter integrates IoT technology to enable remote monitoring and management, thereby improving maintenance efficiency and operational effectiveness.

(d)

Sustainability and Ecology. In water resource utilization, innovative vertical greenery systems often incorporate rainwater harvesting and utilization systems to reduce dependence on municipal water supplies. Regarding energy efficiency, renewable energy sources such as solar power are employed to energize irrigation and environmental control systems, thereby enhancing energy utilization efficiency.

As exemplified by KR102268653B1 [88] (Figure 17A), this architecture integrates vertical green walls with ventilation systems to enhance vegetation efficiency through air purification mechanisms. Specifically, electrostatic precipitator-equipped ventilation systems demonstrate superior air purification capabilities by leveraging negative ions generated by plants to improve anion absorption efficiency. Beyond capturing fine dust via stomatal trichomes and absorbing VOCs/NOx through plant transpiration, the system employs soil filters and fibrous filters through which water flows to physically absorb and wash away fine dust. The filtered water is subsequently reused for plant irrigation. Similar approaches are observed in KR102136364B1 [87] (Figure 17B) and KR102238511B1 [86] (Figure 17C), both of which combine vertical greenery with ventilation systems to achieve air purification functions.

In terms of planting system innovation, with the rapid development of intelligent technologies, vertical greenery systems are increasingly equipped with intelligent management and monitoring. Using sensors to monitor plant growth environments (e.g., soil moisture, temperature, and light intensity), combined with wireless communication and data analytics technologies, real-time monitoring and adjustment of plant growth conditions can be achieved, thereby enhancing the efficiency and sustainability of vertical greenery systems. Intelligent management systems integrated with IoT technology enable remote monitoring and management, improving maintenance efficiency and operational effectiveness.

In US20200163285A1 [89] (Figure 18), IoT technology is integrated into a vertical mushroom planting machine located in a supermarket, allowing consumers to visually observe the growth process of the crops and make purchases. Through this device and sales model, not only did it showcase the freshness of the product to customers but shortened the time for transporting the mature crops to the supermarket for sale and reduce the number of intermediate links.

In US11771016 [90] (Figure 19A), a system is invented for planting plants and monitoring plant growth. The sensors and cameras in this system can log data corresponding to the conditions of the horticultural system and the health status of the plants. Based on the data, the server can employ machine learning algorithms to determine the optimal plant growth thresholds and can send control commands to the controller of the horticultural system to modify one or more conditions of the system. In WO2011148011 [91] (Figure 19B), the inventors designed a vertical greenery system where excess water is collected in channels, then filtered, analyzed, and enriched with fertilizers and acids as appropriate, all controlled by a computer, and finally discharged back into the recycling loop.

Sustainability and eco-friendliness mainly encompass two aspects: water resource utilization and energy-efficiency improvement. The former can be achieved through innovative rainwater collection and utilization systems, reducing reliance on urban water supply. The latter employs renewable energy such as solar energy to power irrigation and environmental control systems, improving energy utilization efficiency. The trend of vertical greenery is placing greater emphasis on sustainability and eco-friendliness. Adoption of more environmentally friendly materials, energy-saving and emission-reduction designs, and management strategies will reduce the consumption of natural resources and the impact on the environment, achieving green development and ecological balance.

WO2019137063A [80] (Figure 20A) presents a building exterior shading device. It involves a smart remote-controlled, adjustable rotating, and vertical greenery with netting as the shading material for the exterior shading device of a building’s protruding window. By integrating the vertical greenery with netting and the protruding window, it also increases the green space within the building. CN212414007U [77] (Figure 20B) is an ecological garden landscape wall, which is equipped with a drive cylinder for driving the rotation of the shielding plate, and the piston rod of the drive cylinder is oriented towards the shielding plate. By adopting the above technical solution, in adverse weather conditions such as strong wind and heavy rain, the drive cylinder at the bottom of each support plate is activated to lift the corresponding shielding plate, thereby providing protection for the flowerpots below and reducing the direct contact of plants with strong wind and heavy rain.

In patent CN102177821A [75] (Figure 20C), when the sunlight is overly intense, the controller will control the extension of the functional baffle, allowing it from the upper bracket box to extend downward to cover the planted plants in front of the lower bracket box. This protects the plants from sun damage and also enables the absorption and utilization of solar energy.

CN212079128U [76] (Figure 21A) showcases a double-layer window suitable for green buildings. By locating a planting board between the inner and outer windows, green plants can be grown in the cavity, making full use of the space and adding oxygen and vitality to the interior. Rainwater can be collected through the rain shield to water the green plants, conserving water.

CN112177098A [78] (Figure 21B) has an inwardly recessed balcony set on the wall, forming an inwardly recessed space that can create shade and provide sun protection and rain shelter. Simultaneously, the large number of green plants set on the inwardly recessed balcony allow people to get close to nature. Green plants can absorb carbon dioxide and release oxygen, assist in eliminating some residual heat indoors, and regulate indoor temperature, reducing the residents’ reliance on air conditioners. The rainwater collection components set on the roof collect rainwater and use it to water the green plants, reducing water consumption.

Social and Cultural Values

In the aspect of social value, vertical greenery often contributes to society by improving the living environment of residents, promoting health and social interaction, and strengthening community cohesion [6]. Regarding artistic design, some vertical greenery combines art and design, that is, adding ornamental value and merging them with the architectural style. Vertical greenery can add esthetic charm to urban landscapes, enhance the visual appeal of buildings, incorporate natural elements, and create unique urban styles (Figure 22).

Figure 22A presents a 220 m long and 5 m high three-dimensional landscape flower wall on the west side of Yannan Road in Qujiang, Xi’an, China. A variety of colorful flowers and plants form a vast panorama, attracting passers-by to stop, admire, and take photos. This case utilizes vertical greenery to create the shape of mountains and waters, with the background being the ancient Chinese painting “A Thousand Miles of Rivers and Mountains”, attempting to create an artistic mood similar to that in the ancient painting. Figure 22B shows Jupiter, Sainte Genevieve Des Bois in France, completed in 2013. Designed by Patrick Blanc, this case employs plants of different colors to form color blocks of different colors, achieving an abstract and simplistic artistic effect. It is worth noting that the designer is also the inventor of modern vertical hydroponic gardens.

These two cases demonstrate that vertical greenery designers in different regions often create works of different styles due to their distinct cultural backgrounds. For instance, in traditional Chinese garden art, the aim is to represent large rivers and lakes with a small amount of water and large mountains with small rockeries. This influence is also manifested in the field of vertical greenery. French vertical greenery is influenced by European classical garden art and modern design trends, featuring a more prominent esthetic expression. Greening itself often participates in cultural narratives as part of buildings or cities. Of course, due to cultural differences, other regions with different cultural attributes have their own distinctive forms of vertical greenery. For example, Japanese vertical greenery is influenced by traditional courtyard design, pursuing simplicity and deep integration with nature [94]. Singapore is renowned as a “garden city”, and its vertical greenery reflects a high degree of integration of ecology and urban development [95]. German vertical greenery focuses on environmental protection technology and energy-saving benefits, reflecting its rigorous design philosophy [96]. With social changes and the development of the times, designers from different countries learn from each other, and more and more vertical greenery with exotic flavors will be observed.

Returning to the relevant patents under discussion, the combination of vertical greenery and community agriculture is a relatively significant trend. Future vertical greenery systems may integrate the cultivation of vegetables, fruits, and herbs to meet the demand of urban residents for fresh and sustainable food and reduce carbon emissions from food transportation. CN205491894U [79] provides a climbing frame vegetable balcony planting rack, which can enhance the convenience of planting climbing frame vegetables on balconies. This device utilizes a vertically positioned rectangular mesh planting structure, with a water tank at the bottom. Its design is relatively simple; therefore, no additional illustrations are provided.

Regarding the artistic aspect, related architectural innovations include endowing the vertical greenery with an artistic shape as a whole, presenting a certain shape or artistic effect in a part of the vertical greenery architecture, or combining related technologies to interact with the viewer or achieve a certain artistic effect. In CN213030385U [92] (Figure 23B), the intervention combines parametric pattern optimization and anthropometric rack redesign, demonstrating enhancement in both esthetics and maintenance convenience. In CN220586953U [93] (Figure 23A), the spray device with the red and blue growth lights ensures the necessary lighting conditions for plant growth, and takes into account the overall artistic quality.

4.3. Research Gaps, Development Challenges and Academic Debates

Despite extensive scholarly investigations into the thermal, acoustic, wind-resistant, and energy-efficient performances of vertical greenery systems, three critical research gaps remain under-explored and inadequately addressed in existing literature. First, research pertaining to urban biodiversity enhancement facilitated by vertical greenery remains limited. Most existing empirical observations predominantly focus on avian activities, while lacking long-term monitoring programs and quantitative assessments regarding insect communities, pollinator dynamics, plant community succession, and the ecological network connectivity enabled by vertical greenery infrastructures. Second, the mitigation efficacy of light pollution has not been sufficiently investigated, with a notable scarcity of quantitative analyses on canopy light attenuation, glare suppression, and optimal plant configuration strategies for alleviating urban light pollution. Third, the hydrological regulation and stormwater management functions of vertical greenery systems remain understudied. Few studies have quantified the runoff retention efficiency, pollutant interception capacity, and hydrological regulatory performance of modular vertical greenery systems under varied rainfall regimes, and a mature theoretical and applied framework for sponge city implementation is yet to be established. Future research should prioritize targeted, in-depth empirical and mechanistic investigations into these three underexplored dimensions.

Beyond the descriptive categorization of patents and practical engineering cases, the innovative development of modern vertical greenery is characterized by a prominent coupling relationship between structural innovation, intelligent control technology, and socio-cultural value, rather than the isolated development of these three independent dimensions. Structural innovations, including modular assembly design, lightweight substrate optimization, and flexible wall attachment systems, constitute the fundamental technical backbone of advanced vertical greenery. These innovations effectively resolve the inherent limitations of traditional vertical greenery technologies, such as low environmental adaptability, short service lifespan, and high maintenance costs and difficulty, thereby laying a solid foundation for intelligent operational management and large-scale urban popularization. On this structural basis, intelligent control technologies—represented by Internet of Things (IoT)-enabled real-time monitoring, automated irrigation systems, and adaptive environmental regulation mechanisms—further improve the operational efficiency and comprehensive environmental performance of optimized structural systems, enabling precise regulation of plant growth dynamics, building energy consumption, and microclimate optimization. Technological and structural breakthroughs ultimately translate into tangible socio-cultural value. Standardized, intelligent, and highly adaptable vertical greenery systems integrate multiple functions including urban ecological restoration, architectural esthetic enhancement, and public environmental education, transforming single-functional ecological installations into comprehensive urban public assets with dual ecological and cultural significance. Nevertheless, current patent innovations and practical applications suffer from fragmented development. Existing studies predominantly focus on single-dimensional structural optimization or intelligent equipment upgrading, while systematic integration of structural adaptability, intelligent operation, and cultural embedding remains insufficient. This research gap constitutes the core bottleneck restricting the high-quality development of vertical greenery technologies. Future innovative research and practical development of vertical greenery should break through the single-technology research paradigm and focus on the integrated innovation of structural design, intelligent control, and socio-cultural value empowerment. It is imperative to develop multi-scenario adaptive structural systems applicable to diverse building envelopes and climatic conditions, equip such systems with matched intelligent monitoring and precise regulation modules, and further explore the cultural embedding modes and public value expression pathways of vertical greenery in the contexts of urban renewal, community construction, and architectural design. The establishment of a systematic innovation framework integrating structural practicality, intelligent operational efficiency, and long-term social sustainability will define the core developmental trajectory of future vertical greenery research and application.

The current limitations and challenges of innovative vertical greenery structures can be systematically summarized from three interrelated dimensions: structural and equipment performance, control and management mechanisms, and socio-cultural value realization. In terms of structure and equipment, the adoption of advanced materials and cutting-edge technologies leads to high initial installation costs and subsequent maintenance expenditures, restricting large-scale popularization. The technical complexity of innovative systems requires professional installation and maintenance expertise, limiting their applicability to diverse urban scenarios. Additionally, plant adaptability and pest management pose persistent challenges: most plant species are not suitable for vertical cultivation environments, and high-density planting layouts are vulnerable to pest and disease infestations, necessitating continuous monitoring and targeted maintenance. Under vertical suspension conditions, lightweight substrates are prone to compaction, sedimentation, and nutrient leaching, which degrade soil air permeability and water retention capacity over time. Structural defects are also prevalent at modular connection joints, frequently causing water seepage and root overflow problems. For high-rise building applications, wind-induced structural vibrations trigger fatigue damage to greening components and increase the risk of fastener fracture, while the long-term structural safety and durability of such systems lack sufficient empirical validation. In terms of control and management, intelligent systems are constrained by high deployment and maintenance costs, potential sensor and automatic component failures, and substantial upfront investment requirements for sustainable technological applications, alongside stringent professional maintenance demands. Moreover, the limited root growth space within modular units may induce module deformation, fixing bolt loosening, and even wall anchoring failure. From the perspective of socio-cultural value, primary limitations stem from design trade-offs between esthetic presentation and functional performance. Furthermore, public acceptance of vertical greenery remains low in some residential communities, requiring long-term popular science education to improve public awareness and recognition. Despite these prevailing challenges, innovative vertical greenery structures possess broad development potential across structural optimization, intelligent management, and socio-cultural value enhancement. Continuous technological iteration and in-depth research are expected to progressively address these limitations, enabling vertical greenery systems to generate greater ecological, economic, and social benefits for urban built environments.

A prominent scholarly debate persists regarding the winter energy performance of vertical greenery systems (VGS). While the summer cooling benefits of VGS derived from facade shading, plant transpiration, and thermal insulation have been well corroborated by existing studies, multiple empirical investigations have confirmed a non-negligible increase in building heating demand during cold seasons, primarily attributed to reduced solar heat gain on vegetated building facades. Notably, this seasonal energy trade-off is neither universal nor linearly correlated, and comprehensive evidence synthesis indicates that the annual net energy balance of VGS is highly dependent on regional climate characteristics and system configuration. In cooling-dominated climatic zones, the winter energy penalty is negligible or absent, rendering VGS an effective energy-saving strategy. In temperate oceanic and Mediterranean climates, the winter heating penalty generally ranges from 3 to 5% [41], which can be fully offset by substantial summer cooling energy reductions of 15–30% or higher [47]. In contrast, cold temperate climates may witness winter energy penalties exceeding summer energy savings unless deciduous plant species or adaptive shading systems are implemented. Furthermore, living wall systems exhibit superior summer thermal insulation performance but incur more significant winter energy penalties than traditional green facades, due to their thicker substrate layers and enclosed air cavities. Importantly, several empirical studies conducted in Mediterranean and oceanic climatic regions have observed no additional winter energy consumption, verifying that targeted optimization strategies—including the selection of climbing plants with moderate leaf area index, reserved air buffer gaps, and seasonal pruning management—can effectively mitigate the seasonal energy trade-off. Collectively, no single VGS configuration can achieve optimal energy performance across all climatic contexts. The most robust design strategy lies in climate-adaptive customization: the adoption of deciduous or semi-deciduous plant species in temperate regions, deployment of retractable or hybrid VGS, and integrated application of VGS with high-performance building thermal insulation. From a holistic perspective, the winter energy trade-off should not be regarded as a critical defect of VGS, but as an adjustable design variable that can be optimized through context-specific engineering design. Future research should prioritize long-term full-year field monitoring and the development of predictive models for seasonal energy performance balance, so as to transform this inherent seasonal trade-off into a viable optimization opportunity for climate-adaptive green building design and practice.

5. Conclusions

This study systematically synthesized the multifaceted impacts of vertical greenery on the urban built environment, covering thermal, acoustic, wind, energy, air quality, ecological, and psychological dimensions, thereby fulfilling the first objective. Through the analysis of global case studies and patent innovations, it further categorized technological advances into structure and equipment, control and management, and socio-cultural values, addressing the second objective while outlining current trends and future research directions. Conclusions can be drawn from the following aspects:

(a)

Impact of outdoor vertical greenery

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Vertical greenery regulates the urban microclimate by absorbing solar radiation through the photosynthesis and transpiration of plants; it reduces the temperature of building surfaces and interiors through the shading effect of plant leaves and transpiration, thereby lowering building energy consumption and enhancing the durability of building envelopes.

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The species of plants, leaf area index (LAI), coverage area, and plant thickness significantly affect the efficiency of vertical greenery in regulating the microenvironment.

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Vertical greenery has a significant positive effect on noise absorption. At high frequencies, noise reduction is mainly achieved through the scattering effect of plants; at medium and low frequencies, it is mainly through the absorption effect of the substrate. Since the background noise in cities mostly falls within the medium and low frequency range, which is also within the effective absorption and attenuation range of vertical greening, it can be an effective measure for noise reduction in public places.

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Vertical greenery can trap, adhere, and absorb fine particulate matter through plants. It absorbs carbon dioxide and releases oxygen through photosynthesis, maintaining the carbon–oxygen balance in a certain area.

(b)

Impact of indoor vertical greenery

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Vertical greenery regulates indoor air temperature and humidity through the transpiration of plants and the moisture in the substrate, significantly improving human comfort.

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Vertical greenery improves the acoustic comfort of indoor spaces by increasing the sound absorption area.

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Vertical greenery can purify indoor air quality, effectively removing or reducing most air pollutants, including VOCs, CO₂, PM, etc.

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Indoor plants can create an interesting environment, not only alleviating fatigue and anxiety in learning and working environments but also improving learning concentration and work productivity. The potential of vertical greenery in this aspect still needs to be confirmed by research.

(c)

Innovations in vertical greenery

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Structural and Equipment Design: Novel lightweight, modular and flexible structures have replaced traditional rigid designs. Optimized components and soilless cultivation resolve the drawbacks of conventional planting. Integrated water management systems greatly boost water self-sufficiency.

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Monitoring and Operational Management: Smart technologies including IoT and machine learning achieve refined monitoring and automatic control. Hybrid vertical greenery systems are effective in removing airborne pollutants.

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Socio-Cultural Value: Vertical greenery has become a multi-functional carrier of ecology, production and culture. It meets residents’ diverse demands and presents distinctive regional artistic features.

In summary, vertical greenery is set for further development and wider application with intelligent monitoring and deeper integration into sustainable urban construction. Relevant research on its social and psychological values will expand its use in public buildings. Its capabilities in regulating outdoor microclimates, saving energy, reducing noise and purifying air are well documented, but studies on biodiversity, light pollution, bacteria and rainwater management are lacking. For indoor scenarios, its effects on thermal comfort and air quality have been proven, yet its health benefits and potential risks such as carbon dioxide accumulation, bacteria and mosquitoes require more exploration. Overall, vertical greenery delivers remarkable ecological and livability advantages and will play a vital role in future urban development.

6. Limitations and Future Directions

6.1. Limitations of the Study

This review has established a relatively comprehensive research framework, but it still has several limitations, which are summarized as follows:

(a)

Literature coverage: The literature search was mainly based on Web of Science and Google Patents, which may have missed non-English literature or local practice cases (such as small-scale innovations in developing countries).

(b)

Data comparability: Experimental conditions in different cases (such as climate types and measurement methods) vary significantly, and some conclusions need to be interpreted in the context of specific situations.

(c)

Limitation in economic evaluation: Comprehensive quantitative economic and cost–benefit analysis was precluded because key on-site economic parameters were inaccessible for collation.

These limitations provide directions for improvement in subsequent research, such as through multilingual literature reviews and longitudinal comparative analyses to further validate the conclusions.

6.2. Future Directions

As an important strategy for urban sustainable development, future research and practice on vertical greenery can focus on the following areas:

(a)

Interdisciplinary integration

Future research should move beyond vague advocacy of interdisciplinary cooperation and carry out targeted explorations based on specific research gaps: further evaluate the habitat support provided by vertical greenery for pollinating insects and soil fauna in addition to birds; quantify the light attenuation coefficient of foliage by combining ray-tracing algorithms and plant canopy models to alleviate light pollution; calculate stormwater retention capacity through modular lysimeter experiments under diverse rainfall intensities; deploy low-cost IoT sensor networks embedded with machine learning early-warning functions to monitor adverse indoor impacts including nocturnal carbon dioxide accumulation and microbial proliferation.

(b)

Technological innovation

Priority core technologies should address seasonal trade-offs and maintenance barriers by developing adaptive seasonal systems—such as thermochromic cladding or retractable green screens—automated by AI-driven microclimate forecasting to minimize the winter heating penalty, deploying intelligent low-maintenance monitoring where long-range wide-area network sensors are coupled with digital twins for real-time assessment of plant health, substrate moisture and air quality, and advancing low-cost biodegradable modules made from mycelium-based materials or recycled polyethylene terephthalate composites whose structural integrity is validated over 5–10 years.

(c)

Social participation

Moving from esthetic demonstration to scalable community models means quantifying yield, maintenance needs and social outcomes like food literacy and cohesion for edible living walls, estimating willingness to adopt through discrete choice experiments that value policy incentives such as floor area ratio bonuses or tax reductions, and applying user-centric design in which VR preference surveys combined with post-occupancy sensor data link specific design features to long-term engagement.

(d)

Climate adaptability research

Focusing on extreme weather and long-term performance calls for testing vegetation under heatwaves, droughts and heavy rain using environmental chambers with programmable profiles, establishing side-by-side multi-year monitoring of deciduous–evergreen mixed matrices to optimize the seasonal energy balance, and building long-term degradation and life-cycle assessment knowledge—including 5–10 year degradation curves for substrates and modules, together with carbon payback time under climate change scenarios such as SSP (Shared Socioeconomic Pathways) 2–4.5, supported by digital twinning.