Toward Adaptable and Industrialized Vertical Greenery Systems: A Critical Review and Future Developments

Abstract

Among nature-based solutions, Vertical Greenery Systems (VGS) are widely recognized as effective solutions for improving the environmental performance of buildings and urban areas. Although their benefits have been extensively studied and demonstrated, their large-scale implementation remains limited. This paper explores the hypothesis that the main barriers to the widespread adoption of VGS—and especially Green Facades (GF)—are not related to their environmental performance but rather to their lack of industrialization and to purely technological and construction-related aspects concerning support and anchoring systems. Following an in-depth review of the scientific literature published since 2006, the study found that most publications focus primarily on the environmental performance of green roofs, while the structural and technological aspects, as well as the potential for adaptation to existing buildings, remain largely unexplored areas. This is also reflected in construction practice, highlighting how most existing solutions are based on specific, case-by-case design approaches, limiting replicability and large-scale implementation, especially in existing buildings. The paper identifies the concept of construction adaptability as a potential direction for innovative research aimed at developing industrialized systems that are replicable and adaptable even to existing buildings, thereby promoting the large-scale use of GF.

1. Introduction

Rapid population growth has played a key role in the rise in urbanization, leading to an increasing concentration of the population in urban areas and a gradual increase in building density. Cities are home to more than half of the world’s population, a figure expected to rise to 70% by 2050 [1], placing pressure on natural resources, the urban environment, and quality of life.

The continued expansion of impervious surfaces and the reduction in available green spaces have significantly contributed to the intensification of phenomena associated with urbanization, with negative effects on environmental quality, urban comfort, and the health of residents [2]. In this context, the integration of vegetation into the built environment has been increasingly recognized as an effective strategy for mitigating the urban heat island effect, improving the sustainability of cities, and promoting healthier and more resilient urban environments [3].

The integration of green systems into buildings can occur on both roofs and façades. Although green roofs have been extensively studied and recognized for their positive effects on the energy and environmental performance of buildings, vegetated vertical surfaces offer particularly interesting application potential, especially in high-density urban contexts where horizontal space is limited.

The use of vegetation in buildings is not a recent development. Since ancient times, various civilizations have experimented with ways to integrate architecture and nature to improve environmental comfort and enhance the aesthetic appeal of built spaces. The Hanging Gardens of Babylon are one of the most famous historical examples of the use of vegetation in building structures, while during the Roman era it was common practice to place trees and plants on terraces, courtyards, and rooftops to provide shade and mitigate the effects of high summer temperatures. However, it was not until the 20th century that these practices began to evolve into technologically advanced systems designed according to scientific criteria.

A major turning point was the patent for the “Vegetation-Bearing Architectonic Structure and System,” developed by Stanley Hart White in 1938 and considered the first modern vertical greenery system [4]. Subsequently, research and technological innovation fostered the evolution of increasingly sophisticated solutions, culminating in the 1980s with the development of the “Mur Vegetal” by French botanist Patrick Blanc. This system introduced an innovative approach based on growing plants on vertical surfaces using artificial supports and integrated irrigation systems, paving the way for the contemporary proliferation of green walls and vegetated facades.

Since the 2000s, interest in Vertical Greenery Systems (VGS) has grown significantly, both in the world of research and in professional practice. The ability to use the vertical surfaces of buildings as a support for vegetation has made it possible to overcome one of the main limitations of high-density urban areas: the scarcity of space available for new green infrastructure. In this context, VGS represent a particularly effective solution since they allow for an increase in vegetation without taking up additional space from the established urban fabric [5].

1.1. Features and Performance of VGS

VGS encompasses a diverse range of design solutions that differ in construction characteristics, vegetation growth patterns, irrigation systems, and maintenance requirements. Among the most common types, based on the growth pattern of the vegetation layer and the support system, two categories stand out: Green Facades (GF) and Living Walls (LW).

GF are established using climbing or trailing plants. The plants can grow directly on the building’s surface (direct greenery system) or use support elements such as metal grids, nets, modular trellises, cables, or ropes (indirect greenery system).

LW are constructed using prefabricated modular panels—often pre-planted—that are attached directly to the building’s masonry or to a vertical support structure. These panels contain the substrate and the technological systems necessary for supporting and fostering the growth of plant species [6].

Table 1 lists the main distinguishing characteristics of GF and LW.

Table 1. Classification of VGS.

VGS Type	Vegetation Support	Vegetation		Crop Type	Modularity	Industrialization
		Development	Placement
GF direct system	None	Climbing on the exterior surface of the building	Ground- based	Traditional	No	No
GF indirect system	Grids, nets, trellises, cables, or ropes	Climbing or falling on support elements	On the ground or in containers	Traditional	Almost always	Only for support elements
LW	Frame or cell-based substructure	Primarily on textile substrates	Contained in prefabricated panels, often pre-vegetated	Hydroponics	Yes	Yes

In recent years, new configurations have also emerged, including advanced modular systems, integrated bio façades, and multifunctional solutions capable of combining environmental, energy, and architectural performance, which are described in detail in the following paragraphs.

The growing popularity of VGS is closely linked to the many benefits these systems can provide. Scientific literature has extensively documented the role of vegetation as a passive tool for controlling the microclimatic conditions of buildings. Various studies have shown that shading provided by vegetation can reduce the direct exposure of building surfaces to solar radiation, limiting overheating of the building envelope and helping to reduce energy consumption associated with cooling interior spaces [5,7,8,9,10], as well as contributing to the mitigation of the urban heat island effect [11,12]. In addition to energy-related benefits, the presence of vegetation in buildings has been linked to improvements in users’ health and psychophysical well-being [13,14], the removal of air pollutants [15,16,17], and improved air quality [18], as well as the conservation of urban biodiversity and the creation of favorable habitats for local flora and fauna [19]. Furthermore, in many urban contexts, green facades are considered tools for urban regeneration, capable of enhancing the appearance of buildings and increasing their economic value [20].

Finally, green facades are generally closer to users and public spaces, contributing significantly to improving the microclimate as perceived at pedestrian level [21].

1.2. Manufacturing Processes and Their Limitations

Despite the large amount of literature demonstrating the environmental benefits of VGS, their widespread adoption remains limited compared to their potential. This suggests that the current barriers are no longer primarily related to environmental performance, but rather to technological integration, constructability, and industrialization.

The main challenges include high initial installation costs, the need for specialized maintenance, water management, the durability of components, and uncertainty regarding long-term performance. Further obstacles stem from the lack of widespread technical knowledge among designers, construction companies, and public administrations, as well as the absence of standardized tools for evaluating the most appropriate solution among the various available options.

One of the most debated aspects in the literature concerns the classification of VGS. Unlike other green infrastructures, such as green roofs, for which there are well-established and widely accepted classification criteria, VGS are described using a variety of terms and definitions that vary depending on the geographical, disciplinary, and commercial context. Terms such as “green facade,” “living wall,” “vegetated wall,” “vertical garden,” “green wall,” and “bio façade” are frequently used interchangeably, even though they often refer to systems characterized by different construction principles and performances. This terminological heterogeneity makes it difficult to compare scientific studies and limits the transferability of results to design practice [22].

Although numerous literature reviews on vertical green systems have been published in recent years, most studies focus on specific aspects, such as thermal performance, energy efficiency, plant species selection, water management, or environmental impacts. Less common, however, are analyses that take an integrated approach to the evolution of VGS, the different construction types, and, above all, the technological aspects related to support structures and methods of integration with the building envelope. This fragmentation highlights the need for a critical synthesis of the available knowledge that, in addition to comparing the various configurations of vertical greenery systems, would help identify the main gaps still present in the research.

In particular, a preliminary analysis of the literature reveals that the design of support substructures and anchoring systems is still predominantly based on solutions developed ad hoc for the specific characteristics of individual buildings. While this approach allows for a high degree of customization, it limits the standardization of systems and reduces their replicability, representing one of the main obstacles to the widespread adoption of GF as an intervention strategy for existing buildings.

1.3. Structure of the Study and Research Questions

Based on these considerations, this study proposes a shift in perspective regarding the analysis of VGS in general and GF in particular.

Through a critical review of the scientific literature in the field and a comparative analysis of recently developed commercial systems and research prototypes, this paper aims to identify the barriers to the widespread adoption of GF, shifting the focus beyond performance-related aspects to encompass construction and implementation processes, thereby addressing a potential gap in the literature. More specific criteria, including transferability, reusability, and adaptability to different buildings, are introduced to assess how explicitly constructability and adaptability have been addressed in previous studies. Furthermore, the development of modular and industrializable systems for building renovation is examined.

Specifically, the study addresses the following research questions:

RQ1. What are the main barriers limiting the widespread adoption of GF, despite their well-documented benefits?

RQ2. How many studies have examined the implementation aspects of VGS, rather than focusing exclusively on their performance?

RQ3. To what extent are the vegetation support systems used in VGS designed to be transferable, reusable, and adaptable to different buildings and construction contexts?

RQ4. Have any studies addressed the issue of constructability and adaptability with a view to promoting the wider adoption of VGS?

RQ5. How can scientific research on constructability and adaptability contribute to the development of modular, industrialised systems that are more compatible with the requirements of retrofitting the existing building stock?

2. Methods

For this study, a comprehensive review of the literature on VGS was conducted, with the aim of critically examining the available evidence, evaluating its methodological and technological contributions, and synthesizing the results in order to provide an up-to-date overview of the state of the art.

The literature search was conducted by consulting major scientific databases, including Web of Science, Scopus, ScienceDirect, and Google Scholar. Search strategies were developed using combinations of keywords and Boolean operators (AND, OR) to maximize the sensitivity and specificity of the search. To ensure the broadest possible coverage of the relevant literature, synonyms and terminological variants referring to the same concepts were included.

The data collection for systematic classification covered publications from January 2006 to February 2026. The choice of this time frame does not imply that 2006 marks the beginning of studies on VGS, nor does it exclude the relevance of earlier contributions. On the contrary, the definition of the theoretical and epistemological framework also took into account earlier literature, including studies dating back to the 1970s as well as the first documented research and application efforts in Berlin during the 1980s [23,24,25,26]. These contributions were considered part of the historical and scientific background necessary to understand the evolution of the systems and their related design and construction approaches. The time frame adopted for the classification was therefore defined to focus the analysis on the most recent developments, while limiting the scope of the bibliographic corpus and enabling a systematic and comparable examination of the contributions. In accordance with the specific objective of the study, attention is therefore directed toward contributions that document the evolution of technical solutions and design and construction processes, including in relation to the prospects for standardization, industrialization, and the development of contemporary building systems. Studies published before 2006 were used to provide context for the historical and conceptual evolution of the field, but were not included in the corpus subjected to systematic classification.

In the first screening phase, the following keywords were used: “Vertical Greenery System,” “Living walls,” and “Green façades.” This initial search identified a total of 4329 records.

The second phase involved applying additional combinations of keywords related to the performance and technological aspects of VGS, including terms such as “Vertical green structures”; “Market classification”; “Green infrastructures”; “Life Cycle Assessment”; “Energy performance”; “Thermal performance”; “Urban heat island”; “Biodiversity”; “Air quality”; “Sustainability”; “Building envelope”; and “Climate adaptation,” reducing the number of results to 626 articles.

Subsequently, in the third phase, duplicate records were removed, and articles not written in English, non-peer-reviewed contributions, and opinion pieces were excluded. At the end of this process, 531 articles were selected.

The fourth phase involved screening the article titles to verify their relevance to the objectives of this review. Studies that did not address VGS at the building scale or those dealing exclusively with other types of green infrastructure, such as green roofs, urban parks, landscaping projects, or vegetation systems not integrated with the building envelope, were excluded. This phase resulted in the exclusion of 185 articles, leaving 346 potentially relevant articles.

In the fifth phase, an in-depth evaluation was conducted of the abstracts and full texts of the 346 selected articles. Only studies concerning VGS intended to improve the technology of building envelopes were included, with particular reference to original and distinct classifications of the systems, design and construction characteristics, the development of new prototypes and advanced technological solutions, the improvement of indoor comfort, economic and maintenance aspects, and methods for applying VGS to buildings and the urban context.

The following studies were excluded:

(i)

Articles that reiterated established classification systems or adopted previously proposed taxonomies without introducing novel analytical criteria or methodological contributions;

(ii)

Studies focusing exclusively on indoor greenery systems, vertical farming, vertical greenhouses, or agricultural applications not integrated into the building envelope;

(iii)

Works addressing solely agronomic or botanical aspects without examining the performance of these systems or their integration into the building envelope.

At the end of the selection process, 125 articles were included, as listed in the Appendix A (Table A1). The process of identifying, screening, assessing eligibility, and including studies was summarized in a flowchart (Figure 1).

Figure 1. Article selection process for the review.

The selected articles were subjected to thematic analysis and categorized according to the predominant broad areas of investigation (Table 2), including system type, technological configuration, environmental benefits, maintenance aspects, and classification criteria. Since several publications take a multidisciplinary approach by addressing multiple topics simultaneously, individual studies have been assigned to more than one category. The results were subsequently synthesized and discussed to identify emerging trends, knowledge gaps, and prospects for the sector’s development, providing useful insights for answering the research questions formulated earlier.

Table 2. Number of papers for each topic.

Topic	Number of Papers	Number of Papers by System Type
		VGS (GF + LW)	GF	LW
Thermal Benefits	89	39	29	21
Classification Criteria	23	22	0	1
Technological Configuration	35	18	3	14
Vegetation	37	15	10	12
Maintenance	30	23	2	5
LCA	8	4	0	4
Environmental Benefits	34	18	4	12
Modularity and Industrialization	7	3	1	3
Support and Fastening Systems	12	5	3	4

The distribution of articles across various topics reveals limited attention to the construction and industrialization aspects of VGS. In particular, only a very small number of papers address topics related to the study of support substructures, fastening and anchoring devices, modularity, and the industrial production of system components. It should therefore be noted that, to date, research has focused primarily on performance, neglecting the issue of the industrialization of the final product.

To address the research questions listed above, the objective of this paper is to identify the main obstacles to the large-scale adoption of GF, despite the widely recognized benefits associated with their use. The study is based on an analysis of the scientific literature in the field to determine how many studies focus on the construction aspects of green roof systems in general and green roofs in particular, compared to those that evaluate only their performance. Furthermore, again based on the literature review, the study aims to determine to what extent vegetation support systems are designed to be adaptable to different buildings and construction contexts, and how many studies have addressed the issue of construction adaptability.

3. Critical Analysis of VGS

An analysis of the state-of-the-art highlights how the evolution of VGS has been characterized by differing development dynamics depending on the type of system. Although GF and LW are generally grouped together in scientific literature as the two main categories of VGS, they exhibit different technological development dynamics that have distinctly shaped both the evolution of commercial solutions and research activities.

This distinction is a key prerequisite for understanding the current challenges facing the sector. A comparative analysis of the two types allows us to examine not only the differences in technological configurations and performance but also the varying degrees of development of construction solutions and design strategies aimed at their application. In particular, for GF systems, it is essential to assess whether and to what extent technological evolution has facilitated the development of support systems adaptable to different building conditions and whether these aspects have been adequately investigated in scientific literature.

From this perspective, the critical analysis aims to correlate the evolution of the systems, the level of detail in their respective construction solutions, and their potential for large-scale application, highlighting unresolved issues and knowledge gaps that may limit the transition from experimental solutions—or those specifically designed for individual contexts—to systems that are more replicable and adaptable.

In the case of LW, the increased technological complexity of the system favored an integrated design approach. In fact, the construction of a LW requires the coordinated design of the supporting structure, the vegetated modules, the growing medium, the irrigation and drainage systems, and the selection of plant species. These components constitute a single technological system, designed and developed as a unified whole, in which overall performance depends on the mutual integration of all elements. This complexity has led to the emergence of numerous design variations and a much broader commercial offering. Consequently, scientific research and commercial production have followed a largely convergent evolutionary path, focused on the development of complete, high-performance systems.

A different situation characterizes GF, however. In this case, the system can be broken down into relatively independent subsystems -vegetation, plant support elements, load-bearing substructure, anchoring devices, and fastening components- which can be developed, produced, and selected separately. While this configuration ensures greater flexibility in application, it also leads to fragmentation in both commercial production and scientific research.

The manufacturing sector offers a growing number of commercial systems and components but does not provide methodological tools to guide their use and integration into the building envelope.

Research proposes experimental systems that are increasingly advanced in terms of technology and performance; however, these are primarily developed for specific applications and rarely consider the building configurations already on the market or how these can be adapted to different buildings. This misalignment represents an obstacle to the widespread adoption of GF as a systematic solution for the retrofitting of existing buildings.

Since GF are a technologically simpler, more economical solution with lower maintenance requirements, further exploring their performance and application potential represents a possible research direction toward more accessible and sustainable greenery solutions.

In light of these considerations, this section critically analyzes the two main lines of development that have emerged from the literature: on the one hand, the GF systems currently available on the market; on the other, the most recent developments in scientific research, with the aim of highlighting their strengths, limitations, and potential areas of convergence.

3.1. GF on the Market

Although the market currently offers a wide variety of products, studies systematically examine support substructures, fastening systems, anchoring devices, component modularity, and methods of adaptation to different building contexts are rare.

One of the few studies addressing this topic is the work by Ogut et al. (2022) [27], which presents a systematic review of the VGS market with the goal of developing a taxonomy of available products and identifying their main evolutionary trends. The authors highlight how the rapid expansion of the market necessitates comparative analyses capable of evaluating not only the technological characteristics of the systems but also economic, maintenance, and environmental aspects, in order to support designers and operators in selecting the most appropriate solutions.

The study is based on an analysis of 142 products marketed by 58 international manufacturers and shows that the market is currently heavily skewed toward LW, which accounts for approximately 83% of the systems surveyed, compared to 17% for GF.

The taxonomy proposed by the authors classifies VGS according to their main components—support structure, vegetation, substrate, drainage, and irrigation—highlighting that, in the case of green façades (GF), the configuration of the load-bearing substructure is the defining element of the entire system. Specifically, the choice of constituent material—coated stainless steel, galvanized steel, aluminum, or plastic—determines the system’s weight, profile thickness, durability, and cost, thereby influencing both the aesthetic and functional properties of GF [28].

An analysis of commercial products shows that indirect GF can be broadly categorized into two main construction configurations: systems based on modular trusses and systems consisting of tensioned cables or ropes. The former involves lightweight lattice structures, generally made of aluminum or steel, combined with modular nets or panels designed to support the vegetation. The latter, on the other hand, use systems of metal cables, wires, or nets anchored to the building’ r façade using specific fastening and spacing devices. Although these configurations have different geometric and material characteristics, they share the same construction principle, based on the use of a substructure anchored to the building that supports the vegetation and transfers loads to the building envelope.

The examples analyzed by Ogut et al. are divided into:

• Modular trellis systems, such as Gsky Basic Wall, are characterized using fiberglass containers to which a standard-sized mesh is attached. The planters can be mounted on the structure or on a built-out sub-structure using light brackets.
• Cable/rope systems, which include:
  • Two-dimensional solutions consisting of vertical cables, horizontal cables, rods, and grids, and three-dimensional solutions consisting of panels with fixed length, width, and depth, known as the Greenscreen trellis system produced by Greenscreen;
  • Products such as Green Trellis and Webnet by Jakob Rope Systems, which use stainless steel cables suitable for use on building facades up to 150 m high and applicable both on the exterior and interior of buildings.

In addition to systems developed specifically for GF, design practice frequently relies on components derived from other industries and subsequently adapted to the needs of vertical greening.

Among the most widely used solutions are:

• • The GRIPPLE^® system, which uses polymer strands tensioned by self-adjusting clamps originally developed for agricultural applications and subsequently adapted to support vegetation on building facades;
  • Seilsysteme systems employ orthogonal grids of stainless-steel cables secured using tensioning devices and metal spacers;
  • The TENAX^® system consists of prefabricated plastic grids anchored to the facade using anchors and brackets.

Despite differences in technology and materials, these solutions share similar construction principles, based on the use of simple, lightweight, and easily assembled components.

A comprehensive analysis of the systems currently on the market leads to a particularly interesting observation. The variety of available solutions might suggest a high level of standardization in GF systems; however, a more in-depth analysis reveals a different reality. In fact, it is not the standardization of components that represents the main challenge, but rather that of the system as a whole. Cables, nets, grids, tensioning devices, brackets, and anchoring systems are now widely industrialized components available in numerous technological configurations. What continues to require specific design, however, is their integration into a structural configuration consistent with the geometric, dimensional, and technological characteristics of the individual building. Design therefore retains a significant element of artisanal customization that limits the replicability of solutions and represents one of the main factors hindering the wider adoption of GF in the redevelopment of existing building stock.

3.2. Evolution of Research

In parallel with the development of the commercial systems market, scientific research has followed a different evolutionary path, focusing primarily on improving the environmental performance associated with the integration of vegetation into buildings, with particular attention to the effects on the urban microclimate, the thermal performance of the building envelope, air quality, and occupant comfort. As knowledge regarding these benefits has gradually solidified, scientific attention has progressively shifted toward the development of more technologically advanced solutions capable of integrating functions beyond the simple greening of surfaces.

This evolution has led to the emergence of increasingly complex systems, characterized by the use of new materials, prefabricated components, control devices, and integrated management strategies [29]. In Nanjing, China, a new method was proposed to assess the direct cooling benefits of green facades based on infrared thermal data and three-dimensional point clouds [30]. Another study presented a prototype of a solar-powered fertigation system designed to automate the recirculation of drainage water within the system using recycled materials [31]. As part of another research project, a modular LW system was designed that utilizes recycled materials known as Geogreen—derived from mining waste (geopolymers)—and locally available materials, such as expanded cork panels, along with climate-appropriate plants [32].

However, a review of the literature shows that this development has primarily occurred through the evolution of systems designed on a case-by-case basis for individual buildings, rather than through a review of the technological solutions available on the market and their adaptation to different building contexts [29]. Most of the prototypes identified fall into the LW category.

The modular cork panel system developed by Cortês et al. (2021) is a significant example of this trend, as it proposes a rethinking of the construction process through the introduction of materials with reduced environmental impact and the optimization of the system’s life cycle [33]. The authors described the design process of a new modular LW system made of insulation cork boards (ICBs) (Figure 2). This process was carried out by considering the main environmental critical issues identified in a comparative life cycle assessment (LCA) conducted for the production phase of five different modular wall systems. To reduce these impacts, the new system replaces commonly used plastic components with ICB modules, a natural material derived from cork byproducts, characterized by good water retention and drainage capabilities. Additionally, ICB modular blocks were developed so that they could be fastened directly to the bearing wall by means of a waterproofing adhesive mortar, replacing the most used metal fasteners while also ensuring a continuous layer with thermal and acoustic insulation properties, as well as a protective function.

Figure 2. (a) Schematic representation of the new ICB module for LW. (b) Illustration of a modular LW built with the new ICB modules. (c) Illustration of a person climbing the LW, simulating the loads generated by doing so. (d) Illustration of a ladder propped against the LW, representing a maintenance operation [33].

The prevalence of studies on LW in the literature can be attributed to their technological configuration itself; as previously noted, they require the development of vegetated modules, artificial substrates, irrigation systems, and dedicated structural components. GF, on the other hand, are generally based on simpler and relatively well-established construction principles, such as mesh, cables, and metal support structures, and for this reason have been less frequently the subject of technological experimentation. This situation appears paradoxical when one considers that GF are precisely the most widespread systems and potentially the most suitable for extensive applications in the existing building stock.

Among the most recent developments in the field of GF, the Adaptive Photovoltaic Green Facade (APVGF), proposed by Li et al. (2025), represents a significant contribution [34].

The system consists of an innovative multifunctional vegetated envelope that combines an adjustable photovoltaic awning system with a green facade. The goal of the proposal is to combine the environmental benefits associated with vertical greenery with renewable energy production, through movable photovoltaic components capable of adapting their orientation to operating conditions. As shown in Figure 3, plants grow between the photovoltaic shades and the exterior wall, providing dual solar shading to prevent excessive solar radiation from entering the interior and to reduce heat buildup in the rooms during the cooling season. Furthermore, plant transpiration cools both the photovoltaic shades and the adjacent wall. The layer of vegetation gives the building a pleasant and aesthetically pleasing landscape effect, while the plants’ leaves provide favorable diffused light and a beautiful view for the interior spaces. The photovoltaic awnings not only allow climbing plants to grow but also effectively protect both the building and the plants from extreme temperatures, cold winds, hail, and other adverse weather conditions. Furthermore, the self-adjusting photovoltaic shades can adjust their angle based on the angle of incidence of solar radiation, maximizing the use of solar energy while always maintaining a perpendicular position relative to the incident radiation beam. This system is also capable of flexibly adjusting the angle to meet the needs of natural lighting and views.

Figure 3. Structure and solar energy utilization of the APVGF [34].

The examples provided summarize a recurring trend that emerged in numerous studies analyzed as part of this research. Despite the technological and construction differences that characterize the identified prototypes, the vertical greenery systems examined share the same design approach: they are generally developed for specific building configurations, often involving new construction or unique application cases. In this context, the issue of standardizing construction solutions and adapting substructures to the different characteristics of buildings -geometric, dimensional, morphological, and technological- remains largely marginal. Consequently, the recently developed prototypes can be interpreted as examples of performance-based innovation rather than examples of construction-based innovation: they improve the system’s performance but do not substantially alter the design paradigm, which continues to be based on defining specific solutions for individual application contexts.

The “artisanal” approach adopted thus far for the design of facade greening projects represents a critical issue that appears particularly relevant in the case of retrofitting projects for existing buildings, as the structural configurations of GF systems are defined based on the specific characteristics of the building, through design processes that involve adapting grids, cables, or frames to the geometric conditions of the facade. Although this approach allows for an effective response to the needs of each individual project, maintaining a significant artisanal component in the design process limits the replicability of the solutions, hindering the large-scale adoption of GF.

It is noteworthy that this tendency to develop tailor-made solutions for individual projects is also evident in high-profile projects and design significance, such as those carried out by architect Stefano Boeri on the ALER public housing units in Monza or in a public housing neighborhood in Prato [35]. In the first case, a climbing greenery system was integrated into the building facades, supported by metal cables anchored to the ground, with vegetation planted directly in the areas adjacent to the building to promote growth and reduce maintenance. In the second case, the redevelopment of an office building and a public housing complex involves introducing trees and plants onto the facades and roofs of the existing buildings, selecting native plant species with a high capacity for CO₂ sequestration and absorption of atmospheric pollutants [36]. Although implemented on existing buildings, these projects are highly context-specific and developed on a case-by-case basis, rather than as systems that are easily transferable and adaptable to other similar situations. In view of these considerations, there is a need to direct research toward the concept of structural adaptability. This can be defined as a system’s ability to adapt to different structural, volumetric, and morphological characteristics of buildings through the reconfiguration of standardized components, without requiring a complete redesign of the substructures.

The concept of design adaptability presupposes the simultaneous presence of specific requirements such as:

• System modularity;
• Standardized components;
• Dimensional flexibility;
• Configurable joints;
• Dry assembly;
• Retrofit compatibility.

Among the few studies that explicitly address the issue of structural adaptability is the “Vertical Greening Frame for Existing Buildings” (VGF4EB). This is a modular, versatile VGS support system adaptable to existing buildings, developed by the authors as part of research on the integration of vertical greenery into the building envelope [37].

It was designed to facilitate the application of green facades to existing buildings and consists of a modular, configurable construction system—classified as an indirect continuous-cable system—made of tubular steel profiles assembled using dry-assembly threaded joints (Figure 4). The innovative aspect of the project does not lie in technological innovation, but rather in the construction logic adopted, which is based on the combination of a limited number of standardized components capable of generating different configurations through flexible assembly processes.

Figure 4. VGF4EB elementary module. All system components are shown divided into invariant and combinable elements [37].

By combining the various components, it is possible to cover surfaces of various sizes, vary the distance of the green wall from the existing facade, and adapt the vegetated screen to the presence of balconies or overhangs. This approach moves beyond the traditional logic of ad hoc design for individual buildings and introduces a development method more consistent with the principles of industrialization.

The design of building systems based on the concept of construction adaptability does not necessarily entail the standardization of the final result.

Traditionally, standardization has been associated with the repetition of identical solutions, while customization required the design of specific components.

Building systems designed according to the concept of construction adaptability could effectively help demonstrate that design flexibility—and thus also the uniqueness of the final product—can be achieved through different combinations of standardized components.

From this perspective, adaptability is not an alternative to industrialization, but rather one of its key prerequisites.

The ability to generate different configurations from a limited number of prefabricated elements makes it possible to combine:

• Industrial production;
• Application flexibility;
• Design simplification;
• Cost reduction;
• Greater replicability of solutions.

The concept of construction adaptability should therefore not be interpreted exclusively as a technical characteristic of the system, but as a design principle capable of overcoming the misconception that standardization and originality must necessarily be mutually exclusive. Research and development of industrialized construction systems characterized by high versatility and adaptability could represent a valuable contribution to promoting the widespread adoption and replicability of GF, even in existing buildings.

4. Conclusions

The analysis of the literature and case studies examined in this review highlights how the growing adoption of VGS has been accompanied by significant advances in the assessment of the environmental, energy, and functional performance of these systems. However, there also appears to be limited attention paid to the technological and construction aspects aimed at integrating GF into the building envelope, particularly with regard to support substructures and strategies for adapting to different application contexts. Design practice has focused primarily on refining individual systems and defining specific, case-by-case solutions. This approach constitutes a limitation that hinders the large-scale adoption of these solutions, especially at a time when the energy and environmental retrofitting of the existing building stock is one of the main tools for ecological transition and adaptation to climate change.

This paper proposes a conceptual shift from performance-oriented research to feasibility-oriented research.

In this context, construction adaptability emerges as one of the keys, yet still largely unexplored, areas of development for the future evolution of GF. The ability to design systems based on industrialized, modular, and reconfigurable components would make, in fact, possible to overcome the traditional dichotomy between production standardization and design customization, thereby promoting greater applicability of these solutions to retrofit processes, the renovation of existing buildings, and environmental mitigation. From this perspective, adaptability is not merely a technical characteristic of the system, but a design principle capable of supporting its replicability, flexibility of application, and potential for industrialization.

Future research should therefore focus on the development of support systems and anchoring devices characterized by high versatility and design flexibility, capable of accommodating the volumetric, morphological, and structural variability that characterizes the existing building stock. At the same time, it seems appropriate to expand the investigation to include the materials used in the construction of support structures, promoting the adoption of solutions with a reduced environmental footprint.

In this context, particular attention could be given to the use of natural, recyclable, and environmentally friendly materials, both for elements designed to support vegetation and for load-bearing substructures. Possible future research directions include the use of natural fibers, such as jute, as a substitute for traditional metal or plastic cables or trellises to support vegetation, as well as the use of materials such as wood, bamboo, or recyclable bioplastics for the load-bearing substructure. It represents possible avenues for development aimed at increasing the environmental sustainability of GF without compromising their technical and structural performance.

The integration of construction adaptability, modularity, and material sustainability therefore appears to be a particularly promising prospect for the future evolution of GF, contributing to the development of systems that are more compatible with the needs of building stock revitalization and with sustainable development goals in the construction sector.