Professor in Residence, Department of Architecture, GSD, Harvard University, Cambridge MA, USA
Policy
Open Access
Type
Article
ABSTRACT -
Urban landscapes are characterized by adaptable urban ecosystems that integrate natural and human-made aspects. This paper argues that building-scale biofacades can make key contributions to these ecosystems beyond conventional green facades. The paper introduces the concept of biofacades as a means of integrating biological processes into facade design, supporting diverse organisms across scales and fostering interconnected urban ecosystems. The Biofacade Classification system is introduced as a framework for vertical building–nature integration. The framework organizes biofacades according to wall layer position, biotic distribution, and operational mode, while also describing associated ecosystem services. Case studies illustrate its capacity to clarify the complexity of building–nature interactions and to encompass engineered solutions ranging from microalgae facades to microbial growth-promoting materials. By positioning facade design as a part of urban biomes, the framework supports architects, planners, and other stakeholders in establishing goals and communicating integrated performance benefits in the effort to create more resilient and ecologically integrated cities.
Contemporary cities face a multitude of ecology-related challenges, from habitat fragmentation and biodiversity loss to urban heat islands and atmospheric pollution. Conventional urban development has often prioritized human-centric buildings and infrastructure to the detriment of ecosystem resilience and quality of life. This paper argues that a shift in architectural design, moving away from an anthropocentric to more inclusive and ecologically integrated perspective, is essential for fostering urban ecosystems that are mutually beneficial for humans, plants, animals, and the built environment (Fig. 1). We posit the building facade at the center of this integrative strategy as it makes a vast, underutilized vertical landscape available for new types of bio-integrated design interventions.
Figure 1.
1
Hierarchy of environmental ethical perspectives
This article introduces and elaborates on the concept of “biofacades” as a comprehensive framework for vertical building–nature integration. Moving beyond established green wall typologies focused primarily on human amenity,1 the biofacade concept encompasses a broader vision. It involves the intentional integration of diverse organisms, from micro to macro scales, in a range of combinations of natural and artificial, into the building envelope to create active, living systems that participate in urban ecological systems and processes.2 Biofacades can function as nodes within larger networks of ecosystems, enhancing ecological connectivity and supporting vital cycles of air, water, nutrients, and life across urban environments and urban communities.
Due to the novel nature of these systems, a primary impediment to their implementation is the absence of a unified, design-oriented language to articulate their multifaceted benefits and complexities to a diverse range of stakeholders.3 Addressing this gap, this paper presents the Biofacade Classification system. This framework is designed to analyze and clarify the core aspects of building–nature integration from an architectural design perspective, focusing on three primary dimensions: the wall layer position of the biological system, the tectonics and distribution of biota, and the type of ecosystem services. The framework further catalogs the resulting ecosystem services, expanding their definition to include performance benefits for the building, human populations, and non-human species alike. By illustrating the classification in a range of case studies, from microalgae bioreactors to microbial-growth-promoting materials, the classification system demonstrates its utility in capturing a spectrum of designs that blur the boundaries between the artificial and the natural in new types of urban ecosystems.
Biofacades provide multiple benefits, but they also present several interlinked challenges that limit wider implementation. Key challenges include high upfront and maintenance costs compared to traditional facades; a lack of standardized technical guidelines (e.g., intensive engineering requirements, code compliance, operation and maintenance standards, and plant performance guidelines); gaps in policy, regulations, and industry certification frameworks; and limited culture and education about green facades and urban ecology.4 We propose the biofacades framework as a design tool for architects, planners, and developers. It offers a structured approach not only for categorizing existing innovations but also for envisioning and implementing a new generation of architectural facades that actively contribute to the ecological vitality and resilience of urban ecosystems.
THEORETICAL BACKGROUND: URBAN ECOLOGY AND THE BUILT ENVIRONMENT
This research is based on the premise that architecture and nature can have a reciprocal relationship within urban ecosystems, and that architectural design can structure and organize this relationship. Urban ecologists understand ecosystems as social-ecological systems. Urban ecology posits that cities are complex and heterogeneous ecological systems in which biological, social, and built components are inextricably linked.5 In urban ecosystems, urban form is a primary driver that shapes ecological patterns and processes (including hydrology, biodiversity, and nutrient cycling), with buildings constituting key structural elements within the larger urban ecosystem. The built environment can positively contribute to ecosystem connectivity, where flora and fauna, and air, water, and land cycles, operate freely in coordination with human-built infrastructure. For example, wetlands can be restored and designed to enhance recreational opportunities. The concept of ecosystem services is commonly used to describe the benefits that humans receive from nature, recognizing that human health and security is tied to the health of natural ecosystems.
While vertical green elements on buildings are considered as key parts of ecology-supporting urban green infrastructure,6 few previous ecological studies have discussed the role of individual building facades or their design within the broader framework of human-shaped urban ecosystems. Architects and urban planners are increasingly interested in ways that environmental systems, urban infrastructure, building enclosures, and biological organisms can cooperatively intersect to contribute positively to climate change adaptation to support human well-being and biodiversity in urban ecosystems.7 Moving beyond a solely anthropocentric perspective, concepts like multispecies design represent a shift toward a biocentric mindset.8 In this context, the design of cities requires an increasingly interdisciplinary approach. Early on, publications like Victor Olgyay’s
Design with Climate (1963) 9 and Ina McHarg’s Design with Nature (1969) 10 recognized the need for architects and planners to consult a wide body of environmental knowledge beyond their respective fields. Like bioclimatic design, building–nature integration requires significant knowledge of local climate and cultural patterns of occupation.
Following the research of Casey Visintin et al.,11 this paper advocates the idea of “everyday nature,” where biodiversity experiences are an integral part of daily urban life, rather than isolated parks. This represents a shift from simply adding ecology to adopting a more strategic approach toward ecological connectivity. Looking at connectivity helps identify where to add green spaces and target species, creating everyday-nature networks at the building scale. Biofacades can serve as connectors by stitching sites into continuous green corridors and incorporating appropriate crossings and micro-links that connect nature, humans, and buildings.
The built environment literature has widely explored green infrastructure in a range of scales, from wildlife corridors, wetlands, to green streets. At the building scale, green roofs and green walls have been shown to offer multiple benefits for the building as well as the surrounding environment – including reducing energy use and managing stormwater – with positive impacts to air quality, heat, and atmospheric carbon levels in urban communities, provision of wildlife habitat, and psychological benefits to people.12 The many types of walls that incorporate living plants are commonly described as green facades or living walls, under the umbrella term of vertical greening systems, or VGS.13 Terminology is borrowed from green roof and facade design to categorize the application of greenery, for example, direct vs. indirect, continuous vs. modular,14 and extensive vs. intensive.15
Beyond ecosystem services and technical performance benefits, buildings have a formal dialogue with surrounding landscapes. Building design can adopt various degrees of taming, response, appropriation, and control of nature, such that nature integration may originate from practical or humble gestures such as a sod-roofed house or an ivy-covered wall to more elaborate or engineered constructions. A correspondence can be drawn between the built environment and nature by observing the ways that humans have positioned nature vis-a-vis buildings in the form of volumetric shapes and angled, horizontal, or vertical planes. From a Cartesian viewpoint, the x-axis and z-axis are firmly anchored in current architectural discourse by green roofs and green walls.16 As environments are increasingly urbanized, recognition of humans’ innate need to connect with nature has turned attention toward biophilic design. Abundance and diversity of life, ecological health, and accessibility to nature are now measures of urban environmental quality.17
Though not codified under any singular definition yet, the term “biofacade” has been occasionally used to describe different types of vertical greening systems,18 but has been most commonly employed to describe facades that integrate algae or bacteria as photobioreactors (PBRs) for solar cultivation of microorganisms.19 Integrating the urban ecological concern, we propose a wide perspective on biofacades, with the prefix ‘bio’ adopted to include biological processes in a general sense. Accordingly, the Biofacade Classification system embraces the full biological potential of living organisms, which may include microorganisms, insects, and animals as well as plants, integrated with construction.
THE BIOFACADES CLASSIFICATION SYSTEM
The Biofacades Classification System is a framework for vertical building–nature integration. It is intended to assist a range of stakeholders to establish goals and communicate performance benefits in the complex process of developing bio-integrated building enclosures. The process of creating the framework builds on previous taxonomical analysis of facades. The double-skin facade typology presented in Mary Ben Bonham’s Bioclimatic Double-Skin Facades 20 provides the basis of a classification system that organizes interdependent tectonic and functional aspects of facades.
The Biofacades Classification System extends the work of Bonham, Kyoung Hee Kim, and Christiane Herr 21 who defined biofacades as building enclosures that integrate biological systems and discuss performance benefits, challenges, and taxonomies of building–nature integrations. To validate the outcomes and methodology, the authors previously presented a draft of the Biofacades Classification System 22 to industry specialists, including facade designers, manufacturers, and architectural educators. The refined classification system presented in this article crucially integrates ecological knowledge into the categorization. It examines how facades can performatively contribute to ecosystem services for both human and non-human stakeholders, and aims to provide accessible and applicable design language to break down the complexity of building–nature integration.
Biofacades Objectives
Biofacades extend conventional green facades through attention to the dynamics of living processes at a more comprehensive level. When building enclosures are considered as dynamic processes rather than static configurations, more disciplines must join the discourse to manage various aspects of change over time. Such interdisciplinary efforts present differences in perspectives as well as methods, requiring new language for exchanges to communicate between the observational focus of science, the interpretive focus of sociology, the methodological focus of engineering, and the anticipatory approach of design. In the processes and policies guiding urban development, the planning of single buildings needs to be considered within complex urban fabrics. In this context, the biofacades nomenclature and classification can assist stakeholders in the effort to establish goals and communicate performance benefits in the multifaceted process of developing bio-integrated building enclosures.
In the broader understanding we argue in this article, biofacades include not only plants but various types of organisms, from the micro to the macro scales. Ecosystem services provided by biofacades are accordingly extended from human benefit to wider urban ecology benefit, as illustrated in Figure 1. Facade performance goals conventionally derive from an anthropocentric perspective, focusing on light, heat, health, thermal comfort, ventilation, acoustics, energy, and now, acknowledging the human impact on climate, carbon emissions. Adopting an ecocentric and biocentric view, we position ourselves in nature rather than separate from nature, such that ecosystem services are recognized as the performance measure of ecological reciprocity. This multicriteria approach acknowledges that different services can take priority depending on what is to be protected, maintained, or sustained. As living and constantly changing processes, biofacades require mutual adaptation over time, where biological agents, humans, and buildings are linked in active feedback cycles.
Dimensions of the Biofacades Classification System
The Biofacades Classification (Table 1) organizes the taxonomical dimensions of biofacades. In the first layer of hierarchy are the interdependent dimensions of wall layer position, tectonics, and ecosystem services. Categorization begins with the position of biotic matter relative to wall construction. Tectonics categories describe the type and distribution of biota, and the mode of operation. Ecosystem Services categories consist of building, human, and non-human performance benefits. Following a brief description of each category, several case studies are presented to illustrate how the framework can capture the complexity of building–nature integration.
Table 1.
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Biofacades classification.
Wall Layer Position categories describe where the biotic integration occurs in relation to the building enclosure (Fig. 2). Working from the outside to the inside, we delineate “exterior indirect” systems that are offset from facade surfaces and ‘exterior direct’ systems that are directly positioned on facade surfaces. “Exterior indirect” includes cable systems and other forms of screen-like green facades. “Exterior direct” systems can be versatilely configured including planter boxes and living wall systems with modular or continuous substrates. Moving closer in, biotic matter can be “integral to cladding,” for example, in the form of algae cultivated inside glazed panels. Plants or other biotic matter located between the layers of a double-skin facade are “integral to cavity.” Finally, biotic matter can be located on the ‘interior’ side of the facade zone in a wide range of forms and functions such as living walls with active biofiltration.
Figure 2.
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Biological components in relation to building envelopes: wall layer taxonomy.
Tectonics categories describe how biological agents interact with building forms, materials, and systems. Biota distinguishes flora, fauna, and microorganisms as three broad categories of biota for inclusion in biofacades. Distribution describes the building components that support the biological matter. Mode refers to the operational characteristics of the wall and living systems. Bioclimatic systems refer to operations that occur passively in response to climatic conditions, as opposed to active systems that utilize electrical or other types of generated power to drive hydroponic or other mechanical systems. Ecosystem Services categories distinguish between performance factors offering benefits to the building, to humans, and to non-human living systems and life-cycle dynamics.
CASE STUDIES
A growing body of scientific research demonstrates that green facades deliver measurable environmental benefits of biofacades, including energy savings, heat island mitigation, air quality improvement, greywater treatment, biodiversity, and acoustic barriers, as well as health performance and psychological well-being.23 However, specific biofacades may only provide a selection of these benefits. The following four case studies were selected to illustrate a broad range of biofacade principles and means of integrating biological processes into facade design. The case studies chosen for this analysis cover a range of climatic contexts to illustrate wide applicability of the classification system, with future development of climate-specific versions of the system a possibility. Analysis of the case studies using the Biofacades Classification System demonstrates the utility of a unified language to articulate their multifaceted benefits and complexities. When taken together, the case studies reveal commonalities as well as particularities of existing integration strategies and point to as yet untapped potential for facades to foster architecturally designed contributions to urban ecosystems that are mutually beneficial for humans, plants, animals, and the built environment.
Case Study 1: Algae Windows, City of Charlotte Innovation Barn
Algae facades have attracted the interest of researchers and designers worldwide, beginning with the pioneering BIQ House in Hamburg. Algae integration can be categorized into four levels of intervention: infrastructure, including applications such as energy generation, food production, and wastewater treatment; urban, such as parking canopies, bus shelters, and algae gardens; building, including bioactive primary building enclosures and retrofitting applications; and products, such as algae-based lamps, architectural tiles, and interior elements 24 The Algae Window system at the City of Charlotte’s Innovation Barn (a public circular economy demo hub) exemplifies vertical building–nature integration within a biofacade design framework (Fig 3). The Algae Window system incorporates chlorella microalgae in a photobioreactor designed to perform as an air purifier and shading device.
3
ALGAE WINDOWS at the City of Charlotte Innovation Barn. Architect: Kyoung Hee Kim. Date constructed: 2024. Building use: Recycling plastic lab. Location: Charlotte, NC.
Climate: Koppen-Geiger Cfa humid subtropical; ASHRAE 90.1 zone 3A warm humid;
microalgae window facing southwest.
Figure 3.
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Biofacades classification for algae windows at the City of Charlotte Innovation Barn. (a) View from interior; (b) View from interior.
The system is carefully tuned to Charlotte’s humid subtropical climate (Köppen-Geiger Cfa; ASHRAE 90.1 zone 3A warm-humid), with its microalgae-filled window units oriented southwest to optimize solar exposure for photosynthesis. In this way, local climatic conditions directly inform the depth and orientation as well as cultivation cycles of the microalgae window assemblies. Its positionality is expressed through the integration of the microalgal biomass within the glazed units or photobioreactor, with strategic controllability to cultivate living components – all while serving as a novel tectonic element that merges biological processes with built form. The distribution is designed for an extensive modular system and integrated with active mechanical systems for operation and maintenance.
At the building service level, the Algae Window provides insulation and solar shading capabilities that contribute to energy savings and daylight illumination. On the human service level, it enhances interior environmental quality by filtering pollutants, such as PM2.5, VOCs, and CO2. This air filtration is supported by biological productivity in which chlorella produced 175 mg/L-day and Chlorococcum produced 80 mg/L-day in the microalgae window system, confirming the feasibility of microalgae-based building enclosures as a practical strategy for real-world carbon capture.25 A real-time dashboard tracks carbon capture, pollutant reduction, and oxygen generation. The dashboard is accessible to building occupants and the public. This connects the facade’s living aesthetics to health and environmental benefits. Such symbiotic sustainability practices encourage user interaction and greater environmental awareness.
From an ecosystem perspective, the system provides an optimum growing environment through balanced automatic nutrient dosing and controlled light regulation, through leveraging static indoor conditions such as temperature and CO2 level from indoor application. Growth rate measured through biomass (g/l) and cell counts (cell numbers/ml) serves as evidence of successful ecological cultivation. The Algae Window provides additional ecosystem services by sequestering carbon and generating oxygen. The microalgae’s oxygenic photosynthesis supports mycelium biomaterial cultivation. In return, the CO2 generated from the mycelium is recirculated to grow algae in a symbiotic closed loop. Through this building–nature integrated approach, the Algae Window exemplifies how architectural, human, and ecological performance objectives can be synergistically achieved under the biofacade framework, effectively bridging architecture and biology.
Case Study 2: Living Wall and Planter Boxes, One Central Park
Our next case study focuses on One Central Park designed by Ateliers Jean Nouvel with botanist Patrick Blanc (Fig 4). The project integrates vertical biofacades with urban ecology in a thirty-four-story high-rise building. The project is located in Sydney, Australia, which is in the Köppen-Geiger Cfa humid subtropical climate zone. Both the local climate and immediate urban environment, as well as local ecological considerations, influenced the design of the biofacades, which consist of two primary types of wall positions. The exterior indirect system uses vertical stainless steel cables anchored to planter boxes distributed at various building levels, allowing climbing plants to ascend and weave across the surfaces like a suspended green screen. The exterior direct system employs living wall modules, combining modular trays and monolithic felt layers to secure a wide array of vegetation directly to the facade.
4
ONE CENTRAL PARK. Architect: Atelier Jean Nouvel with Patrick Blanc, Botanist. Date constructed: 2014. Building use: Mixed use residential, office, retail. Location: Sydney, Australia. Climate: Koppen-Geiger Cfa humid subtropical.
Figure 4.
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Biofacades classification for One Central Park, Sydney, Australia. (a) View from street; (b) Elevation view.
The biota supported by these systems are remarkably diverse. A total of 35,200 plants from 383 different species are arranged in dense patches and textured mosaics, covering 1,120 m2 [12,056 sq. ft.] of the biofacades with some native species such as Acacia plicata, chosen for their adaptability to Sydney’s climate. The distribution of these species is achieved through planters, extensive modular living wall system trays, and extensive monolithic living wall system felt. The planters use minimal soil, and the living wall plants attach their roots to trays and felt soaked with mineralized water, reducing the structural load on the building structure while maintaining system integrity. The lush greenery attracts animals, insects, and other pollinators which thrive in the vertical biofacades. The mode of operation for the biofacades relies on bioclimatic strategies and active systems, through which drip irrigation and nutrients are distributed throughout the high-rise biofacades. Graywater is also used to irrigate the biofacades, conserving water use.26
As a result, the biofacades’ ecosystem services in this building are wide ranging. On a building scale, the biofacades effectively manage solar exposure and air humidification, creating favorable microclimates and mitigating the urban heat island effect.27 For users, maintaining contact with the biofacades helps improve thermal and visual comfort, filter and oxygenate the air, and provides strong biophilic effects.28 For non-human life, the biofacades provide natural habitats and food sources for other organisms, promoting ecological linkages to neighboring parks and greenspaces. They integrate into larger cycles of water and air, interlacing urban nature systems.
This project demonstrates how a high-rise can become a living interface where biofacades enhance user benefits, support urban ecology, and deliver improved building performance. The main challenge for the biofacade implementation lies in relatively intensive maintenance of both greenery and mechanical systems, and the management of the boundary between green walls populated by various organisms and the variety of inhabitant attitudes to allow at least some crossing of boundaries. Overall, One Central Park presents a replicable pathway for bio-regeneration in urban environments, positioning architecture not just as a passive recipient of nature’s resources but also an active participant in its restoration.29
Case Study 3: Green Screen, M6B2 Tower of Biodiversity
In the Tower of Biodiversity, the Maison Édouard François integrates a variety of sustainable design strategies into the sixteen-story residential tower in Paris, France (Fig. 5). The main facade of the building employs conventional sustainable facade materials and a recyclable titanium cladding. A biofacade forms a secondary facade layer which gives center stage to a series of native trees and vertically climbing plants. All chosen plants are native to the region around Paris and were selected for their ability to tolerate the challenging conditions of the exposed facade location with limited natural soil available.30 The wall layer position category of the vegetated balconies that line the building perimeter is exterior indirect. In distribution tectonics, the plant biota grow in soil inside tubular stainless steel planters that punctuate the edges of concrete balconies.
5
TOWER OF BIODIVERSITY
Architect: Maison Édouard François with landscape architects BASE and École du Breuil. Date constructed: 2015. Building use: Residential. Location: 13e Paris, France. Climate: Koppen-Geiger Cfb temperate oceanic climate.
Figure 5.
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Biofacades classification for the Tower of Biodiversity, Paris, France. (a) View from street; (b) Flora studied by the École de Breuil for use in the tower planters. Top left: European honeysuckle (Lonicera periclymenum); Bottom left: rock cherry (Prunus mahaleb); Right: Scots pine (Pinus sylvestris).
Climbing vines spread vertically on a continuous surround of stainless steel netting. The mode of the biofacade is bioclimatic with an active component due to the automated irrigation system. Rainwater is collected from the balcony surfaces. The design integrates multiple dimensions of ecosystem services such as shading and water management from a building perspective, and thermal, visual, and biophilic effects from a human perspective. Non-human ecosystem services are central to the concept: plant species are chosen with advice from experts to become a viable and beneficial addition to the surrounding urban ecosystem. From the elevated position of these plants, native seeds will be spread out into the surrounding dense urban fabric. Behind the vegetated screen, the building is clad with green titanium panels, intended to be reminiscent of moss, another expression of the intent to extend a ‘green aura’ to the urban landscape.31
The architects collaborated with additional partners to realize the success of the planting scheme. The École du Breuil in partnership with Paris Habitat, the botanical garden of the City of Paris, conducted an experiment to study plants grown within tubes with drip irrigation. The study monitored temperatures of the substrate, plant growth, water consumption, quantity, and length of roots. The plants chosen to decorate the tower are chasmophytes, plants that grow in the crevices of rocks, endemic to the Parisian climate.32 In this biofacade, living organisms are knitted into the building’s structure and fabric with pattern and control as if they are another architectural material. While the application of the flora to the facade is abstract and symbolic, the connection between the building and the surrounding patrimonial landscape is carefully constructed.
Case Study 4: Integral to Cladding, School for Sciences and Biodiversity
The Primary School for Sciences and Biodiversity by ChartierDalix architects (Fig. 6) illustrates a biofacade that is integral to cladding. It provides a vertical habitat for diverse locally sourced and adaptable biota through simple but well informed and meticulously designed passive design strategies that work with the mass and volume of the exterior modular concrete wall. This case study exemplifies the multidisciplinarity and ongoing cooperation required to integrate buildings and nature. As a part of the larger urban development plan for the Seguin Rives de Seine area, the project is located on the former Renault factory grounds. A master plan for redevelopment of the area set the goal to integrate green spaces and use regional plant species to enhance urban comfort and connect to the greater biotope.
6
PRIMARY SCHOOL FOR SCIENCES AND BIODIVERSITY
Architect: ChartierDalix Architecture with Aurélien Huguet Ecologie, Ecology Consultant. Date constructed: 2014-15. Building use: Residential. Location: Boulogne-Billancourt. France. Climate: Koppen-Geiger Cfb temperate oceanic climate.
Figure 6.
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Biofacades classification for the Primary School for Sciences and Biodiversity, Boulogne-Billancourt, France. (a) Exterior view of facade and roof garden; (b) View of entrance.
The city of Boulogne-Billancourt commissioned the school project to the winning team of Agence ChartierDalix with AEU and F. Boutté. The construction project management agency SAEM Val-de-Seine and ecologist Aurélien Huguet worked closely with the architects to conceptualize the school as a “nature island” with ecological engagement expanded beyond traditional green roofs.33 The methods drew from ecological engineering of restoring natural spaces rather than horticulture. Many collaborators were engaged in the process: target species were identified with assistance from a national institute, Urban Ecology Workshop, to be implemented in the project, and seeds for sowing into the wall pockets and green roof were extracted from neighboring meadows and natural areas with the help of volunteers.34 The wall layer position category of the biodiverse block wall is integral to cladding.
Distribution of biota in the concrete block wall cladding was planned block by block to locate the type and position of wildlife-reception features including nest boxes, cracks, and perforations. The mode of the biofacade is bioclimatic. The resulting ecosystem services are targeted to enhance conditions for biodiversity and improve environments for human and non-human life alike. Fauna and flora inventories between 2015 and 2019 and monitoring of the colonization of nest boxes on the facade document the presence of five species of orthoptera, around twenty species of birds, including sparrows, and two species of bats, in a clear demonstration of the site’s value as an urban nature island.35 The absence of cascading plants on large portions of the cliff-like masonry wall subverts the preconception that greenery is a prerequisite for biophilia or biodiversity.
DISCUSSION: IMPLICATIONS FOR ARCHITECTURAL DESIGN IN THE CONTEXT OF URBAN NATURE AND POLICY
Urban environments across the world are in urgent need of maintaining and improving their livability, not only for the benefit of human populations but also for the benefit of other living beings. As previous studies have shown, the integration of nature into cities presents a clear strategy to support this goal, offering multiple benefits in terms of services to both human health and well-being as well as more quantitative goals, such as reducing energy use and carbon emissions. In this paper, we discuss biofacades as a way to include biological elements into facade assemblies across a range of design approaches, from custom-designed vertical ecosystems to the farming of microorganisms in bioreactors. Despite the increasing number of built works, different facade design approaches integrating living systems have rarely been linked or discussed from a broader integrated perspective.
We present the Biofacades Classification System as a response to the increasingly diverse landscape of specialized approaches of including biological elements within architectural facade systems. Employing four key case studies, we demonstrate how the Biofacades Classification System can be used to describe and compare a variety of biofacades, enabling stakeholders from various disciplines to assess design potentials and set performance goals. The analysis of the four case studies within the Biofacades Classification System shows that almost all of them integrate ecosystem services for both human and non-human inhabitants. This feature, however, can be achieved in several ways, as the highly diverse architectural implementations in the case studies show. Ecosystem services for the building typically include shading, whereas the most common ecosystem service for human inhabitants consists of the biophilic effects that can be provided in diverse ways.
Aside from these general observations, it is, however, important to note that the analytical descriptions of the case studies do not primarily serve the purpose of comparison. Instead, they are intended as tools for raising awareness and reflecting on omissions and opportunities that arise from mapping the case studies’ characteristics to the classification system. From a design perspective, the integrated nature of the framework offers a broader range of possibilities and allows for creative bridging of conventional distinctions, for example, between artificially maintained algae facades and initiatives to increase biodiversity through greening strategies for building facades. Microbial biodiversity, for example, not only offers a promising pathway toward quantifiable health benefits but also encourages the presence of natural soil at various elevations of building facades.36
Meanwhile, green facades have been framed as a device to provide cooling or shading, with their potential to enhance biodiversity or human well-being mostly left untapped. The discussed case studies are selected to illustrate a range of possibilities that allows for both integration and innovation. We emphasize the urban nature of biofacades which can act as the integrative tissue between humans, nature, and cities, contributing a wider range of ecosystem services than currently realized. The analysis of case studies further demonstrates that a careful balance between planning, control, and, on the other hand, a new degree of openness toward change, is needed to support successful implementation of biofacades.
An example of creative bridging of disciplines is found in the collaboration between landscape architect Thomas Hauck and biologist Wolfgang Weisser, who developed a set of design standards that include life-cycle fact sheets for different animal species that can be used to improve conservation and planning efforts. Weisser and Hauck speculate on the potential to incorporate nesting boxes in line with insulation layers added to existing facades, a solution that simultaneously addresses issues of obsolete enclosures, climate change mitigation, and habitat conservation.37 The team has been involved in several built projects, including a new public housing project in Ingolstadt, Germany, where the design was adjusted for three target species to thrive: the house sparrow, the European hedgehog, and the red admiral butterfly. Nest boxes were integrated into building eaves, in coordination with measures beyond the facade including sand areas for bathing, drainage areas to provide a water source, and management of an adjacent meadow area.38
Other researchers have proposed additive manufacturing as a means to customize the integration of animal habitats into site-specific facade-cladding materials based on ecological study of targeted species.39 Despite their potential to enhance urban ecology, biofacades still face barriers to widespread implementation. A primary challenge is the reliance on active systems for irrigation or nutrient provision and maintenance, which introduces a high operational burden and risk of malfunction, deterring stakeholder adoption. This is compounded by high upfront costs and a persistent lack of clearly articulated long-term economic and environmental benefits in quantifiable terms at a project’s outset. Limited policy support and the absence of specific code regulations further slow market acceptance, as architects and developers navigate uncertain approval pathways, while operation and maintenance burdens slow implementation as well as the building of public trust.
Consequently, for biofacades to become a mainstream sustainable facade solution, their documented benefits must demonstrably outweigh these practical issues of cost, operation, and maintenance. We argue that effective installation approaches such as modular prefabrication, combined with automation and sensor features, can balance human comfort and nature protection. Thorough investigation and planning will be required to meet both needs, with enhanced cross-disciplinary collaboration a crucial ingredient for effective integration of nature, building, and site. As shown by examples like Singapore, the quality enhancement of urban environments through the integration of natural elements on building facades can be transformative of even high-density environments. Supportive policies at city and building scale, facade guidelines and inclusion of related targets in sustainability rating systems will be required for wider biofacade adoption in the future.
CONCLUSION AND FUTURE DIRECTIONS
Reflecting a broad shift from an anthropocentric focus of nature integration in architecture and cities toward a mutualistic perspective on the built environment, we introduce and discuss the Biofacades Classification System as a tool to articulate and coordinate design and policy goals for architectural design in support of ecological cities. The inclusion of biological systems in building facades with a focus on ecology, from the urban to the microbial scale, draws attention to a wider set of ecosystem services – where ecosystems serve people and buildings, while in turn buildings also serve ecosystems at various scales.
Biofacades promise multifaceted benefits for human health and well-being at the building and city scale in addition to contributions to urban ecology, but their broad implementation relies on streamlined technical integration, market adoption, policy support, and public trust. Overcoming these barriers necessitates cultivating sustainability leadership and cross-sector collaborations in promoting biofacades and urban ecology, supported by dialogue between building owners, operators, designers, and ecologists along with support from policy framework and building regulations. In our future work, we aim to survey operators and users of completed biofacade projects and document successes, challenges, and areas for improvement. Anecdotal evidence suggests that stakeholder concerns can relate significantly to diverging cultures of use and regionally different openness to biological dynamics.
The inclusion of bioreactor facades in the broader framework of biofacades offers new possibilities and still requires exploration of how their processes and technologies can be integrated into new facade typologies. Opening considerations of biodiversity across a new range of scales and introducing biological productivity as well as human nature co-living in new ways, the extended bioreactor-inclusive biofacades can include biofilm and foam-based design approaches to maximize ecosystem benefits. Future research investigating novel symbiotic and process-driven relationships between organisms at various scales and humans, such as mycelium-microalgae complementary growth on the surfaces of buildings can lead to productive and scalable architectural applications. The Biofacades Classification System is an invitation to researchers as well as architectural practitioners to reconsider the role of architecture in general, and building facades in particular, to foster rich and resilient future urban ecologies.
Notes
1
Maria Manso and João Castro-Gomes, “Green Wall Systems: A Review of Their Characteristics,” Renewable and Sustainable Energy Reviews 41 (2015): 863–71 – doi: 10.1016/j.rser.2014.07.203.
2
Wolfgang W. Weisser and Thomas E. Hauck, “Animal-Aided Design – Planning for Biodiversity in the Built Environment by Embedding a Species’ Life-Cycle into Landscape Architectural and Urban Design Processes,” Landscape Research 50, no. 1 (2025): 146–67 – doi: 10.1080/01426397.2024.2383482.
3
Yasha J. Grobman et al., “Architectural Multispecies Building Design: Concepts, Challenges, and Design Process,” Sustainability 15, no. 21 (2023): 1–29 – doi: 10.3390/su152115480; and Soultana Tanya Saroglou et al., “Utilizing Design Objectives and Key Performance Indicators as a Means for Multi-Species Building Envelopes,” Buildings 14, no. 1 (2024): 250 – doi: 10.3390/buildings14010250.
4
Thácia Danily de Oliveira Santos et al., “A Systematic Analysis on the Efficiency and Sustainability of Green Facades and Roofs,” Science of The Total Environment 932 (2024).
5
Steward T. A. Pickett et al., “Urban Ecological Systems: Linking Terrestrial Ecological, Physical, and Socioeconomic Components of Metropolitan Areas,” Annual Review of Ecology and Systematics 32 (2001): 127–57.
6
Puay Yok Tan and Chi Yung Jim, eds., Greening Cities: Forms and Functions. Advances in 21st Century Human Settlements (Springer Singapore, 2017).
7
Nathalie Butt et al., “Opportunities for Biodiversity Conservation as Cities Adapt to Climate Change,” Geo: Geography and Environment 5, no. 1 (2018) – doi: 10.1002/geo2.52.
8
See Grobman et al., “Architectural Multispecies.”
9
Victor Olgyay, Design with Climate: Bioclimatic Approach to Architectural Regionalism (Princeton University Press, 1963).
10
Ian L. McHarg, Design with Nature (Natural History Press, 1967).
11
Casey Visintin et al., “Designing Cities for Everyday Nature,” Conservation Biology 39, no. 1 (2025) – doi: 10.1111/cobi.14328.
12
Flavie Mayrand et al., “Vertical Greening Systems as Habitat for Biodiversity,” in Nature Based Strategies for Urban and Building Sustainability, ed. Gabriel Pérez and Katia Perini (Butterworth-Heinemann, 2018).
13
Mina Radić et al. “Green Facades and Living Walls – A Review Establishing the Classification of Construction Types and Mapping the Benefits,” Sustainability 11, no. 17 (2019) – doi: 10.3390/su11174579.
14
See Manso, “Green Wall Systems.”
15
See Mayrand, “Vertical Greening Systems.”
16
Mary Ben Bonham and Kyoung Hee Kim, “Biofacades: Integrating Biological Systems with Building Enclosures,” Facade Tectonics, July 15, 2022 – https://www.facadetectonics.org/articles/biofacades-integrating-biologic....
17
Timon McPhearson and David Maddox, “What Is One Thing Every Ecologist Should Know About Urban Ecology?” The Nature of Cities, January 29, 2018 – https://www.thenatureofcities.com/TNOC/2018/01/29/one-thing-every-ecolog....
18
Pasinee Sunakorn and Chanikarn Yimprayoon, “Thermal Performance of Biofacade with Natural Ventilation in the Tropical Climate,” Procedia Engineering 21 (2011): 34–41 – doi: 10.1016/j.proeng.2011.11.1984;Fodil Fadli et al., “Smart Biofacades: An Innovative Living Construction Technology,” in Proceedings of the Fifth International Conference on Sustainable Construction Materials and Technologies, ed. Peter Claisse et al. (CRC Press, 2019) – http://www.claisse.info/Proceedings.htm; and Atikah Amir et al., “The Most Effective Malaysian Legume Plants as Biofacade for Building Wall Application,” Journal of Sustainable Development 4, no. 1 (2011): 103–11 – doi: 10.5539/jsd.v4n1p103.
19
See Bonham and Kim, “Biofacades.”
20
Mary Ben Bonham, Bioclimatic Double-Skin Facades (Routledge, 2019); in particular, pp. 41–75.
21
See Bonham and Kim, “Biofacades.”
22
Mary Ben Bonham et al., “BioFacades Classification – A Framework for Building-Nature Integration,” presentation at “Facade Tectonics 2024 World Congress,” University of Utah, – https://www.facadetectonics.org/papers/biofacades-classification.
23
Rosamina A. Bustami et al., “Vertical Greenery Systems: A Systematic Review of Research Trends,” Building and Environment 146 (2018): 226–37.
24
Kyoung Hee Kim, Microalgae Building Enclosures: Design and Engineering Principles (Routledge, 2022); and Flora Girard et al., “System Modeling of the Thermal Behavior of a Building Equipped with Facade-Integrated Photobioreactors: Validation and Comparative Analysis,” Energy & Buildings 292 (2023).
25
Kyoung Hee Kim et al., “Microalgae-Integrated Building Enclosures: A Nature-Based Solution for Carbon Sequestration,” Frontiers in Built Environment 11 (2025).
26
Chris van Uffelen, Green Greener Greenest: Façades, Roofs, Indoors (Braun, 2017).
27
Jean Nouvel and Betram Beissel, “Case Study: One Central Park, Sydney,” CTBUH International Journal on Tall Buildings and Urban Habitat IV (2014): 12–18 – https://global.ctbuh.org/resources/papers/1836-Nouvel_2014_OneCentralPar....
28
Mike Horne, “Inside the World’s Best Building,” News.com.au, November 14, 2014 – https://www.news.com.au/lifestyle/australians-are-high-rise-lovers-but-w....
29
Cooperative Research Centre for Water Sensitive Cities, “One Central Park Green Wall” (2019) – https://watersensitivecities.org.au/wp-content/uploads/2019/05/3-Central....
30
“M6B2 Tower of Biodiversity,” UrbanNext, September 5, 2017 – https://urbannext.net/m6b2-tower-biodiversity/.
31
École Du Breuil website, “M6B2: Protocole Experimentale” – https://www.ecoledubreuil.fr/jardin/les-experimentations/m6b2/.
32
Ibid.
33
Aurélien Huguet website, “Boulogne - École des sciences et de la biodiversité” (2019) – https://www.ahecologie.fr/boulogne-ecole-de-la-biodiversite.
34
ChartierDalix, Welcome the Living. Thinking Architecture as an Ecosystem (Park Books, 2019).
35
Aurélien Hueget Ecologie and Ecolo GIE, “Diagnostic ecologiques et inventaires faune-flore” (2022) – https://www.ahecologie.fr/_files/ugd/83c7bf_bba466ed60ad4466a07dd4afb042....
36
Christiane M. Herr et al., “Designing Biodiverse High-Rise Façade Microbiomes for Healthy Urban Environments,” CTBUH Journal IV (2022): 20–27 – https://global.ctbuh.org/resources/papers/4601-Herr_DesigningBiodiverseH....
37
Weisser, “Animal-Aided Design,” 159.
38
Nate Berg, “Creature Comforts,” Landscape Architecture Magazine, June 11, 2019 – https://landscapearchitecturemagazine.org/2019/06/11/creature-comforts/.
39
Iuliia Larikova et al., “Additively Manufactured Urban Multispecies Façades for Building Renovation,” Journal of Facade Design and Engineering 10, no. 2 (2022): 105–26 – doi: 10.47982/jfde.2022.powerskin.7.
Acknowledgment
The Southern University of Science and Technology provided financial support for the open access publication fees for this publication, awarded to Christiane M. Herr.
All authors contributed to the conception of the work. They also were involved in drafting or revising the article critically for intellectual content. All approved the final version.
Credits
Figure 1: adapted from Thomas Schaubroeck and Benedetto Rugani, “A Revision of What Life Cycle Sustainability Assessment Should Entail: Towards Modeling the Net Impact on Human Well-Being,” Journal of Industrial Ecology 21, no. 6 (2017) – doi: 10.1111/jiec.12653.
Figure 2: drawing by © Mary Ben Bonham.
Figure 3a and 3b: photos by © Kyoung Hee Kim.
Figure 4: photos by © CC BY-SA Sardaka.
Figure 5: photos by (a) © CC BY-SA Chabe01; (b) Top left: © CC BY-SA sannse; Bottom left: © CC BY-SA Jean Tosti; Right: © CC BY-SA Jean-Marc Pascolo.
Figure 6a and 6b: photos by © Christiane M. Herr.
Table 1: by © Mary Ben Bonham, Kyoung Hee Kim, and Christiane M. Herr.
Mary Ben Bonham, AIA, NCIDQ, LEED-AP, is Professor of Architecture and Interior Design at Miami University, where she teaches design studios and seminars in environmental systems and sustainability. She holds a M.Arch from the University of Pennsylvania, a B.Arch from the University of Texas at Austin, and has a record of professional practice. Bonham is the author of Bioclimatic Double-Skin Facades (2019) among other peer-reviewed publications. Her research has been supported by grants, including the Nuckolls Fund for Lighting Education, for which she co-developed interdisciplinary teaching modules.
E-mail: bonhammb@MiamiOH.edu
Kyoung Hee Kim, Ph.D., AIA, NCARB, NOMA, is Professor of Architecture at UNC Charlotte, and Director of the Integrated Design Research Lab, where she advances net-zero design and regenerative technologies. A licensed NC architect, she founded EcoClosure, a university spin-off, and is Design Principal at HKDnA PLLC. Formerly a Senior Associate at Front Inc., she specializes in high-performance building enclosures. Kim has authored over fifty peer-reviewed publications and a book, securing $2M+ in grants from NSF, DOE, EPA, AIA, and others. E-mail: kkim33@charlotte.edu
Christiane M. Herr is Professor and Director of the BEng Industrial Design program at the Southern University of Science and Technology, Guangdong, China. With a background in architecture and engineering, she leads the Future Ecologies Research Group, focusing on cross-disciplinary ecological design. She holds a Ph.D. from the University of Hong Kong and a Dr.-Ing. from the University of Kassel. Herr has authored over 120 peer-reviewed publications and co-edited the book Design Cybernetics: Navigating the New (2020).
E-mail: cmherr@sustech.edu.cn
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Print Publication Date
February, 2026
Electronic Publication Date
Tuesday, February 10, 2026
