Adaptive Energy Skins: A Climate Zones-Based, Multi-Scale Analysis for High Performance Buildings

Abstract

Adaptive facades represent the result of a complex combination of innovative technologies, components, and materials, as well as mechanical, electronic, or digital technologies from sectors outside the construction world (technology transfer), which require a constant multidisciplinary systemic approach. Unlike traditional envelopes, adaptive facades integrate aesthetics, functionality, and energy performance within a single system. This field of research has long been the subject of study by important institutions and research groups that have identified the macro-categories of adaptive envelopes that cover the largest share of the market and have defined the first ISO standards related to dynamic shading, chromogenic envelopes, and active ventilated facades. From the state-of-the-art analysis, adaptive facade systems exhibit short response times, measurable in seconds or minutes, while medium- to long-term adaptability remains underexplored. The objective of this study is to address this gap by considering durability and circularity. Analysis of a database of 329 building envelopes reveals a predominance of short-term strategies within the environmental domain, while long-term strategies focus on material durability and resilience through system regeneration and reuse. These strategies allow for maintaining energy performance by reducing degradation. Ongoing research integrates these strategies with reusability and circularity, extending the perspective beyond the building’s service life to support sustainable lifecycle approaches.

1. Introduction

The concept of adaptive building envelopes has gained increasing attention in architecture, engineering, and construction due to their potential to enhance comfort, energy efficiency, and sustainability. Adaptive façades respond to environmental changes over multiple time scales; however, most studies focus on short-term responsiveness, often overlooking how façades can evolve over decades while integrating material durability, component reuse, and circularity.

This paper addresses this gap as part of the ongoing research project “START—SusTainable dAta-dRiven manufacTuring” led by the University of Sassari in partnership with the Ministry of Economic Development (Italy), GRESMALT S.P.A., EURIT S.R.L., SACMI Cooperativa Meccanici Imola, the University of Calabria, and the Free University of Bolzano. Within this initiative, the University of Sassari leads WP3—from factory to user— the “Artificial Intelligence supporting Architectural Design 4.0+ for indoor comfort”, focusing on adaptive building envelopes, with particular attention to ceramic-based solutions. The creation of a case study database represents the first step of this research programme. This paper aims to provide a theoretical basis for the future integration of adaptability evaluation metrics—such as those proposed in the European Level(s) framework [1] and based on ISO 20887:2020 [2]—with evaluation metrics for adaptive façades, such as the SRI (Smart Readiness Indicator), currently under development within the European Union.

At first, the paper explores the concept of adaptive building envelopes, focusing on their capacity to respond to changing conditions not only in the short term (seconds to minutes) but also in the long term (seasons, years, and decades).

To achieve the study objectives, an exploratory, multimodal methodology was designed around: a comprehensive literature review to establish a theoretical framework on adaptive building envelopes; identification of relevant case studies from scientific and professional sources; data collection using ISO 52016-3:2023 [3] as an operational definition of adaptivity, with each case analyzed through “adaptivity arrays” capturing strategy, transitory conditions, reversible properties, and time horizon; and classification of 130 unique arrays into five domains (environmental, material, user-driven, safety/emergency, and ecological).

Emerging strategies were analyzed via dynamic scenario models and performance indicators, with the database supporting efficient navigation and extraction of insights. The main contribution of this research is the development of a framework that connects short- and long-term adaptivity within a single approach. This broader perspective also raises critical questions regarding policies, both current and under development, which influence architectural strategies aimed at reducing greenhouse gas emissions (GHGs). Are these metrics creating conflicting objectives by considering different time scales of adaptivity in isolation?

Overall, this study lays the foundation for a comprehensive understanding and classification of adaptive strategies, demonstrating how buildings can respond meaningfully to change, whether occurring in minutes or over decades, while supporting sustainable development goals.

1.1. Literature Review

This literature review aims to clarify the conceptual foundations of adaptive building envelopes, highlighting both short- and long-term adaptability strategies. The focus is on identifying key research trends, technological solutions, and design strategies relevant to sustainable adaptive façades. The review synthesizes previous studies and projects through a historical and thematic lens, focusing on technological, environmental, and user-driven approaches.

Adaptive building envelopes have been the focus of extensive research in the architecture, engineering, and construction (AEC) sector. A major contribution in this field has come from the European Cooperation in Science and Technology (COST), particularly through Action TU1403—Adaptive Facade Network. This group defines an adaptive envelope as “a highly multifunctional system in which the physical barrier between indoor and outdoor environments is capable of modifying its functions, characteristics or behaviour over time in response to transient performance requirements and boundary conditions, with the aim of improving the building’s overall performance” [4,5]. Central to this definition is the role of the building envelope as a mediator between external and internal environmental conditions.

This research orientation began to take shape following the energy crises of the 1970s [5] and gained further prominence in the early 2000s, catalyzed by the Kyoto Protocol [6], which encouraged the development of architectural solutions responsive to climate challenges. COST Action C13 (1999–2005) initiated a systematic investigation into glass and interactive façades [7], resulting in foundational works such as Intelligent Skins by Wigginton and Harris [8]—precursors to the TU1403 initiative. From 2005 to 2007, the BestFacade project further expanded the research by documenting the state of the art in double-skin façade systems across Europe, with an emphasis on their dynamic thermal performance [9]. Between 2010 and 2012, the Dutch project FACET (Façade als Adaptief Comfortverhogend Energiebesparend Toekomstconcept) introduced the term Climate Adaptive Building Skins (CABS) [10].

These various research threads culminated in the COST Action TU1403 (2014–2018), which consolidated prior findings and laid the groundwork for standardization [11].

To study adaptive façades, a COST TU1403 case study database of 165 examples was developed, classifying elements into materials, components, and façade systems. Representative cases illustrate different paradigms of adaptive architecture. Thermal Bimetal “Bloom” (Los Angeles, 2011) and Hygroscope (Centre Pompidou, Paris, 2012) exemplify intrinsic kinetic architecture (Control Type: Intrinsic), responding to thermal and humidity inputs, respectively, with visible, actuator-free adjustments. BIQ—The AlgaeHouse—(Hamburg, 2013) represents a fully integrated façade system (Control Type: Extrinsic) producing energy and biomass in response to solar radiation, with response times on the order of hours. These cases highlight adaptive strategies at material, component, and system levels, demonstrating façades’ ability to respond to environmental stimuli with varying complexity [4]. The outcomes of TU1403 have since informed ISO standardization processes, particularly ISO/TC 163/SC 2/WG 15, which directly involves former TU1403 authors such as Attia and Favonio [12,13]. In September 2023, this resulted in the publication of ISO 52016-3:2023 [3]: Energy Performance of Buildings—Part 3: Calculation procedures regarding adaptive building envelope elements, with a supplementary technical report (ISO/TR 52015-4:2024) expected in October 2024.

In parallel to this dominant ISO-driven trajectory, other research streams have investigated adaptivity through different paradigms.

1.2. Theoretical and Design Foundations

Kinetic architecture, as conceptualized by Zuk and Clark (1970) [14], foregrounds movement as a compositional element and is associated with early 20th-century modernist and avant-garde ideologies (e.g., Le Corbusier, Italian Futurism, and Russian Constructivism). This lineage includes both contemporary adaptive systems—such as the Al Bahar Towers and the Institut du Monde Arabe—and historical precedents, like Konstantin Melnikov’s 1925 rotating building for Leningrad Pravda, and the 1935 rotating Villa Girasole designed by Angelo Invernizzi and Ettore Fagiuoli [15,16,17].

Another significant line of inquiry is responsive architecture, initially conceptualized by Negroponte and cybernetic theorists in the 1970s [18]. This approach emphasizes user-system interaction and has informed projects where technology is harnessed to enhance user experience, communication, and spatial interactivity—examples include the kinetic façades of Ned Kahn [19], the MegaFaces Pavilion in Sochi [20], and the works of Hoberman Associates and Studio Roosegaarde. In these cases, expressivity and media responsiveness often take precedence over environmental performance or technical innovation [21].

Given this diversity, the notion of the adaptive envelope resists a singular definition. Is it a pinnacle of contemporary technology aimed at addressing climate change, a critique of classical static architecture, or a medium for communication?

1.3. The State of Research

Numerous literature reviews and research papers have sought to define the scope of adaptive envelopes [14,22,23,24,25,26], often supported by databases compiling emblematic case studies [4,8,9,21,27,28,29,30,31,32,33].

Despite this abundance, there remains a marked scarcity of primary research. For example, Khraisat et al. (2022) [25] conducted a bibliometric survey using keywords such as kinetic façade, dynamic façades, and environmental control systems, identifying 1662 papers, from which only 24 were retained after refinement—among these, only one was classified as primary research. This lack of empirical data contributes to stagnation in advancing the field and impedes the emergence of new developmental trajectories [34].

A critical limitation lies in the construction of case study databases themselves. The over-reliance on pre-existing definitions and the absence of historical–critical scrutiny have created significant gaps, making it difficult to distinguish genuinely adaptive systems from nominally adaptive or purely symbolic ones. Furthermore, a proliferation of secondary studies has contributed to the formation of a canonical bias, reinforcing certain interpretations of adaptivity while excluding others. One particularly problematic distortion concerns the response time of adaptive strategies.

Analysis of the TU1403 database [4] reveals that nearly all case studies exhibit short-term response times, measured in seconds or minutes. Such studies offer little insight into whether adaptive façades can respond over longer timescales—seasons, years, or even decades—or whether they can accommodate changes related to material ageing, system regeneration, and component reuse. This raises questions about whether current assessment frameworks should expand beyond energy performance to include indicators of circularity, resilience, and long-term adaptability [35,36,37].

These dimensions—circularity, resilience, and adaptability—share conceptual ground with adaptivity, in that all involve transformations of the architectural object under certain conditions, with response time being the critical variable. For instance, the Resilient Design Institute [38] defines resilience as “the capacity to adapt to changing conditions and to maintain or regain functionality and vitality in the face of stress or disturbance.” This is conceptually akin to traditional definitions of adaptivity, differing mainly in intent—resilience aims to maintain functionality, whereas adaptivity aims to improve performance [4]. Nonetheless, these objectives are intrinsically linked.

At the heart of these inquiries is a fundamental concern for the future of sustainable urban development, particularly beyond the 2050 decarbonization targets. While adaptive envelopes with short-term responsiveness may contribute to energy-efficient architecture, reliance on disposable solutions with limited operational lifespans and no clear strategy for long-term transformation would undermine sustainability goals. “There is no consensus on how long a building should last”, and current guidance is based heavily on cultural bias [35]. Standard assumption of a 50-year building lifespan—and an even shorter one of around 25 years for curtain wall systems— does not align with actual architectural practice, which often demands significantly longer durability and adaptability over time [39].

A historical example that embodies this principle is the Piazza dell’Anfiteatro in Lucca, a Roman amphitheatre from the 2nd century AD, which has undergone numerous transformations and functional changes while maintaining its vitality across centuries. Borrowing from evolutionary biology, this phenomenon has been recently conceptualized not as adaptation but as exaptation of architectural forms—structures initially designed for one purpose, or emerged with no purpose at all, later repurposed through their existence [40].

2. Materials and Methods

As shown in Table 1, this research was carried out as part of the START WP3 programme, which focuses on adaptive building envelopes, particularly ceramic-based systems. The focus of this first phase was to develop a comprehensive, searchable database of case studies with four goals:

Table 1. Research phases of the research carried out within START WP3: Phase 1, discussed in the current paper; Phase 2, currently under development.

Phase 1: Analysis	Phase 2: Evaluation and Comparison of Data
Systematic collection and analysis of case studies to identify and classify adaptive strategies according to the definition of ISO 52016-3:2023	Evaluation of emerging adaptive strategies through scenario simulations, performance indicators, and classifications by time horizon and adaptive domain.
Case Study Identification: - 329 case studies	Indicators: - Energy performance, resilience, durability, circularity, adaptability (ISO 20887, Level(s), Smart Readiness Indicator)
Analysis Criteria: ISO requirements (response to changing conditions + reversible physical properties)	Methods: Dynamic scenario modelling, scoring system
Methods: Definition of adaptivity arrays and adaptability domains	Tools: Simulations, conceptual framework, and metrics (ISO 52016-3, Level(s), SRI), pgAdmin
Tools: PostgreSQL database, PostGIS, QGIS, Appsmith

• Provide an updated overview of adaptive envelope solutions;
• Describe and categorize adaptive design strategies;
• Explore whether adaptivity is influenced by climate;
• Investigate resilience, reuse, and circularity in adaptive design.

To do this, we used an exploratory, multi-method qualitative approach based on literature review, case study collection, and thematic analysis, as shown in Figure 1. We did not begin with a fixed definition of adaptive envelope, but rather used the research process to shape one, adopting an inductive and interpretive stance [41]. The results were validated through scientific references and technical and photographic documentation.

Figure 1. Scheme of the research.

2.1. Literature Review Method

We began with a broad literature review using platforms such as Semantic Scholar, ResearchGate, ScienceDirect, and specialized sources with a focus on facades, such as the PowerSkin Conference and the Facade Tectonics Institute database. Rather than rely solely on keyword searches, we focused on citation trails and key authors to trace how the concept of adaptivity has evolved across research, standards, and policy (al listed in Appendix A).

The literature highlights a high degree of terminological and definitional ambiguity regarding the concept of adaptability [23,26,27,32], which makes it challenging to develop a neutral classification system.

We found a lack of clarity and consistency in how adaptivity is defined in research literature. To address this, we turned to published standards, focusing on ISO 52016-3:2023 [3], which provides two clear criteria for an envelope to be considered adaptive:

• It must respond to Transient Conditions or Changing Priorities;
• It must have physical properties that can be reversibly modified.

This ISO definition became our benchmark for evaluating case studies and conceptualizing adaptive features. The presence of both conditions is also necessary to build dynamic models that simulate their performance. This definition, focused on environmental adaptability, is integrated with other approaches, such as the European Level(s) framework and the ISO 20887:2020 standard [1,2], which consider adaptability in the long term, through scores assigned to design features such as flexibility of use or the possibility of disassembly.

2.2. Case Study Identification

The case study collection began alongside the literature review. We started with established databases, including TU1403 and sources focused on ceramic facades. From there, we expanded to include more recent or lesser-known projects sourced from platforms like ArchDaily, Dezeen, Instagram, and LinkedIn. Selection criteria included the following:

• Visual and conceptual similarity to known adaptive projects;
• Alignment with theoretical concepts from the literature;
• Evidence of adaptive strategies that were underrepresented in existing datasets.

For cataloguing purposes, a PostgreSQL relational database with the PostGIS extension was created, supported by QGIS 3.40 software for data input and georeferencing. The relational database format was chosen because it can be integrated with other geospatial data to develop maps and spatial queries. We aimed for the database to achieve conceptual saturation, capturing a broad spectrum of adaptivity types, and geospatial completeness, ensuring global coverage across various climates. To this end, we adopted, at the beginning of the research, a benchmark of 12–16 case studies per climate area, with a minimum threshold of 2 case studies per area, aiming to cover at least 10 climate types worldwide. To define the climate areas in QGIS, we used the Köppen–Geiger climate zone maps published by Beck et al., 2018 [41], with a 1 km resolution and coverage of past, current, and future climate scenarios. For spatial queries analyzing the distribution of case studies across climate zones, we selected three of these scenarios:

• 1991–2020—historical data;
• 2041–2070—SSP2-45, “middle-of-the-road” scenario;
• 2071–2099—SSP2-45 scenario.

It is important to note that while this numerical benchmark helped guide the search process, the research approach remained fundamentally qualitative. The study was not designed for statistical analysis of variance or correlation across the gathered data.

2.3. Thematic Analysis

The relational database structure was developed in two stages.

In the first stage, we initially implemented a simple case study datasheet schema to record basic information for each case study identified, including location, year, authors, project type, reason for inclusion, a brief project overview, drawings and photographs, bibliography, and useful links. At this point, no structured analysis of adaptivity was conducted, only a preliminary understanding of why each project might be relevant to the study.

In the second stage, after gathering enough case studies to meet the pre-set geographical distribution benchmark and having reached an acceptable conceptual saturation level, we developed the database schema to aid a thematic analysis of adaptive features and design strategies present in the case studies.

Each adaptive feature was organized into an “adaptivity array”, structured to include the ISO 52016-3:2023 [3] adaptivity definition criteria, which captured

• The design strategy used;
• The specific conditions it responds to;
• The physical property that changes;
• The timeframe over which that change occurs.

The pieces of information composing the array were organized in separate primary tables.

Once enough case studies had been gathered, as a starting point for the coding, we established a few typical and recurring adaptivity arrays and 5 Adaptivity Domains:

• ENC: Environmental conditions (e.g., solar radiation and temperature);
• Building materials conditions (e.g., wear and tear and moisture cycles);
• UDC: User-driven conditions (e.g., comfort, privacy, and biophilia);
• SEC: Safety and emergency conditions (e.g., fire and seismic activity);
• ECC: Ecological conditions (e.g., bioreceptivity and resource use).

During the coding, the initial arrays and Adaptivity Domains were used as examples and guidance to build new and more specific arrays to suit each case study’s adaptive features, which emerged through the authors’ interpretation of the bibliography, photographs, and drawings collected during the Case Study Identification process. New arrays could either recombine previously coded design strategies, Transient Conditions, and physical properties in new permutations or introduce new line items to each of the primary tables.

This structure allowed us to systematically expand the pool of adaptivity arrays, reduce duplication during the coding process, and consolidate overlapping codes.

To support real-time implementation and monitoring of the coding process, the database was deployed to a cloud environment. It was accessed locally via QGIS for data input, while a web interface was developed using Appsmith to allow multiple users to navigate the database, perform search and filter queries, and dynamically generate datasheets for each case study.

A small number of additional case studies were added during the coding phase, beyond those identified in the initial Case Study Identification phase. Finally, upon completion of the coding process, more complex queries were executed in pgAdmin to extract .csv files to assess the coded data and pinpoint emerging patterns.

3. Results

3.1. Database Composition

This study analyzed 329 case studies of building envelopes, with greater emphasis given to non-speculative projects, as shown in Figure 2. Of these case studies, 266 were classified as adaptive based on our thematic framework and an adaptivity score greater than zero—i.e., they had at least one adaptivity array assigned. The remaining 63 non-adaptive projects were retained for comparison, mostly ceramic facades included to support broader WP3 goals, or projects initially assumed adaptive but ultimately excluded due to lack of qualifying features.

Figure 2. Database composition: adaptive projects by project type.

The minimum threshold for geospatial coverage was achieved, encompassing 14 Köppen–Geiger climate zones, based on the 1991–2020 interval [42], each represented by at least two adaptive case studies. However, only five zones met or exceeded the target range of 12–16. The two zones that dominated are as follows:

• Cfa (Temperate, no dry season, hot summer): 61 case studies, 51 non-speculative;
• Cfb (Temperate, no dry season, warm summer): 86 case studies, 68 non-speculative.

These correspond to highly urbanized global regions such as Central–Northern Europe, southern China, Japan’s coastlines, southeastern Australia, the southern U.S., and the Río de la Plata basin.

Mapping the data revealed spatial imbalances: Europe holds the largest share of case studies, followed by North America, Asia, and Oceania, while South America and Africa are underrepresented, as shown in Figure 3. Absence of case studies in underrepresented regions does not imply a lack of adaptive solutions—whether recent or vernacular—but likely reflects linguistic and logistical barriers, such as limited data availability within the online sources explored. We also included two case studies from Antarctica, not referenced in any prior studies on adaptive envelopes reviewed in this research. These are the Amundsen–Scott and Halley VI research stations, both adopting the adaptive strategy Dynamic foundation system with jackable footings for building shell elevation adjustment to respond to snow deposit changes, an environmental condition which in this climate context poses a big challenge to the durability of the building, given the quantum of height change and horizontal drift of the deposits where the stations rest.

Figure 3. Spatial distribution of the case studies mapped in the database. The base of the map shows the Köppen climate zones, as proposed by Beck et al. (2018) [41], for the time period 1991–2020.

The dataset includes both historical and contemporary examples. The earliest is the velarium of the Colosseum (80 AD), a retractable shading system in Roman amphitheatres that anticipates modern stadium operable roofs [43]. Most projects date from the early 20th century through 2024, with notable clustering between 2006 and 2016 due to the integration of the TU1403 database as shown in the Table 2 and related projects selected via similarity criteria, as shown in Figure 4.

Table 2. Case studies by reason for inclusion, assigned after the project adaptivity analysis phase.

Reason for Inclusion	Number of Case Studies
Adaptive envelopes	231
Adaptive ceramic envelopes	35
State-of-the-art ceramic envelopes	60
Non-adaptive, non-ceramic	3

Figure 4. Number of adaptive projects (including adaptive ceramic and non-ceramic) by year.

3.2. Clustering by Adaptivity Domains

Through thematic analysis, we identified 130 unique adaptivity arrays, based on 53 design strategies, 28 changing conditions, and 72 reversible physical properties (as listed in Table A2). These adaptivity arrays were clustered in five Adaptivity Domains, as previously noted. 73% of the adaptivity arrays fall into the ENC and UDC domains, and 27% into the other three domains, as shown in Figure 5. Each changing condition is unique to its domain. However, strategies often appear in multiple domains, depending on the conditions and the physical properties with which they are associated. These strategies collectively form the adaptivity array, as shown in Figure 6.

Figure 5. Number of adaptivity arrays by Adaptivity Domain.

Figure 6. Number of adaptivity arrays by adaptive strategy and Adaptivity Domain.

For example, we have mapped a variety of case studies showing different design approaches that implement the adaptive strategy vegetation buffer system incorporated into the building facade, which is typically underrepresented in the existing adaptivity databases. This appears in multiple domains:

• Facade vegetation can respond to conditions such as solar radiation and daylight availability, as it happens in the Bosco Verticale case study, where the deciduous planting enables a reversible seasonal change in the visible light transmittance property;
• Vegetation growth can be tuned in time with pruning and replanting to affect lines of sight. This can be used as an adaptive response to privacy and security needs, a set of Changing Priorities which belong to the UDC domain;
• Planting also interacts with water. Through micro and macro structural changes, plants can vary the water retention capacity of the facade. Therefore, a green facade can interact dynamically with wet–dry cycles of materials, a transient condition belonging to the BMC domain.

Adaptive strategies in the ENC domain often also appear in the UDC domain because responses to environmental factors—such as temperature, solar radiation, and daylight—that alter the building envelope’s physical properties can also be understood as efforts to influence occupants’ perception of indoor comfort, a user-driven Changing Priority. We have separated environmental factors and user factors in different domains because not always strategies that operate in the ENC domain also operate in the UDC domain.

An example is the adaptive strategy called photocatalytic surface technology, using TiO₂ for air purification and self-cleaning. This strategy

• Interacts with air quality (ENC domain);
• Affects surface bioreceptivity (ECC domain);
• Responds to material components wear and tear (BMC domain).

To describe the adaptivity of case studies was often deemed necessary to identify multiple adaptive strategies operating across multiple Adaptivity Domains. This reflects the multidimensional and complex nature of adaptivity and contradicts the tendency to simplify adaptive envelope systems as serving a single goal or performance domain.

3.3. Short-Term and Long-Term Adaptivity Examples

Most of the adaptivity arrays in our database correspond to short-term response strategies. However, approximately 26% reflect long-term adaptivity. These long-term responses are found across all five Adaptivity Domains, while short-term responses were absent in the SEC domain, as shown in Figure 7.

Figure 7. Number of adaptivity arrays clustered by Adaptivity Domain and adaptive response horizon.

3.3.1. Environmental Conditions Domain

Short-term ENC arrays typically represent responses within daily cycles to environmental conditions such as temperature fluctuations and solar availability. Examples of strategies used in these arrays include the following:

• Operable shading devices integrated into the façade;
• A dynamic roof system for adopting the building shell’s enclosure capabilities;
• An adaptive glazing system with electrochromic properties;
• A curtain wall system with integrated mechanical vents for adaptive ventilation.

In contrast, long-term ENC arrays represent adaptations triggered by slower environmental changes or as accumulated effects over time. Examples include the following:

• Dynamic foundation systems with jackable footings (found in the polar research stations Amundsen–Scott and Halley VI) respond to months or years of snow buildup and ice banks drifting.
• Photocatalytic surfaces using TiO₂ gradually purify air. While this effect is negligible in the short term, its adaptive benefits accrue over extended exposure.

3.3.2. Building Material Condition Domain

Short-term arrays in the BMC domain represent responses to Transient Conditions occurring within the material or the facade components, noticeable within a 24 h daily cycle. An example of this type of adaptive feature is the control joints of a curtain wall responding to the thermal expansion cycles of materials. The goal of adaptivity here is not responding to an environmental condition but to a normal behaviour of the assembly, which, if not accounted for in the detailing, could lead to damage to the assembly.

Long-term BMC arrays address material durability and resilience responding to the changing conditions, namely the wear and tear of the materials and components. Examples of strategies for composing these arrays include the following:

• PV system regeneration replacing the fluid running into the panel. This is a strategy found in the case study Regenerable PV with hydrogel, a prototype developed by Hyung-Jun Koo and Orlin D. Velev, also described in the TU1403 case studies database [12].
• Impressed current cathodic protection, supplying an external current that donates electrons to a metal structure, preventing its oxidation. This strategy is used on reinforced concrete structures to counteract reinforcement oxidation.
• Self-healing material technology utilizing bacteria and microorganisms. This strategy is used for crack bridging in concrete structures requiring long-lasting water penetration resistance—e.g., underground structures.

Other long-term BMC arrays describe adaptive re-use and architectural exaptation [40] as strategies responding to the purposes of the materials and components, which is interpreted as a Changing Priority. Case studies include the following:

• EU Headquarters in Brussels, designed by Studio Valle, Buro Happold, and Samyn and Partners: A double-skin curtain wall composed of reclaimed single-glazed windows on the outer skin. We have described this strategy as an adaptive reuse of components, without functional shift or co-optation, to form a new facade system [44].
• The drum wall designed by Steve Baer for his house in Corrales, New Mexico, also known as the Zome House [45]: The wall is composed of a series of water-filled oil drums, mounted on a steel rack, placed behind a south-facing glass facade. We have identified the re-use of oil drums to form the thermal mass of the wall assembly as Exaptation type 1—functional shift in components to form a new facade system.
• Terrabyte, a project by CoolAnt and Ant Studio [46], with two sister companies based in Noida (India): A humble toilet building used as a prototype to test one of the ceramic evaporative cooler systems developed by CoolAnt. The project features two cylindrical enclosures without a roof, constructed with gabion walls filled with ceramic scraps (broken bricks, roof tiles, and pottery). The walls function as large-scale evaporative coolers, using a series of perforated pipes embedded within them to moisten the ceramic material, which is then dried by air flowing through the gabion structure. We have identified the re-purposing of broken ceramic materials, which could no longer be used for the functions for which they had been originally conceived, as Exaptation type 2—functional co-optation of components to form a new facade system.

3.3.3. User-Driven Condition Domain

UDC arrays are typically short-term and describe the interactive nature of adaptivity in response to users’ Changing Priorities: comfort, space usage needs, privacy and security needs, emotional needs, communication intent, and biophilia.

Notable case studies include the following:

• Window antenna, by RISE-Research Institute of Sweden [4]: A case study contained also in the TU1403 database, which uses Radio signals shielding and amplification through an electrically conductive coated surface as an adaptive strategy to respond to privacy and security needs. This system modulates media connectivity (not lines of sight) to control privacy and security.
• Digital Water Pavilion (Expo 2008) by Carlo Ratti, studio FM, and Arup [47]: A pavilion with a water curtain facade. The water nozzles around the roof eave are digitally controlled to work similarly to an inkjet printer, creating patterns through the regulation of water flow. We have associated with this case study a UDC array combining communication intent and a dynamic screen system strategy with media display capabilities, and another, also in the UDC domain, combining biophilia and the strategy system replicating a cascading waterfall.
• Various case studies of stadiums with operable roofs, which respond to space usage needs through the strategy dynamic roof system for adapting the building shell’s enclosure capabilities.
• Heliotrope, by Rolf Disch [48]: A cylindrical rotating building. The dynamic foundation system of this project has been associated with the UDC condition called occupant visual comfort, but also associated with emotional needs, since the ability to re-orient aspects of the entire building can affect views, lines of sight, as well as the mood, defined by the interaction of space and light, to suit the user’s mood.

3.3.4. Safety and Emergency Conditions Domain

All adaptivity arrays in this domain exhibit long-term response horizons due to the rare or extreme nature of the events they address—e.g., earthquakes, fires, and high winds.

Some of the adaptivity arrays we associated with this domain are widespread design practices and are required by building codes and standards. Examples of strategies found in these arrays include the following:

• Fire-protective coating technology with intumescent materials, used to allow the steel structure to adapt its thermal conductivity in a fire event to slow down the increase in core temperatures to critical levels compromising stability;
• A system using water to form a curtain or screen, a strategy used by sprinkler drencher systems to spray glazed curtain walls to increase their fire separation properties and prevent a glass explosion;
• Facade system incorporating movement joints for stress absorption as a passive–adaptive strategy to respond to seismic events.

Besides these widespread strategies, there are also more unique ones in this domain. An example is the external shading system with automatic retraction to reduce wind stress, triggered by anemometer sensors, in response to extreme wind conditions. Case studies where we have found this strategy documented in the literature are the Al Bahar Towers, by Aedas Architects, and the Milwaukee Art Museum by Santiago Calatrava [49,50].

3.3.5. Ecological Conditions Domain

In the ECC domain, adaptive systems are viewed as ecosystems where the adaptive strategies allow the formation of ecological niches to support life forms. In this domain, the bioreceptivity condition describes the system’s capacity to support non-human life forms and the variation in time of this capacity. The resource availability condition describes the system capacity to generate or transform resources to support human life forms using and living in the building.

Short-term arrays in the ECC domain are created with strategies such as

• Systems with transparent water-filled panels containing and modulating microalgae density associated with bioreceptivity. This strategy is found in the BIQ Das Algenhaus case study [51], by Splitterwerk and Arup, where the facade system was engineered to boost micro algae growth to use them as biomass in other systems of the building. The speed of regulation of bioreceptivity in this case is key for the success and meaningfulness of the strategy; therefore, it was classified as a short-term response.

Long-term arrays in the ECC domain are created with strategies such as

• Photocatalytic surfaces using TiO₂ responding to bioreceptivity.
• Building-integrated energy systems utilizing photovoltaic with fixed solar panels or with solar-tracking functionality, which are two strategies responding to resource availability.
• Heat displacement system utilizing water-filled facade panels linked to building services, responding to resource availability. Water House 2.0 [52], by the startup Water-Filled Glass Ltd, is an example of a case study associated with this array. This prototype, built in Taichung, Taiwan, utilizes a curtain wall system, where the glazed units of the curtain wall are filled with water and connected to a centralized energy management system.

4. Discussion

4.1. The Temporal Boundaries of Long-Term Adaptive Response

The response horizon of an adaptive strategy is not univocally definable. This largely depends on the point of view through which the adaptivity is thematized and the temporal boundaries of the system considered.

Generally, adaptivity cannot exist in a discrete time space, only in a transient continuum. Transitoriness is well understood when we look at short time spans, especially when we have environmental indicators to be able to relate the time span to. For instance, it is easy to understand a dynamic shading system as adaptive as it responds to sunlight within a 24 h time span.

However, to explain why we can talk about long-term adaptivity, such as when we use the terminology “adaptive re-use” and to understand the long-term transitoriness of the condition these strategies respond to often poses a challenge. This is also due to the fact that there is no agreement on how long is long-term in architecture [35].

One way to define the temporal boundaries of a long-term horizon is to look at the entire life of a building. In our interpretation, the life of a building does not reset when the building is expanded, repurposed, refurbished, or its systems are maintained and regenerated, but extends from when the building is built from foundations up, to when it is fully demolished to its foundations.

We have used these boundaries when coding the adaptivity arrays of the SEC domain. The SEC adaptive features allow a building envelope to survive catastrophic events, often accounting for some degree of damage and repair. Considering the state of the building before and after the event, when the systems have been regenerated, as part of the same continuum, and considering that throughout the life of the building, the event may happen more than once, the SEC conditions are not discrete but transient.

Similarly, to describe long-term adaptive features associated with the BMC domain, we have interpreted as boundaries of the response horizon as the life of building components. In our interpretation, the life of a building component does not reset when it changes its place or function within the building. This is also not the case if the component is applied first to a building, then to another, or when it is broken, but it can still be repurposed, as we have seen in the Terrabyte case study [46]. On these grounds, we have considered conditions such as materials and components’ purpose, and similarly, the wear and tear of materials and components, as transient and not discrete.

4.2. Adaptive Strategies and Climate Change: The Environmentalist Fallacy

In our literature review, we have identified a dominant point of view that considers adaptive envelopes as “the last frontier of contemporary architectural and technological research” [4], addressing contemporary issues related to climate change by increasing the operational efficiency of buildings to reduce GHGs. This view is eloquently expressed through the concept of Climate Adaptive Building Systems introduced by the FACET project, where environmental responsiveness prevails over other types of adaptivity.

Focusing solely on short-term environmental responses to improve operational efficiency is an arbitrary limitation. This approach is also counterproductive when attempting to identify ideas of adaptivity that could significantly contribute to reducing GHGs. As we have seen, adaptive strategies are found in both ancient and recent architectures, and short-term strategies enhancing operational efficiency are inseparable from long-term strategies that promote durability, resiliency, and circularity, thereby providing meaningful life cycle GHG reduction benefits.

Furthermore, adaptive envelopes cannot be reduced to designs that have been climate-optimized to outperform their static counterparts. Often, the decision to adopt an adaptive strategy is supported by its capability to respond to a range of conditions across several Adaptivity Domains. For this reason, it is difficult to interpret an adaptive strategy as being solely driven by the environmental conditions found in a specific climate.

We have tested the hypothesis of climate specificity in adaptive solutions belonging to the ENC domain by georeferencing 73 examples of stadiums with operable roofs distributed across the globe. We have classified these case studies as projects responding to environmental conditions such as temperature fluctuations, rain, and wind, to improve operational efficiency, as well as to user-driven conditions such as varying space usage needs. The mapping shows that stadiums with operable roofs are found in all climate types: tropical, arid, temperate, and cold. Taken together, these 73 case studies indicate that while environmental aspects of the operable roof solution may still be relevant for a stadium, they generally assume secondary importance compared to user-driven aspects. For instance, the need to accommodate both outdoor and indoor sports may be a sufficient reason to include an operable roof in a stadium design brief if the decision to play those sports indoors or outdoors is set by the rules of the game rather than by convenience.

There is another critical issue with viewing adaptive strategies exclusively as a problem of environmental response optimization: overfitting. By analyzing the locations of adaptive case studies in our database, we were able to identify projected climate shifts in future scenarios and relate them to the adaptive strategies of the projects. Many of these locations are projected to change climate zones in the 2041–2070 and 2071–2099 scenarios, as shown in Figure 8. This suggests that, in the long term, projects incorporating strategies that can adapt to multiple climates will be more effective and will suffer less obsolescence than those optimized for a single climatic zone. However, among the adaptivity arrays identified in the ENC domain, we can argue that only the array associated with South Pole stations responds to a truly climate-specific condition: snow deposit changes and drifts, which are Transient Conditions unique to the ice bank terrain found in the polar climate. In contrast, strategies such as operable shading devices integrated into facades are found in case studies across nearly all climates, as they allow a high degree of calibration of response to environmental conditions in multiple climates. Another factor is the multi-domain response: in the operable shading example, these respond also to UDC conditions such as privacy, visual comfort, and emotional needs—e.g., outdoor awareness.

Figure 8. Adaptive projects, including both ceramic and non-ceramic envelopes, categorized by Köppen climate zones [42]. The chart shows each project along the horizontal axis and the corresponding Köppen climate zone along the vertical axis, indicating the zone in which the project is located during the 1991–2020 period (blue dot), where it is projected to be in the 2041–2070 scenario (orange dot), and subsequently in the 2071–2099 scenario (grey dot).

Therefore, overfitting adaptive envelope projects to a specific climate is relatively low risk, provided the adaptive design strategies account for a flexible environmental response behaviour, capable of capturing multiple climate conditions, and/or address changing conditions across multiple domains, to preserve purpose and meaning beyond the environmental response.

4.3. Adaptivity Emerging from Interactions

One of the study’s findings, which emerged through the case study analysis, is that adaptivity does not reside solely in individual building elements but can emerge from the interaction between multiple components. The project Apple Piazza Liberty [53], for example, does not feature adaptive solutions when considering its entry glass façade alone. However, when this glass box is combined with the adjacent water fountain, the facade becomes a dynamic system modulating shading and providing evaporative cooling. This shifts the focus of adaptivity from the single element to the relationships between the different systems used within and around the envelope.

4.4. Limitations of the Study: Can Architecture Be Non-Adaptive?

In the conceptual framework outlined in this study, while it is possible to demonstrate that a project is adaptive, it is not possible to definitively prove that it is not. The absence of adaptive features, as identified through our thematic analysis, reflects the interpretation of the authors and the limitations of the source material. A different analyst, whether a designer, stakeholder, or researcher, might interpret the same project differently and uncover adaptive qualities we did not register.

This raises a fundamental question: Is all architecture inherently adaptive?

The boundless scope of adaptivity is a known epistemological issue that the authors of this study acknowledge. It would be problematic, for instance, if we were to attempt, based on our study, to quantify how many projects are adaptive and how many are not, and to confute, based on project dates, that adaptive envelopes are the pinnacle of modern and contemporary architecture as opposed to ancient static architectures. That would require demonstrating that pre-modern projects were non-adaptive. The case studies of the spandrels of the velarium of the Colosseum [43] and Piazza dell’anfiteatro in Lucca that we have mentioned previously suggest there are forms of short-term and long-term adaptivity in ancient architecture, and the fact that these have never been considered by the previous research literature on adaptive envelopes is not a sufficient reason to justify the “static” interpretation.

In other research fields, such as evolutionary science, the attribution of adaptivity as a blanket statement justification to explain reality has been identified as a limitation, as it cannot capture non-causality in evolutionary timelines [54]. In our field of study, this limitation is only applicable to a certain extent, since architectural forms, born without purpose through human creativity, find meaning in purpose, on a timescale that includes future time spans, which are not relevant to explain reality but to design reality. This human-driven purpose, whether it is epistemologically legitimate or a fallacy, affects and shapes reality. In architecture, the life of buildings, as well as the life of building components, is heavily influenced by aleatory purposes and wrong interpretations, from the way they are designed to the way they are operated and lived.

“Purpose” is the original definition of “adapt”, from the Latin “aptus ad”, which can be roughly translated as “useful for”. However, not all design purposes can be associated with adaptivity. In our framework, adaptivity is only referenced with respect to the design purposes that can be formulated through the parameters defined by the ISO 52016-3:2023 [3]—a system responding to changing conditions and defined with reversible physical properties.

A wrong attribution of adaptivity in our framework would be, for instance, including case studies such as the Hanwha Headquarters Remodeling by UNStudio [54], among case studies showcasing adaptive screen systems. The screening method in this project has undergone an optimization process and has been adapted to the conditions of the context during the design. However, the screen was conceived as a form with physical properties to be frozen at the time of construction. While this type of “blueprint adaptivity” is valued in the other literature—the TU1403 case studies database describes the design strategy of the Hanwha Headquarters screen as adaptive in response to thermal and visual comfort—we have only considered post-construction adaptivity [4].

Despite this delimitation of the scope given by the ISO 52016-3:2023 [3] adaptive envelope definition, it is still possible to identify a large number of adaptive traits, even on design strategies which may seem obvious or trivial. Movement joints and passive fire strategies, such as intumescent coatings, are an example. While we have included these strategies in the database, we have adopted our own judgement to associate them with case studies only where highly relevant in order to work in conjunction with other more prominent and less known adaptive features. No case studies with solely these trivial adaptive features were collected. The goal was to minimize redundancy and effects on the Adaptivity Scoring index calculation. This index does not have statistical value, but it was implemented in the database to improve users’ navigation and provide a degree of differentiation, as well as to identify case studies adopting more non-trivial strategies across multiple domains.

5. Conclusions

The study developed a framework to distinguish between short- and long-term adaptive strategies, with the aim of making the attribution of adaptive features more understandable, debatable, and falsifiable. The inductive approach allowed us to overcome the limitations of existing literature, which often classifies adaptive strategies solely based on a predetermined notion of adaptivity imposed by the authors, without accounting for critical understanding by the reader.

Based on the findings of this study, this work opens new perspectives for further exploration of adaptivity in architecture. Possible future directions include the following.

Expansion of the database through field research: The inclusion of vernacular case studies and systems adopting low-tech upcycling solutions in the database has helped begin to broaden the perspective to underrepresented contexts, highlighting under-documented or entirely missing forms of adaptivity in existing literature databases. However, the database presented in this study still shows a geographic and cultural bias. To overcome this bias, it would be necessary to build an internationally oriented network that enables field research to investigate local, vernacular, and contemporary adaptive solutions from contexts underrepresented in the current literature.

Development of AI-based tools: The data gathered on this structured database could be further refined and expanded to include quantitative data to be used as a training base for artificial intelligence and machine learning algorithms, contributing to the automated classification of adaptive strategies and the assisted design of adaptive systems.

Analysis of the effectiveness of adaptive strategies over time: Another possible development involves analyzing the catalogued projects through simulations based on models constructed starting from the adaptivity arrays outlined in the database, to quantitatively assess the performance of adaptive strategies in relation to material ageing and climate change.

Development of integrated sustainability metrics: Similarly to the Smart Readiness Indicator (SRI), currently being implemented in the European context to complement national energy performance certificates and map the short-term adaptive potential of the building stock, integrated metrics could be developed to evaluate both short- and long-term adaptivity. This would allow adaptivity to be assessed with a consistent method, not only in terms of environmental responsiveness over the building’s lifespan but also in relation to sustainability potential in the areas of material life cycles, circular economy, and resilience.

In conclusion, the analysis of a structured database of 329 building envelopes, developed following ISO 52016-3:2023 [3], reveals a predominance of short-term strategies within the environmental domain, whereas long-term strategies emphasize material durability and system resilience through regeneration and reuse, thereby ensuring sustained energy performance over time. The integration of adaptive façade case studies with extended response times informs public policy development and enables a comprehensive evaluation of envelope adaptivity across the full building life cycle, in alignment with international and European standards for energy efficiency and sustainability. The implementation of life cycle thinking principles and design for disassembly and adaptability (DfAD), as outlined in the European Level(s) framework [1] and consistent with ISO 20887:2020 [2], optimizes façade longevity and service life, enhances energy efficiency, and facilitates material and component reuse, streamlining end-of-life processes through systematic recovery, recycling, and reuse. Continuous technological innovation constitutes a pivotal factor in maximizing the utility of the structured database, as the incorporation of long-term adaptive technologies allows for improved energy performance throughout the building life cycle. The convergence of technological advancement, structured empirical data, and policy frameworks supports an integrated, evidence-based, and replicable methodology for adaptive architecture, fostering the adoption of sustainable building practices consistent with greenhouse gas (GHG) mitigation objectives.