Keywords

1 Introduction

Design for adaptability (DfA) is a Circular Economy (CE) strategy of intentionally designing buildings with consideration of change along their lifecycle. By considering the end-of-life (EoL) options, DfA facilitates implementing circularity strategies in buildings, such as design for disassembly (DfD), material reuse and upcycling.

Building adaptability has been defined as “the capacity of a building to accommodate change in response to the emerging needs or varying contextual conditions, therefore prolonging its useful life while preserving the value for its users over time” [1]. Accommodating change requires having a broader design perspective than the one defined by the immediate need and actual context. Similarly, thinking of time allows a building to be perceived as a dynamic system, interacting with rising demands for change [2]. Buildings are usually designed to be fixed objects of fixed use, ignoring their context's temporal reality. Having the capacity to adapt creates continuous possibilities over time, allowing a building to maintain an extended useful life which cannot happen with a one-time solution. A useful life can only be realised when there is persistent value for users, who are a constant in the equation as buildings change to accommodate their needs, provide better service, and ensure their comfort and protection. However, the value for users is often lost in conventional building design as unavoidable mismatches develop over time between the space supply and demand [1].

The massive amount of construction and demolition waste (CDW) resulting from recurrent arbitrary demolition and rehabilitation activities proves a critical deficiency in how buildings are designed, operated and renovated. The one-time solution of defined form and function approached by the predominant design culture of our buildings leads to one end-of-life option—demolition. As a critical driver for change, physical obsolescence is the primary cause of demolition activities. Still, many drivers for change are external. Building obsolescence usually results from changing operational conditions, emerging user needs, and other varying environmental and external factors. Those include social and local factors (e.g., user's preferences, cultural demands, existing materials), environmental motives (e.g., natural hazards, climatic changes such as heat waves), technical requirements and functional performance (e.g., to embrace technological improvements, energy efficiency requirements), economic factors, legislative issues (e.g., regulations and policies, building codes), and stakeholders’ interests [1].

2 Materials and Methods

The methodology draws on the analysis of multiple adaptability and circularity assessment models performed in [3]. The analysis studies eight adaptability assessment models and examines the implementation and role of adaptability in multiple circularity frameworks. As a result, change enablers and adaptability requirements are identified and then analysed against their implementation in the common European framework for sustainability—Level(s). The DfA indicator in Level(s) is examined, defining its objective, levels and aspects of assessment, and interrelation with other CE indicators in Macro Objective 2. The shortcomings and possible improvements are then identified in light of the requirements previously defined.

3 Results

3.1 Change Enablers and Adaptability Requirements

The notion of “Design for Adaptability” originated from enhanced resilience of the built environment against vulnerabilities and disruptions on the one hand and the efficient implementation of sustainability in the built environment on the other. The capacity of a building to respond to emerging changes stems from the early design decisions in the first place [2]. Applying adaptability, therefore, requires transforming the usual focus of form and function determined by immediate needs towards employing a context and time-based perspective for long-term uses [2]. By this meaning, the adaptable capacity of a building determines its future potential [4].

Adaptability requirements are identified using the review and analysis performed in [3] of multiple adaptability assessment models and circularity frameworks that consider adaptability an essential criterion in their methodology. The identified change enablers and adaptability requirements are presented in Fig. 30.1.

Fig. 30.1
A tree diagram of adaptability requirements branches out into 3.Design factors and strategies branches out into 7 elements, most of which further branch out. Material specifications branches out into 3, and Processs and information flows branches out into 4 elements of B I M models.

Adaptability requirements

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Design Factors and Strategies. Seven strategies are identified as essential facilitators for design for adaptability (DfA).

System Separation. The functional Independence of major building systems is identified as a critical adaptability enabler in literature studies. Two main concepts are recognised in adaptability assessment models and criteria: Support-infill Separation and The Shearing Layers. Support-infill Separation distinguishes between two types of elements; “Base building” and “Fit-out”. The base building is the durable static part represented by structural support elements. The fit-out is the flexible infill subject to occupiers’ recurrent modifications with minimal interface problems, allowing the building to adapt to the user's needs over time. The idea is brought by the “Open Building” concept of Habraken [5], delivering insights into adaptable design and process flexibility, particularly in residential buildings. Layers Independencies introduced by the shearing layers concept of Brand [6] help to change the general perception of buildings from fixed objects to dynamic systems. Brand's model suggests that a building comprises six layers with different timescales (site, structure, skin, services, space plan, and stuff). The layers should be functionally separated, each containing similar lifespan elements. Understanding a building's composition and identifying the temporal layers of its components is an important strategy to enable its adaptive capacity by allowing flexibility to shorter-life layers or elements and durability to longer-life layers and elements [1].

Simplicity. Designing simple structural systems (e.g., repeating layouts and grids, larger but fewer components) creates easily understood load paths, reducing the uncertainty for the designer working on adaptable solutions. Moreover, the absence of complex systems is vital for the continued operation of the building.

Open plans. Designing layouts free of structural, mechanical and other obstructions allows easy reconfiguration of space plan components to suit changing functional requirements. Open plan layouts grant facilitated adaptation of interior spaces with minimised impact on the existing structure and systems.

Design for Disassembly (DfD). DfD implies that all materials and products used at every level in a building can be neatly disassembled and recovered. By this means, building materials and components have the potential to be reused to their highest extent [1]. DfD goes beyond a building service life by addressing the destination of its materials and components, accounting for the end-of-life (EoL) scenarios at the early design stages [7]. DfD firmly adheres to adaptability as a strategy in which particular components can be changed in response to external factors [1]. By this meaning and considering the EoL in mind, DfD calls for adaptability in its methodology [1] and vice versa since extending the life of a building should think that multiple elements need to be replaced at different stages. DfD relies on achieving Functional Independence of layers and components using Mechanical Connections instead of chemical ones. It also provides easy separation of elements and materials without force, minimising contamination of materials and damage to elements during deconstruction and adaptation.

Standardisation and Modularity. Designing modular components and standardised building products facilitates the process of disassembly and reuse, therefore, adaptability. Standardisation can be achieved at three levels: material, component and connection. However, each level has a distinct advantage. For example, standardised materials allow for more efficient recycling, while standardised components create specific conditions for connections between those [4]. Since connections are recognised as essential change facilitators, their standardisation enhances modular design efficiency by ensuring easy removal and replacement of components and exempts those from being standardised. Furthermore, using standardised grids and modularisation also facilitates component interchangeability which is seen as a great enabler of adaptability.

Design for Resilience. Resilient design is achieved using Redundant Systems with overcapacity to support change scenarios, making buildings more adaptable. Examples include clear story height and cavity floors that meet floor-height requirements of different uses. Robustness and Durability also ensure design resilience by granting the ability to withstand the impacts of stressors and external disturbances without major damage or functional failure. In addition, robustness ensures the structure's durability, securing its strength to cater to multiple uses and loading scenarios. Combining the adaptability of use with the required structural robustness under certain conditions contribute to high levels of durability and longevity.

Maintainability. It is the accessibility for assessment to inspect the functionality of varying lifespan elements, especially the shorter-life ones for replacement or repair. Maintainability can be achieved by creating specified Access Zones in the functional layers of systems and elements. Many adaptability mechanisms rely greatly on maintainability and how easily elements are reachable for safe removal and replacement.

Material Specifications. Proper materials selection can significantly impact adaptability values [7]. For example, buildings containing contaminating materials (e.g., asbestos) have less potential for adaptive reuse because of the high risk and rising costs associated with extraction or containment [7]. Conversely, Durable, Non-toxic materials are essential enablers for adaptive reuse projects where they contribute to the prolonged functional life of a building and the reuse of its components in other projects [1]. Moreover, keeping records of materials and Documenting their Specifications facilitates the process of disassembly and appraisal of the most advantageous adaptability scenarios.

Process and Information Flow. Adaptability at its highest level in buildings is a complex procedure that requires an efficient collection of high-quality data on applied materials and products, their characteristics, supply chain information and other important features that facilitate future scenarios [4]. Material and Building Passports are concepts that emerged in the light of CE to grant efficient reporting of all materials and components composing a building describing all characteristics, including composition, value for recovery and recycling, reuse potential, and Eol financial value. Moreover, establishing a common language for data sharing among stakeholders along the value chain facilitates adaptability and disassembly mechanisms. The use of Classification Systems for building systems and elements delivers vigorous means to produce detailed descriptions and categorisation of all building-related data. Furthermore, to ensure facilitated and smart resource reuse and management, a complete knowledge of the building over its entire life span, including all the changes it has undergone is necessary. Studies suggest that Building Information modelling (BIM) could efficiently compile and interpret data and information needed. BIM allows for establishing a Circular Feedback System using a centralised model with all information important to all stakeholders in a Digital Form. BIM Models enable tracking the components’ geometric and mechanical characteristics, composition, recycling value, reuse potential, and expected life cycle.

3.2 Level(s) Framework

Description. Level(s) framework is developed to be a common EU framework for a holistic approach towards sustainability assessment in new and existing office and residential buildings. The framework is designed considering the CE action plan, which involves a lifecycle thinking from cradle to cradle, reflected in the utilisation of value and risk rating system [8]. The 16 core sustainability indicators constituting the six Macro-objectives of the Level(s) framework mainly focus on the environmental performance of buildings along their lifecycle. The framework is structured to meet the EU target areas, including energy, resource use, waste production water, and indoor comfort in addition to lifecycle costs. The framework relies on reporting by involved actors on building performance at multiple project stages, from planning and design through implementation, completion and operation to the projected end of life. To achieve this objective, the framework supports three levels of performance assessment: common, comparative and optimised, allowing a progression in accuracy and expertise.

The consideration of the circular economy of building manifests in Macro Objective 2 “Resource efficient and circular material life cycles” which includes 4 core indicators:

  • 2.1 Bill of quantities, materials and life spans

  • 2.2 Construction and demolition waste and materials

  • 2.3 Design for adaptability and renovation

  • 2.4 Design for deconstruction, reuse and recycling

Design for Adaptability and Renovation Indicator. This indicator considers addressing future emerging needs by ensuring a building's design capacity since the early project stage to keep fulfilling its function and extend its service life. DfA in Level(s) counts on more efficient use of space throughout the life cycle of a building to increase its longevity and improve its operational performance, contributing to minimising its environmental impacts over the lifecycle [9].

Levels of assessment: The DfA indicator provides a continuous view into the flexibility of design aspects through consequent life cycle stages by promoting three levels of assessment as follows:

  • Level 1 of the assessment introduces design concepts in the form of two checklists, one for residential buildings with 8 design aspects and one for office buildings with 12 design aspects helping architects and structural engineers appraise design factors that facilitate future adaptability to emerging needs.

  • Level 2 of the assessment relies on detailed design drawings to help configure spatial dimensions and access zones to services during construction. Design alternatives can be assessed and compared at this level, allowing informative decision-making.

  • Level 3 of the assessment evaluates the value of design features in the use phase for potential future adaptations.

Assessment Aspects. The multiple aspects considered in the three levels of assessment are presented in Table 30.1.

Table 30.1 Assessment aspects in the three levels of indicators 2.3
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Interaction with other Level(s) indicators. Adaptability scenarios have different impacts on input and output flows along a building's lifecycle. The framework, therefore, establishes connections between the DfA indicator and other indicators. The considerations taken by other indicators influencing DfA indicator are presented in Table 30.2.

Table 30.2 Interrelation of Level(s) indicators with indicator 2.3
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The input–output relationship among the previous indicators enables comparisons in terms of resource efficiency, allowing users to define advantages and barriers for each and identify potential trade-offs.

3.3 Analysis of Adaptability Requirements in Level(s) Framework

This section addresses the analysis of adaptability requirements against their implementation. The framework's shortcomings and possible improvements are also analysed, particularly for indicator 2.3. Table 30.3 presents the consideration of adaptability requirements in DfA indicators and others addressed by other Level(s) indicators.

Table 30.3 Implementation of adaptability requirements in Level(s) indicators
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Observations and Shortcomings and Improvements. Some of the adaptability requirements identified in this study are split between indicators 2.2, 2.3 and 2.4. Therefore, assessing one of these indicators results in an uncomprehensive outcome. For example, material specification is not addressed in indicator 2.3 but in 2.2. This argument reinforces the necessity for a single circularity index that englobes all aspects in the interrelated indicators of Macro Objective 2, allowing making beneficial trade-offs between indicators (e.g., between DfA and DfD) to reach higher circularity values. Also, introducing a circularity index building on Macro objective 2 indicators allows benchmarking circularity values in buildings and identifying added value to sustainability (using indicators 1.2 and 6.1), enabling decision-making regarding the most beneficial circularity aspects to all sustainability dimensions.

The scope of analysis, particularly the layers of consideration in the different indicators in Level(s), is not coherent. For example, in indicator 2.3, the scope considers the structure, façade, space plane and services, whereas in the other indicators of Macro objective 2 the layers are shell, core and external elements. Layering and classifying systems and components using a common methodology recognised by all stakeholders ensure coherent evaluation and more straightforward trade-offs between circularity options. A proper classification must be established since the creation of the bill of quantities and materials, then adopted in the other interrelated indicators. Adopting a coherent layering also allows for assessing each layer's impact on the overall project.

Although the framework mentions that structure and façade have the largest share of the environmental impact of a building project, the sum of weights given to this category in the office buildings weighting system (10.5) is equal to the category of space plan (10.5) and less than the services category (12). The reason is either the design aspects are not attributed to their proper categories or the design aspects for structure and façade are not inclusively addressed. In both cases, the weighting system should be revised considering a coherent attribution of elements to proper categories and allocation of objective weights. Moreover, the weighting and scoring systems in Levels 2 and 3 for indicator 2.3 are only developed for office buildings, with no systems for residential buildings. Therefore, the next version of the framework should address creating a weighting and scoring system for residential buildings. Also, changes from one use to another (from residential to office and vice versa) should be considered.

In its current status, the framework lacks the integration of recent information management tools such as material passports and digitalised information and calculation of indicators. Automating the indicators using a BIM environment could deliver more efficient assessment and centralised management where all stakeholders can interact and provide insights on circularity, testing multiple alternatives and appraising best options.

4 Conclusion and Future Work

This paper addresses adaptability requirements drawing on a review study analysing renowned assessment models and frameworks for adaptability and its role in enhancing building circularity. The requirements are analysed against their implementation in Level(s) framework, allowing for improvements to be introduced for more practicality and objectiveness. The conclusion can be made that although Level(s) embraces circularity as a modern-day requirement for sustainability in a well-established and accessible-to-all framework, it lacks some coherence in its methodology. Since Level(s) is still undergoing developments and updates, some shortcomings are addressed and further improvements are proposed to ensure a more inclusive and objective assessment focusing on Macro Objective 2. A potential future work may consider analysing the rest of the circularity requirements against their implementation in Level(s) to identify an overall circularity index. Testing and refining should also be performed using case studies. Future developments should also address the digitalisation of information requirements and automation of indicators and circularity index for interactive assessments.