T H E C I R C U L A R FA C A D E D E S I G N I N G B U I L D I N G S A S M AT E R I A L B A N K S
R E S E A R C H + D E V E LO P M E N T
Author: Dave Austin Associate Architectural Technologist
CONTENTS INTRODUCTION
BUILDINGS AS MATERIAL BANKS (BAMB)
RECOVERY INFRASTRUCTURE
CONCLUSION
INTRODUCTION In an era where resource scarcity, carbon reduction, retrofit, and reuse are central to industry discourse, should the building envelope be approached more innovatively than through the current linear cycle of design, detailing, installation, and disposal? If industries such as aerospace and automotive can lease their products with performance guarantees, is it time for construction to explore alternative models for how projects are designed and executed - placing renovation and reuse at the forefront of decision-making? In Mckinsey 2026 Quarterly, it is estimated that the construction industry currently reuses less than 1% of building materials at the end of their typical life. Meanwhile, according to Dr. Fatih Birol Executive Director of the International Energy Agency (IEA), the built environment is simultaneously expanding by the size of Paris every week. This highlights an urgent need to address sustainable approaches not only in new construction, but also in renovation and retrofitting. With predictions suggesting that two-thirds of the buildings that will exist in 2050 have already been built, a dual approach is required. This must both significantly reduce reliance on virgin materials through the reuse and renovation of existing building stock and prioritise design for disassembly, alongside future renovation and reuse, from the outset. Beyond these statistics, it is estimated that between 10% and 30% of the building’s total embodied carbon is attributed to the façade. This highlights the significant opportunity, and responsibility, to reduce carbon from the outside in. However, achieving meaningful reductions cannot be driven by a single strategy or discipline alone. Instead, it requires the integration of multiple approaches, forming a holistic design, detailing, and procurement strategy that supports long-term sustainability objectives. The successful integration of these strategies alongside core circular economy principles is fundamental to realise a circularity loop that preserves material value and performance, fostering reuse and extending the productive life of materials across multiple lifecycles.
© Hundven-Clements Photography
BUILDINGS AS MATERIAL BANKS An overarching concept linking circular economy strategies is the notion of ‘Buildings as Material Banks’ (BaMB). By viewing a building as a repository of materials, rather than something constructed, demolished, and ultimately discarded, its inherent value and long-term potential can be more fully realised. As with any asset within a bank, materials must retain value that can be recovered at the end of use. This value is determined across multiple metrics, including monetary worth, life expectancy, performance, and other qualitative measures. To successfully implement this concept, it must be supported by complementary strategies that enable value retention and recovery. These include Design for Assembly (DfA), Design for Disassembly (DfD), urban mining, and enabling measures such as robust detailing principles, material passports, and a comprehensive understanding of the building lifecycle, from individual components through to systems and the overall envelope. While circular economy principles should now be considered a default in response to carbon reduction targets, the interdependency of these strategies places greater responsibility on their integrated application. This is particularly critical given that, at the end of a façade’s life, its components are intended to be reused, making upfront decisions fundamental to future performance and value recovery.
Circular Construction Lab
ABOVE Building + Constructing a Circular Economy diagram (c) Felix Heisel and David Perovsek, Circular Construction Lab: https://labs.aap.cornell.edu/ccl/whitepaper
2.1 Façade-as-a-Service As with conventional financial systems, material banks require deposits to retain value and enable future transactions. Within the built environment, the façade can be considered such a deposit; however, over a building’s lifetime, façades inevitably deteriorate resulting in the depreciation of stored value. Façade-as-a-Service (FaaS) shifts the façade from a one-off product to an on-going service and in doing so, manufacturers and suppliers become ongoing stakeholders, maintaining a vested interest in the building’s performance, ensuring that systems meet indoor comfort requirements over a defined period and safeguarding the value of the original material deposit.
This model enables guaranteed performance for the end user while introducing greater flexibility within the building envelope, allowing for component interchangeability to meet evolving performance demands. Retained ownership further incentivises suppliers to maximise durability, extend service life, and minimise intervention. At the end of use, façades that are no longer suitable for their original application can be repurposed in lower-performance contexts or recycled for future reuse. This approach aligns with the broader concept of Product-Service Systems (PSS), which have been successfully adopted across industries such as electronics, automotive, and aerospace. In the latter, for example, aircraft are often leased for primary passenger use before being redeployed for less demanding functions over time, demonstrating the viability of extended, performance-based lifecycle models.
Option 1:
Option 2:
Solid panels could be introduced to upgrade appearance, improve thermal efficiency, and/or enhance privacy.
An openable window could be introduced to support natural ventilation.
In 2016 TU Delft installed a technology demonstrator pilot project on the EWI building showcasing what were then, state-of-the-art façade-integrated technologies. This was developed further in 2019 through the implementation of a FaaS model on the east elevation of the CiTG building, where a 1960s structure was retrofitted with a new façade installed on a leased basis.
compelling and potentially advantageous alternative.
The project was evaluated against two alternative scenarios: business-as-usual minimal maintenance and traditional façade replacement. Findings indicated that the FaaS PSS model offered a more attractive cash flow over a 30-year period, albeit with increased legal and financial complexity.
The limited number of comparable applications raises important questions regarding broader feasibility, particularly within privately financed projects. As a result, it remains uncertain whether FaaS can transition from a predominantly academic and research-led concept into a commercially viable solution, or whether it will continue to be constrained to experimental and institutional contexts.
Given that façades can account for up to 95% of renovation costs and are the primary determinant of a building’s thermal and energy performance, a leased, performance-based approach presents a
While there are real-world examples of demountable façades used in tandem with material passports, TU Delft remains the leading example of a fully implemented FaaS model delivered under a comprehensive contractual framework and used as the basis of detailed study.
Option 4:
Option 5:
Option 6:
A green wall could be installed to support wellbeing or a wider biodiversity enhancement strategy.
Photovoltaic panels or heat exchanger ventilation systems could be introduced to support renewable energy generation and mechanical ventilation.
LED displays could be introduced to host advertisements or signage.
ABOVE Diagram showing different ways a facade panel could be adapted and reused in the future
2.2 Design for Disassembly Design for Disassembly is a fundamental principle underpinning not only the successful implementation of FaaS, but façade design more broadly when aligned with circular economy ambitions. The concept gained prominence in the 1990s, evolving from the earlier principle of Design for Assembly, which emerged in the 1970s to promote efficiency through standardisation and optimisation of components.
Aluminium Mullion Fully recyclable. Reference Service Life: 40 years (powder coating gloss and fastness) 50+ years (profile)
Although DfD rose to prominence relatively recently, its underlying principles can be traced to much earlier precedents. Notable examples include Joseph Paxton’s Crystal Palace and Zehrfuss and Prouvé's UNESCO Building, both of which embodied disassembly, adaptability, and reuse well ahead of their time.
Aluminium transom
Gasket
When successfully implemented, DfD enables the effective separation and reclamation of building elements. However, this approach often conflicts with the requirements of high-performance contemporary façades, which typically rely on multi-layered assemblies, adhesive connections, integrated building services, and composite materials, factors that significantly hinder disassembly and material recovery.
Seal to glazing Non-recyclable. Reference Service Life: 25 years
Thermal break Non recyclable. Reference Service Life: 25 years.
This inherent contradiction introduces an ongoing design tension, requiring careful balance between material circularity, embodied carbon reduction, operational energy performance, and overall system complexity.
Key considerations for DfD in design: •
Mechanical connections - to allow for disassembly,
•
Accessibility - connections to be located in
bolted, screwed and clipped connections are required
accessible areas with their operation avoiding damage
rather than the use of irreversible adhesive and
to adjacent components.
sealants • •
•
Hierarchy of service life - design to consider façade
Material separation - where materials have differing
components have differing service lives with non-
end of life pathways and expectations, these should
structural element having shorter lives, layers within
be separable. Avoidance of composite materials is
build-up to be designed to allow for independent
required.
replacement.
Standardisation and modularity - if direct reuse is aspired, components should be designed to standard dimensions to enable interchangeability and reapplication.
•
Documentation - recording of connection details and material compositions to guide future disassembly.
Spacer bar Potentially recyclable (dependant on material choice for spacer and requires specialised recovery methods). Reference Service Life: 25 years (dependant on IGU lifespan)
Double glazing Typical hard and soft coated glazing potentially recyclable but requires specialised recovery methods. Reference Service Life: 30 years (dependant on seals)
Aluminium cover plates & caps Fully recyclable. Reference Service Life: 40 years (powder coating gloss and fastness) 50+ years (profile)
ABOVE Detail axonometric diagram of a facade
RECOVERY INFRASTRUCTURE As noted, contemporary façade design can limit the full realisation of DfD, often requiring compromises across performance, complexity, and material strategies. However, an alternative pathway to circularity, urban mining, is increasingly being integrated into façade design.
Urban Mining ‘Urban mining’ has been a term coined and used in the late 1960’s by the industrial sector, however it’s overall definition can be translated into the built environment by viewing cities as material reservoirs, where existing resources can be extracted, reprocessed, and reintroduced into new applications. Within the built environment, this enables materials from previous generations to be retained within the resource cycle, rather than discarded. The application of urban mining can operate across multiple scales, from individual materials and components to entire buildings, and ultimately at an urban level. Regardless of scale, the potential impact is significant. Given that façades account for approximately 10–30% of a building’s embodied carbon over its lifecycle, even incremental improvements achieved through material recovery and reuse warrant careful and deliberate consideration. The combination of DfD and urban mining forms two core principles underpinning a circular façade. The reuse of materials provides a renewed lifecycle for components that would otherwise be downcycled or sent to landfill, reducing the need for additional virgin material. In parallel, DfD enables the disassembly and potential reuse of façade systems at the end of their service life. With FaaS now being tested in real-world applications, it introduces a potential third component to this framework. Together, these strategies raise the question of whether their integration could form a fully realised “circularity loop”, or, effectively, a self-sustaining system capable of maintaining material value, performance, and reuse across multiple lifecycles. Challenges and Constraints – What does the industry require to adapt and adopt? Embodied carbon can account for approximately 50% of whole-life carbon emissions, with the façade itself contributing between 10% and 30% of a building’s total embodied carbon. As such, adopting a combination of the strategies outlined above is critical to minimising these
ABOVE Different scales of recovery infrastructure
impacts by reducing embodied carbon across multiple lifecycles uses. This is becoming increasingly important as carbon reporting requirements tighten under growing pressure from both local and national governments.
Material level: Reuse of material in part
Stricter regulation and improved carbon accountability will strengthen the commercial case for these approaches. Transitioning to DfD and potentially FaaS models incentivise suppliers to prioritise durability and reusability, as they retain ownership and are responsible for future repurposing. This, in turn, promotes longer-lasting systems and reduces the need for replacement, lowering overall embodied carbon. However, these approaches introduce their own practical limitations and implications: Reuse vs Virgin Materials: Despite advances in deconstruction, recycling, and reuse technologies, a significant barrier remains in the inherent cost, both financial and temporal, when compared to the use of virgin materials or landfilling. Payback periods for reused materials often exceed what clients are willing to accept, and without regulatory or financial mechanisms to bridge this gap, the commercial case remains unconvincing.
Building level: Reuse of all material of a building
However, the cost of virgin materials rarely reflects the ‘true cost’ borne by the environment and society, both today and by future generations. The environmental and social impacts associated with material and components creation, including production by-products such as pollution, industrial waste and increasing energy consumption are typically treated as externalities and therefore not considered in pricing. As a result, the apparent affordability of virgin materials often fails to account for their wider long-term consequences. Addressing this imbalance requires a shift in both industry mindset and policy. Targeted interventions, whether through financial incentives or regulatory mandates, must be implemented across all stakeholders. Emerging frameworks, such as EU mandates (2028), NZCBS, and local policies like the London Plan, begin to establish requirements that drive this transition, but broader alignment is needed to make reuse a viable default rather than an exception. Legal and financial constraints:
Urban level: Mapping of material stock across cities for strategic recovery planning
The viability of FaaS is significantly influenced by both legal and financial mechanisms. Legally, the principle of accession dictates that once a component is affixed to a building, ownership transfers to the building owner. This conflicts with the FaaS model, where the façade remains leased and under supplier ownership.
This complexity is further compounded in project financing. Conventional funding models rely on clear ownership and quantifiable asset value, both of which are challenged when key building components are neither owned by the client nor easily valued over the short or long term. As a result, traditional financing routes become difficult to secure. While these constraints have been navigated in precedent examples, doing so requires innovation within what is largely an archaic system, as well as a shift in perspective. Such approaches should not be viewed as delivering immediate gains, but rather as long-term investments aligned with extended value horizons. Contractor & supplier business model: In industries such as aerospace, industrial machining, and automotive, there has been a clear shift from selling products, to bundling products with services, and ultimately to providing access and guaranteed outcomes rather than ownership. While this transition has proven successful in these sectors, replicating it within construction presents a significant challenge. Adopting a similar model for the building envelope would require transforming an already established delivery approach into one that assumes responsibility for ongoing performance beyond typical periods of involvement. This represents a substantial shift in both risk and operational scope for suppliers. For such a model to become viable and desirable, clear incentives are required, whether environmental, economic, or driven by a broader paradigm shift in business priorities and value perception. Building owner vs tenant benefits: While the successful implementation of FaaS at TU Delft demonstrated that a façade lease model can provide a more attractive cash flow over a 30-year period, this building is both owned (mostly) and occupied by the academic institution. As a result, the financial and operational benefits generated by the arrangement are realised primarily by a single stakeholder. However, the situation becomes more complex where buildings are developed with the intention of being leased to tenants, retained as an investment asset or sold in the future. In such cases, questions arise regarding who benefits from
the model, how value is measured and how those benefits are distributed among stakeholders. For tenanted buildings, mechanisms may be required to quantify the operational carbon savings and efficiency gains delivered by a consistently high-performing façade throughout the buildings service life. These performance improvements could reduce energy consumption and associated operating costs, creating tangible financial benefits for the occupiers. However, as the landlord is responsible for procuring the façade as a performance-based service, consideration must be given to how these benefits can be shared equitably between the owner and tenant. This challenge does not arise to the same extent in buildings that are both owned and occupied by the client; where the benefits of improved performance are captured directly. A different consideration emerges, however, when the property is sold. Under a FaaS model, the purchaser would be acquiring a building without ownership of the façade itself, as the façade remains subject to a service agreement. While this arrangement is not entirely dissimilar to the established relationship between freeholders and leaseholders, careful considered would be required to ensure the transference of contractual obligations and responsibilities between successive building owners. Material passports & unique architecture: Two key considerations must be carefully addressed by the design team when pursuing these approaches. The first relates to material passports and the viability of available data. As discussed, both financing and material feasibility are dependent on intrinsic material properties that must be accurately tracked, quantified, and verified. While material passports have been successfully trialled on select projects, they remain in their infancy and rely on consistent input across the entire supply chain, something that is not yet reliably achievable. The second consideration relates to design implications. To enable FaaS, DfA, and effective reuse with minimal waste, buildings may need to adopt more regimented and repetitive forms. This facilitates the straightforward repurposing or adaptation of components. However, such an approach can conflict with the aspirations of contemporary architectural design, which often prioritise uniqueness and variation.
© Hundven-Clements Photography
CONCLUSION
Despite its potential, FaaS may not be universally applicable across all sectors or business models. Nevertheless, the experience of TU Delft demonstrates that, when supported by carefully managed strategic partnerships and the patience required to establish appropriate contractual and commercial mechanisms, the model can be successfully implemented. As such, FaaS presents a promising opportunity, particularly within the industrial and commercial sectors where long-term asset performance is closely aligned with investment objectives. When strategic design decisions are informed by the principles of FaaS, DfD, adaptability, and the circular economy from the outset, it becomes possible to deliver the façade systems that are both high-performing and inherently flexible. Such systems can maintain their functional and environmental performance while accommodating changing user requirements, technological advancements, regulatory standards and evolving aesthetic preferences. While this approach may not align with every ownership or operational model, it has particular relevance for long term investment institutions and Real Estate Investment Trusts where the combination of guaranteed performance, adaptability and asset longevity could provide financial, operational and flexible accommodation for tenants needs. DfD and urban mining are already well-established concepts within the construction industry, with numerous projects demonstrating their effectiveness in reducing embodied carbon through material reuse and recovery. However, these approaches predominantly address the embodied impacts of the built environment and do not, in isolation, fully respond to the operational carbon emission that persist through a building’s lifespan. To achieve meaningful whole-life carbon reductions, façade performance must therefore be maintained not only at practical completion, but through the asset’s operational life. The integration of FaaS, DfD and urban mining offers a complementary tri-factor framework capable of addressing both embodied and operational considerations. Together these approaches can support the creation of a genuinely circular façade ecosystem, where material value is retained, performance is preserved, and components are continually reused and repurposed across successive lifecycles. Through this combined strategy, a more complete circularity loop can be established, strengthening both the environmental and economic sustainability of the built environment.
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