Construction projects are resource-intensive, often leading to significant waste during the end-of-life (EoL) phase. The transition to a circular economy—moving from a take-make-waste model to a take-make-recover-transform-repeat approach—addresses issues of unsustainable resource use and waste generation. The Circular Economy aims to keep products in the value chain at the highest possible quality for as long as possible, reducing raw material usage, waste generation and carbon emissions. Kirchherr et al. (2017) conceptulised a cascade of circular actions to promote resource efficiency, conscious design and consumption, and prevent waste generation, as shown below. 

Figure 2 The Circular Economy hierarchy, developed from Kirchherr et al. (2017)

Reusing a construction product after its life cycle ends is highly encouraged for two main reasons: it saves raw materials and reduces carbon emissions by eliminating the extraction and production phases in the second life cycle, which are particularly carbon and material-intensive. Since it is not always feasible to reuse an item exactly as it is after the EoL phase, a hierarchy of lesser circular possibilities has been established.

Reusing a product implies it is passed from one hand to another. Therefore, a novel mechanism in the circular construction supply chain is needed to connect the reclaimed, reusable pieces with potential buyers. This is where material banks, or marketplaces, come into play. Material banks link the end-of-life phases of a building component (e.g., deconstruction audit and deconstruction) to a new life cycle (e.g., design with reuse). They often serve as both physical locations for storing and reselling reusable construction products post-deconstruction and digital platforms to enhance the accessibility and visibility of available reusable materials and components. Additionally, they recertify the reusability of materials and components, ensuring they meet the required standards for new applications and possess adequate environmental, structural, and chemical performance. Having material banks, which serve as repositories of reusable items, facilitates reuse and thereby extends the lifecycle of building components.

Figure 3. Material banks interact with the parallel worlds of digital and physical workflows

DOR’s taxonomy is comprehensive, with logically interconnected classes and properties that allow for the development of chain axioms.These axioms are elaborated to avoid binary dead-ends and encourage detailed elaboration of circular information requirements. The novelty of DOR is to avoid binary dead-ends and enable a machine-readable flexible, tailored and expandable chain axiom understandable by all circular actors. While the DOR bSDD and ontology list properties that ensure materials, products, components and buildings are circular, there is a need for guidelines on how and when to use these properties.

The D2R Information Delivery Manual (IDM) and Use Case Management (UCM) offer state-of-the-art workflows that ensure a product is designed for reuse or becomes reusable. D2R encompasses various processes, each capturing, consuming, or producing different circular-related information from DOR. Since not all actors and phases have the same information needs, the D2R process maps are designed to provide the right amount of circular information necessary for each operation but they also need to be communicated and passed by via material banks. 

The DOR is influenced by ISO 19650-1. It aims to create a minimum vocabulary usable by both Project Information Models (PIM) and Asset Information Models (AIM); as such, DOR supports both existing assets (including reclaimed, reusable components) and new assets designed for deconstruction (and reuse in the future) through same standardised vocabularies. The D2R supports circualr construction in the absence and presence of a PIM or AIM. Many existing buildings and reclaimed products lack information models, a factor that has been considered in the process maps of the D2R.

The process maps are delivered following the interviews with circular construction experts. The interview questions were influenced by the ISO 29481 series to see what is examined when, with whom, and how. This step was intended to optimise and validate the DOR properties and provide process maps that support real-world applications.

The proposed bSDD is in perfect alignment with the Level of Information Need concept as outlined in the EN 17412-1:2020 standard (Building Information Modelling - Level of Information Need - Part 1: Concepts and principles). This alignment ensures that DOR provides a minimum set of circular construction vocabularies that serve the purpose and avoid redundancy, thereby complying with industry standards.

The project aligns with European and international standards for sustainability and circular economy, such as ISO 20887, ISO 21930, Product Circularity Data Sheet (PCDS, ISO 59040) and several European Commission's guidelines. The bSDD aims to create a minimum vocabulary for the circular economy, fostering a more objective and standardised approach to circular construction.

This DOR bSDD has a trans-perspective nature, meaning that different perspectives of reusability and circularity, which are currently subjective due to the infancy of the circular economy, can be modelled. The idea is to accommodate the diverse and evolving nature of the circular economy projects in the construction industry. To this aim, DOR's set of classes and properties make circular economy understanding and discourse more objective. This information helps to host many projects with the same capabilities for different groups of people in different countries. The present UCM and process maps support the trans-persepctive nature of the DOR.

The process maps and information exchange procedures have been well-received by both field practitioners and academics. After nearly six years of extensive multi-step research, this UCM provides a comprehensive guideline to ensure that relevant actors deliver the right information at the appropriate time, using standardised vocabularies and processes. This approach ensures the continued integration of circularity in current practices and helps future-proof information exchanges for long-term sustainability.