The environmental impact of the construction industry has left its mark on today’s society over the last decades, also in the Netherlands. In addition, the Dutch construction industry faces a major challenge in the replacement and renovation (V&R) task of the current infrastructure. Among others, many viaducts will be at the end of their functional lifespan. A transition to a closed resource loop along with the V&R task provides the Dutch construction industry an opportunity to extent the lifespan of elements and objects of end-of-life viaducts and reuse them in new viaducts while reducing the resource flow and its environmental impact. Although many circular initiatives and practices have been researched and developed by companies, there are still certain barriers that prevent the application of them to realise circular viaducts. The objective of this research is to identify the existing barriers that hinder a closed resource loop to enable circular viaducts in the construction industry and contribute to the circular transition.

The main barrier of circular innovations in the construction industry is the balance between supply (availability of materials) and demand (circular requirements in tenders). A sufficient volume of reusable elements must be created. Meanwhile, circular requirements are needed in tenders for the application of these elements in projects, proper assessment tools must be developed, and additional regulations and legislation is needed. In addition, there are still uncertainties with respect to the material specifications, ownership and warranty and the business case. Reusable elements are more expensive as they need to be harvested. Supply chains and collaboration form such as consortia are needed as portfolio contracts will become the new normal. Transparency is needed between the stakeholders in the industry and knowledge should be shared among parties.

A change in mindset is needed. Clients must be willing to pay more for circularity and market parties should accept the uncertainties of the transition. Additional roles and expertise’s are needed within the industry and supply chains must be organized.
Appropriate circular assessment tools have to developed, other design strategies of resource flows may assist the transition to a closed resource loop system, asset management, and additional client perspectives.

Contemporary project-based organisations recognise the importance of leveraging past project knowledge for competitive advantage. By leveraging the lessons learned from previous and ongoing projects, organisations can benefit from managing learning within and across projects effectively. Despite these benefits, challenges persist in effectively reusing captured knowledge. This qualitative study addresses this gap by investigating knowledge reuse in project-based organisations, with a focus on social learning mechanisms. The results underline the pivotal role of collaboration and social interactions in facilitating tacit knowledge sharing and reuse, along with the significance of learning on the job.

The research identifies drivers, barriers, and guiding principles for promoting knowledge reuse, addressing barriers such as motivation, resistance to change, and knowledge silos. Recommendations include establishing comprehensive databases, fostering collaboration, and strengthening Communities of Practice aligned with organisational goals. Moreover, the study emphasises that true organisational learning primarily occurs through social interactions, advocating for a shift from 'learning from repositories' to 'learning through social means.' It underscores the role of organisational culture, particularly trust, in enhancing learning and knowledge reuse, promoting personal networks, communities of practice, and blame-free cultures. Lastly, guiding principles advocate for both top-down and bottom-up approaches to foster knowledge reuse across all organisational levels.

This research extensively examines the pivotal shift toward circularity within the European construction and building sector, with a specific emphasis on HVAC systems in utility buildings. It commences by underscoring the pressing urgency precipitated by the Paris Agreement of 2015 and subsequent climate objectives, necessitating reductions in greenhouse gas emissions and resource utilization. The construction and building sector's notable contributions to energy consumption, waste production, and material extraction highlight the imperative to address circularity within this industry.
The report delves deeply into the notion of the circular economy (CE), emphasizing its potential to disassociate economic growth from resource depletion and waste generation. While acknowledging the growing scholarly and corporate interest in CE, exemplified by industry giants such as Philips and IKEA, this study highlights the limited practical application of circular principles, particularly within the HVAC systems sector.
Recognizing the multifaceted and varying interpretations of circularity, the report seeks to demystify the concept by conducting a thorough literature review and interviews. Through a thematic analysis, it identifies existing challenges, proposes potential solutions, and evaluates the feasibility of implementing circular strategies for HVAC systems. Key findings encompass project-specific considerations, the influence of location and climate, and the imperative need for legislative reforms to expedite the transition.
Ultimately, the research provides a valuable starting point for MEP consultants, equipping them with a pragmatic decision support framework and a categorized repertoire of circular strategies. It encourages industry professionals to embrace circularity in HVAC design, bridging knowledge gaps and promoting sustainable practices. While acknowledging the study's limitations, including its qualitative nature and potential for bias, this study calls for future research to validate the framework through real-world cases, expand performance evaluation criteria, and advocate for policy reforms across the broader built environment. In summary, this study constitutes a vital stride toward fostering circularity and sustainability within the construction and HVAC sectors.

The current market forces of infrastructural projects in the Dutch construction sector necessitate public clients to divide a large-scale multidisciplinary project into multiple contracts. This causes diverse contractors to have to work simultaneously. Interfaces arise between the contracts, which require a deeper collaboration to align all activities. Coordination becomes a very important factor in such projects. Current attempts to create better coordination focus mainly on clients' contractual and organizational measures. This research aims to map the importance of the human aspect within coordination and help a client organize itself to create a better coordination process. This is done by looking at the contractual and organizational instruments that stimulate coordination. Hereby, the organizational measures are divided into relational, personal, and governance aspects.

Through a literature review, the steering mechanisms for good coordination within the contractual, relational, personal, and governance contexts were established. A case study provided the issues of coordination in practice and laid down the basis of possible instruments to help a public client with the coordination process. The main takeaways were the misinterpretation and misalignment of the specifications of agreements, choosing the wrong coordinator, the lack of attention to relations, and the unclear governance from the client’s side. After this, a preliminary framework of the coordination process was reviewed through expert sessions. Together, this created the basis for the final framework of this thesis.
The key findings of this research were the need to facilitate coordination and collaboration during the pre-execution through requirements in the contracts and a start-up period with the involved clients and the co-contractors. During the execution phase key findings were the need to facilitate coordination and collaboration by the attention to the human aspect and its process, besides aiming for the best project result. This research contributed to the current literature by showing how the current coordination processes of a public client within the Dutch construction sector lack attention to the human side during projects.