Joey Nijnens holds a Master's degree in industrial ecology from Delft Technical University and Leiden University, as well as a Master's degree in supply chain management from Groningen University. He is employed at Monitor Deloitte as a strategy consultant, the strategy practice of Deloitte Consulting in the Netherlands, where he focuses on energy transition strategy and circular economy. Over the past years, his academic pursuits have centered around critical raw material supply, clean energy production dynamics, and clean energy supply chains. In his current role, he actively contributes to shaping national energy transition strategies and advancing clean energy investments. Paul Behrens (UK) is an author and associate professor at Leiden University. His research and writing on climate, energy, and food has appeared in outlets such as the BBC, Thomson Reuters, Politico, Nature Sustainability, Nature Energy, PNAS, Nature Food, and Nature Communications. His popular science book, “The Best of Times, The Worst of Times: Futures from the Frontiers of Climate Science” (Indigo Press, 2021) describes humanity's current trajectory and possible futures in paired chapters of pessimism and hope. Paul won International Champion in the Frontiers Planet Prize and the Falling Walls Prize in 2023. Oscar Kraan is a senior manager at Monitor Deloitte, the strategy practice of Deloitte Consulting in the Netherlands. He has more than 10 years of experience supporting governments and companies in the energy sector navigate the future of energy. Since 2018, Oscar has been part of Deloitte, where he focuses on developing decarbonization strategies and supporting the development of the hydrogen market. He co-leads Deloitte's Global Hydrogen Center of Excellence and the Future of Energy practice within Deloitte. In his work at Deloitte, he continues to be involved in scientific research around energy system integration, wherein he combines scientific insights with policy and business challenges. Before Deloitte, Oscar obtained his PhD on the topic of energy transition scenarios, wherein he applied agent-based modeling to energy and electricity system modeling. Before and during his PhD, Oscar worked 6 years with Shell's Scenario Team and Shell's New Energies Strategy Team. Benjamin Sprecher is an assistant professor of circular product design at the Delft Technical University. His main research interests are sustainable design, quantification of environmental impacts, and industrial ecology. His current work explores how quantification of environmental impacts can inform sustainable and circular design and how decisions at the product design level relate to system-level concepts such as circular economy. His PhD and postdoc were focused on critical raw materials and supply chain resilience, and he remains working on these topics, as well. René Kleijn is a professor of resilient resource supply at Leiden University in the Netherlands. He serves as the department head of the industrial ecology group at Leiden University and the scientific lead of the Circular Industries Hub at the Leiden-Delft-Erasmus Centre for Sustainability. His research primarily centers on sustainability matters, employing quantitative methods like life cycle assessment and substance and material flow analysis. Kleijn's expertise extends across various industries, including chemicals, energy, and recycling, where he effectively applies these methodologies to address environmental challenges. He has actively participated in numerous large consortia as part of EU-funded research projects. In recent years, his research has focused on critical raw materials, resilient supply chains, circularity, and material constraints within the evolving landscape of the energy transition.

In terms of mass, construction materials and construction and demolition waste make up the largest part of humankind's material and waste footprints, particularly after an energy transition has largely phased out fossil energy. However, a circular use of building and construction materials is fraught with challenges.

Energy efficiency plays an essential role in energy conservation and emissions mitigation efforts in the building sector. This is especially important considering that the global building stock is expected to rapidly expand in the years to come. In this study, a global-scale modeling framework is developed to analyze the evolution of building energy intensity per floor area during 1971–2014, its relationship with economic development, and its future role in energy savings across 21 world regions by 2060. Results show that, for residential buildings, while most high-income and upper-middle-income regions see decreasing energy intensities and strong decoupling from economic development, the potential for further efficiency improvement is limited in the absence of significant socioeconomic and technological shifts. Lower-middle-income regions, often overlooked in analyses, will see large potential future residential energy savings from energy intensity reductions. Harnessing this potential will include, among other policies, stricter building efficiency standards in new construction. For the commercial sector, during 1971–2014, the energy intensity was reduced by 50% in high-income regions but increased by 193% and 44% in upper-middle and lower-middle-income regions, respectively. Given the large energy intensity reduction potential and rapid floor area growth, commercial buildings are increasingly important for energy saving in the future.