The built environment sector is by far the largest emitter of greenhouse gases, responsible for at least 37 percent of the global emissions. Yet it has received only a small fraction of climate-focused development funding, compared to other sectors. Until now, most of the progress in the sector has been made on reducing the “operational carbon” of a building – the emissions created from heating, cooling, and lighting, which are projected to decrease from 75 percent to 50 percent of the sector in the next few decades. However, solutions for reducing the “embodied” carbon emissions from the design, production, and deployment of building materials such as cement, steel, and aluminum have lagged far behind. The reasons for this are complex and many actors are involved. Therefore, the incentives for decarbonization need to simultaneously enable decision makers, from producers to consumers across the global material supply chains, in both informal and formal building sectors. This report highlights the urgent need to develop new models for cooperation on the decarbonization of building materials if the world is to reach its goals for net zero emissions from the built environment sector by the mid-century.