The built environment sector is by far the largest emitter of
greenhouse gases, responsible for at least 37 per cent 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 per cent to 50 per cent 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 aluminium have lagged far behind. The
reasons for this are complex and many actors are involved.
Therefore, the incentives for decarbonisation 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
decarbonisation of building materials, if the world is to reach
its goals for net zero emissions from the built environment
sector by the mid-century.

Why has it been so difficult to decarbonise building materials,
and what can be done about it? People have not always built
with carbon-intensive materials and their future use is not
inevitable. Before the middle of the 20th century, the vast
majority of cultures built large buildings and cities out of
indigenous earthen, stone and bio-based materials – such as
timber, cane, thatch and bamboo. However, during the last
century, with ever greater access to fossil fuels, the global
extraction and production of carbon-intensive, mineral-based
materials (such as concrete and steel) exploded and became
widely associated with the image of modern progress,
strength and expediency.
Yet many contemporary building structures and materials
only give the illusion of durability, as they were “designed for
obsolescence”. Building assemblies with limited lifespans are
now destined for landfills at demolition, as they have been
procured through complex supply chains and are not designed
for easy disassembly or re-use. An example is the vast number
of failing concrete structures with steel and glass façades
across the developed world that need to be replaced just a
few decades after they were built. Meanwhile, stone, wood
and even massive mud buildings have been maintained for
centuries with their structures intact.