Repurpose existing buildings to cut new construction carbon emissions, UN says

The sector is already responsible for 37 per cent of global CO₂ emissions, and it will need to curtail this rapidly if goals to reach net zero by 2050 are to be achieved.

In a new report, Building materials and the climate: constructing a new future, the UN said that repurposing existing buildings typically achieves a 50-75 per cent saving on emissions.

It also called for construction attempts to use fewer materials and embrace those with a lower carbon footprint, such as timber, bamboo and biomass.

While the shift towards bio-based materials could lead to compounded emissions savings in many regions of up to 40 per cent in the sector by 2050, significant policy and financial support is needed to ensure the widespread adoption of the materials.

The report also said that more action would be needed to improve the decarbonisation of conventional materials that cannot be replaced. This mainly concerns the processing of concrete, steel and aluminium – three sectors responsible for 23 per cent of overall global emissions today – as well as glass and bricks.

Priorities should be placed on electrifying production with renewable energy sources, increasing the use of reused and recycled materials, and scaling innovative technologies.

Efforts to do this could be ramped up significantly through changes to building codes, certification and labelling, and the education of architects, engineers and builders on circular practices.

“Until recently, most buildings were constructed using locally sourced earth, stone, timber and bamboo. Yet modern materials such as concrete and steel often give only the illusion of durability, usually ending up in landfills and contributing to the growing climate crisis,” said Sheila Aggarwal-Khan, director of the UN Environment Programme’s (UNEP) Industry and Economy Division.

“Net zero in the building and construction sector is achievable by 2050, as long as governments put in place the right policy, incentives and regulation to bring a shift in industry action,” she added.

To date, most climate action in the building sector has been dedicated to effectively reducing “operational carbon” emissions, which encompass heating, cooling and lighting.

Thanks to the growing worldwide decarbonisation of the electrical grid and the use of renewable energies, these are expected to decrease from 75 per cent to 50 per cent of the sector in the coming decades.

Anna Dyson, founding director of the Yale Center for Ecosystems and Architecture and lead author on the report, said: “Since the built environment sector is so complex, with interdependencies across actors, all hands on deck are required to decarbonise. We can’t leave anyone behind.

“Policies must support the development of new cooperative economic models across the building, forestry and agricultural industries in order to galvanise a just transition towards circular, bio-based material economies that can also work synergistically with the conventional material sectors.”