Retrofit buildings and build less to reduce emissions: UN

14-09-23

• A UN report found that every five days as many buildings are constructed around the world as already exist in Paris.

The housing construction sector needs to retrofit existing buildings and use more bio-based materials such as wood and bamboo to reduce its growing CO2 emissions, which already account for 37% of the global total, a UN report released on Tuesday said.

The report, by the UN Environment Programme (UNEP) and Yale Center for Ecosystems + Architecture (Yale CEA), noted that globally, urbanisation is proceeding so rapidly that as many buildings are being constructed worldwide every five days as already exist in Paris.

This rate of building is causing the construction sector to currently account for 37 per cent of all global carbon dioxide emissions, although this proportion is increasing.

The director of UNEP's Industry and Economics Division, Sheila Aggarwal-Khan, said that emissions are rising in part because in many countries traditional building materials are being replaced by more environmentally costly ones.

"Until recently, most buildings were constructed using local materials such as earth, stone, wood and bamboo," she said in presenting the report.

"But modern materials such as concrete and steel often only give the illusion of durability and end up in landfills, contributing to the growing climate crisis," Aggarwal-Khan added.

The report, which falls under the mandate of the Global Alliance for Buildings and Construction (GlobalABC), a platform created at COP21 with 298 members of which 40 are countries to achieve zero emissions in the sector, suggests a three-pronged strategy for eliminating CO2 emissions.

Firstly, avoiding waste by retrofitting existing buildings, which reduces emissions by 50-75% compared to the construction of new structures. At the same time, it is necessary to promote construction with fewer materials and with those that have a lower environmental impact.

In this sense, the second proposal of the authors of the report is the replacement of materials such as cement, steel and aluminium with renewable and bio-based products such as wood, bamboo and biomass.

Experts estimate that replacement could accumulate savings in many regions of the world of up to 40 per cent of the sector's emissions by 2050.

And finally, the report notes that where materials cannot be replaced by renewable and bio-based alternatives, the production process for cement, steel, aluminium, glass and bricks needs to be upgraded.

The production of cement, steel and aluminium for building construction alone accounts for 23% of global carbon dioxide emissions.

To decarbonise the production of these building materials, the use of electricity from renewable sources, the increased use of recycled materials and the use of innovative technologies are a priority.

In this sense, the authors said in a statement, if future building materials come from the carbon capture process, the buildings could even be "carbon negative", i.e. not only would they not contribute to CO2 emissions, but they would participate in their removal from the atmosphere.

Aggarwal-Khan, one of the researchers, believes that if governments put in place "appropriate policies, incentives and regulations" along these lines, the building sector can achieve zero emissions by 2050, according to the statement.

Anna Dyson, the report's lead author and founding director of Yale CEA, added that "policies should support the development of new models of cooperation around the building, timber and agricultural sectors to galvanise a just transition to circular economies based on bio-based materials".

So far, the study added, most policies and initiatives in the sector have been aimed at reducing emissions from building operations, such as heating, cooling or lighting.

These initiatives have been successful as the measures in place are expected to reduce emissions from building operation by 50-75%.