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UN publishes Pathway to decarbonise the built environment

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The UN has published a pathway report that promises massive emission cuts in the construction sector – the most polluting and toughest to decarbonise.

  • The built environment accounted for over 34% of energy demand and around 37% of energy and process-related CO2 emissions in 2021.
  • Eight major real estate companies have committed to the WEF’s Green Principles but the sector needs wholesale change, not simply individual leadership.
  • The proposed plan to avoid, shift and improve could act as a framework for many different sectors – and highlights the need for cross sector collaboration. 

Rapid urbanisation worldwide means every five days, the world adds buildings equivalent to the size of Paris, with the built environment sector already responsible for 37% of global emissions.

It’s latest report, Building materials and the climate: Constructing a new future, identifies ways to decarbonise the buildings and construction sector, as well as ways to reduce its waste.

Published by the UN Environment Programme (UNEP) and the Yale Center for Ecosystems + Architecture (Yale CEA), under the Global Alliance for Buildings and Construction (GlobalABC), it suggests a three pronged approach that would enable policy makers, manufacturers, architects, developers, engineers, builders and recyclers  to reduce “embodied carbon” emissions. This would also avoid the negative impacts on natural ecosystems from the production and deployment of building materials (e.g., cement, steel, aluminium, timber, biomass).

The UN’s three pronged approach to decarbonisation

The first step is to avoid waste through a circular approach: building less by repurposing existing buildings is the most valuable option, generating 50-75% fewer emissions than new construction; promote construction with less materials and with materials that have a lower carbon footprint and facilitate reuse or recycle.

The second step would be to undertake a shift to ethically and sustainably sourced renewable bio-based building materials, including timber, bamboo, and biomass. The shift towards properly managed bio-based materials could lead to compounded emissions savings in many regions of up to 40% in the sector by 2050. However, more policy and financial support is needed to ensure the widespread adoption of renewable bio-based building materials.

Finally the sector needs to support improvements in the decarbonisation of conventional materials that cannot be replaced. This mainly concerns the processing of concrete, steel, and aluminium – three sectors responsible for 23% 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. Transformation of regional markets and building cultures is critical through building codes, certification, labelling, and the education of architects, engineers, and builders on circular practices.

According to the report, the three-pronged Avoid-Shift-Improve solution needs to be adopted throughout the building process to ensure emissions are slashed and human health and biodiverse ecosystems are protected. The solution also requires, in its implementation, sensitivity to local cultures and climates, including the common perception of concrete and steel as modern materials of choice.

The report includes case studies from Canada, Finland, Ghana, Guatemala, India, Peru, and Senegal, demonstrating how decarbonisation takes places using “Avoid-Shift-Improve” strategies: developed economies can devote resources to renovating existing ageing buildings, while emerging ones can leapfrog carbon-intensive building methods to alternative low-carbon building materials.

Shifting focus on decarbonising buildings

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 renewable energies, these are set to decrease from 75% to 50% of the sector in coming decades.

“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 UNEP’s 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 the industry action,” she added.

The importance of reducing embodied carbon

Since buildings contain materials produced in disparate regions across the globe, reducing “embodied carbon” emissions from production and deployment of building materials requires decisionmakers to adopt a whole life-cycle approach. This involves harmonised measures across multiple sectors and at each stage of the building lifecycle – from extraction to processing, installation, use, and demolition.

Government regulation and enforcement is also required across all phases of the building life cycle – from extraction through end-of-use – to ensure transparency in labelling, effective international building codes, and certification schemes. Investments in research and development of nascent technologies, as well as training of stakeholders in the sectors, are needed, along with incentives for cooperative ownership models between producers, builders, owners, and occupants to the shift to circular economies.

“The decarbonisation of the buildings and construction sector is essential for the achievement of the goal of limiting global warming to 1.5°C. By providing cutting-edge scientific insights as well as very practical recommendations to reduce embodied carbon, the study ”Building materials and the climate: Constructing a new future” advances our joint mission to decarbonise the sector holistically and increase its resilience”, said Dr. Vera Rodenhoff, Deputy Director General for International Climate Action and International Energy Transition of the German Federal Ministry for Economic Affairs and Climate Action (BMWK), which together with the German Federal Ministry for Economic Cooperation and Development (BMZ) has funded the study.

The role of cities in building decarbonisation

Cities worldwide can drive the implementation of decarbonisation. Many are already integrating vegetated surfaces, including green roofs, façades, and indoor wall assemblies to reduce urban carbon emissions and cool off buildings, increase urban biodiversity and more.

More importantly cities can set planning and development regulations, or set up green procurement schemes, that require developers to build with new materials, process waste differently and implement green practices.

Developers themselves need to be engaged with such practices and find ways of working across the famously disagregated building sector but the report outlines just how progress can be made.

SGV Take

Recognition of the importance of embodied carbon is a critical step towards decarbonisation of the built environment. While the majority of buildings related emissions relate to buildings already in place (and that are expected to still be in place in 2050) it is critical to ensure that there is a shift in trajectory in new builds.

New building materials and waste management practices are the first steps, but they are central to the evolution of the sector.

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