[Report] Building materials and climate: constructing a new future

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 energy- and process-related CO2 emissions and over 34% of energy demand globally.

A report published today by the United Nations Environment Programme (UNEP) and the Yale Center for Ecosystems + Architecture (Yale CEA), under the GlobalABC, offers solutions to decarbonize the buildings and construction sector and reduce the waste it generates.

The report, Building Materials and the Climate: Constructing a New Future, offers policy makers, as well as manufacturers, architects, developers, engineers, builders and recyclers, a three-pronged solution to reduce “embodied carbon” emissions and the negative impacts on natural ecosystems from the production and deployment of building materials (e.g., cement, steel, aluminium, timber, biomass): 

• Avoid waste through a circular approach: building less by repurposing existing buildings is the most valuable option, generating 50-75 per cent fewer emissions than new construction; initial planning using computer-aided design optimisation to promote construction with less materials and with materials that have a lower carbon footprint and facilitate reuse or recycle. 
• 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 emission savings of up to 40 per cent in the sector by 2050 in many regions. However, more policy and financial support is needed to ensure the widespread adoption of renewable bio-based building materials.
• Improve 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.  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.

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

Sheila Aggarwal-Khan, Director, Industry and Economy Division of UNEP, said:

Until recently, most buildings were constructed using locally sourced earth, stone, timber, and bamboo. Yet modern materials such as concrete and steel often only give the illusion of durability, usually ending up in landfills while contributing to a growing climate crisis.

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.

To date, most climate action in the building sector has been dedicated to effectively reducing “operational carbon” emissions encompassing heating, cooling, and lighting. Thanks to worldwide decarbonisation of the electrical grid, using renewable energies, these are set to decrease from 75 per cent to 50 per cent of the sector in coming decades.

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

Government regulation and enforcement are 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 in order to enable the shift to circular economies. 

Case studies from Canada, Finland, Ghana, Guatemala, India, Peru, and Senegal, demonstrate 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.

Cities worldwide can be a driver for implementing decarbonisation. Many are already integrating vegetated surfaces – green roofs, façades, indoor wall assemblies – to reduce urban carbon emissions and cool off buildings, increase urban biodiversity and more. The report calls to consider making such regreening of cities mandatory through legislation.

Download the report!