CaDCR staff writer
Every five days the world adds buildings equivalent to the size of Paris, and the built environment sector responsible for 37 per cent of global emissions, according to a report published by the UN Environment Programme (UNEP) and the Yale Center for Ecosystems + Architecture (Yale CEA).
The report, Building materials and the climate: Constructing a new future, offers a three-pronged solution to reduce “embodied carbon” emissions and the negative impacts on natural ecosystems from the production and deployment of building materials including 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; 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 emissions savings in many regions of up to 40 per cent in the sector by 2050. 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 approach would be adopted throughout the building process. The solution also requires sensitivity to local cultures and climates, including the common perception of concrete and steel as modern materials of choice.
“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.
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, the report concludes, with harmonized measures across multiple sectors and at each stage of the building lifecycle – from extraction to processing, installation, use, and demolition.
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 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, according to the report.