Reducing embodied carbon and climate change
Together, emissions from building operations and the construction industry were responsible for 38 per cent of global energy-related carbon dioxide emissions in 2019. About three quarters of that consisted of heating, cooling and lighting buildings. The remaining quarter, often overlooked, came from embodied carbon, which the World Green Building Council (WGBC) defines as “carbon emissions associated with materials and construction processes throughout the whole life cycle of a building or infrastructure.”
This includes emissions from raw material extraction, transportation of raw materials to a factory, manufacturing of building materials at the factory, transportation of building materials to the building site, building construction, and demolition. Global building stock is predicted to double between now and midcentury, so ignoring building emissions will result in us not being able to meet the 2015 Paris agreement climate change goal developed to address this global emergency.
Typically, reducing operational emissions has been the focus. According to the WGBC, however, just upfront carbon — which is embodied carbon emissions due to buildings before building use — “will be responsible for half of the entire carbon footprint of new construction between now and 2050, threatening to consume a large part of our remaining carbon budget.” We thus need to focus on minimizing embodied carbon.
If a building has to be built, embodied carbon can be reduced by performing a life cycle assessment (LCA) before construction. An LCA for a building determines environment-related inputs and outputs (e.g. water, energy, raw materials and airborne emissions) for each stage of a building’s life cycle and subsequently determines corresponding environmental impacts such as climate emissions. Known as a whole-building LCA, these assessments use documents known as Environmental Product Declarations (EPDs) containing lifetime impacts for each building material. Countries worldwide are thus building EPD databases for materials from local manufacturers to assist in performing LCAs for local construction projects.
An example from Green Building Canada notes that “assessing the sustainability of two similar bamboo floors isn’t so obvious unless conducting an LCA. How far did the flooring travel before eventually getting installed? How much embodied energy went into it? What effect will its disposal have?”
The results of a whole-building LCA performed in the building design stage can, according to the Atmospheric Fund report entitled “Embodied Carbon in Construction: Policy Primer for Ontario,” help reduce embodied emissions by choosing materials that can be reused or recycled, materials that require less maintenance and repair, materials that can be locally sourced, as well as materials with highly efficient manufacturing processes.
Embodied carbon reduction policies are being put in place around the world and some policy examples are worthy of mention. In Germany, a whole-building LCA is required for new federal building projects and a free national LCA software tool along with an EPD database for Germany has been developed to assist with this. In Switzerland, a whole-building LCA is required for new government buildings in certain municipalities. In the Netherlands, embodied carbon reporting is required for new residential and office buildings over 100 metres square.
Progress is being made in Canada to achieve embodied carbon reductions. Vancouver has set a goal to reduce embodied carbon emissions by 40 per cent below 2018 levels in new buildings and other construction projects by 2030. Building climate calculator tools are being deployed by governments.
In Ontario, a provincial government spokesperson stated that a new building carbon calculator tool will be launched in the next few months that “will support the increased use of low-carbon building materials in building construction,” such as wood-based constructions.
Examples of next steps for Ontario to reduce embodied carbon include building a complete EPD materials database as well as whole-building LCA tools that all developers in the province can use to provide consistency when comparing buildings.
Ontario also should require mandatory embodied carbon performance targets in the building code and have reporting requirements for new constructions. The province should work with municipalities to provide monetary incentives to reduce embodied carbon — such as reducing development fees. These measures will help us not lose sight of embodied carbon emissions while working to ensure that building operational emissions are reduced as well.