Tackling the climate emergency is the order of the day and there is increasing global interest (alongside welcome progress) in the reduction of operational emissions. The built environment is improving its energy efficiency and pushing for renewable energy production at the point of use. However, one would question whether this is enough to achieve the targets to keep the global temperatures at tolerable levels. Materials still emit massive amounts of carbon long before a building starts being used. Hence, a thoughtful design process, led by architects and consultants, is of vital importance to tackle embodied carbon.
What is embodied carbon?
The name of it might sound familiar by now, but what exactly is it? Embodied carbon encompasses the total impact of both CO2 and other greenhouse gases emitted by the construction and materials of our built environment. The term is often used to refer only to the ‘Upfront Carbon’ (emissions corresponding to sourcing raw materials, manufacturing, transport and construction stages), nonetheless a comprehensive whole life cycle analysis also considers the embodied carbon related to maintenance, repair, demolition and disposal stages, known as ‘Cradle to Grave’ as shown in the diagram below.
Source: Irish Green Building Council
Embodied carbon and the construction industry. The big picture
Building materials and construction CO2 emissions are 11% of total global emissions. Together with 28% emissions for building operations, construction is one of the most polluting and damaging industries in the world. The upfront carbon on its own is responsible for at least half of the entire footprint of new construction between now and 2050. This suggests a carbon neutral built environment starts with design, and highlights the responsibility that we architects, designers, engineers and all the construction professionals have in order to respond effectively to the climate crisis.
Reducing the amount of carbon generated by the fossil fuels we burn to operate our buildings is crucial, but it should go hand in hand with reducing embodied carbon. After all, while operational emissions can be reduced over time with building energy efficiency renovations and the use of renewable energy, embodied carbon emissions are locked in place as soon as a building is built. Actually, as buildings become more energy efficient (their operational carbon reduces), embodied carbon becomes proportionally greater and hence, more important.
Source: West Coast Climate Forum
Although the benefits of considering embodied carbon are evident, analysing the footprint of the built environment presents some challenges. Environmental Product Declarations (EPDs) of specific products are used to compare the carbon intensity of available materials but cannot be analysed in isolation. The only way to get a clear picture of how a material or system compares to another in the context of a building is to do a whole life cycle assessment. Based on this, each country has developed its own methodology for measuring the embodied impacts of construction products. As a result, international standardisation has been necessary. European Standards give a common methodology for providing EPD across Europe in EN 15804 and links to a common methodology for the assessment of building Life Cycle Assessment (LCA) in EN 15978.
Additional resources, like RICS Professional standard on Whole life carbon assessment, the LETI Embodied Carbon Primer and RIBA 2030 Climate Challenge Plan work as a framework for professionals in the UK. Moreover, national databases are increasingly becoming available to provide accurate information and scenarios; they are not always public or easily accessible though. The Inventory of Carbon and Energy (ICE) has remained the default source of embodied carbon data for construction products in the UK, this meaning that building-level embodied carbon assessments rather than LCA studies are the norm here.
Retrofit vs. new building
Although it might seem complex, the key question to reduce embodied carbon is to effectively apply a series of beneficial strategies. From the very first stages of a project, all these strategies should be considered (amongst others):
- Design long term rather than short term, using adaptable solutions
- Optimize building shape and design for low maintenance
- Allow deconstruction and re-use
- Use low-carbon and recycled materials
- Reduce transport emissions by using local materials
- and, of course, prioritise retrofit where possible.
We cannot meet the 2050 carbon emission targets unless we tackle carbon emissions in our existing building stock. Retrofit reduces operational emissions but also avoids the embodied carbon of demolition. By considering our existing built environment as stock and making use of the already existing resources, we avoid the use of new materials and their impacts altogether.
Every project counts
The construction industry is responsible for such a large percentage of global carbon emissions but it is not a question of apportioning blame. The power lies not only in the hands of Governments and policymakers but also in the ability of all professionals and individuals to get involved and feel empowered by the opportunities for improvement and effectively achieve the targets set to fight the climate emergency. Thankfully, there is an opportunity for reducing the carbon footprint of every project.
Now Senior Sustainability Engineer at Enhabit’s sister company QODA Consulting