Whether six stories or 600 meters tall, buildings can have a big carbon footprint. According to the International Energy Agency (IEA), more than 30 percent of carbon dioxide (CO2) generated globally comes from the built environment. This is primarily from materials production and the energy required to operate building systems, such as heating and ventilation. As the AEC industry steps up the effort to create higher-performing structures, there is an increased focus being placed on reducing the embodied carbon in construction materials.
The IEA, an organization that provides advice and data on global energy policies, is embarking on a project to analyze material efficiency and use trends in different sectors of the economy, including building construction. It recently hosted a daylong experts’ workshop in Paris, France, that explored materials use trends, strategies to improve efficiency and methods for assessing current and future materials demands in the construction sector. The March 9 event brought together professionals from across the building community, including representatives from the world’s leading research universities, metals manufacturers, advocacy groups, investment banking and engineering firms. Duncan Cox, a London-based associate in Thornton Tomasetti’s Sustainability practice and manager of the firm’s Embodied Carbon Project, was invited to the meeting and shared his knowledge of tracking embodied carbon and research into low-carbon structures.
Here are Duncan’s top three takeaways from the event:
The Growing Popularity of Concrete
The steel industry is working to reduce the production of CO2 in steel by using hydrogen as the reducing agent. However, steel is no longer the go-to material for tall buildings. There is an increasing shift toward composite and concrete-framed structures, with precast concrete seen as being the most efficient. Cement (a major ingredient in concrete) is widely used around the world, since it is so easily available. As land becomes scarcer, buildings will become taller, and because cement intensity increases with the height of a building, it will lead to more demand for this material. Construction materials manufacturers, like LafargeHolcim, are currently conducting studies into 3D printing of concrete as a potential alternative; however, this technology is very much in its infancy.
There was some concern voiced that CO2 reductions in concrete have become stagnant, and in many countries it is obligatory to use OPC (ordinary Portland cement) due to design code restrictions. While OPC is a higher-strength product, it has higher embodied carbon per square meter. However, it has been shown that if structures are ‘overdesigned,’ they can use less volumes of material and reduce reinforcement quantities, which results in less embodied carbon regardless of whether cement replacement materials have been specified. Engineers are being encouraged to look beyond the obvious design solutions and to think more about different material types and efficiencies and building life, which is an approach that we embrace at Thornton Tomasetti.
Increased Regulation Will Lead to More Sustainable Buildings
Some experts believe that building code standards are prescriptive and not based on performance. It is up to the design and construction industry to urge regulatory agencies to change this. There was consensus that the service life of buildings should be increased to reduce embodied carbon; that we should be designing for future change of use as well as for durability and resilience in the face of climate change. However, by increasing a building’s life there is less demand for new material production, which could cause concern among materials manufacturers. One approach to encourage sustainable buildings would be to create incentive programs, such as tax cuts, for building owners and materials suppliers.
The IEA Is Collecting Building Data to Inform Strategies for Material Carbon Reduction
The project will study the demand for key materials that factor into the IEA’s goal of limiting global temperature increase to 2 degrees Celsius and the system-level impacts on energy demand and CO2 emissions of these materials. It is focusing its research on concrete, steel and glass. Thornton Tomasetti will work with the IEA to assist in sourcing relevant material data from the AEC industry. Since 2011, we have tracked the capital carbon in all of Thornton Tomasetti’s structural engineering design projects globally. The firm designs many large high-profile projects and produces a capital carbon report card for each project that is assessed. This is used to demonstrate how the project performs against a number of metrics: company-wide, location, building use, etc. Historically, we have shared our data on materials use and embodied carbon to help combat climate change, and we look forward to assisting with future academic and industry-wide research in this area. My hope is that the IEA will have a greater impact on regulation, as relying on social or corporate responsibility alone is unlikely to affect significant change.