Driving sustainability across the Built Environment – the increasing significance of Embodied Carbon

World Green Building Week

The buildings across our planet contribute to over a third of the world’s greenhouse gas emissions. The built environment faces unprecedented challenges across energy security, carbon reduction, resource efficiency and waste reduction. The sector has a critical role to play in addressing these issues but also plays a significant role in providing sustainable employment and economic growth.

In 2017, we at Anthesis took the step to become the first certified professionals in the UK for Excellence in Design for Greater Efficiencies (EDGE). Our team of experts provide trusted advice to clients, partners and stakeholders on a variety of sustainability issues relevant to the built environment.

With the current focus on net zero buildings, we have put together a short series of content for Green Buildings Week focusing on: energy, carbon, traceability and transparency in supply chains, as well as whole building environment assessment methods and certification – all critical elements to achieving net zero buildings.

Infrastructure and reducing emissions

The 2008 UK Climate Change Act commits to a reduction in GHG emissions to 80% of 1990 levels by 2050, with a 50% target by 2025 looking increasingly out of reach.

Among the key areas we look to make progress on when it comes to GHG emissions is infrastructure. A huge proportion of emission reductions will have to come from infrastructure, where carbon associated with the materials in the built environment represent a substantial share. For this reason we need to start taking embodied emissions seriously. We should explore more opportunities for carbon saving through reducing embodied emissions, both of new buildings and for maintenance and refurbishment of older buildings.

Associated with half of all UK emissions, and a projected contribution of 90% by 2050, the built environment represents huge opportunities to reduce carbon emissions. Until recently, ongoing operational energy consumption has been the greatest source of emissions – and accordingly, where reduction efforts have tended to focus. However, as buildings become more efficient and the greening of the energy sector results in greater reductions in CO2 emissions, the relative contribution of embodied carbon to a building’s lifetime is becoming more important.

What is embodied carbon and why is it important in lifecycle emissions?

Embodied carbon is the CO2 emitted in producing materials. Often overlooked, it can have a significant impact on the lifecycle emissions of buildings’ construction and maintenance, and eventual refurbishment or destruction. An analysis of 90 case studies (Chastas et al, 2017) found that the embodied energy share of conventional buildings was between 6-20%. However, in low-energy buildings this share increased to 26-57%, and in nearly Zero Energy Buildings (nZEBs) this could be up to 100%.

Embodied carbon can be a challenge to assess, and while databases are emerging, comprehensive studies are still relatively thin on the ground. Analysts and lifecycle experts, like the team at Anthesis, model the emissions factors associated with different materials, average lifespans of building elements, and through work with our built environment team, make informed predictions about the end of life.

As well as lower awareness and lack of benchmarking data, a deficiency of skills and knowledge can be barriers to investment in reducing embodied carbon as well as perceived high costs. Examples of industry leadership include Anglian Water, who recently implemented cost-saving and carbon-saving no-dig techniques for their water mains extensions following incorporation of embodied carbon into their sustainability metrics (watch a video of their carbon manager describing this here). The same principle led Crossrail to reduce the cement content of concrete used in the project.

As with many areas, the complexity of the supply chain can also present challenges to carbon management, but the recent update to the core rules for environmental product declarations for construction products and services, ISO 21930:2017, Sustainability in buildings and civil engineering works, should serve to support evaluations, providing analysts with comparable and reliable environmental metrics.

Generally, embodied carbon is most concentrated at the manufacture stage, particularly buildings’ fabric, foundations, superstructure and envelope (ICE, 2017). However, while initial design and construction materials are important, the carbon costs of refurbishment deserve serious attention. Every new building becomes a refurbishment case within just a few months of completion, and reducing the carbon embodied in materials which may be replaced with successive refurbishments can provide opportunity to reduce the total lifecycle carbon of the building. These benefits apply to old buildings as well, vastly increasing the potential impact.

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