Heritage, Buildings and Embodied Carbon

Investing in heritage to avoid embodied carbon emissions

Globally, the United Nations Environment Programme estimates that embodied carbon emissions from the built environment were responsible for some 12% of global carbon emissions in 2021, with operational carbon at approximately 28% (Baker et al, 2021). In the UK, the UK Green Building Council (UKGBC) estimate that embodied carbon from the construction and refurbishment of buildings makes up to 21% of built environment emissions in addition to the direct and indirect emissions from buildings (which only account for 71% of the built environment's greenhouse gas emissions) (UKGBC, 2021).

Over recent years, much work has been done to understand and guide how to reduce operational carbon emissions from buildings. There are now growing calls to focus on embodied carbon emission reductions to significantly impact total carbon emissions from the built environment. The share of embodied emissions is expected to grow over time and is projected to account for over half of the UK's built environment emissions by 2035 (UKGBC, 2021).

Failure to measure and address embodied carbon emissions means we undervalue existing buildings' contribution to climate change mitigation.

Reuse buildings to save carbon

Evidence demonstrates that retaining and reusing buildings rather than demolishing and building new is necessary for a low-carbon future. Retaining and reusing buildings reduces the demand for new construction materials, thereby lowering embodied carbon emissions, and capitalises on the 'stored carbon' within existing buildings. Traditional building materials, if properly looked after, are inherently sustainable as they are durable and can resist wear and decay (Rhee-Duverne, in Heritage Counts 2019).

• A study of an adaptive reuse project found that the renovation of a building helped to avoid 53 to 75% of the environmental impacts that would result from new construction. The retention of the main structure and envelope of the building is crucial, as these elements account for a significant portion of a building's embodied carbon. Thus, their reuse can significantly reduce the environmental burdens of constructing new buildings (Hasik et al, 2019)
• A study by Sheffield University found that by retaining the primary concrete and steel structure of the former John Lewis Building in Sheffield, built during the 1960s, could prevent the emission of approximately 4300 tonnes of carbon equivalent (t.C02e) associated with materials used for the superstructure (Abbey, 2022)
• Analysis by Sturgis Carbon Profiling finds that embodied carbon might represent 35% of the total carbon footprint in the 60-year lifespan of a typical office building. For a warehouse, the proportion rises to 47%; for a residential block, it is up to 51% for a 60-year lifespan (RCIS, 2017)
• In a 50-year building service life, embodied carbon related to maintenance and repair can be as much as 25% of the total lifecycle embodied carbon (excluding demolition emissions) (Resch et al, 2020)

Research commissioned by Historic England examined a typical Victorian terrace's whole life carbon [1] emissions, considering three scenarios: do nothing, refurbishing, and complete demolition and a new build replacement. The research (Carrig, 2019) calculated that:

• By 2050, the life cycle carbon emissions of the three scenarios would be 89 (do nothing), 36 (refurbish), and 42 (demolish and rebuild) tCO2e, respectively
• The construction-related embodied carbon emissions from refurbishment works were estimated to be 1.2 tCO2e, representing just 2% of the building’s total emissions over a 60-year lifespan. In contrast, the embodied emissions from demolition and new construction were substantially higher, amounting to 16.35 tCO2e or 28% of the total emissions
• In other words, the construction of a new home of the same size produces up to 13 times more embodied carbon than refurbishment

Figure EMBC 1 - Victorian terraced house case study, life cycle emissions to 2030 and 2050 in 3 scenarios

Source: Carrig, 2019 

Retrofit to save embodied carbon

Retrofitting traditional buildings provides an opportunity to improve their energy efficiency and preserve the embodied carbon invested in their construction, which would otherwise be lost if these buildings are demolished or abandoned, as supported by research. Retrofitting also creates embodied emissions; however, typically it is a smaller embodied carbon footprint than new construction.

• In the notable case of the proposed demolition of the Marks and Spenser's Building at 458 Oxford Street, London, UK, analysis estimates that the construction of the proposed new building is expected to release just under 40,000 tCO2e into the atmosphere, the equivalent of driving a typical car 99 million miles, further than the distance to the Sun. The total embodied carbon cost over 60 years is just under 53,000 tCO2e and the energy in use expected to be some 81,000 tCO2e. The analysis argues that retrofitting the existing building would result in substantially lower carbon emissions compared to demolition and constructing a new building (Targeting Zero, 2022)

Figure EMBC 2.1 and 2.2 - The overall carbon impacts of the new build scheme and a comprehensive retrofit at 458 Oxford Street.

Source: Targeting Zero, 2022

• A recent study (Mohammadpourkarbasi et al, 2023) compared the carbon footprint of deep and shallow retrofit over a 60-year lifespan. It analysed the whole-life carbon impact of using low embodied carbon 'natural' insulation materials over the 'standard' petrochemical-derived insulation materials. Through a life cycle carbon assessment of various retrofit scenarios, the study aimed to identify the most efficient and effective retrofit strategies to meet carbon reduction targets for a typical Victorian terrace home. The findings reveal that:
  • Retrofitting can achieve significant operational carbon reductions – ranging between 59% to 94% compared to the existing Victorian house built around 1894. It also avoids carbon compared to demolition and newbuild
  • A shallow retrofit using natural materials had the lowest embodied carbon emissions
  • Using natural construction materials in deep and shallow retrofits can reduce total embodied carbon by 7% to 14%. The materials used in the retrofit process have a more significant impact on reducing embodied carbon than the retrofit standard itself
  • Low carbon technologies, such as photovoltaic panels or heat pumps, increase the embodied carbon by 38% to 117% but did significantly decrease operational carbon emissions by 71% (photovoltaics) and 61% (heat pumps)
  • The study concludes that when it comes to reducing CO₂ emissions from buildings, the discussion should not be about whether to refurbish but rather the most effective way to do so
• A study by Carrig in 2019 using a life cycle assessment applied to 3 case studies of traditionally constructed homes demonstrated that:
  • Embodied emissions from refurbishment or retrofit accounted for between 2% and 10% of the building’s total emissions over 60 years
  • Demolition and building new, on the other hand, results in much higher embodied emissions ranging from 28% to 31%
  • Demolition alone is estimated to account for up to 7% of a new building's total carbon emission
  • The study concluded that if we do not count embodied carbon emissions, we underestimate the carbon emissions of a new building by up to 31% over 60 years

Figure EMBC 3 - Embodied carbon as a proportion of life cycle emissions (60 years) in a retrofit vs demolition and new build scenarios for 3 traditionally built buildings

Source: Carrig, 2019

• A Norwegian study (Berg and Fuglseth, 2018). using a lifecycle assessment comparing 3 emission scenarios reveals a compelling case for energy-efficient refurbishments of traditional buildings. The scenarios compared a traditional building before refurbishment, the same building after refurbishment, and its demolition followed by new construction. The study found: 
  • Refurbishing traditional buildings can match or potentially exceed the performance of new construction in reducing Greenhouse Gas (GHG) emissions
  • It would take 52 years for the initial emissions from construction (embodied emissions) of a new replacement building to be offset by the effects of lower in-use energy consumption (operational emissions). This emphasises the immediate benefits of refurbishment over new construction for emissions reduction
  • Emissions related to the construction phase are 12 times higher for the new construction than in the refurbishment scenario. This disparity reflects the extensive materials requirements for new constructions, emissions associated with demolishing the existing building, and the environmental impact of the chosen materials

We need to tackle emissions from the built environment, but it is essential that we address both embodied carbon emissions and operational carbon emissions in the fight against climate change and the pursuit of net zero. Both types of carbon emissions are critical to achieving climate targets and must be consistently considered. By excluding embodied carbon emissions, the true carbon footprint of the built environment is significantly underestimated.

Footnotes

1. Whole life carbon emissions are the sum total of all assets related GHG emissions and removals, both operational and embodied, over the life cycle of an asset (RCIS, 2023)

References

1. Abbey, D (2022). 'The Future of the Former John Lewis Building in Sheffield.' The Lab Observatory. Sheffield University. (Accessed: October 2022)
2. Baker, H. Moncaster, A. Remøy, H. and Wilkinson, S. (2021). 'Retention not demolition: how heritage thinking can inform carbon reduction'. Journal of Architectural Conservation, 27(3), 176-194. (Accessed: November 2023)
3. Berg, F. and Fuglseth, M. (2018). 'Life cycle assessment and historic buildings: energy-efficiency refurbishment versus new construction in Norway'. Journal of Architectural Conservation, 24:2, 152-167. (Accessed: June 2022)
4. Carrig (2019). 'Understanding Carbon in the Historic Environment. Historic England'. (Accessed: November 2022)
5. Climate Change Committee (2023). 'Progress in Reducing Emissions 2023 Report to Parliament'. (Accessed: August 2023)
6. Environmental Audit Committee (2022). 'Building to net zero: costing carbon in construction – Report Summary'. (Accessed: June 2023)
7. House of Commons, Environmental Audit Committee (2022). 'Building to net zero: costing carbon in construction'. First Report of Session 2022–23'. (Accessed: November 2023)
8. Hasik, V. Elizabeth Escott, E. Bates, R. Carlisle, S. Faircloth, B. and Bilec, M. (2019). 'Comparative whole-building life cycle assessment of renovation and new construction'. (Accessed: November 2023)
9. Historic England (2019). 'Carbon in the built environment'. (Accessed: June 2022)
10. Mohammadpourkarbasi, H. Riddle,B. Liu, C. and Sharples, S. (2023). 'Life cycle carbon assessment of decarbonising UK's hard-to-treat homes: A comparative study of conventional retrofit vs EnerPHit, heat pump first vs fabric first and ecological vs petrochemical retrofit approaches'. Energy and Buildings, 296, p.113353. (Accessed: October 2023)
11. Resch, E. Wiik, M.K. Tellnes, L G. Andresen, Selvig, I. and Stoknes, S. (2022). 'Future Built Zero - A simplified dynamic LCA method with requirements for low carbon emissions from buildings'. (Accessed: March 2022)
12. RICS (2023). 'Whole Life Carbon Assessment for the built environment'. (Accessed: October 2023)
13. RCIS (2017). 'Whole Life Carbon Assessment'. (Accessed: March 2022)
14. Targeting Zero (2022). '458 Oxford Street: Why a Comprehensive Retrofit Is More Carbon Efficient than the Proposed New Build'. (Accessed: March 2023)
15. United Kingdom Green Building Council (UKGBC) (2021). 'Net Zero Whole Life Carbon Roadmap A Pathway to Net Zero for the UK Built Environment'. (Accessed: March 2023).
16. United Kingdom Green Building Council (UKGBC) (2017). 'Embodied Carbon: Developing a Client Brief'. (Accessed: November 2023)