The journal “Retention, not demolition: how heritage thinking can inform carbon reduction” by Hannah Baker, Alice Moncaster, Hilde Remøy, Sara Wilkinson focuses on the two most commonly cited benefits of retention – heritage conservation and reduction in embodied greenhouse gases emissions from construction materials and compares if and how they are included in decisions to retain or demolish existing buildings.
The article draws attention to heritage conservation and its evolution throughout the years and then goes ahead and points out the two climate mitigation methods suggested by the Intergovernmental Panel on Climate Change for the building sector to minimise their carbon emissions contribution. They are – limiting individual buildings’ operational impacts and decreasing individual buildings’ embodied impacts. The energy used in the day-to-day operations of a building and in sustaining the inside environment, such as space heating and cooling and lighting, is referred to as operational energy.
According to the author, the reduced operational impact of new structures compared to existing buildings are frequently highlighted as a barrier to retention and are thus often used as an argument in favour of destruction and new construction. As a result, embodied impacts must be included when evaluating the entire life cycle environmental impact of a building’s retention and demolition decisions. The manufacturing of materials and components, their transportation to site and construction operations, their maintenance, repair, and replacement, and their final demolition, processing, and disposal are all elements of embodied impacts. If an existing building can be retrofitted to meet the same or similar operational energy standards as a new building, the retrofitted building’s life-cycle impact will likely be lower, as refurbishment projects require far fewer raw materials in the construction process than decommissioning and new construction, lowering the embodied impact.
In all of the case studies conducted at three different locations, heritage was the main driver behind the decision to retain the building. Many expert interviews also pointed into this direction. While heritage assertions could be used to propose policy drivers for preservation and against demolition, as well as the conversion of environmental value into economic uplift, the author points out that the key component of retention and demolition decisions is a tension between the need for economic growth and conservation. In the case of embodied impacts, however, the focus of whole-life energy and carbon effects is frequently on operational impacts, with a lack of policy cited as the primary reason for the absence of such impacts.
Both have been found to have validity in research, with heritage value having beneficial social and economic consequences and maintaining and upgrading buildings having reduced environmental implications. However, the case studies show that heritage is by far the most prevalent cause for buildings to be preserved. Embodied carbon, on the other hand, is rarely a factor in retention/demolition choices, with the major environmental arguments focusing on operational implications.
The reasons for the disparity in the strength of the two arguments are complicated in some respects but simple in others. Global, national, and municipal policies have long supported the preservation of history. In contrast, embodied carbon concerns had no role in any of the case studies’ choices to keep or demolish buildings. While the effects of human activities on the environment have been a source of concern for many years, the direct effects of energy use have been the focus of attention in the built environment. Therefore, the presentation of policy appears as a barrier to the demolition of buildings with ‘heritage value’, in a way that does not currently exist for structures with ‘embodied carbon value’. In terms of policy, there is one more point that emerged from the case studies. Buildings have been demolished despite being listed on the National Register of Historic Places in a few situations, with justifications made for the public benefit of an alternative. This inherent flexibility is likely to be critical in the industry’s acceptance of any regulatory obligations.
The author argues that for whole life (embodied as well as operational) energy and carbon impacts to be widely accepted, the calculation of embodied impacts must be included in the regulation, and demonstration of reduced whole life impacts should be a requirement before buildings are demolished. However, it has been highlighted that no adequate computation tools exist at this time; however, approaches will evolve in the future to make it easier to assess a building’s embodied impacts while selecting whether to retain or demolish it.
The article is expository and analytical, and it mostly relies on data from case studies and expert interviews. The text is organised in a unique but efficient way, in my opinion. The conclusions from the global case studies are unlikely to apply to every example of an urban development project. The study’s outcome, on the other hand, was intriguing since it demonstrated how heritage and environmental aspects are treated differently when deciding whether to retain or demolish a building. Despite the fact that the author mentions the limits upfront, the restrictions have left gaps in the research, and the publication was unable to explain how embodied impact may be taken into account when making retention choices due to lack of methods and inventions in the subject. The author managed to present architecture data and details in an easy-to-read manner, diluting the material with quotations from insiders, and explaining complicated terms simply. I give credit to the author for a unique take on the future of our economic, social and environmental values by addressing some of the important issues in the building sector.
- Hannah Baker, Alice Moncaster, Hilde Remøy & Sara Wilkinson (2021): Retention, not demolition: how heritage thinking can inform carbon reduction, Journal of Architectural Conservation, DOI: 10.1080/13556207.2021.1948239
- Encyclopedia.pub. 2022. Adaptive Reuse of Architectural Heritage. [online] Available at: <https://encyclopedia.pub/3050#:~:text=The%20adaptive%20reuse%20is%20seen,economy%20and%20socio%2Dcultural%20aspects.> [Accessed 19 March 2022].
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