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The UK government has committed to reducing carbon emissions by 78% by 2035, and to become Net Zero Carbon by 2050. This means that all industries, including construction – estimated to produce around 40% of total UK carbon emissions – will need to make a big effort to reduce their environmental impact. Due to the many benefits offered by adaptive reuse architecture, the practice should be embraced as part of the industry’s shift towards more sustainable design.
Over the last few years, the construction industry has focused on the improvement of Building Regulations (including planned changes in Part-L in 2022 and 2025) and the adoption of more ambitious standards and carbon targets for new construction, following initiatives from LETI, RIBA and UKGBC. The impact of existing buildings, however, has been left unattended. New initiatives, however, are highlighting the importance of adaptive reuse, which focuses on the refurbishment of existing buildings (retrofitting) in order to help the UK meet its carbon targets.
To give a sense of the scale of the importance of adaptive reuse: according to LETI’s analysis, 80% of residential buildings that will exist in 2050 have already been built; and most of the buildings currently under construction will need to be partially or totally retrofitted before 2050.
A substantial proportion of the carbon emissions from existing buildings can be reduced by adopting simple retrofit measures, which could potentially be subsidised by the government. These would include: adding thermal insulation, upgrading windows or exchanging gas boilers for electric heaters and air source heat pumps.
There are multiple benefits to promoting a national-scale retrofit of existing buildings. The advantages of adaptive reuse architecture include:
Retrofitting also has notable health and wellbeing benefits derived from better thermal and acoustic comfort and air quality (including the reduction of dampness and risk of fungi / mould). Cutting energy bills is beneficial in addressing fuel poverty, especially in the context of a global energy crisis, where electricity is more expensive than gas. Lastly, improving the efficiency of existing buildings with adaptive reuse will attenuate the peak demand on the national grid, which is under growing pressure due to the electrification of buildings and transportation.
The downside of retrofitting and reusing buildings is that renovated buildings are, in most cases, still not as energy efficient as new buildings. Depending on the extent of the upgrades in the reused buildings, air quality, thermal insulation and visual experience may not be as good, are not always suitable and may not be flexible enough to accommodate different uses.
It is worth noting that the potential effects of building refurbishment, in terms of operational carbon, embodied carbon and wellbeing, are specific to the characteristics of the existing building. The best results are achieved when the refurbishment is planned carefully from a holistic point of view, addressing all the different factors of the retrofit together.
Bryden Wood’s approach to adaptive reuse uses a clear operational and embodied carbon hierarchy, as shown in the diagrams below. Our sustainable design approach prioritises the reduction of energy demand via a ‘fabric first’ approach, combined with passive and active design measures (‘be lean’). To reduce operational carbon, we first explore any possibility of reusing buildings that already exist ‘build nothing’) as the main route to reducing embodied carbon. Further, all our projects are based on ‘lean design’ with the use of Modern Methods of Construction (MMC) where feasible (‘build less’).
Reusing buildings can produce a substantial saving in embodied carbon, but the quantum depends on the extent of the refurbishment. On the other hand, a reduced scope of refurbishment, which does not include a façade and HVAC systems upgrade, can mean that operational carbon emissions are high due to the inefficient performance of the building.
The question is: which is the correct level of refurbishment to ensure that the embodied carbon benefit outweighs the reduced operational carbon performance? Light refurbishment, retaining as much of the building as possible? Or a deeper retrofit, which retains only certain structural elements?
Bryden Wood has carried out an operational and embodied carbon analysis on three different levels of intervention on an existing commercial building:
The calculation consists of a whole life cycle carbon analysis (WLCA) of the three options, including operational and embodied carbon (A-C). The embodied carbon figures used are estimations based on LETI 2020 benchmarks for office buildings, excluding sequestration. The operational carbon estimates are based on RIBA ‘business as usual’ (light-touch refurbishment), our own assessment of 2020 good practice (full adaptive reuse refurbishment) and RIBA 2030 targets (new construction). The operational carbon emissions are based on the assumption that at the current rate of decarbonisation, the emissions by 2040 will be 67gCO2/kWh (BEIS 2040), and that by 2050 they will be zero carbon.
The charts below show the total accumulated carbon emissions and the detailed 60-year projection of the three cases. Looking at the total emissions after 60 years, light refurbishment is the most advantageous adaptive reuse option (26% less carbon than new construction), followed by a full refurbishment (23% better than new construction). A red dotted line in the graphs below identifies the potential additional embodied carbon reduction from materials due to the decarbonisation of the grid. The quantum of the reduction from the decarbonisation of materials would be highly dependent on where they are produced and the characteristics of the grid in those countries.
The 60-year projection charts clearly show that the new construction option would have a much higher impact on the first year of use, due to the embodied carbon of construction using new materials. Even though the new construction option benefits from a better operational carbon from day one, the decarbonisation of the grid ‘flattens’ the operational carbon emissions in the retrofit options, dampening the difference with a new build.
It is worth highlighting that the climate emergency is happening today, and so it is now that we need to reduce carbon emissions that produce global warming. We cannot wait 20 or 40 years for the benefits of more efficient new buildings. This is the main reason why it is important that we prioritise refurbishment, reusing buildings that already exist.
If we account for the decarbonisation of material manufacturing (red dotted line), the difference between the adaptive reuse of buildings and new construction is even greater.
As part of this analysis, we calculated the WLCA using different performance benchmarks to prove that the conclusions would not depend on a specific baseline selected. The results below on the left, are based on LETI 2020/RIBA2025, and the ones on the right are based on LETI 2030/RIBA 2030. In both cases of adaptive reuse, the light-touch refurbishment and full refurbishment are more advantageous than new construction.
It is important to flag that this trend favouring the reuse of buildings does not necessarily apply to every building. The results will vary depending on the structural and architectural characteristics of the building and its life expectancy.
Whilst carbon emissions are a key point of decision when considering adaptive reuse, other factors, such as the resilience of the grid, the impact on fuel poverty and wellbeing, the adaptability of the building for a new use (for example converting offices to residential) need to be quantified and added into the discussion.
The Climate Emergency requires that we pay more attention to the refurbishment and reuse of existing buildings, with a focus on energy and carbon efficiency.
The main benefit of the refurbishment of the urban fabric is a substantial saving in embodied carbon, but a new building can benefit from lower carbon emissions in operation.
Bryden Wood has carried out a detailed WLCA analysis of a light-tough refurbishment, full refurbishment and new construction for a commercial building based on benchmark from LETI and RIBA in order to understand which option is less carbon intensive after 60 years. The results clearly show that adaptive reuse is more beneficial in both the short and long term.
It is important to re-iterate that the climate emergency is happening right now. We need to focus on solutions that have an immediate positive impact. The adaptive reuse of existing buildings will help us to create a more sustainable future.
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