We live in an era where CO2 emissions from buildings and construction hit record highs despite the growth in climate awareness. Building energy consumption creates over 6.5 billion tonnes of CO2e, making up 17.5% of greenhouse gas (GHG) emissions globally. While prevalent thinking has led to the demolition and reconstruction of our buildings to improve performance while meeting specific desired stakeholder values, retrofit is an alternative that can reclaim a place within mainstream thinking.

Retrofit is essential in achieving net-zero targets. With its influence on energy consumption and GHG emission, the retrofit of existing buildings should be given due attention concerning sustainable development. Retrofit packages encompass a range of improvement activities to enhance existing buildings and return them to regular use. Well-done retrofits can deliver enhancements for all building stakeholders, save energy, preserve heritage, and reduce greenhouse gas emissions with no heavier financial burden than rebuilding and similar environmental and social parameters.

Buildings are responsible for much of the world’s energy use and GHG emissions. In the United Kingdom (UK), buildings consume approximately 40% of total energy, while in the United States (US), this ratio is approximately 50%. Of the total energy use of buildings, 80-90% of life-cycle energy demand is derived from the operational phase. This highlights our existing buildings’ significant position in current energy use statistics and how necessary reductions are to achieve net-zero targets. Governmental policy changes emphasise energy reductions, for example, the UK’s “Minimum Level of Energy Efficiency” standard from 2018, which sets a minimum energy efficiency level for domestic private rented properties. The standard is enforced by legally requiring all domestic private rented properties to have an Energy Performance Certificate (EPC) of at least E, with proposals raising this limitation to an EPC rating of C by 2028[1].

Retrofits provide opportunities to preserve and protect existing buildings, maintaining their cultural heritage while innovating to improve energy efficiency. It has been found that 14% of European building stock dates before 1919, with another 12% dated between 1919 and 1945. This corresponds to 55 million homes housing approximately 120 million people. However, historic buildings are often excluded from retrofit initiatives due to the desire to maintain the architectural and/or historical interest that they show, preventing the necessary work needed to be undertaken to reduce operational energy and meet modern criteria. These protections are enshrined in law, such as the UK’s Planning (Listed Buildings and Conservation Areas) Act 1990, which provides legal protection for our historic structures at the expense of preventing any such work occurring on these structures. Exceptions to the protections are only assessed on a project-by-project basis, with the listed building consent for Trinity College, Cambridge’s retrofit on grade 1 listed “New Court” only being granted after a three-year analysis period ending in presenting the findings to local authorities.

Major motivating factors for retrofit are mainly related to financial profitability, including a long-term reduction in energy costs, the reduction of operating expenses, and short amortisation periods. However, funding concerns are cited by 74% of housing associations as a pivotal obstruction to retrofit, both in scale and pace of intervention. Subsidies are available in some territories, with the Kreditanstalt für Wiederaufbau (KfW), a public German banking group, providing three different routes to funding based on appropriate criteria. Grants, tax exemptions, or reductions that directly and indirectly reduce the retrofit costs also exist across European countries to stimulate energy efficiency retrofits in residential and non-residential buildings. Energy savings are comparatively small for heating system retrofits, but retrofit cost-benefit ratios are better than building envelope adjustments. Overall, retrofits have been found to decrease operational costs to between 15% and 62% of the initial value.

Social value proves challenging to quantify and struggles to account for the views of the end user/occupier. Beyond the more common measure of cost-benefit ratios, the impact retrofit can have has been demonstrated in domestic and non-domestic settings. Building energy improvements can create jobs, totalling an estimated 141,000 in the New York City (NYC) region by 2030. In a domestic environment, the health of residents is being jeopardised as homes are not kept dry and warm. The direct medical cost savings from retrofitting these dwellings would be around €9 billion per year if the remedial works were undertaken from the time of publishing (2016). The environmental value of retrofit can be demonstrated over reconstruction by preventing 90% of the construction and demolition (C&D) debris associated with demolition, equating to 170 million tons in the US. The same sustainability standards exist for both retrofit and rebuild, so retrofit can separate itself through the prevention of emitting the embodied carbon “stored” within the construction materials, as well as the C&D debris and its downstream reuse or landfill waste.

With an ever-growing breadth of knowledge surrounding retrofit and the broadening list of exemplary projects within our built environment, this report attempts to find the reasoning for choosing to rebuild over retrofit.

If you have any questions or thoughts, please do not hesitate to reach out to me. I would love to hear what you have to say.

[1] On 20 September 2023, the UK Government announced that the proposed energy efficient targets for households raising the minimum EPC rating to be raised from E to C would be scrapped.