Irrespective of recent national political announcements, the UK has been one of the global leaders in its commitment to reducing carbon emissions and that approach needs to be reflected in how we sustainably retrofit our historic buildings.
More than 300 local planning authorities have set ambitious targets for reaching net zero by 2030, some of which have begun to promote “retrofit-first” policies.
In some quarters, major landowners are leading the way in understanding the issues and delivering sophisticated strategies across portfolios. Grosvenor, for example, has undertaken a retrofit programme across 100 buildings contributing to a 25% carbon saving since 2013. Grosvenor’s research in Heritage and Carbon: Addressing the Skills Gap not only conveys its commitment to this area, but the inherent issues such as the need for an additional 105,000 full-time workers specialised in retrofit to improve our historic building stock by 2050.
This research is echoed by Historic England’s commitment to improving knowledge through its team focusing on the adaptation of historic buildings to tackle climate change.
We are also seeing increasing numbers of developers who are more conscious about the decisions they are making.
In urban areas such as central London there is a market for thoughtful and sensitive retrofits of traditional buildings because those assets can be, and often are, resilient, adaptable and attractive for end users.
Similarly, the large department stores of the mid-to-late 20th century tend to offer the characteristics needed for viable retrofit, such as generous floor to ceiling heights; spacious floorplates; flexibility to adapt internal layouts; and the load-bearing capacity to support extensions.
Plainly, in most locations historic buildings have an important role to play in tackling climate change: simple and sensitive adaptations can reduce emissions. However, there remains uncertainty as to what can be achieved and how to achieve it.
What are the options?
First, there is no “one-size-fits-all” approach to retrofitting historic buildings. By their nature, historic buildings are often more complex due to their longevity as well as construction techniques that differ from today.
Properties constructed before 1919 are often built from different materials and were designed to operate differently to modern buildings. The former normally allow moisture and air to pass through the structure, whereas the latter are designed to be less permeable to improve energy efficiency. These important differences require nuanced and bespoke measures requiring expert advice to avoid catastrophic harm to fabric.
In contrast to pre-1919 buildings, heritage assets from the mid-to second half of the 20th century have different characteristics that can be more challenging to work with. To achieve a successful retrofit here, designers often need to respond to issues such as compromised floorplates, inflexible structural grids, toxic materials such as asbestos and corrosion-related issues affecting the structure. Indeed, we wait to see the full implications of RAAC, which has been widely reported to survive in schools particularly, but we anticipate will be found in some of the country’s finest post-war buildings.
Adapting in such circumstances requires commercial resilience and creative approaches for introducing new uses, otherwise the development economics can be fatal.
Being innovative in the heritage context can bring conflict with heritage protection. The National Planning Policy Framework gives great weight to the conservation of designated heritage assets such as listed buildings and conservation areas. It rightfully reflects statute to ensure that our nation’s heritage is protected. However, the NPPF does not afford an equivalent weight to reducing carbon emissions and so practitioners often find that the harm outweighs the benefits.
One might argue that achieving energy efficiency in a historic building is a public benefit in the widest possible sense – for the public good – as well as helping to secure the future use and function of the asset. Until the heritage and sustainability scales are balanced it is easy to see how significant and even modest carbon savings for individual assets will be refused. To counter this issue, development plan policies might treat such benefits at a broader scale, where the small gains of individual sites might accumulate across a local authority to be considerable and therefore a weighty benefit.
The answer may also lie in the bold decisions taken by Cambridge City Council or the Royal Borough of Kensington and Chelsea, where photovoltaic panels have been approved through the planning process, or in the use of listed building consent orders despite the perceived harm to listed buildings. Decision-makers might also consider the use of permitted development to encourage energy improvements in unlisted heritage assets which would introduce consistency in decision making.
To assist the industry there is also a need for good data and reliable case studies. In these times where the industry is moving rapidly to understand the requirements of retrofit, decision-makers require evidence that new approaches can be successful. The industry would benefit from a consistent approach to the measurement of embodied and operational carbon in order to compare whole lifecycle performance on a like-for-like basis. Similarly, the sharing of case studies that are transparent about the lessons learnt will help the industry upskill at a far quicker rate.
These measures will help to ensure that owners of historic buildings can make informed decisions about how those assets can be upgraded. This will be a particular focus for owners of commercial assets that face the anticipated legislative requirement to reach EPC B by 2030. If the buildings of the past are not adapted in the present, they will lose their relevance in the future.
Timur Tatlioglu and Tim Miles are partners at Montagu Evans
