Decarbonisation of the built environment is a complex challenge, with no one-size-fits-all approach to transforming the properties that we use for housing, work, education, leisure and other services. Nevertheless, change is essential and in the case of traditional buildings, it requires a delicate balance of looking ahead to the future, while also being cognisant of the past.

Estimates suggest there are around 460,000 listed buildings across the UK, which play an important role in towns and cities, helping to preserve their local heritage and unique character. While reducing the carbon footprint of the built environment is essential for delivering net zero ambitions, we must also focus on protecting the history and heritage that is captured in the architecture of so many of these buildings.

The challenge, however, is that many of the construction methods used for historic properties are now largely out of favour, presenting significant challenges in terms of energy efficiency. Almost a quarter of all UK emissions can be attributed to the built environment and buildings that are old, cold and potentially damp inevitably require significant amounts of energy to ensure they are warm enough for use year-round. For the owners or occupiers of listed buildings, this can come at a significant cost – both financial and environmental.

Historic construction methods

There are several design choices adopted throughout history that would be discouraged today. For example, properties built in the early 20th century were designed with an emphasis on ventilation for health reasons and infection control, as well as to accommodate paraffin and gas lighting. This simply means they are not airtight, and warm air will be escaping through deliberate gaps that were once deemed essential.

The materials used for traditional buildings were also much weaker and more porous than what we use today. While this was designed to ensure ‘breathable construction’ that would prevent dampness and decay, it can also lead to draughts and wasted energy. When it rains, the external walls are supposed to absorb moisture before it eventually evaporates with the wind and sun, and internal walls were finished to help draw out water vapour.

Sash window frames, single glazing, poor insulation, and inefficient heating systems are just some of the additional factors that cause listed buildings to consume, and then potentially lose, large amounts of energy. Retrofitting to boost energy efficiency and meet net zero goals is, therefore, an essential part of securing the future of these buildings - but, inevitably, that comes with its challenges.

A specialist approach

Undertaking retrofit works on listed buildings requires a degree of caution and a well-considered plan of action. Because of their protected status, listed building consent may be required from the local authority, as well as planning permission, depending on the extent of the works planned.

The first stage is to survey the building and put together a detailed understanding of how it runs and operates, before creating a list of options for the manager or landlord to consider. This will include a range of bespoke and off-the-shelf measures, with differing degrees of complexity. If the property is part of a portfolio, this can be treated holistically, looking at how the same upgrades can be made across the group at one time.

Upgrading to LED lighting, for example, could be one of the most straightforward ways to reduce a building’s carbon footprint. Other relatively quick wins could include installing new slimline or double-glazed windows or looking at new insulation for floor voids and attic spaces to improve heat retention.

On the other hand, changes associated with the decarbonisation of energy and heating sources are likely to be more expensive and time-consuming. An air source heat pump would require a significant amount of new pipework and new radiators to be installed, and PV panels may not be viewed as in keeping with the aesthetics of the property.

The potential for progress

Innovation in materials and techniques, combined with a drive for net zero from investors and occupiers of buildings, is likely to lead to more progress in the decarbonisation of listed buildings. But, it also requires an appropriately skilled workforce to complete the work to the required specialist standard, ideally with an appreciation of historic techniques.

The looming net zero deadline, combined with more guidance from policymakers and an industry focus on best practice, will contribute to an accelerating pace of change when it comes to listed building retrofit. Ultimately, it’s about finding the right balance of old and new – protecting the building’s heritage and aesthetic features, while also making it fit for a greener future.

Thomas & Adamson is part of Egis Group