24 YEARBOOK 2026 SUSTAINABLE RETROFIT IN HISTORIC BUILDINGS MANAGING CHANGE WITH CARE STEVE BERRY THE SUSTAINABLE adaptation of historic buildings is often framed in terms of performance targets, but in practice it is more fundamentally concerned with continuity. Conservation has always been about the management of change, and where buildings are concerned, change is necessary if they are to remain in use. While we would prefer that that use remains generally the same as the one it was built for, if that use is no longer viable, adaptation and conversion for a new use is essential. A building that falls out of use quickly becomes vulnerable, whereas one that continues to function is maintained, valued and sustained. From both a heritage and an environmental perspective, this continuity is critical. The environmental case for retaining historic buildings is well established. The existing fabric represents a considerable investment of energy and material, and retention of this ‘embodied’ energy avoids the need for the manufacture, transportation and assembly of new materials. However, the question of how these buildings should be adapted to meet modern expectations of comfort and energy use is more complex. There is no single approach to retrofit that can be applied universally. Buildings differ in their construction, condition, significance and use, and the extent of intervention must be judged accordingly. Much current guidance promotes high levels of thermal performance, often derived from new-build standards. While understandable, these approaches do not always translate well to traditionally constructed buildings. Achieving low U-values frequently requires the introduction of multiple new layers, such as insulation, vapourcontrol membranes and finishes, which can significantly alter how a building manages heat and moisture. Externally, little may appear to have changed, but internally the construction can become increasingly complex, with established evaporation pathways disrupted. In this context, the question is not simply how much performance can be improved, but how far the building can be altered before its inherent stability is compromised. This is not an argument against retrofit. On the contrary, adaptation is essential if historic buildings are to remain viable for modern living and for future generations. Approximately 14 per cent of the UK’s energy is used to heat our existing buildings, and expectations of comfort and energy use have changed: buildings must respond if they are to remain occupied and valued. However, in traditionally constructed buildings, even modest interventions represent a departure from long-established patterns of behaviour. The addition of insulation, new linings or altered heating regimes may seem minor, but can fundamentally change how A Grade II* gatehouse on an estate in North Wales undergoing sensitive conservation and retrofit to suit its new use as a home (All photos: Steve Berry)
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