Words by Malene Holmsgaard, Martin Sing and Chessa Stevens
“There is a tension at the heart of heritage work. Regulations for listed buildings tend to restrict changes, making it difficult to reduce their energy use. But they must adhere to modern functional and energy-efficiency requirements as far as possible in order to remain viable and useful”
Climate change threatens the past as well as the future
Conserving our global heritage and tackling climate change share a common ethos. Heritage conservation principles teach us the value of preserving and protecting historic buildings for future generations, while sustainability teaches us the value of preserving and protecting all resources for future generations. Historic buildings can be seen as a resource too: by conserving and updating them, we can avoid expending the embodied carbon inherent in new development. There is a tension at the heart of heritage work, however. Regulations for listed buildings tend to restrict changes, making it difficult to reduce their energy use. But they must adhere to modern functional and energy-efficiency requirements as far as possible in order to remain viable and useful. At the same time, climate change is making the need to protect our built heritage all the more urgent, with extreme weather placing new demands on ageing fabric and structures.
Treat existing buildings as a resource and use what’s there
Not all buildings can be upgraded to modern energy efficiency standards, but significant carbon savings can be achieved with bespoke solutions, particularly when the embodied carbon of the existing structure and the relatively short lifespan of new technologies is taken into account. WSP and the Technical University of Denmark have calculated that rather than replacing draughty wooden windows, insulation standards could be met by retaining and properly maintaining them, and installing secondary glazing. This will result in significant reductions in carbon, overall cost and resource consumption — especially since older windows have a lifespan of well over 100 years, compared to just 30 for thermal glazing. At Copenhagen City Hall, meanwhile, the new heating and ventilation strategy makes full use of the 120-year-old building’s original infrastructure, including brick ventilation ducts, roof pipes and basement corridors. In combination with a state-of-the-art building management system, this is expected to use 80% less energy.
Work with the structure, not against it
One of the core tenets of restoring any heritage asset is that we must first understand its significance, how it is made and how it performs compared to current requirements, before deciding on a solution — and each time the answer will be different. Preservation strategies may not always be large-scale or intensive. In Akaroa, New Zealand, the pre-1900 seawall was suffering from erosion and structural damage and under threat from more frequent storms and rising sea levels. Our team took a conservative approach that prioritized its historic value. The repair methodology focused on strengthening the existing walling and its foundations rather than making new interventions, slowing the rate of deterioration while maintaining the integrity of the structure and minimizing the loss of original stonework.