Climate change resilience of energy retrofit interventions in historic urban areas

Decarbonizing the built environment has become a critical priority in addressing the impacts of climate change, necessitating comprehensive and effective energy retrofitting of existing buildings. Many historically significant cities feature urban centers rich in cultural and artistic heritage. Authorities impose restrictions on buildings under preservation order but must also assess retrofitting interventions on nearby non-protected structures to preserve the area's cultural integrity. In Padua, a historic area spanning 126,000 m2 was analyzed to identify the most effective energy retrofitting strategies, aiming to provide clear operational guidelines. A modeling approach based on building-plant system dynamic simulation of archetypes shows that interventions on building systems outperform those focused on building envelope insulation. Solar shading systems were incorporated in all retrofit scenarios, whereas other passive strategies were excluded due to their limited applicability in densely built and protected historical areas. Notably, the results highlight the highest energy savings achieved with heat pumps combined with photovoltaic systems, which are also less architecturally invasive, particularly when building-integrated photovoltaic systems and geothermal heat pumps are employed. Ultimately, the combined implementation of energy system measures and building envelope improvements resulted in energy savings of up to 83.9 % of the total energy consumption in the analyzed buildings. Thus, even buildings in historic areas can contribute significantly to achieving the energy transition goals set for 2050. A key factor in reaching this conclusion was the projection of the study into the SSP5-8.5 climate scenario for 2050, the most extreme pathway developed by the IPCC. Despite substantial differences in climate and in the energy behavior of buildings by 2050, new evaluations under this scenario confirmed the results obtained under current climate conditions. Consequently, the proposed intervention strategies remain effective through 2050, even under the most radical climate change projections.