Abstract

Decarbonizing historic urban centres is challenging due to strict architectural and landscape conservation constraints, which limit conventional energy efficiency and renewable solutions. This study investigates three districts in the UNESCO-protected historic centre of Quedlinburg (Germany), assessing the potential of integrated interventions including internal wall insulation, window upgrades, hybrid heating systems, and building-integrated photovoltaics (BIPV). Results indicate that envelope improvements combined with hybrid gas boiler–air/water heat pump systems reduce heating demand by over 35%, with a further 10% decrease under projected 2050 climate conditions. BIPV integration contributes to an approximately 30–35% reduction in non-renewable primary energy, depending on roof orientation and available surface area. hDistrict-level analysis confirms the scalability of these measures, demonstrating that conservation-compatible strategies can achieve significant energy and emissions reductions while respecting heritage constraints, providing a replicable framework for other historic centres