Most of Europe’s building stock is labelled inefficient, calling for building envelope retrofitting to reduce energy demand and emissions. Positive Energy Districts (PED) aim for urban decarbonisation by generating more renewable energy within the district boundaries than they import from the grid. Such an ambitious requirement needs energy-efficient building stock as a basis. Thus, this work analyses the economic, environmental and grid-related values of building stock retrofitting in electrified PEDs. To do so, this study uses mixed-integer linear programming to compare different optimised PEDs across European climate zones, settlement densities and building standards. Results indicate that retrofitting for PEDs is essential in districts located in colder climates and dense settlement patterns such as in northern European urban areas. Furthermore, building envelope retrofitting benefits energy flexibility towards the grid and reduces ${\mathit{CO}}_2$ emissions. Finally, this study determines a specific PED retrofitting threshold cost, depending on climate, population density and the electricity tariff. Thus this work unveils essential information about building envelope retrofitting for PEDs during the planning phase.

欧洲的大多数建筑存量都被贴上了低效的标签，呼吁对建筑围护结构进行改造以减少能源需求和排放。正能量区 (PED) 旨在通过在区域边界内产生比从电网进口更多的可再生能源来实现城市脱碳。如此雄心勃勃的要求需要节能建筑存量作为基础。因此，这项工作分析了电气化 PED 中建筑库存改造的经济、环境和电网相关价值。为此，本研究使用混合整数线性规划来比较欧洲气候区、沉降密度和建筑标准的不同优化 PED。结果表明，在气候较冷和居住模式密集的地区（例如北欧城市地区），对 PED 进行改造至关重要。${\mathit{一氧化碳}}_2$排放。最后，本研究根据气候、人口密度和电价确定具体的 PED 改造阈值成本。因此，这项工作揭示了在规划阶段为 PED 改造建筑围护结构的基本信息。