The stakeholders in the AEC (Architecture-Engineering-Construction) community generally agree that the existing building stock plays a crucial role in the building-related energy consumption and emissions. In this context, prefabricated buildings (especially those constructed in the time-period between 1950 and 1980 in a number of East and Central European countries) require careful attention. In this context, the following observations are of relevance: (i) Prefabrication was utilized to industrially build a large number of widely identical buildings, and a major part of these buildings still exist with little to no modifications; (ii) In most cases, these buildings do not meets today's thermal and energy performance standards. As such, appropriate retrofit schemes could be applied several times, or in other words, retrofit planning efforts for this building typology can significantly reduce energy use and environmental emissions; (ii) Due to the prefabrication character, the complexity of these buildings' envelope details regularly is readily manageable. Thus, retrofit solutions for prefabricated buildings can be prefabricated as well; (iii) In many European cities, such buildings form a large fraction of available (social) housing units, and thus are an important resource, given the ongoing growth of the cities of the 21st century. Demolishing and replacing entire blocks of such buildings does not appear to be neither simple nor efficient, given the associated implications regarding cost and environmental impact. As a consequence, retrofitting seems as a more viable and logical choice for the future of 20th century prefabricated building stock. In this contribution, we present method and results of a research effort pertaining to performance-based retrofit options of a prefabricated building typology from former Yugoslavia, which can be found not only in Zagreb, but also in other parts of the Balkan Peninsula. The effort involves the systematic deployment of parametric simulation runs toward the comprehensive investigation of the impact of different retrofit options. Thereby, multiple scales were taken into consideration, including both building components (i.e., thermal bridging effects of construction joints) and whole-building thermal performance.