There is a deep and often impassioned postulation that preservation is virtuous for societal well-being, collective identity and for the environment. This idea is an important paradigm to guide rehabilitation strategies for historic buildings. However, there is a need for data and research in order to validate the contribution of preservation to environmental and cultural sustainability. These research results will support preservation-related decision-making, in which tensions and conflicts with sustainability goals are a routine. Nowadays, there is a strong belief that historic buildings of the 20th century also need to be preserved to create the identities of neighborhoods and cities and suitable strategies need to be applied to extend their lifespan in an environmentally friendly and sustainable way. This research, based on the assumption that integrating sustainability considerations in historic buildings needs a quantifiable approach, selected eight refugee block apartment flats dating back to the interwar period—endowed with architectural, aesthetical and urban history-related values and acknowledged as exceptional examples of Bauhaus architecture in Greece—for an experimental procedure based on life cycle analysis (LCA). Taking into account the deteriorated state of conservation of the buildings, different preservation interventions were analyzed, focusing on the conservation of the initial architectural form of the buildings and critical issues such as the increase in energy efficiency after restoration. The research concludes that this type of assessment can inform urban strategies, making a nexus between preservation and the environmental component of sustainability.