Abstract
Circular architecture increasingly treats existing buildings as resources whose value can be prolonged through maintenance, adaptation and successive cycles of use. In historic public buildings, however, material retention must be reconciled with heritage significance, functional change, safety, technological upgrading and future adaptability. This study investigates selective conservation as a framework for making these decisions explicit within adaptive reuse. The framework combines four intervention modes—retain, adapt, integrate and replace—with seven whole-life criteria and a four-level evidence code. It is tested on Buildings 5 and 15 within the regeneration of the former Sant’ Osvaldo Psychiatric Hospital in Udine, Italy, using project documentation as empirical evidence. The application shows that circularity cannot be reduced to maximum material retention: selective replacement and new additions can extend the useful life of retained building resources when they are compatible, maintainable and appropriately documented. The framework therefore reads selective conservation as a decision logic linking treatment of existing resources to their consequences over time, without collapsing heterogeneous design choices into a single circularity score.