The present thesis discusses social, cultural, economic and environmental aspects of problems related to heritage building depreciation, homelessness and lack of affordable housing, with a focus on the more vulnerable social groups. It additionally argues the mitigation of the impact of the cities and the building sector on climate crisis. The aim of the thesis is to find a sustainable, in terms of longevity and feasibility, connection between the unexploited building stock and the shelter-less people, for the benefit of the users, the society and the environment alike, through zero-energy design and circular adaptation.

The study analyzes the possible approach of renovation and adaptive reuse of the existing, untapped, residential buildings in order to meet the current climate regulations and future occupants’ needs. A literature review examines three main domains separately: zero-energy design, circularity and collective housing. A case study analysis of alternative collective housing models in particular monitors the porosity of this plan and its ability to be combined with zero-energy and circular principles. This research offers the opportunity to recognize possible methodologies that can then be applied on a specific case study.

Research is consolidated in the case of the refugee settlement complex of Alexandra’s Avenue (1933-36), in the city of Athens, and seeks to propose a number of recommendations for its renovation, energy upgrade, redevelopment and reuse. The fact that the research refers to listed buildings, constitutes the biggest limitation, in terms of design decisions. The case study it-self, clearly depicts the afore-mentioned issues in the Athenian context, and alongside includes building, social, historic and other characteristics that compose an ideal example for an energy efficient, user-oriented, adaptive reuse.

A step-by-step approach is adopted in order to develop (re)design methodologies for the energy transition and circular adaptation of the case study. In addition, a possible network of interactions between the involved stakeholders is proposed so as to create a holistic and functional business model. Ultimately, the thesis proposes an inclusive and integrated framework for the renovation of the existing, old, heritage, building stock, driven by zero-energy and circular principles, for the less-favored, towards a new typology of social and collective housing. The development of this framework is based on facts and data that can make it potentially applicable to similar cases elsewhere.

Further research on the topic would help facilitate the transition to integrated frameworks of renovation processes.