This paper proposes a novel and innovative methodology to assess the degree of Circularity in one of the most resource-consuming and impactful economic activities: the building construction and/or renovation works. The proposed approach measures the ratio of circular flows in three aspects: energy, water and materials consumption; and combines them with the measure of social added value and economic value of the entire activity along its life cycle, regardless of being a new building construction or a major renovation work. The whole methodology has been developed under a life cycle perspective, incorporating into the analysis all material flows and social, environmental and economic impacts from cradle to grave, i.e., from resource acquisition to end of life treatment processes or disposal. The proposed Key Performance Indicators (KPIs) measure different and non-directly related parameters (energy, materials, social impact…) and they are both quantitative and qualitative metrics. Hence, the proposed methodology performs the indicators calculation procedure independently. The methodology has been tested with a conventional energy renovation process consisting of an installation of an External Thermal Insulation Composite System (ETICS) – one of the most prevailing façade energy retrofitting alternatives – combined with a rooftop solar PV system. In this way, a calculation example is shown and some lessons can be extracted regarding the degree circularity of current building construction and refurbishment practices. Results show that current building envelope solutions – even including an efficient rooftop PV system – are far from being considered circular: whereas a significant 51% of Energy Circularity is achieved, only a 29% and a 21% degree of Circularity is observed for the materials and social aspects, also with high payback periods – above 20 years – on the economic side. The methodology also succeeds in showing the potential for improvement and its location along the building life cycle. It is also shown that buildings behave significantly different in each of the addressed CE aspects: materials, energy and water use, social added value and life cycle cost; showing also different potential of improvement.