Abstract
Introduction: In Europe, around 75% of the existing building stock dates back to before the 1990s (Building Performance Institute Europe, 2017) and is characterized by remarkable energy demand levels, spanning from 200 to 300 kWh/m2y for the residentialand the non-residential sector1, respectively. Within this energy demand, around 70% is ascribed to households at European level. This allows to easily infer that renovating the existing residential building stock is a major priority to be addressed in order to meet current European decarbonisation targets (Marina Economidou, 2011).Buildings are assets with an expected service life up to 50 or more years. Hence, 75-90% of those standing today are likely to be still in use in 2050. Considering the current demolition rates (0.1% per year), and low rate of construction of new high energy efficient buildings (1% per year), the European energy efficiency challenge in buildings can be mainly addressed through investments in renovation of the existing building stock. However, as the renovation rate of the existing stock is still limited (1-1.5% per year), a significant acceleration is needed (Ad-hoc Industrial Advisory Group, 2010). Recently, retrofit actions have been focusing on single aspects of building performance. This can be ascribed to the combined effect of several root causes, such as: capital investment costs, technological constraints, complexity in planning construction time schedules and decision-making procedures. Hence, deep renovation is a challenge that is rarely tackled applying a standardised approach, provided that each building has its own story, in terms of technical and morphological features. Nevertheless, addressing the building renovation process has provided successful results in several cases, where a comprehensive approach based on systemic technology packages to face the multiple and interconnected retrofit needs has been adopted.