In situ thermal characterization of existing buildings aiming at NZEB standard: A methodological approach

Abstract Building performance is strongly influenced by the performance of their structural parts, consequently affecting annual energy demands. The thermal characterization of building components can be achieved thanks to the knowledge of their internal layers and the thermal properties of each material. Considering existing buildings, technical data may be unidentified and heat transfer phenomena between walls and environments can be influenced by air-conditioning systems and local thermo-fluid dynamic conditions. Moreover, the conversion of an existing building into a Nearly Zero Energy Building (NZEB) requires accurate measurements and simulations compared with Standards suggestions, based on simplified procedures. Therefore, on-site surveys become fundamental. Standards suggestions can help engineers or technicians to define some unknown information related to heat transfer coefficients and thermo-physical properties. Nevertheless, can Standards' suggestions be considered reliable in every situation? This paper tries to answer this question, debating some investigations conducted in the last years and proposing a methodological approach.