The retrofitting of the existing building stock is one of the most important goals to bepursued to meet European targets. In this context, the RenoZEB project has developed a modularmethodology for the deep retrofitting of buildings, which is enabled by a prefabricated plug-and-playfaçade that integrates different on-market technologies to achieve nZEB standards. This articlereports on the activities conducted in the study and design of the RenoZEB prefabricated envelopesystem, providing insights on the tests conducted and the results achieved for the façade system,with a specific focus on the use of technology laboratory facilities for real-environment validation,which revealed the system to be in line with the project objectives.