Energy retrofit with prefabricated timber-based façade modules: pre- and post-comparison between two identical buildings

The introduction of prefabrication into the building façade retrofit market is still difficult due to many financial, economic, and social constraints, as well as technical and performance requirements that differ from those of new construction. The technical feasibility, construction details, and actual comfort and energy-saving benefits provided by the installation of prefabricated façade modules are still being investigated, as is one goal of the specific case study presented here. The Renew-Wall project aims to create a new modular, timber-based, non-intrusive system for retrofitting buildings, developing a series of significant and fully customisable innovations compared to currently available solutions. This paper describes the main properties of the designed prefabricated façade system, with a focus on its energy and thermo-hygrometric performances. Simulation and laboratory tests are compared with an experimental analysis conducted on two identical mock-up buildings (test cells) during a two-year monitoring campaign in which only one of the two test cells was retrofitted. The results show simulated average annual energy savings of 67%, perfectly in line with what was measured on-site. The prefabricated façade system also demonstrates efficient vapour release and a reduced risk of mould and fungus attack.