Risks and benefits of internal insulation as a measure for historic buildings energy renovation

European historic buildings account for more than a third of the total energy consumption of buildings. Therefore, it is vital to reduce their energy demand, while maintaining their architectural and cultural heritage. Installing internal insulation is an effective measure, however it entails a certain risk of failure due to possible hygrothermal damages. Furthermore, several insulation systems are available in the market, thus building owners and practitioners need knowledge on how to handle internal insulation in an effective way. This paper reports the outcomes of an extended monitoring of the hygrothermal performance of two insulation systems (on “capillary active”, the other “vapour tight”) installed in a real historic building. Results highlights how the hygrothermal behaviour and the built-in moisture due to the installation operations can critically affect the energy performance of the wall, thus providing suggestions for the planning phase of a historic building renovation.