The risk analysis of moisture-related damages can potentially be carried out with the use of heat and moisture transfer simulations. These models require weather files as boundary conditions but, for most locations, the only weather files available are Typical Reference Years, for instance the TRYEN defined in accordance with EN ISO 15927-4:2005. These reference years do not provide the critical conditions that should be used in risk assessments. In this work, two procedures to define Extreme Moisture Reference Years (ERYm1 and ERYm2) are presented. ERYm1 and ERYm2 are designed to generate critical weather files to be used in simulations for the assessment of moisture related risks. The presented procedures are structure-independent and suitable for risk assessments that involve high air moisture content and low air temperature values. In order to assess the capabilities of ERYm, five types of walls with different materials are simulated, considering three Italian climates (those of Gemona del Friuli, of Legnaro and of Trento) and four wall orientations (North, East, South, West). The results of simulations with ERYm1 and ERYm2 as weather files showed higher wall moisture contents and interstitial moisture accumulation risks than those with TRYEN. This suggests that ERYm could be used as a valid alternative to the TRYEN in decision making frameworks and legislations that cannot include the ad hoc definition of a weather file for each structure, exposure and location.
