The Standard EN ISO 15026:2007 suggests that, in Heat and Moisture Transfer (HAMT) simulations, a Moisture
Reference Year (MRY) should be used, built upon a sufficiently long recording period. However, many
studies rely on widely available Typical Weather Years (TWY), although these are not prepared ad hoc to
investigate moisture-related risks. This paper aims at understanding to what extent these weather files are
interchangeable in a warm climate, through hygrothermal simulations performed with Delphin 6.1.2 on a typical wall assembly retrofitted by wood-based materials. All tested weather files refer to the same location (Catania, Italy) and reference period. The results are compared in terms of mold growth and moisture-dependent increase in heat losses.