Fibre-reinforced composites based on epoxy resins with fibres are used in such restoration, for example in the recent restoration of the Basilica di S. Francesco in Assisi, Italy. In the study presented, the epoxy resin (Epojet), which was used as the matrix in the composite, was analyzed with regard to its durability under different environmental conditions. Thermal, spectroscopic and mechanical properties have been evaluated on samples aged, after curing, in different environmental conditions. The comparison between the properties of the cured resin, calculated before and after exposure to levels of humidity, temperature and water above the ordinary values, provided information on the durability of these products under severe conditions. In particular, it was found that thermal treatments lead to an increase in glass transition temperature and to a strengthening of the system, that the exposition to moisture or water reduced Tg (final glass transition temperature) and that the effects of thermohygrometric treatments are even more complex. -- SCMRE