This article summarizes the main results obtained by the investigation of annealing and degradation mechanisms observed for amorphous silicon (a-Si) modules. This interest comes from the encouraging results obtained by thermally insulated a-Si PV plant. Findings showed that the better thermal behaviour and annealing processes of a-Si compared to c-Si technologies compensated a significant part of losses due to the nearly horizontal roof integration. The study focuses on the characterization of the annealing process, in terms of temperature and heating duration. Other aspects investigated are the stability of annealing and stability of degradation, the degradation dependence on the module load and the contrasting effects occurring to a-Si module power due to a temperature increase.