The ACCESS (Array of Cryogenic Calorimeters to Evaluate Spectral Shapes) project aims to establish a novel technique to perform precision measurements of forbidden β-decays, which can serve as an important benchmark for nuclear physics calculations and represent a significant background in astroparticle physics experiments. ACCESS will operate a pilot array of cryogenic calorimeters based on natural and doped crystals containing β-emitting radionuclides. In this way, natural (e.g. Cd-113 and In-115) and synthetic isotopes (e.g. Tc-99) will be simultaneously measured with a common experimental technique. The array will also include further crystals optimized to disentangle the different background sources, thus reducing the systematic uncertainty. In this dataset, we collect the Monte Carlo simulations (based on GEANT 4 and stored as ROOT files) that we developed for the design study of an indium iodine based detector to measure the In-115 decay.