The modules of InstalSystem package for designing heating and cooling installations enable the use catalogues of circulating mediums (the so-called media) during the design of installations. The information contained in the catalogue about the dependence of physical properties of the media on the temperature and concentration of the medium allows to take into account the characteristic parameters of the circulation medium during calculations. The user can select the type of medium and in the case of mixtures with glycol determine its concentration. InstalSystem package includes a neutral media catalogue containing such mediums as: water, ethylene glycol, propylene glycol. It is also possible to include a company catalogue containing media with other properties.