Reliability of the numerical simulation results strongly depends on the input data, in particular on the thermo-physical properties of the furnace components, e.g. graphite thermal conductivity and steel surface emissivity. Uncertainties are always involved in the measurement of these parameters. A set of global 2D simulations has been carried out in order to investigate the impact of each property on the growth conditions in Czochralski silicon growth furnaces. The results indicate that steel emissivity and felt conductivity have significant impact on the calculated thermal field and energy consumption.