Abstract Taking a dormitory building in Beijing as an example, this paper presents researches about impacts of radiator selection on indoor thermal environment and energy consumption for space heating by using DeST-h software. Simulation results quantitatively indicate the variation of heating effect with radiator type (cast-iron radiator, steel radiator and copper-aluminium radiator), radiator size and water flow rate. Moreover, the negative impact of water flow rate under design value on indoor thermal environment has been highlighted, by which the suggestion to have better understanding about the hydraulic misadjustment degree of heat pipeline has been given. Additionally, cast-iron radiator has been demonstrated to be better than the new type of copper-aluminium radiator in terms of room air temperature.