A numerical analysis of a ceiling-type radiant panel heater system was performed to examine the heating performance under different parameters, using the FloEFD code. Three-dimensional models of the room and radiant panel heater were created, and the effects of the Reynolds number, water inlet temperature, pipe diameter and pipe runs on the heating performance of the system were examined in detail. The effects of these parameters on the total heat load, the net radiation rate, and the average surface temperature on the sheet and insulation material have been presented. The total heat load and net radiation rate obtained from the system increase with the increase in the Reynolds number. In addition, a rise in the water inlet temperature increases the heat output of the system. An increase of approximately 500 W was observed in the total heat output as the pipe diameter increased. It was observed, too, that the heat output increased with an increase in pipe runs, although above a certain value the heat output became almost constant. The results of this study could offer information to engineers and manufacturers on the design and use of hydronic radiant systems.