Heating, ventilation, and air conditioning engineers still face several obstacles when designing radiant systems. The use of prefabricated radiant panels simplify the design and construction of such systems, providing a certain accuracy in their performance. However, the nominal cooling capacity provided by manufacturers is insufficient to accurately calculate the cooling capacity in practical use. Therefore, an experiment was conducted to obtain the unique heat transfer coefficients of a radiant panel for the calculation of surface temperature and heat loss. Test chamber experiments revealed that the heat loss was a function of the operative temperature difference between the room and the ceiling chamber. The heat transfer coefficients obtained from the experiment could accurately calculate the heat loss and surface temperature of the panels. Such measurements should be conducted and provided by manufacturers for engineers to use in the design of radiant systems.