In this paper, we have developed a calculation method for estimating heat fluxes from ceiling radiant panels, using pipe density on panels and the temperature difference between the room air and the supply water. We then measured heat fluxes from panels in an environmental test room. After comparing the values estimated by our calculation method to the experiment's data. the calculated values closely match the values obtained from experiments, which means that this calculation method is practical in estimating the radiant panel performance in the design phase. (C) 2009 Elsevier B.V. All rights reserved.