This article aims at determining an optimal modeling method for heat transfer calculation of low thermal mass hydronic radiant cooling or heating panels with serpentine tube layout. It introduces a new semi-analytical procedure based on a well-known analytical modeling method to relax the thermal symmetry condition between tubes that is traditionally used. For the standard reference case presented, the temperature asymmetry was important, reaching 29% of the half inter-tube distance. However, the heat transfer performances were not significantly affected compared to results achieved by assuming thermal symmetry. It is also shown that this result implies that no significant performance gap between parallel layout and serpentine layout panels is expected. The effect of the 1D heat conduction assumption and of straight tube endings in the modeling were also quantified using a 2D finite volume code. None of these assumptions caused significant errors on heat transfer calculations. The same results apply to a large range of panel geometries and operating parameters. (C) 2011 Elsevier B.V. All rights reserved.