When a building is heated to a steady internal temperature, equilibrium is established in which the heat power into the building equals the rate at which heat is lost from the building. A good approximation of heat losses can be determined using the conventional generic equations which give a relatively accurate value of the heat loss; however these equations can be inaccurate, especially in applications where radiative heating is used. In this article simple predictive tools are developed to estimate the characteristic temperature ratios for both panel radiator and high temperature radiant strip systems. The calculated results can be used in follow up calculations for a model, which fully takes into account the radiation heat transfer occurring within a room space. The results of the proposed method are found to be in excellent agreement with reported data in the literature with average absolute deviation being around 0.2%. The predictive tool is simple and straightforward and it can be readily implemented in a standard spreadsheet program. The prime application of the method is as a quick-and-easy evaluation tool in conceptual development and scoping studies where a panel radiator system and a high temperature radiant strip system are being considered. The method may also serve as a benchmark in numerical and rigorous simulation studies. (C) 2012 Elsevier B.V. All rights reserved.