Estimating heat emission losses of heating systems is an important task of energy efficiency assessments in buildings. To this aim, the present international standards contain tabulated values for different emitter and control system configurations, without however explaining how to compute the effect of increased setpoint temperatures on the system losses. Moreover, the effects of each component are treated as independent, while e.g. vertical stratification and temperature control of the system are cross-related. In this paper we attempt to fill this gap by proposing a calculation method to calculate the product category specific setpoint variations for space heating emitters, accounting for the overall heat balance in the enclosure and including the cross-correlations of each component as well. The emission losses of a heating system are computed using a temperature setpoint variation method that is imposed on annual energy calculations. This complements the procedure presented in the Standard EN15316-2, also providing the possibility to use product-specific values of setpoint variations instead of tabulated values. As the main finding of the study, the calculation process is defined for a European Reference Room, namely for a specific enclosure that allows an accurate and transparent evaluation of the total setpoint variation. The product-specific values of setpoint variations are calculated from measured vertical stratification and control parameters with an annual simulation model of the European Reference Room. The total setpoint variations were simulated for a set of heat emitters and controllers in order to quantify and compare the energy performance of a new and an old type building located in Strasbourg. We find that the total setpoint variation required to overcome emission losses is up to 2.00 °C in the old building and 1.20 °C in the new building, corresponding respectively to an increase in total heating energy usage of up to 22% and 20%.