Plenty of technical norms, included in the EPBD umbrella, assesses the performance of buildings or its sub-systems in terms of efficiency. In particular, EN 15316 and its sub-sections determine the efficiency factors of a space heating system. This paper focuses on the estimation of efficiency factors for hydronic panel radiators. The assessment of efficiency factors occurs by evaluating the amount of heat emitted from the heat emitter and the thermal losses towards building envelope. A factor that influences the heat emitted is the location of radiator connection pipes. Connection pipes can be located on opposite side or at the same side of the radiator. To better estimate the heat emitted from the radiator with different location of connection pipes, a transient model with multiple storage elements is implemented in a commercial building simulation software and validated versus available experimental measurements. Sensitivity analysis encompasses the variations of heat losses due to the building location in different climates, the changing of the active thermal mass and the type of radiator local control. The final outcome of this paper is a practical support where designers and researchers can easily assess the efficiency factors for space heating system equipped with hydronic panel radiators of buildings located in Sweden. As main results, (i) the efficiency factor for control is higher in Northern climates (Luleå) than in Southern climates (Gothenburg), (ii) heavy-weight active thermal masses allow higher efficiency factors than light active thermal masses, and (iii) connection pipes located on the same side of the hydronic panel radiator enable higher efficiency factors than pipes located on opposite side.
