Sizing method and heating capacity evaluation of a hybrid convective/radiant system for heating historical buildings

Historical buildings are important and the need of improving comfort conditions in heating season has been increased in the last years. In historical buildings many times the floor and the walls have to be kept intact, hence not intrusive systems have to be considered. The work here presented refers to a mixed radiant and convective system based on a raised wooden floor, which allows to maintain the floor covering. The proposed technique is particular suitable for churches, but it can be applied to any historical building. The work regards measurements for evaluating the heating output capacity of the system itself and to tune a simplified model which considers the different heat exchanges within the structure of the heating system. Another aspect which has been investigated is the determination of the heating capacity of a building with very high mass and low thermal resistance of structures with intermittent operating conditions. In these cases in fact the standard EN 12831 is not suitable, since it is based on steady state conditions, while in cases of historical buildings heated occasionally, the heat up capacity should be usually higher. In the paper a simplified method has been compared with dynamic simulations based on EnergyPlus.