Heat accounting in historical buildings

The “individual” accounting of thermal energy in household applications (heating, cooling, hot water) is avery essential tool for increasing energy efficiency of buildings equipped by central plants. Furthermore,the availability of real time energy consumptions data, typical of smart metering, enables users to identifythe causes of any waste of energy and consequently to adopt adequate strategies to improve energyefficiency.Modern devices for thermal energy measurement and accounting are rarely present in historical build-ings, despite energy consumptions are not negligible. In fact, historical buildings exhibit architecturalconstraints and plant configurations that strongly discourage the use of direct heat meters, both on atechnical and economic point of view.This paper primarily deals with an in-depth analysis of thermal energy measurement devices for his-torical building applications. Furthermore, the authors show the results of a specific metrological analysisthat enables both a comparison among the different options and the evaluation of the main criticalitiesabout thermal energy measurements in historical buildings. The authors estimated typical uncertaintiesin heat accounting systems ranging from about 4.4% (direct heat meters) to 21.6% (insertion time countercompensated with degree-days). Intermediate performance for uncertainty has been estimated for heatcost allocators (about 9.2%) and for not compensated insertion time counters (about 13.4%), respectively.