Heat accounting in historical buildings - La contabilizzazione del calore negli edifici storici

Modern devices for thermal energy measurement and accounting are rarely available in historical buildings, despite energy consumptions are not negligible. On the other hand, historical buildings exhibit architectural constraints and plant configurations that strongly discourage the use of direct heat meters, both on a technical and economic point of view. In such context, the "individual" accounting of thermal energy in household applica- tions (heating, cooling, hot water) represent a very essential tool for increasing energy ef- ficiency in buildings in which a centralized heating/cooling plant is available. In fact, merely sharing the costs of thermal energy as a function of the real consumptions of each user can be a strong incentive to adopt energy-saving behaviors. Furthermore, the availa- bility of real time energy consumptions data about, typical of a “smart” metering architec- ture, enables the users to identify the causes of any waste of energy and consequently adopt adequate strategies to improve energy efficiency. Finally, the ability to adjust ther- mal energy consumption curve in the logic of "demand-side management" could be en- couraged. In this paper and with particular reference to historical buildings, the authors analyze direct thermal energy measurement and indirect devices used to share thermal energy con- sumptions among users. These devices are often the only ones applicable to retrofit histor- ical buildings where centralized plants with vertical distribution column are normally pre- sent. The authors, finally, after a brief description of the technological evolution of such devices, show the results of a specific metrological analysis that enables both a compari- son among the different options, and the evaluation of the main criticalities about thermal energy measurements in historical buildings.