Dynamic analysis of the heat theft issue for residential buildings

European Union is facing a dramatic energy crisis, due to the huge increase of the natural gas cost, due to the Russian-Ukrainian war. In this framework, the fair allocation of natural gas costs, used for space heating purposes in residential centralized heating systems, is becoming a crucial issue. These systems suffer for the heat theft phenomenon, where an unheated apartment may benefit of the heat transfer from the surrounding heated apartments. Unfortunately, there is no consensus regarding a suitable heat accounting method, implemented in order to limit heat thefts. In this work, two novel billing strategies are proposed. In the first one, the heating cost includes both a variable fee and a constant fee. The second one also considers a penalty for the unheated apartments. A case study is analyzed. It consists of a multifamily building including 4 floors and located in Naples. This building is equipped with a centralized heating system, coupled with radiators, variable speed pumps, thermostatic valves, and heat metering devices. A suitable dynamic simulation model is developed in TRNSYS 18 environment to analyze the energy and economic performance of the system. The comfort parameters of unheated users are also analyzed and discussed. The proposed billing strategies are able to smooth the heating bill increase for the heated apartments adjacent to the unheated user. The novel billing strategy proposed by this research can significantly mitigate the heat theft issue. In particular, results show that the penalty should be almost 2.5 times the constant fee for preventing the unheated user issue. Simulations also show that installing a suitable thermal insulation for the walls among adjacent apartments may dramatically limit the heat thefts. However, insulating such walls may result often unfeasible for the owners of the apartments, due to reduction of the floor area and to the major refurbishment required.