Detailed Analysis of the Causes of the Energy Performance Gap Using the Example of Apartments in Historical Buildings in Wroclaw (Poland)

Abstract

This paper presents the results of measuring and calculating the final energy consumption for heating and domestic hot water preparation in six apartments located in pre-war tenement houses in Wroclaw (Poland). The calculations were carried out based on energy models of dwellings calibrated with measurement data. Calculation variants were characterized by seven internal parameters (indoor air temperature, heat transfer coefficient by transmission through the internal partition, internal heat gains, air exchange multiplicity in the dwelling, domestic hot water consumption, and domestic hot water temperature and cold water temperature) and two external parameters (outdoor air temperature and insolation). By comparing calculations with measurements, the energy performance gap (EPG) values associated with each parameter were determined. The presented results indicate how much of the differences could be attributed to weather conditions and how much to other factors. It is quite common for the influence of some factors to cancel out the influence of others. Identifying and understanding the real causes of the energy gap may allow for the proposal of better retrofitting solutions or appropriate financial support to households at risk of energy poverty. It is important to note that only in-depth interviews with residents and measurements, such as those carried out in this case, allow such situations to be identified in detail.