**4. Conclusions**

The conducted in situ research made it possible to identify user behavior and helped to calibrate energy models of apartments in pre-war tenement houses, that allowed to perform simulations helping to analyze the energy performance gap on several levels connected to the apartment's utilization and ambient temperature. On this basis, the energy performance gap for heating and DHW production has been analyzed. The calculated values turned out to be significant and negative, reaching even −0.78. Only in one considered case, the value obtained was positive and equaled to 0.3. The detailed analysis allowed us to refine crucial issues. The size of the energy gap is influenced not only by the ambient and internal temperature, but also by the temperature of surrounding spaces (for example: empty premises or stairways), which is di fferent from the assumptions for the calculations. User behaviors that influence the size of the EPG can be divided into typical (energy saving or excessive energy consumption) and forced (energy poverty, response to the environment around the apartment, technical limitations). The former (typical) behaviors were the origin of the energy gap in the apartments heated with natural gas and district heating (A9–A15). The latter (forced) were the origin of the gap in the apartments heated with mostly electricity and solid fuel (A1–A8). The only exception was the apartment A8, that utilized the district heating. The most important forced aspects observed during the research were as follows: not heating some rooms, providing additional heating with gas cookers, covering the ventilation grids, limiting ventilation of the rooms, and consuming very little domestic hot water. Correctly determining and classifying the energy performance gap between expected and actual energy consumption can be important for the proper planning and implementation of thermal modernization in pre-war buildings. It may allow for better determination of energy and cost savings by considering the specific nature of the use of such buildings. It is important, because the high energy consumption of premises in tenement houses and the related high costs are the common problems faced by the residents. The connection between the heating resources cost and the heating habits has been clearly observed in the research. Solid fuel is a cheap energy resource in Poland, and it is currently used by the poorest part of the society. Electricity is expensive and requires significant savings. Heating with district heat usually allows residents to maintain thermal comfort, while natural gas, the cheapest source of thermal energy, combined with the good condition of tenement houses allows residents to freely manage their resources. The research results show that a good energy standard of a building together with a modern and cost-acceptable heating source help to eliminate the forced energy gap. Further research on the impact of resident's behavior on the energy consumption and the size of the energy gap may be crucial for micro-scale modeling. Studying these behaviors requires an interdisciplinary approach, in particular a combination of engineering and social sciences. Energy behavior is not static; it changes with accumulated experience and financial and technical possibilities and is often inconsistent. These factors increase research di fficulties and should be considered in any energy behavior analysis to minimize inaccuracies in assessing the situation.

**Author Contributions:** Conceptualization, M.S.-Z., E.S. and K.P; Methodology and Validation, M.S.-Z., E.S., K.P., A.C.; Formal Analysis and Investigation, M.S.-Z., E.S. and K.P; Resources and Data Curation, M.S.-Z., E.S., K.P., A.C. and M.K.; Writing—Original Draft Preparation, E.S., M.S.-Z.; Writing—Review & Editing, E.S., M.S.-Z.; Visualization, K.P.; Supervision, M.S.-Z.; All authors have read and agreed to the published version of the manuscript.

**Funding:** The project was implemented thanks to the "Divercity 4—Polish-Norwegian cooperation in the field of creating modern development solutions in cities" project with an EUR 300,000 gran<sup>t</sup> from Iceland, Lichtenstein, and Norway through the EEA and Norway Grants. The initiative aims to identify the most effective solutions and create a cooperation network as well as exchange experiences between Polish self-governments and the Donor States, with particular emphasis on the subject of social participation in urban renewal and improvement of the urban environment. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

**Conflicts of Interest:** The authors declare no conflict of interest.
