 Multifamily buildings are the most common type of housing in Poland, making up approximately half of all residential buildings. Additionally, they make up around 70% of the urban population. These buildings often require thermal refurbishment, which can be costly and time-consuming. To help reduce costs and speed up the decision-making process, evaluation of a building's energy performance using correlation models has not been widely used in Poland. This method is simple, fast, and can improve the decision process on thermal modernization. It is especially important at the pre-designed stage of planned investments. This paper presents an attempt to develop correlations that could be used in the energy assessment of multifamily buildings. Using a dataset of 29 audits of multifamily buildings, the authors found strong correlations between thermal demand for space heating or domestic hot water and ventilation airflow, as well as thermal transmittance of windows. After designed modernization, these correlations were reduced, but still present. Furthermore, energy for domestic hot water was found to be strongly correlated with the number of inhabitants, while energy for space heating was correlated with the number of users and heated volume of a building. This article was authored by Piotr Michalak, Krzysztof Siksotka, and Jakub Cimak-Sak. We are article.tv, links in the description below.