**Application of Rough Set Theory (RST) to Forecast Energy Consumption in Buildings Undergoing Thermal Modernization**

#### **Tomasz Szul \* and Stanisław Kokoszka**

Faculty of Production and Power Engineering, University of Agriculture in Krakow, 30-149 Kraków, Poland; s.kokoszka@urk.edu.pl

**\*** Correspondence: t.szul@urk.edu.pl; Tel.: +48-12-662-46-47

Received: 8 February 2020; Accepted: 7 March 2020; Published: 11 March 2020

**Abstract:** In many regions, the heat used for space heating is a basic item in the energy balance of a building and significantly a ffects its operating costs. The accuracy of the assessment of heat consumption in an existing building and the determination of the main components of heat loss depends to a large extent on whether the energy e fficiency improvement targets set in the thermal upgrading project are achieved. A frequent problem in the case of energy calculations is the lack of complete architectural and construction documentation of the analyzed objects. Therefore, there is a need to search for methods that will be suitable for a quick technical analysis of measures taken to improve energy e fficiency in existing buildings. These methods should have satisfactory results in predicting energy consumption where the input is limited, inaccurate, or uncertain. Therefore, the aim of this work was to test the usefulness of a model based on Rough Set Theory (RST) for estimating the thermal energy consumption of buildings undergoing an energy renovation. The research was carried out on a group of 109 thermally improved residential buildings, for which energy performance was based on actual energy consumption before and after thermal modernization. Specific sets of important variables characterizing the examined buildings were distinguished. The groups of variables were used to estimate energy consumption in such a way as to obtain a compromise between the e ffort of obtaining them and the quality of the forecast. This has allowed the construction of a prediction model that allows the use of a fast, relatively simple procedure to estimate the final energy demand rate for heating buildings.

**Keywords:** building energy consumption; building load forecasting; energy e fficiency; rough set theory; thermal improved of buildings
