energies Article Maintenance of Passive House Standard in the Light of Long-Term Study on Energy Use in a Prefabricated Lightweight Passive House in Central Europe Krzysztof W ˛ as * , Jan Rado ´ n and Agnieszka Sadlowska-Sal ˛ ega Faculty of Environmental Engineering and Land Surveying, University of Agriculture in Krakow, Al. Mickiewicza 24/28, 31-059 Kraków,Poland; j.radon@ur.krakow.pl (J.R.); agnieszka.sadlowska@urk.edu.pl (A.S.-S.) * Correspondence: krzysztof.was@urk.edu.pl Received: 22 April 2020; Accepted: 29 May 2020; Published: 1 June 2020   Abstract: This article presents the results of experimental research on energy consumption of a prefabricated lightweight passive house located in the south of Poland. The key design parameters of the building were as follows: orientation maximizing heat gains from solar radiation, high thermal insulation of partitions, heat provided by ground source heat pump, and mechanical ventilation system with the heat exchanger. The measurements were performed in normal operating conditions in an inhabited building, throughout the years 2011–2019. For the year 2012, the article also presents the detailed structure of electricity used for particular devices. The objective of the research was to verify whether, in the long term, the building fulfils the energy consumption requirements for passive buildings. The measurements showed that energy consumption for heating was 50% lower than the value required from passive buildings. However, primary energy consumption for the entire building was exceeded already in the second year of research. This was caused by two factors: human behaviors and the type of primary energy source. The research concludes that the maintenance of passive house standard is vulnerable to human impact and difficult in the case of power source characterized by high index of expenditure on non-renewable primary energy. The article also presents recommendations on how to restore the passive house standard in the building. Keywords: passive architecture; energy consumption; long-term measurements 1. Introduction The building sector is receiving increasing attention in policies for sustainable development across the globe. This attention arises from its energy consumption and greenhouse gas (GHG) emissions, which in developed countries represent 30% and 40% of the total values, respectively. The Energy Performance of Buildings Directive (EPBD) [1] aims to improve the overall efficiency of buildings, taking into consideration local conditions, indoor climate, and cost-effectiveness. It is considered that the use of renewable energy in buildings and the promotion of energy-efficient buildings are the best means for resolving the global challenge of climate change and eliminating CO 2 emissions. While there is consensus that the use of energy by buildings and their environmental impact must be reduced, there have been many discussions in the recent years as to the proper means of achieving this. Specifically, the debates [2,3] have focused on the advantages and disadvantages of low-energy buildings, net-zero energy buildings (NZEB), nearly Zero Energy Buildings (nZEB), Passive Houses (PH), green buildings, solar houses, sustainable buildings, and energy-plus buildings. All of these concepts are convincing by themselves, as proven by the large number of exemplary projects around the world. However, we can observe varying definitions for the abovementioned terms in different countries. In fact, they are often confused with each other [4]. Energies 2020, 13, 2801; doi:10.3390/en13112801 www.mdpi.com/journal/energies