Conventional Building Energy Performance and Actual Energy Costs: A Critical Reflection

Energy Performance Certificates (EPCs) provide information about the energy consumption of the building under conventional climate and use conditions. The calculation method compares the envelope efficiency, energy consumption and carbon emissions of the building with those of a “reference building”, of the same location, size, geometry, use and boundary but with thermo-physical characteristics corresponding to the minimum energy requirements in force. Due to its intrinsic definition, the reference building might actually be highly energy-consuming and costly, allowing the actual building to reach a higher energy class thanks e.g., to the use of renewable energies or more performing windows or walls. This study proposes an in-depth analysis of the actual energetic and economic sustainability of buildings on top of the conventional energy classification concept. By exploring variables such as glass surfaces, imported energy consumption and architectural design, the study aims to develop a novel approach to EPCs, based on a novel concept of reference building. The work aims to contribute to the evolution of the EPC definition, providing a more complete overview of the energy and economic performance of buildings. New qualitative indicators are proposed to be included in the EPCs, depicting a more informative picture of the building energy performance. Results show that for the selected case studies, according to the actual EPC methodology, the quality of the envelope would be medium-high, while the novel indicators would present a rather worse envelope performance. The divergence is particularly evident in the case of highly glazed buildings.