The reduction of energy consumption in buildings is the focus of the European strategy to ensure that future climate and energy targets are reached. This paper focus on the definition of Nearly zero energy buildings (NZEBs) that represent one of the greatest opportunities to increase energy savings in Europe. As this term appears subject to different interpretations, the paper explores the NZEB literature to provide an overview of definitions.The analysis underlines inconsistencies and critical issues among them. The paper also assesses the progress of the NZEB implementation in Europe and it evaluates the main debates arisen around NZEBs. Among these topics, there are:the distinction between energy and primary energy, and between energy sources and energy carriers. Special attention is given in defining primary energy factors for energy carriers produced from renewable energy sources on site, nearby or far. After specifying the role of "plus" buildings, a complementary energy index is proposed to overcome the questioning on the "negative" primary energy index that can be achieved using some of current net ZEB definitions. A proposal for clarifying the meaning of near zero, zero and plus energy buildings is also formulated. The analysis enlightens how, although the attention given to NZEBs increased over the last years, the NZEB topic is still under discussion and not uniformly implemented.
Abstract:Buildings are the focus of European (EU) policies aimed at a sustainable and competitive low-carbon economy by 2020. Reducing energy consumption of existing buildings and achieving nearly zero energy buildings (NZEBs) are the core of the Energy Efficiency Directive (EED) and the recast of the Energy Performance of Building Directive (EPBD). To comply with these requirements, Member States have to adopt actions to exploit energy savings from the building sector. This paper describes the differences between deep, major and NZEB renovation and then it provides an overview of best practice policies and measures to target retrofit and investment related to non-residential buildings. Energy requirements defined by Member States for NZEB levels are reported comparing both new and existing residential and non-residential buildings. The paper shows how the attention given to refurbishment of NZEBs increased over the last decade, but the achievement of a comprehensive implementation of retrofit remains one of main challenges that Europe is facing.
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