Zero Energy Buildings: a proposal of a simplified tool for the ZEB status assessment

The European and national standards concerning energy saving strategies are nowadays paying greater and greater attention to the building construction area in order to achieve the ‘Zero Energy Building’ (ZEB) goal. Nevertheless, the available assessment methods are often used as tools to verify and assess the building energy behaviour when the design is already completed, rather than as tools for a preliminary assessment and choice of different design technologies and solutions. Not least, these tools can be not intuitive and suitable for many designers, especially for those working in the field of minor residential constructions, where they have not been used until a few years ago. To solve this gap, after analysing some of the available assessment methods, a simple and intuitive spreadsheet, named ZEBAPD, able to give a first preliminary assessment of the ZEB status, has been developed. The paper describes the structure of the tool: starting from fixing the system boundary conditions, it evaluates the building envelope thermal behaviour, the building services solutions and renewable energy systems. The tool produces as an output the building ZEB status evaluation. This simple spreadsheet can be used to evaluate the effect and the incidence of different technical solutions or building services systems on the building primary energy consumption, giving the designers a quick and intuitive tool to assess the quality and the effectiveness of their design choices for the ZEB goal achievement. Moreover, it shows immediately where are the weaknesses of the analysed building and it allows to clearly identify the possible intervention strategies to improve it, whether regarding building envelope, building services, or both.