Although the EPBD Recast focuses on new buildings, the energy and C02 emissions associated with existing buildings refurbishments towards nZEB are worth being investigated because of their huge energy saving potentialities

This thesis work stemmed from the IEE RePublic_ZEB project, in which the Department of Energy was involved, representing the italian contribution. Among the many european projects that took place in the recent years, this is aimed at supporting the refurbishment of public buildings in southern Europe towards the nearly zero energy target. The nZEB concept regarding renovations, in fact, still does not seem to be easily applied by member countries: the past and current IEE programs efforts clearly show that required investments and optimal integration of the technologies suitable for the buildings renovation are among the major barriers to the implementation.

Furthermore, the lack of confidence in the real energy performance of nZEBs and the real risks associated to new technologies of the buildings industry and building owners seem to represent one of the keypoints the resolution of which could possibly solve the problem related to the high investments required in the process. In this context, the RePublic_ZEB proposal is focused on economically sustainable strategies and policies aimed at enforcing the refurbishment of the public building stock towards nZEB levels, according to EU 20/20/20 target. Thus the main objectives are to encourage the South-Eastern European countries to promote on the market a set of concrete technical solutions for the refurbishment of their public building stock towards the nearly zero energy target by increasing the involved key actors' confidence in nZEB, this way taking tangible steps to accelerate the renovation process and boost a real market demand to such buildings.

In order to achieve the above mentioned goals, the key actors addressed are meant to be builders and public building owners, policy developers (authorities), building technology industries and national professionals associations referred to the building industry (as architects and engineers).

The thesis mainly concerned Work Package n° 3 (Assessment of the status quo and analysis of opportunities for refurbishing public buildings towards nZEB) and Work Package n° 4 (Costs/ benefits analysis of the "packages of measures" for the refurbishment towards nZEB): these were also the steps taken in our work, applying cost optimality on the school case study.

Within the first step, the energy efficiency measures to be applied through deep refurbishment interventions on schools were detailed. The interventions were related to the building envelope, HVAC, DHW and lighting systems, including technologies based on the usage of RES. This stage was aimed to define a set of the most suitable building technologies (Energy Efficiency Measures) available on the italian market to reach the nZEB target for the public building stock. Local installers, manufacturers and technicians were involved in the market survey. We committed to being as precise as possible regarding the costs of the several interventions, going beyond the Piedmont Price List in order not to underestimate the evaluations and trying to provide data as close as possible to reality, assuming the real implementation of such a project.

In the following phase, corresponding to the WP4, the most suitable building technologies and technical systems were organized into packages of measures for the cost optimal energy and economic analysis. The aim of this step was to provide quantitative results in terms of saving energy and corresponding cost benefits that, in case of a real refurbishment, could increase builders' confidence in nZEB projects.

For the application of this methodology, an Excel format calculation tool was developed by the Department of Energy at the Polytechnic of Turin, consisting in a series of interconnected sheets able to provide, for each case study considered, the best cost-benefit technology solution aimed at reducing energy consumption, both for new buildings and existing ones undergoing total renovation. The energy assessment was conducted using a quasi-stationary methodology,

in accordance with technical specifications UNI/TS 11300-1/4, in order to predict global energy consumption for individual buildings; the economic assessment was conducted in accordance with standard UNI EN 15459 with the aim to predict the overall cost in a context of new construction or total renovation.

In conclusion, it can be said that, as the nZEB is not yet considered cost-efficient, cost optimal and nZEB requirements still have to be reconciled so that a smooth transaction from cost optimal requirements to nearly zero energy buildings could be guaranteed. This will require significant policy interventions, including increased support for research, development, deployment and demonstration of advanced building technologies. Such european projects are essential for policy makers as they can provide them tools to critically analyze the incentive system of our country, to identify any inconsistencies introduced in the recent past and to search for the opportunities offered by new technologies, in order to optimize the efforts. This is even more important for italian public existing buildings, for which nZEB renovations requirements have just been introduced and common practices still need to be assessed.