## 1 Introduction
#### State of the Art  
[PERSON] and [PERSON] [12] illustrate the Italian pilot action in the IEE-EPISCOPE project [13], focusing on the analysis of energy refurbishment trends of the Piedmont region residential building stock. Three realistic scenarios are investigated by the authors. The first one considers the annual current refurbishment trend and the most common energy efficiency renovation measures. The second scenario applies the measures resulting from a cost-optimal analysis. The third scenario considers the mean annual refurbished floor area necessary to meet the climate protection targets. The main conclusion reached is the need to perform major refurbishments, rather than tighten the requirements. The main differences with the methodology proposed in this paper are:  
1. It was performed for one region, studying the most typical kind of building. 2. The type of refurbishment measures and thermal performance parameters of the elements of the envelope and systems are always an input for the model and as a consequence they are not calculated following a cost-optimal methodology, although one scenario is called \"cost-optimal analysis\". In this paper we will analyze the renovation measures of a pilot building under the scope of a cost-optimal methodology in order to determine the best energy-saving solutions following the recommendations of the Directive 2010/31/EC [11] and the amending EPBD 2018/844/EU [14]. In this sense, the present study is similar to that of other authors who have focused their research on pilot buildings studies, which will be analysed below, highlighting the updates of the present paper. [PERSON] et al. [15] performed an LCC analysis to determine the optimal renovation of a pilot apartment building in Norway. The authors performed an inventory analysis in a similar way to this study, although they do not show the renovation alternatives. As an innovation, the present paper presents the different renovation measures that were considered for the sake of clarity and comprehensibility. [PERSON] et al. [16] show a cost-optimal analysis following the suggestions by the EPBD recast EU directive. Three pilot apartment buildings in Italy were considered. In the LCC methodology assessed by the authors, the alternatives and the optimal renovation measures selected were not explicitly shown in terms of their thermal parameters (U-values of envelope elements) and thermal systems or equipment were not considered. Global alternatives to interventions and results in terms of payback period, net present value and global cost are shown in a very similar way to the Packages of Optimal Solutions in the present study. [PERSON] et al. [17] analysed the renovation of a pilot office building in a warm climate following an LCA methodology. The main difference with the present study is that the building was for office use rather than residential. Nevertheless, the methodology and the main points of interest for the renovation are the same. In this sense, [PERSON] et al. considered 10 different measures for the renovation of the external walls and the effect of thermal bridges in the roof and window joints. The present paper differentiates because it also presents the alternatives considered for roofs, floors, windows, ventilation system and other thermal bridges. [PERSON] et al. [18] showed how the renovation of an existing apartment building in Bologna (Italy) affected its energy performance and indoor temperatures. The study focused mainly on improvements to the facade, which comprised adding insulation and other features (winter gardens, sunspaces, and buffer zones). Ventilation, infiltration and the different U-values of glazing units are considered. The renovation of thermal bridges, roofs, slabs/floor, or active air conditioning systems were out of the scope of the study. This, together with the absence of a LCC calculation, an economic approach and the fact that only one apartment was simulated constitute the main differences with the present work. [PERSON] et al.