## 2 Background
In particular, the Authors have proposed a hedonic model by which housing values increase by about $20 for every $1 reduction in annual utility bills. On average, for each additional kWh/[m\({}^{2}\)] of energy consumption, the price is reduced by 0.05% of the total value, whereas a 1-euro reduction in annual energy costs is associated with an increase of 15.5 euro of the property price per m\({}^{2}\)[46; 48]. With reference to the residential rental market, the unit rental price increase reaches 6.22 euro per 1 euro of energy costs saved. Moreover, a decrease of annual energy costs by 1 euro leads to an increase in annual rental income by approximately 0.23 euro per m\({}^{2}\)[49]. In general terms, in the studies aimed at determining the influence of renovation interventions on existing residential assets prices, different methodological approaches capable of evaluating the post-energy intervention economic benefits have been used [50; 51; 52]. In the context outlined, [PERSON] [53] has highlighted that one of most relevant housing refurbishment advantages concerns the increase in value associated with intervention, assuming that the renovation costs are recovered though the property sale. Furthermore, according to [PERSON] et al. [54], the existing renovated properties could achieve high quality equal to a more recent or even new residential property. Moreover, [PERSON] et al. [55] have analyzed the residential buildings market appreciation related to refurbishment initiatives through the creation of a House Price Index (HPI), by estimating an increase of 23% on the final price post renovation. With reference to the real estate market of the Republic of Lithuania, [PERSON] et al. [56] have found an increase in selling price of refurbished residential units equal to 25%. In the European context, the studies carried out by [PERSON] and [PERSON] [23] have analyzed the effects of the Energy Performance Certification (EPC) on the residential prices: by detected a sample of about 32,000 properties, the premiums/discounts in terms of increase/decrease in housing prices resulting from a building renovation have been estimated. In particular, by starting from a housing property characterized by an energy label \"D\" and by considering a sample of residential units with different energy labels and with all other similar characteristics, a rise equal to 10% for label \"A\", 5.5% for label \"B\", and 2% for label \"C\" has been assessed, whereas the discount on the selling price of properties with lower energy label (equal to \(-0.5\%\) for label \"E\", \(-2.5\%\) for label \"F\" and \(-5\%\) for label \"G\") has been observed. Furthermore, in a report developed by Bio Intelligence Service in 2013 [57], the economic benefits deriving from the possession of EPCs both on selling prices and on rental prices for various countries such as Austria, Belgium, France, and Ireland have been investigated. The proposed hedonic regression model has allowed one to determine an average percentage increase for each energy label: in particular, in Austria an increase of 4% for rent and 8% for selling have been observed, in Belgium a growth equal to 2.7% for rent and 4.1% for selling have been found, in France a positive change of 3.2% for leases and 4.3% for sale have been seen, and in Ireland an appreciation of 1.4% in rental market and 2.8% for the sale market have been recorded. With regards to the context of Germany, [PERSON] and [PERSON] [58] have defined a functional correlation between energy savings in monetary terms and the differential on the selling price. Based on a study sample of about 2600 individuals, for energy savings of 1%, an increase of 0.45% on market values has been pointed out. Analyzing the Irish real estate market, [PERSON] et al. [28] have found a relationship between the selling prices and the energy labels of buildings: by analyzing about 15,000 samples and compared to a property of energy label \"D\", increases equal to 9.3% for label \"A\" and to 5.2% for label \"B\" have been identified.