## 1 Introduction
### The Role of Perceived Benefits  
Energy efficiency benefits can be divided into two groups: Macroeconomic ones (environmental, economic and social) and private ones (user level as building quality, economic and users' wellbeing) as shown in Figure 1. This section looks in particular at a small part of private co-benefits, mainly economic and wellbeing (thermal and environmental) as these aspects are more tangible for users in a first awareness phase, especially the advantages of energy efficiency improvements in residential context, but also seems to be the most influential in fostering the diffusion of efficient premises. Regarding private co-benefits studies, at a European level it can be noted some tendencies on co-benefits categories with higher representativeness on energy retrofits. [PERSON] et al. (2015) found that thermal transmittance improvement (i.e., reduction) is perceived as a way to improve thermal comfort and external noise, gain certainty on energy bills (since it is exposed to energy price fluctuations) as well as providing social pride and prestige. This latter \"signalling effect\" has also been pointed out by [PERSON] et al. (2016). That evidence is in line with the work of [PERSON] et al. (2017) that stress the relevance of energy efficiency co-benefits especially in the case of low-income households. Accordingly, for that group these benefits positively affect community pride, improved access to local services and social cohesion ([PERSON] et al., 2017). Thus, private co-benefits are presented also in the form of sociological rewards for responsible consumption. Previous research has also assessed the relevance of co-benefits. Table 1 contains a selection of studies aimed at quantifying direct benefits and co-benefits of thermal retrofits in three countries coming from the review of [PERSON] et al. (2018). The co-benefits assessed in such a table include comfort, avoided CO\({}_{2}\) and other non-Greenhouse Gases pollutants (e.g., of non-GHG: SO\({}_{2}\), NO\({}_{2}\) or PM), reduction of hospital admissions, avoided excess winter mortality and morbidity, as well as reduction in days away from  
Figure 1: Energy performance’s benefits and co-benefits classification. Source: Self elaboration from the study “Impact of co-benefits on the assessment of energy related building renovation with a nearly-zero energy target” ([PERSON] et al., 2015). school and work. Clearly, as shown in Table 1, the ratio of benefits to costs (B/C) increases when considering co-benefits. In Ireland the ratio is 1.7 considering only net direct benefits such as energy-savings and it increases up to 2.0 when co-benefits are included; in New Zealand it increases from only 0.44 or 0.35 (depending on the discount rate) to 1.87 or 1.51; and in Hungary it increases from 0.9 to 2.6 (in a middle-intensity retrofit scenario--MID retrofit scenario) or 1.7 (in a deep retrofit scenario--DEEP scenario), suggesting that intensive retrofit scenarios are not necessarily the most profitable. Table 1 also provides the relative importance of co-benefits according to its net present value at the indicated discount rates. Interestingly, if only energy savings are taken into consideration, the paybacks are measured in decades, while if co-benefits were included, such time would be dramatically reduced. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Ireland** & thermal & \multirow{2}{*}{Control} & \multirow{2}{*}{31} & \multirow{2}{*}{5\%} & \multirow{2}{*}{1.7} & \multirow{2}{*}{1111 MC} & \multirow{2}{*}{2.0} & \multirow{2}{*}{3124 MC} & \multirow{2}{*}{75\%} \\ \cline{5-5} \cline{8-10} source: [PERSON] et al. [19] & thermal & & &  
Regarding health co-benefits [PERSON] et al. [22] stress the relevance of some of them which especially affect the low-income households:  
* Indoor average temperatures: As example, the indoor temperatures should be maintained above 18 \({}^{\circ}\)C, otherwise the prolonged exposure to lower temperatures may cause physical unrest and even mental diseases [23; 24].