# Energy Renovation of Residential Buildings in Hot and
## 2 Methodology
### Estimation of the Best Energy Renovation Solutions
#### 2.6.2 Estimation of the Economic Impact  
The annual heating and cooling energy cost per unit of exchange surface of element \(y\) of the building, \(EC_{heat,y}\) and \(EC_{cool,y}\), respectively, in \(\upxi\)/m\({}^{2}\cdot\)year, are calculated using the following equations:  
\[EC_{heat,y}=\frac{0.024\cdot HDD\cdot C_{fuel}\cdot U_{y}}{\eta} \tag{28}\]  
\[EC_{cool,y}=\frac{0.024\cdot CDD\cdot C_{elce}\cdot U_{y}}{\varepsilon} \tag{29}\]  
Equations (28) and (29) were adapted from [17]. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **NRPE Conversion Factor** & **TPE Conversion Factor** & **CO\({}_{2}\) Emissions Conversion** \\  & **(kWhNRPE/kWhFE)** & **(kWhTPE/kWhFE)** & **Factor (kg CO\({}_{2}\)/kWhFE)** \\ \hline Mainland electricity & 1.954 & 2.368 & 0.331 \\ Non-mainland electricity & 2.937 & 3.011 & 0.833 \\ Heating oil & 1.179 & 1.182 & 0.311 \\ Natural gas & 1.190 & 1.195 & 0.252 \\ Densified biomass (pellets) & 0.085 & 1.113 & 0.018 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Factors of conversion from final energy (FE) to non-renewable primary energy (NRPE), total primary energy (TPE), and CO\({}_{2}\) emissions [53]. factors such as the air exchange per hour, the thermal bridges, the internal thermal loads, the use profiles, and the climate data of reference climates. The process followed is as follows:  
1. Thermal simulation of the building with HULC [42] in the corresponding reference city (Table 3) to obtain the heating and cooling energy demands of the building per unit of living area per year, in kWh/m\({}^{2}\cdot\)year, taking into account 1.50 air exchange/h for existing buildings [39; 55] and 0.63 air exchange/h for renovated buildings [42]. 2. Evaluation of the final energy consumption for heating, cooling, and DHW and the total of the building per unit of living area per year, in kWh/m\({}^{2}\cdot\)year, using Equations (23)-(26), taking into account the DHW energy demands of [52] for existing buildings and those of [35] for renovated buildings, a null solar contribution for existing buildings, the solar contributions in Table 5 for renovated buildings, the respective thermal performance or seasonal coefficient of performance of the heating system and the thermal efficiency or seasonal energy efficiency ratio of the cooling system (Table 6). 3. Evaluation of the non-renewable primary energy consumption of the building per unit of living area per year, in kWh/m\({}^{2}\cdot\)year, using Equation (27). 4. Evaluation of the total primary energy consumption of the building per unit of living area per year, \(TPEC_{total}\), in kWh/m\({}^{2}\cdot\)year, which is calculated using the following equation:  
\[TPEC_{total}=FEC_{heat}.f_{TPE}^{fuel}+FEC_{cool}.f_{TPE}^{elc}+FEC_{DHW}.f_{TPE} ^{fuel} \tag{34}\]  
where \(f_{TPE}^{fuel}\) is the conversion factor from the final energy to the total primary energy for the fuel used, in kWh\({}_{TPE}\)/kWh\({}_{FE}\), and \(f_{TPE}^{elc}\) is the conversion factor from the final energy to the total primary energy for electricity, in kWh\({}_{TPE}\)/kWh\({}_{FE}\). The aforementioned conversion factors were obtained from IDAE [53] (Table 8) and are the same as those used by HULC [42]. 5. Evaluation of the CO\({}_{2}\) emissions of the building per unit of living area per year, \(EM_{total}\), in kg CO\({}_{2}\)/m\({}^{2}\cdot\)year, which are calculated using the following equation: \[EM_{total}=FEC_{heat}.f_{EM}^{fuel}+FEC_{cool}.f_{EM}^{elc}+FEC_{DHW}.f_{EM}^{ fuel}\] (35) where \(f_{EM}^{fuel}\) is the conversion factor from the final energy to the CO\({}_{2}\) emissions for the fuel used, in kg CO\({}_{2}\)/kWh\({}_{FE}\); and \(f_{EM}^{elc}\) is the conversion factor from the final energy to the CO\({}_{2}\) emissions for the electricity in kg CO\({}_{2}\)/kWh\({}_{FE}\). The aforementioned conversion factors were obtained from IDAE [53] (Table 8) and are the same as those used by HULC [42]. 6.