# Energy Renovation of Residential Buildings in Hot and
## 2 Methodology
### Case Studies  
This study evaluates the optimum insulation thicknesses to be added to the walls, roof, and FFF of the thermal envelope of the study building that minimize the total heating costs, total cooling costs, and total heating and cooling costs of the energy renovation in each combined climate zone considering four different insulation materials (EPS, MW, PUR, and XPS) and four different systems. Moreover, the existing building openings are replaced by new openings.  
The thermal conductivity of EPS, MW, and XPS is 0.034 W/m\(\cdot\)K, and the thermal conductivity of PUR is 0.025 W/m\(\cdot\)K. The main characteristics of the systems used to meet the heating, cooling, and DHW needs are presented in Table 6. The thermal transmittance of the new openings is 1.92 W/m\({}^{2}\cdot\)K. The new openings are composed of a double-chamber PVC frame and low-emissivity double-pane glass, with 30% of the space occupied by the framework. All the 2018 prices used for the insulation materials [43], the new openings [43], and the different energy carriers (fuels [44; 45; 46; 47] and electricity [48]) are reported in Table 7. Electricity price 1 is used for systems 1, 2, and 3, and Electricity price 2 is used for system 4. The characteristics of the systems used, the insulation materials used, and the new openings, as well as the different prices applied, are the same as in [12], allowing the results of the two works to be compared and to provide an overall reference for Spain.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{1}{c}{**System**} & \multicolumn{1}{c}{**Main Characteristics**} & **Unit** & **Value** \\ \hline \multirow{2}{*}{1} & Thermal performance of the heating oil boiler & - & 0.85 \\ \cline{2-3}  & Thermal efficiency of the electric cooling system & - & 2.00 \\ \hline \multirow{2}{*}{2} & Thermal performance of the natural gas boiler & - & 0.92 \\ \cline{2-3}  & Thermal efficiency of the electric cooling system & - & 2.00 \\ \hline \multirow{2}{*}{3} & Thermal performance of the biomass boiler & - & 0.85 \\ \cline{2-3}  & Thermal efficiency of the electric cooling system & - & 2.00 \\ \hline \multirow{2}{*}{4} & Seasonal coefficient of performance of the electric heat pump & - & 2.50 \\ \cline{2-3}  & Seasonal energy efficiency ratio of the electric heat pump & - & 3.00 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Main characteristics of the different systems.  
\begin{table}
\begin{tabular}{c c c c c} \hline \multicolumn{1}{c}{**Combined Climate Zone**} & \multicolumn{1}{c}{**HED\({}_{\text{lim}}\)**} & \multicolumn{1}{c}{**CED\({}_{\text{lim}}\)**} & **SC** & \multicolumn{1}{c}{**NRPEC\({}_{\text{lim}}\)**} \\ \hline A3-W & 15.00 & 15.00 & 0.60 & 40.45 \\ A3-W * & 15.00 & 15.00 & 0.70 & 48.45 \\ A4-W & 15.00 & 20.00 & 0.70 & 40.45 \\ B3-W & 15.00 & 15.00 & 0.58 & 45.45 \\ B3-W * & 15.00 & 15.00 & 0.65 & 54.45 \\ B4-W & 15.00 & 20.00 & 0.70 & 45.45 \\ B4-X & 15.00 & 20.00 & 0.60 & 45.45 \\ C1-W & 20.45 & 15.00 & 0.30 & 50.68 \\ C2-W & 20.45 & 15.00 & 0.30 & 50.68 \\ C3-Y & 20.45 & 15.00 & 0.60 & 50.68 \\ C4-W & 20.45 & 20.00 & 0.60 & 50.68 \\ C4-X & 20.45 & 20.00 & 0.67 & 50.68 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Limit value of the heating energy demand (HED\({}_{\text{lim}}\)), cooling energy demand (CED\({}_{\text{lim}}\)), and non-renewable primary energy consumption (NRPEC\({}_{\text{lim}}\)), in kWh/m\({}^{2}\cdot\)year, as well as the solar contribution for domestic hot water (DHW) considered (SC), per unit, for the combined climate zones [35]. (*) Non-mainland combined climate zone.  
In addition, the energy, environmental, and economic impacts are assessed for the energy renovation, and the energy renovation is evaluated to determine if it generates an NZEB.