## 4 Discussion
Hence, the apartment unit status was improved from a grade 'C' to 'B', because of the dramatic reduction of the energy consumption of the reference apartment dropping from 123.5 to 75.1 kWh/m\({}^{2}\) (\(\sim\)\(-\)40%), while the corresponding reduction of the apartment's performance dipped from 156.3 to 83.3 kWh/m\({}^{2}\)(\(\sim\)\(-\)47%). \begin{table}
\begin{tabular}{l c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Important Factor Group**}} & \multicolumn{2}{c}{**Sum of**} & \multicolumn{1}{c}{\(p\) & **n**} & **AICc** \\ \cline{2-4}  & **Squares** & & & \\ \hline
**FC2** & 0.3925 & 3 & 14 & \(-\)41.64 \\ \hline
**FC2**, **FC1** & 0.3114 & 4 & 14 & \(-\)40.84 \\ \hline
**FC2**, **FC1**, **FC8** & 0.2293 & 5 & 14 & \(-\)40.06 \\ \hline
**FC2**, **FC1**, **FC8**, **F19** & 0.097 & 6 & 14 & \(-\)45.61 \\ \hline
**FC2**, **FC1**, **FC8**, **F19**, **FC4** & 0.0367 & 7 & 14 & \(-\)50.55 \\ \hline
**FC15** & **FC1**, **FC8**, **F19**, **FC15** & 0.0441 & 7 & 14 & \(-\)43.51 \\ \hline \hline \end{tabular}
\end{table} 
Table 12: The corrected Akaike information criterion scores for sequential factors screening the JR response. \begin{table}
\begin{tabular}{l c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**T**ACTRORS**}} & \multicolumn{2}{c}{**Settings**} \\ \cline{2-4}  & **CODE** & **Original** & **EC** \\ \cline{2-4}  & **Status** & **Solution** \\ \hline
**Automation for Hot Water** & FC1 & no & Yes \\ \hline
**Category of automatic control (choice among 4)** & FC2 & **C** & **D** \\ \hline
**Number of ceiling fan (summer)** & F3 & 0.00 & 5.0 \\ \hline
**Type of heating systems (select from a list)** & FC4 & boiler & Air-cooled heating pump \\ \hline
**Energy source for heating systems (select from a list)** & FC5 & Oil & Oil \\ \hline
**Power of heating systems (only for degree of efficiency)** & F6 & 47.20 & 67.20 \\ \hline
**Energy efficiency ratio of heating systems** & F7 & 0.59 & 0.84 \\ \hline
**Location of distribution network of heating systems** & FC8 & Indoor & Indoor \\ \hline
**Efficiency of distribution network of heating systems** & F9 & 0.86 & 0.96 \\ \hline
**Efficiency of terminal units of heating systems** & F10 & 0.84 & 1 \\ \hline
**Type of cooling systems (select from a list)** & FC11 & Air-cooled & Water-cooled \\ \hline
**Power of cooling systems (only for degree of efficiency)** & F12 & 4.76 & 4.0 \\ \hline
**Energy efficiency ratio of cooling systems** & F13 & 2.36 & 3.72 \\ \hline
**Efficiency of terminal units of cooling systems** & F14 & 0.96 & 0.90 \\ \hline
**Solar water heater** & FC15 & Yes & No \\ \hline
**Power of heating water systems (only for degree of efficiency)** & F16 & 1.27 & 1.27 \\ \hline
**Energy efficiency ratio of heating water systems** & F17 & 1 & 1 \\ \hline
**Recirculation of distribution network (yes or no)** & **FC18** & **No** & **No** \\ \hline
**Efficiency of distribution network of heating water systems** & F19 & 0.84 & 0.92 \\ \hline
**Efficiency of domestic hot water storage system** & F20 & 0.93 & 0.98 \\ \hline
**Type of auxiliary units (select from a list) for domestic hot** & FC21 & No & No \\ \hline
**Type of solar panels (choice among 3)** & FC22 & Simple & Simple \\ \hline
**Utilization rate of solar radiation for domestic hot water** & F23 & 0.34 & 0.34 \\ \hline
**Surface area of solar panels** & F24 & 4.00 & 5.00 \\ \hline
**Energy Consumption of the apartment unit (kWh/m\({}^{2}\)):** & & 156.3 & 83.3 \\
**Energy Consumption of the reference apartment unit** & & **123.5** & **75.1** \\
**(kWh/m\({}^{2}\)):** & & & \\ \hline
**Energy Status Grade (Certification level):** & & C & B \\ \hline \hline \end{tabular}
\end{table} 
Table 13: A comparative energy performance evaluation of the original energy status of the examined apartment unit against a recommended renovation.