## 3 Computational Methodology
### Energy, Environmental, and Economic Performance Indices  
The improvement in building energy performance was evaluated based on energy baseline in conjunction with the key performance indicators for energy (KPI) determined by the ISO 50001:2018 standard [38], which is given as:  
\[KPI=\frac{\sum_{i=1}^{a}E_{m,i}}{\sum_{i=1}^{a}E_{s,i}} \tag{3}\]  
where \(E_{m}\) represents the actual energy consumption measured in the medical center (corresponding to the baseline) and \(E_{s}\) the results of electrical energy consumption estimated from the computer simulation. The comparison period is usually conducted over a month with daily or hourly \"a\" values. If the KPI \(<\) 1, it means that in said month, technologies implementations improve energy performance regarding the energy baseline. On the other hand, values above unity indicate that the implemented strategies are counterproductive. Regarding the reduction in environmental impact, the carbon equivalent emissions index (CEI) was used [39]. For this work, this was defined as the monthly polluting agents emitted to the atmosphere (translated into kilograms of CO\({}_{2}\)) derived from electrical consumption to satisfy the medical center's operational and thermal comfort needs:  
\[CEI=\sum_{i=1}^{a}E_{x,i}EF \tag{4}\]  
where subscript x represents the building electrical energy consumption either for the baseline (\(E_{m}\)) or for the energy improvement simulations (\(E_{s}\)). In the same way, EF is defined as the emission factor of the electric power supplied by the Mexican federal government. The emission factor (EF) value used in this study is reported in Table 6, with information obtained from the Mexican Energy Regulatory Commission (CRE). \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Lot**} & \multirow{2}{*}{**Scenarios**} & \multicolumn{2}{c}{**Passive Systems**} & \multirow{2}{*}{**Active System**} \\ \cline{3-3} \cline{5-5}  & & **Roof** & & **Walls** \\ \hline \multirow{4}{*}{A} & A-I & polyurethane insulation & None & Conventional air conditioner \\  & A-II & reflective coating & None & Conventional air conditioner \\  & A-III & polyurethane insulation/reflective coating & None & Conventional air conditioner \\  & A-IV & green roof & None & Conventional air conditioner \\  & A-V & None & Reflective coating & Conventional air conditioner \\ \hline \multirow{4}{*}{B} & B-I & None & None & Inverter air conditioner \\  & B-II & polyurethane insulation & None & Inverter air conditioner \\  & B-III & reflective coating & None & Inverter air conditioner \\  & B-IV & polyurethane insulation/reflective coating & None & Inverter air conditioner \\  & B-V & green roof & None & Inverter air conditioner \\  & B-VI & None & Reflective coating & Inverter air conditioner \\ \hline \multirow{4}{*}{C} & C-I & polyurethane insulation & Reflective coating & Inverter air conditioner \\  & C-II & reflective coating & Reflective coating & Inverter air conditioner \\ \cline{1-1}  & C-III & polyurethane insulation/reflective coating & Reflective coating & Inverter air conditioner \\ \cline{1-1}  & C-IV & green roof & Reflective coating & Inverter air conditioner \\ \hline \end{tabular}
\end{table} 
Table 5: List of passive and active strategies to reduce energy consumption in the outpatient medical center. Finally, the cost-effectiveness of energy efficiency strategies adopted was evaluated by quantifying the economic indicators: net saving (NS). It estimates the economic benefit considering the evolution of savings and costs over time. According to [PERSON] et al. [35], NS is given by:  
\[NS=-I_{O}+\sum_{t=1}^{N}\frac{S_{t}(1+e_{s})^{t}}{(1+d)^{t}}-\sum_{t=1}^{N}\frac {C_{t}(1+e_{c})^{t}}{(1+d)^{t}} \tag{5}\]  
where \(I_{O}\) is the initial investment, \(S_{t}\) is the saving difference in the year \(t\), \(C_{t}\) is the cost difference in the year \(t\), \(N\) is the number of years in the life cycle, \(d\) represents the discount rate, and \(e_{s}\) and \(e_{c}\) are the annual inflation rate for saving and cost, respectively.