## 3 Discussion and Results
### Comparison of Energy Consumption Based on CTE and ASHRAE Standards  
The mandatory energy regulations for buildings, as outlined in the CTE, are designed to reduce energy consumption, encourage the use of renewable energy sources, and enhance the efficiency of building systems. This is accomplished through measures such as improving thermal insulation, optimizing air conditioning systems, and integrating renewable energy technologies, among other strategies. The energy standards set by ASHRAE are somewhat more stringent and, similarly, aim to mitigate environmental impact while promoting long-term sustainability. A comparison of energy use is carried out. The following table shows the results of the energy simulation calculated using the software EnergyPlus (version 8.5.0), comparing the results obtained for the INDUva building according to the current CTE and to the ASHRAE criteria for LEED sustainability certification. Table 5 shows the final energy consumptions broken down into heating, cooling, lighting, and fans and pumps, if applicable. Considering the emission conversion factor (according to Spanish regulations published by the ministry), energy consumption was converted to kgCO\({}_{2}\) equivalent. If the IndUVa building had been built according to the current CTE energy efficiency limitations, its annual energy consumption would be 1,446,568.9 kWh. In contrast, if it were to comply with the stricter ASHRAE guidelines, this consumption would be reduced to 962,757 kWh per year. The results obtained show that the ASHRAE energy standards would allow energy savings of 33.4% compared to the mandatory requirements of the CTE, which in turn would lead to a 26.8% reduction in total CO\({}_{2}\) emissions to the atmosphere. Furthermore, when compared to the actual annual consumption of the nZEB IndUVa building, savings of 78.4% and 85.6% can be observed with respect to the ASHRAE and CTE criteria, respectively. Considering a useful life of 50 years and the useful floor area of the building, Table 6 presents the value of the operational GWP in three scenarios: the most unfavorable case (complying with the CTE constraints), the most efficient case (adopting ASHRAE regulations), and the real case of the nZEB IndUVa building. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **kg CO\({}_{2}\) eq. (50 Years)** &
\begin{tabular}{c} **Operational GWP** \\ **(kg CO\({}_{2}\) eq./m\({}^{2}\))** \\ \end{tabular} \\ \hline CTE & 19,995,398.02 & 3609.47 \\ ASHRAE & 14,637,151.45 & 2642.22 \\ IndUVa building & 3,331,766.30 & 601.43 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparative in the value of the operational GWP for each case. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \begin{tabular}{c} **CTE** \\ **Final Consumption** \\ **(kWh/yr.)** \\ \end{tabular} & \begin{tabular}{c} **ES CO\({}_{2}\) eq./yr.** \\ \end{tabular} & \
\begin{tabular}{c} **Final Consumption** \\ **(kWh/yr.)** \\ \end{tabular} &
\begin{tabular}{c} **ASHRAE** \\ **(kWh/yr.)** \\ \end{tabular} \\ \hline Heating & 998,814.50 & 251,701.25 & 328,222.00 & 82,711.94 \\ Cooling & 340,139.50 & 112,586.17 & 71,478.00 & 23,659.22 \\ Lighting & 107,614.90 & 35,620.53 & 80,038.00 & 26,492.58 \\ Fans and pumps & \(\xrightarrow{}\) & \(\xrightarrow{}\) & 483,019.00 & 159,879.29 \\ \hline
**Total** & 1,446,568.90 & 399,907.96 & 962,757.00 & 292,743.03 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Final energy consumption and consequent CO\({}_{2}\) emissions in the IndUVa building according to the CTE and ASHRAE criteria. Figure 6 below plots the percentages of operational GWP (based on CTE and ASHRAE energy criteria) versus the percentages of embedded GWP (taking into account several of the recycling scenarios discussed above). After analyzing the results, it can be seen that, in the case of a standard building (Figure 6a), the impact of emissions to the atmosphere during the use phase is slightly higher than the impact generated in the previous phases and during construction.