# From Nearly Zero Energy to Carbon-Neutral: Case Study of a Hospitality Building
## 5 Results
### Environmental Impacts Results
#### 5.2.1 Operational Energy Use Stage B6 Environmental Impacts  
As shown in Table 4, in the CNB scenario, the electric energy supplied by the power grid is equal to 58.05 \(\mathrm{MWh_{EL}}\)/year, or 2902.5 \(\mathrm{MWh_{EL}}\) during the entire life of the building (50 years). In terms of the CO\({}_{2}\)-eq emissions, a factor equal to 0.414 \(\mathrm{tonCO_{2}}\)-eq/\(\mathrm{MWh_{EL}}\)[67, 68] was used. Therefore, the environmental impacts due to the electric energy use are equal to 1201.6 \(\mathrm{tonCO_{2}}\)-eq. In this scenario, in addition to the emissions related to the electricity supplied by the national grid, CO\({}_{2}\)-eq emissions due to the natural gas consumption for the operation of the micro-CHP systems should be considered. Adopting the value reported in Table 4 for electricity and natural gas, and the two allocation scenarios described in Section 4.4.3, the total \(\mathrm{tonCO_{2}}\)-eq emitted during the entire life of the building were calculated and are presented in Table 5. To assess the CHP impacts on the production of electric and thermal energy, the emission factors presented in Section 4.4 were used according to the exergetic (1), and electricity allocation (2), scenarios. The latter is the worst and the more conservative scenario; for this reason, a total environmental impact of the use phase (B6), equal to 3980.7 \(\mathrm{tonCO_{2}}\)-eq \(\mathrm{50\ years}\), was considered for the CNB scenario.  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline \multicolumn{5}{c}{**End-Uses Electric Energy Use per Year**} \\ \hline
**End-Use** & **nZEB Scenario** & **CNB Scenario** & **Unit** & **Difference CNB vs. nZEB \%** \\ \hline Bedrooms & 14.4 & 14.4 & \(\mathrm{MWh_{EL}}\)/year & \\ Common areas lighting & 7.5 & 7.5 & \(\mathrm{MWh_{EL}}\)/year & 0\% \\ Common areas (appliances, etc.) & 6.8 & 6.8 & \(\mathrm{MWh_{EL}}\)/year & \\ DHW & 196.1 & 80.5 & \(\mathrm{MWh_{EL}}\)/year & \(-\)59\% \\ Heating/cooling & 161.6 & 89.5 & \(\mathrm{MWh_{EL}}\)/year & \(-\)45\% \\ Total electric energy use per year & 386.4 & 198.6 & \(\mathrm{MWh_{EL}}\)/year & \(-\)49\% \\ \hline
**Natural gas consumption per year (not available for the nZEB scenario)** & & & \\ \hline CHP & n.a. & 19.710.0 & \(\mathrm{m^{3}}\)/year & n.a. \\ CHP & 210.7 & \(\mathrm{MWh}\)/year & \\ \hline
**Electric energy produced on site per year** & & & \\ \hline Photovoltaic production & 18.5 & 22.3 & \(\mathrm{MWh_{EL}}\)/year & +21\% \\ CHP production & 0.0 & 118.3 & \(\mathrm{MWh_{EL}}\)/year & n.a. \\ Total electrical energy produced on site & 18.5 & 140.6 & \(\mathrm{MWh_{EL}}\)/year & +662\% \\ \hline
**Thermal energy produced by CHP** & & & \\ \hline Thermal energy produced by CHP & n.a. & 47.3 & \(\mathrm{MWh_{TH}}\)/year & n.a. \\ \hline
**Electrical energy supplied by the electricity grid per year** & & & \\ \hline
367.9 & 58.0 & \(\mathrm{MWh_{EL}}\)/year & \(-\)84\% \\ \hline
**Nonrenewable primary energy demand per year** & & & \\ \hline \hline \end{tabular}
\end{table}
Table 4: nZEB and CNB energy performance per year.  
Concerning the nZEB scenario, as shown in Table 4, the onsite production of electric energy is equal to 18.5 MWh/year, and the electric energy use is 367.9 MWh/year. Therefore, considering the same emission factor for electric energy supplied as in the CNB scenario (0.414 tonCO\({}_{2}\)-eq/MWh\({}_{\rm{EL}}\)), and a service life of the building of 50 years, the environmental impact of the use phase in the nZEB scenario is equal to 7615.9 tonCO\({}_{2}\)-eq 50 years-