# From Nearly Zero Energy to Carbon-Neutral: Case Study of a Hospitality Building
## 5 Results
### Environmental Impacts Results
#### 5.2.2 Whole-Building Lifecycle Environmental Impacts  
According to the hypotheses and the calculations described so far, the environmental impacts of both scenarios are presented in Table 6. The CNB demonstrates its capability to reduce overall CO\({}_{2}\)-eq emissions by 55%, compared to the nZEB scenario. The use phase of the building (B6) has the highest impact in terms of emissions in both scenarios, accounting for 79% of the total emissions in the CNB scenario, and for 68% of the total emissions in the nZEB scenario. The second most impactful phase is the one related to the production of construction materials (A1-A3), which accounts for 14% of the total emissions in the CNB scenario, and for 26% of the total emissions in the nZEB scenario. Details about this phase are reported in Table 7. The remaining life cycle phases, i.e., transportation, construction and installation, replacement, and disposal of material, have an overall impact of 7% in the CNB scenario, and 6% in the nZEB scenario.  
\begin{table}
\begin{tabular}{l l c c c c c} \hline \hline  & **Life Cycle Phase** & \multicolumn{2}{c}{**nZEB**} & \multicolumn{2}{c}{**CNB**} & \multicolumn{2}{c}{**Difference CNB vs. nZEB [\%]**} \\  & **[tonCO\({}_{2}\)-eq]** & **[\%]** & **[tonCO\({}_{2}\)-eq]** & **[\%]** & **Difference CNB vs. nZEB [\%]** \\ \hline A1–A3 & Construction materials & 2910.0 & 26\% & 727.4 & 14\% & –75\% \\ A4 & Transport & 57.1 & 1\% & 31.1 & 1\% & –46\% \\ A5 & Construction/installation & 52.1 & 1\% & 52.1 & 1\% & 0\% \\ B4–B5 & Materials replacement & 361.8 & 3\% & 130.4 & 3\% & –64\% \\ B6 & Energy use & 7615.9 & 68\% & 3980.7 & 79\% & –48\% \\ C1–C4 & Disposal/deconstruction & 135.3 & 1\% & 94.5 & 2\% & –30\% \\ \hline  & Total (A1–C4) & 11,132.1 & 100\% & 5016.2 & 100\% & –55\% \\ \hline \hline \end{tabular}
\end{table}
Table 6: Building carbon footprint for the analyzed scenarios (CNB vs. nZEB) in the whole lifecycle.  
\begin{table}
\begin{tabular}{l c c} \hline \hline \multicolumn{2}{c}{**Impacts Due to the Electric Energy Supplied by the Electricity Grid**} \\ \hline Annual electric energy supplied by the electricity grid & 58.05 & MWh/year \\ Electricity emission factor from the national grid & 0.414 & tonCO\({}_{2}\)-eq/MWh \\ Impact of electric energy from the national grid (50 years) & 1201.6 & tonCO\({}_{2}\)-eq\({}_{50\text{ years}}\) \\ \hline \hline \multicolumn{2}{c}{**CHP Impacts**} \\ \hline Annual electricity produced & 118.3 & MWh/year \\ Annual thermal energy produced & 47.3 & MWh/year \\ CHP emission impact Scenario 1 (50 years) & 2743.6 & tonCO\({}_{2}\)-eq\({}_{50\text{ years}}\) \\ CHP emission impact Scenario 2 (50 years) & 2779.1 & tonCO\({}_{2}\)-eq\({}_{50\text{ years}}\) \\ \hline \hline \multicolumn{2}{c}{**Total Environmental Impacts of the Building Use Phase (B6)**} \\ \hline Impacts of CHP (Scenario 1) + impacts due to the electric \\ energy supplied by the electricity grid (50 years) & 3945.3 & tonCO\({}_{2}\)-eq\({}_{50\text{ years}}\) \\ Impacts of CHP (Scenario 2) + impacts due to the electric \\ energy supplied by the electricity grid (50 years) & 3980.7 & tonCO\({}_{2}\)-eq\({}_{50\text{ years}}\) \\ \hline \hline \end{tabular}
\end{table}
Table 5: Total impact during the project building use phase (B6) for the CNB scenario.