# From Nearly Zero Energy to Carbon-Neutral: Case Study of a Hospitality Building
## 6 Discussions and Conclusions  
The case study reported in this paper showed that, in order to deliver a carbon-neutral building compliant with a methodologically sound definition, as the one proposed in Section 3, a massive performance improvement is necessary when typical urban conditions are considered, both in terms of operational and embodied emissions. The nZEB objective, as defined in recent years in Italy, and in a large part of the EU [76; 77], is far from what is required to deliver a CNB (the case study shows a reduction of 59% in terms of primary energy, compared to the nZEB threshold). Moreover, a reduction in the operational energy is not sufficient to reach carbon neutrality, but a parallel effort should be made in the selection of materials that feature the best performance in the overall life cycle, including, therefore, construction, installation, and disposal (the case study is characterized by a reduction of 75% in terms of emissions related to construction, of 46% in terms of transport, of 64% in terms of replacement, and of 30% in terms of disposal/deconstruction). This means not only substantially changing the normal practice for design offices (architecture and engineering firms), but also for the construction industry, that appears to be unprepared for this change, since it is still often struggling with the requirements of the nZEB wave [78]. The final performance of real buildings depends, further, on: (i) Occupant behavior and systems management and; (ii) Construction site management (the quality of the construction phase). Both of these aspects are not under the control of the designer and cannot be easily modeled; thus, carbon neutrality might require even more effort than so far reported. All of this may have direct economic consequences, i.e., a CNB may \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Technological Unit Classes** & **nZEB** & **CNB** & **Difference CNB vs. nZEB [\%]** \\  & **[tonCO\({}_{2}\)-eq]** & **[tonCO\({}_{2}\)-eq]** & **Difference CNB vs. nZEB [\%]** \\ \hline Load-bearing structure & 2430 & 562 & \(-\)77\% \\ Vertical envelope & 102 & 42.4 & \(-\)59\% \\ Horizontal envelope & 62.9 & 7.84 & \(-\)88\% \\ Internal partitions & 225 & 39.7 & \(-\)82\% \\ Systems/Plants & 90.6 & 75.7 & \(-\)16\% \\ \hline Total & 2910 & 727 & \(-\)75\% \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Material construction phase analysis and impact comparison (A1–A3) for the CNB and the nZEB scenarios (see Tables 15 and 16, in the Annex, for further details). require, at least in the initial market phase, more capital investments than an nZEB. The major costs may include: (i) The design; (ii) The materials; (iii) The construction site. Economic savings might be reached in the operational phase if the building is properly operated, monitored, and maintained. Thus, in order to enable a market uptake of CNBs, it is necessary to include (and make mandatory) the environmental costs in the overall economic evaluation of a project. This requires a new methodology and a brand-new vision for the construction market. The case study also shows that carbon neutrality can be a difficult goal to achieve by a building, depending on its characteristics (i.e., geometry, destination, location), and, in some cases (typically urban buildings), it can only be reached through a careful carbon offset plan, which either requires additional economic commitments (i.e., the acquisition of voluntary carbon founds on the carbon market, and the provision of energy supply contracts with guaranteed renewable origins), or space (and money) to deliver a vegetation project. Moreover, in many cases, such as the one investigated in this work, urban lots might be too small to provide space for vegetation to completely offset the building's emissions, or a large enough exposed area to install renewable energy generation systems to cover the overall building energy use [1].