# The Evaluation of Historic Building Energy Retrofit Projects through the Life Cycle Assessment
## 6 Results  
The results of LCA shows that the kg CO\({}_{2}\) equivalent generated during the phases of construction, transportation, and maintenance; the periodic replacement if needed in the time of 60 years considered for the calculation; and end of life with recycling and waste treatment. CO\({}_{2}\) equivalent is a standard metric measure \"used to compare the emissions from various greenhouse gases on the basis of their global-warming potential (GWP), by converting amounts of other gases to the equivalent amount of carbon dioxide with the same global warming potential\" [9]. The \"energy category\" makes us understand how this value decreases, through the different design choices, from 7,854,186 kg of CO\({}_{2}\) of Scenario A to 6,233,867 kg of CO\({}_{2}\) of Scenario C.  
However, the most important significative data was about the \"material category\" for the three different scenarios. Regarding this category, the best value of \"global warming\" was in Scenario A, but it was obvious because there were fewer design interventions. Figure 10: **Scenario C:** Global warming kg CO\({}_{2}\), calculated considering the amount of operational energy. Figure 9: **Scenario C:** Global warming kg CO\({}_{2}\)-life-cycle stages. Scenario B foresaw an increase in global warming kg CO\({}_{2}\) for the material category aspect of Scenario A because we introduced the use of photovoltaic panels. This technology created a greater impact on the building life cycle, especially for its maintenance and disposal. However, in Scenario C, the value of the \"material category\" dropped significantly because of the thermal insulation made of hemp panels. This value changed drastically, despite the fact that photovoltaic panels were also included (Figure 11). The following figures show details of how carbon emissions are generated within the whole life-cycle of the building construction, i.e., all impact categories (in terms of the percentage of CO\({}_{2}\) emitted for use of new materials, interventions of replacement, and end of life) referred to in Scenarios A-C. The following figure shows the percentage of CO\({}_{2}\) released for each category (Figure 12). Finally, the most suitable design project for the energy retrofit of the villa was Scenario C because hemp materials have different properties that can reduce the amount of global warming, in terms of kg CO\({}_{2}\)  
Figure 11: Global warming kg CO\({}_{2}\)-life-cycle stages. Figure 12: Global warming kg CO\({}_{2}\)-life cycle carbon. All impact categories of the three scenarios. The \"material category\" value was reduced mainly because the plant already removes CO2 from the atmosphere when it is growing. There is a substantial difference between the results from the three design scenarios. The interventions of Scenario A were the most adopted to buffer the problems of humidity of historic buildings, but they were the most ineffective ones because they did not resolve the problem. Scenario B, on the other hand, was less convenient in terms of environmental impacts because it proposes the use of synthetic plastic panels compared to a natural insulating panel such as hemp (Scenario C), which greatly reduces CO2 emissions. There are many studies that confirmed the convenience of bio-based materials for the insulation of the building's walls. Hemp has the advantage of absorbing moisture and releasing it over time, and it is a material totally recyclable compared to polyurethane. It is a thermally insulating material, and the savings, in terms of energy costs, are very high--similar to those of a passive house. It has a remarkable ability to absorb CO2 from the atmosphere, releasing oxygen and accumulating carbon. The hemp material removes CO2 from the atmosphere and oxygenates the soil. Hemp captures four times the amount of carbon dioxide stored by the average tree during its growth phase. It is a transpiring material, thus allowing the envelope to \"breathe\", ensuring a high degree of air healthiness.