**5. Discussion**

Overall, it was seen in this study that the installation of photovoltaic panels has a mixed record. Indeed, the installation was heavily oversized. Several results found in this research are similar to those assessed by Lotteau et al. [65,66]. Indeed, those asserted by Lotteau et al. [65] and the divergence of methodology among different researchers with regard to LCA prevented an easy comparison of results at the neighborhood level. However, in the known research, several aspects common to the LCA were studied, such as (i) the operational energy consumption analysis of buildings; (ii) the quantitative analysis of the construction materials; and (iii) the transport requirement analysis and so on. The process ranged from statistical data collection from neighborhoods to detailed simulations based on physical modelling. Mobility management was the most significant element. Indeed, it was the parameter that allowed a reduction in most of the impacts in terms of greenhouse effects, odors, damage to biodiversity and health, acidification, depletion of abiotic resources and photochemical ozone production. The day-to-day use of individual transportation by local residents has a huge impact on the neighborhood's LCA. Eliminating the use of personal vehicles for the benefit of public transport makes it possible to limit the greenhouse effect four times more than to generate all the electricity of the district, thanks to the photovoltaic panels. Thus, mobility management must be one of the issues to be addressed as a matter of priority in any urban reflection. Designing a neighborhood that is sustainable and environmentally friendly, while being disconnected from public transport, is not always the ideal solution. In the past, Mohamad Monkiz et al. [67] also found that mobility management was one of the most important aspects in the LCA study. The criterion of vertical density was also a fundamental element. Increasing the built density of the neighbourhood by elevation of the buildings was environmentally very beneficial. This made it possible to pool many flows, to increase the energy and environmental efficiency of the neighbourhood, and, thus, homogeneously minimize the different environmental impacts. These results were almost similar to those of André Stephan et al. [16], who found that by replacing an area, part suburb, with apartment buildings, allowed to decrease the total energy consumption by 19.6%.

An eco-district must therefore have a certain density. One of the criteria for a sustainable neighbourhood covers this aspect and imposes a density of 30 to 40 dwellings per hectare [68,69]. It was found in this study that the implementation of renewable energy production systems showed a significant environmental balance, as was seen in several research results [70]. This method was useful for limiting the production of radioactive waste and for the cumulative demand for energy. However, the manufacture of photovoltaic panel systems has a negative impact on the LCA in terms of damage to biodiversity and waste produced. Thus, their large-scale implementation does not necessarily seem to be a priority, at least not until their manufacturing and recycling processes are cleaner. On the other hand, integrating rainwater harvesting systems into the neighbourhood has been shown to have a strong impact on the results of an LCA, especially in terms of eutrophication and water use. Intelligent rainwater management should be a priority when designing a neighbourhood. Finally, soil permeability and orientation are parameters that can also improve the environmental record of a neighbourhood, but to a lesser extent. As for the choice of applying the concept of horizontal density to the neighbourhood, by adding more buildings, it can be counter-productive. In the studied neighbourhood, it is seen that the annual energy savings and avoided GHG emissions were less significant than those recorded in one neighbourhood of New York City (7.3 GJ and 0.4 metric tonnes). The main results of this research may be of interest to construction companies, public officials and decision makers for applying the environmental criteria to the planning process of new and existing neighborhoods.
