Are nZEB design solutions environmental sustainable? Sensitive analysis for building envelope configurations and photovoltaic integration in different climates

It is believed that the overall environmental impacts of a nearly zero energy building (nZEB) are lower than conventional buildings. A question remains: is the most energy efficient solution also the best one in term of environmental sustainability? This paper tries to answer to this question by means of a holistic approach for the combined energy and environmental assessment also considering a new impact analysis method with different weights’ assignment. This approach is applied to a case study of a real nZEB. A sensitivity analysis on the materials selection, on the size and type of photovoltaic system with or without storage is proposed for different climates. The overall results of carried out analyses, indicate that a balance point between energy saving measures and renewable energy should be reached for minimizing the environmental impacts according to the life cycle approach. The combined analysis suggests that under both energetic and environmental point of views, in Mediterranean and Continental climates, it does not pay off to further increase the insulation level also by using innovative materials as vacuum insulation panels. Instead, the environmental analysis indicates that the maximization of installed photovoltaic power, without the integration of the storage system, is the best way to nullify the impacts considering a life-cycle of 50 years. On the contrary, the energy analysis does not recommend to exceed with the installed power but it suggests to associate a storage system for increasing the building self-consumption.