The importance of the solar systems to achieve the nZEB level in the energy renovation of southern Europe’s buildings

Nowadays, in the European Union the construction rate of new buildings is very low and therefore achieving the EU targets at the energy consumption level of the building sector is only possible through nearly zero energy renovation of the existing building stock. Reducing energy consumption through passive measures is a priority but this is not enough to achieve the nearly Zero Energy Building (nZEB) level. Therefore, the active systems, namely those that allow harvesting the solar energy to partially replace the use of non-renewable energy, are one of the best solutions to consider. At this level, solar thermal and photovoltaic panels play an important role, mainly in countries with high levels of solar radiation, as in the Southern European countries. Nevertheless, there are still some barriers to overcome for the broader dissemination of the implementation of these systems. One of the most important is that building owners are not fully aware of the life-cycle benefits that systems have at the economic level. As in every new different design approach, the best way to arise awareness is through the analysis of case studies, highlighting the reduced life-cycle costs and potential environmental impacts and other long-term benefits resulting from the integration of these active solutions. Thus, this paper is aimed at assessing the contribution of the solar systems to achieve three levels of energy performance (Basic Renovation, nearly Zero Energy Buildings - nZEB and Zero Energy Buildings - ZEB) in the energy renovation of a multifamily building located in Portugal. From the results, it is possible to conclude that, on an annual basis, and for the Portuguese climate, it is possible to overcome, a large amount of the energy needs for acclimatization and domestic hot water preparation with the integration of these systems. The study also shows attractive cost and carbon payback times resulting from their use.