In Europe coexist a variety of energy concepts and standards with voluntary implementation, all with the common objective of limiting the consumption of resources and streamlining the operation of buildings. Among the best known are the passive houses, zero-energy buildings, active houses, concepts like "minergie" and "effinergie" etc. Moreover, even within these rules there are different approaches, depending on a number of differences: new or existing buildings, residential or non-residential purpose etc. As seen easily, the overall context is quite complex, and a precise and uniform definition of the idea of ​​building with nearly zero energy consumption (so-called "NZEB") constitutes an approach difficult to bring to fruition. The difficulty lies precisely in finding a common ground and define appropriate methods and technologies of execution and assessment - elements that, at present, differ from one European country to another. Typically, buildings with a low energy consumption are equipped with high performance windows in terms of thermal insulation with an optimized coefficient of heat transfer to ensure a high tightness, equipped with devices checked for mechanical or natural ventilation equipped and with systems for heat recovery etc. Through a design that takes into account the principles on buildings liabilities using solar energy, it can get a further improvement in performance, especially by installing mechanisms to collect the sun's heat in the winter and others who reject radiation that during summer. Such objectives can be achieved by integrating modern technologies in real estate assets (such as, for example, solar collectors or photovoltaic panels for electricity production). In addition, any complementary measures are welcome, part of that category, for example, being wind turbines and rainwater collection systems. Still, the current era is dominated by a fairly pronounced confusion regarding the joint strategy which should be adopted in order to achieve the energy efficiency goals.