On 16 February 2005, the Kyoto Protocol entered into force with the aim of facing the increasingly real threat of the greenhouse effect and the associated climate changes. Signed in 1997 by more than 160 nations, the treaty was created with the aim of reconciling environmental interests with those of the economy and obliges the countries of the territory to work to drastically reduce greenhouse gas emissions within the period 2008-2012 . At the end of the Kyoto protocol (2012) the European Union has thought up a series of further measures with the aim of carrying on the Kyoto spirit in the following decade. This package of measures called "Plan 20-20-20" is summarized as follows: reducing greenhouse gas emissions by 20%, increasing the use of renewable sources by 20%, reducing energy consumption by 20%, all by 2020 (compared to 1990). The aim of the provision is to combat climate change and promote energy efciency and renewable sources.
The EU Directive 2010/31 (like the previous EU Directive 2002/91) establishes that all the states of the Union must establish precise criteria and limits to be respected for the energy ef ciency of buildings and the plants they serve. This is to limit emissions, which in Europe are 40% due to the civil sector. This involves, in addition to a greater care for the energy ef ciency of the new building, above all the careful redevelopment. The energy certification of the buildings was introduced in Italy in 2005 by Legislative Decree 192 and fully implemented with the issue, in June 2009, from the National Guidelines on Energy Certification of the Edi ci (DM June 26, 2009). Certification is intended to inform the final user / purchaser of a property about the performance and energy characteristics of the property. So every building and every single real estate unit must carry a "label" with the indication of its energy efficiency class. Just as happened with household appliances, this certification is intended to favor the dissemination of high quality standards from an energy point of view and allows the user to make an informed choice. The energy performance certificate must be drawn up by a professional energy expert of existing marriage, very often built without any care from this point of view. Among the most important innovations introduced by Directive 2010/31 EU is the obligation that all buildings built in Europe from 1 January 2021 (1 January 2019 for public buildings) be AD ENERGY ALMOST ZERO, that is to say, there is an energy requirement very low, significantly covered by renewable sources.