In the last decade, plan of actions and Directives (as last EPBD 2010/31/EC) have been promoted by United Nations and European Union, aiming to reduce construction sector impact, considered one of the most energy consumer. On its side each government has set ambitious goals to reduce energy needs and emissions, not only focusing on new buildings, but also on the existing ones.
According to latest UNEP (United Nations Environment Program, 2016), in fact, built environment would be responsible for 30% of solid waste production, for 1/3 of the pollutant emission in the atmosphere (about 35% of the total) and 39% of global energy consumption - mainly related to heating and cooling systems.
Historic buildings represent about a quarter of the existing building stock: more than 22.3% of European constructions dating before 1946 (in Italy the percentage is slightly higher - 30%) (Eurostat, Census hub HC53, 2011). Built heritage is a unique and unrepeatable cultural value testimony to be preserved over time for our society (Code of Cultural Heritage 42/2004). Even thought, it doesn’t have to comply with minimum energy performance requirements, it is well-known that preservation aim could be guarantee thanks to refurbishment and management actions during its whole life. Nevertheless, refurbishment interventions shouldn’t compromise the uniqueness of existing constructions for achieving excellent performance values and cost savings. Hence, for each building, a specific design approach is required to ensure its usability and protection, avoiding damage problems (e.g. moisture problems, thermal bridges, etc.), reducing energy use and environmental impact without compromising its value (Pracchi, 2016).
Despite this, public and private investors are pushed for a renewal of the existing one with public incentives and campaigns, which are promoting “retrofit actions”for historic building stock as well: last Italian campaign promoted by the Ministry of Cultural Heritage, called “Patrimonio in classe A” (2017), explained the National trend and interest about this topic. In this context, stakeholders (both private and public) have to face a double problem: they are called to control and reduce consumptionsin historical buildings and,at the same time, they will have to renovate to ensure an use over time,without compromising buildings’cultural and historical value.
Retrofit Guidelines at National (Mibact Guidelines) and International level (FprEN 16883 Guidelines) were recently issued to bridge this gap: they represent an instrument to help public authorities and designers to follow an iterative retrofit process for built heritage. In both cases it is possible to notice some difficulties in their application and the need to be implemented: one challenge is to analyse them, to improve the two procedures through an in-depth study.
Historical buildings represent a unique and unrepeatable testimonial of cultural, documentary, historical and artistic value which must be preserved over time for future generations . According to the concept of “integrated conservation” (Amsterdam Declaration, 1975), it is fundamental for our society to obtain the optimal conditionof usability and protection of historical buildings, without compromising their cultural and historical value.
.......
European Directives, National and Regional laws  established minimum standard requirements for renovation works, depending on climate zone (minimum parameters calculated on single building component; energy classification requirements, related to primary energy value for building; implant efficiency requirements; compulsory introduction of renewables):
a. Requirements’ values are constantly more restrictive, because of technology evolution in construction sector. They are not fitted for historic buildings: adapting historic buildings to follow minimum parameters would mean to adopt heavy interventions on the building envelope, which results to be incompatible from theoretical and practical point of view ;
b. Limits and appropriateness of using renewable resources may be discuss for built heritage, especially in historical centre.
........