“Seismic and energy retrofitting” of the historical centres’ buildings. A case study in Enna

Minor architecture of historic centres often shows structural damages leading to partial collapses, caused by lack of maintenance and/or abandonment. The study of methods and techniques for prevention and improvement of minor buildings’ structural performance, characterizing the architectural and technological culture of the place, becomes increasingly important. The paper exemplifies several methods of existing housing recovery through some case studies according to the requirements of "contemporary" functions (static safety, typological adaptation and environmental comfort). Through the analysis of minor architecture of the historical centre of Enna, four case studies were identified with different morphological, typological and technological characteristics, symbolic of part of the existing building stock. These buildings were mostly built in the nineteenth century, up to three floors based on load bearing masonry, iron joists and hollow tiles floors and wooden roofs. Static and energy audits by means of calculation software have been previously made as to develop appropriate interventions taking into account the site characteristics (seismic zone 2 and climate zone E), identifying the seismic risk class and the energy class both before and after the retrofit interventions. The planned structural interventions take into account the necessary changes to create open and flexible spaces instead of rigid division in existing small rooms, imposed by seismic adjustment. Energy retrofitting consists of passive interventions on the envelope insulation (internal and/or external) with high-energy performance and reduced size materials. Finally, the study, basing on the conducted analyses, simulates a strategy of action that gives subsidies related to the effective seismic and/or energetic improvement through measurable parameters and not referring to the total cost of the intervention without verification of achieved results. This political strategy of intervention follows the trends resulting from the recent debate on the "Casa Italia" program following the recent earthquakes in central Italy