Edifici storici ed efficienza energetica. Palermo come scenario di sperimentazione

Energy efficiency is a substantial requirement for buildings but, as far as the architectural heritage is concerned, its necessity and the related consequences are subjects of debate. Since they represent the artistic and technical culture of the past, historic buildings can be considered as non-renewable resources to be preserved for the generations to come. On the one hand, economic incentives and savings can promote energy upgrade measures which may appear not always acceptable for a preservation aim. On the other hand, keeping historic buildings in use is essential to their conservation. As a consequence, reducing the gap of energy performance with refurbished constructions would be of primary importance. The energy upgrade techniques well-established in recent constructions imply significant risks for the architectural heritage, if their extension to its improvement is uncritical. Nevertheless, the priority of conservation does not necessarily conflict with the need of energy efficiency. Decades of structural reinforcements demonstrate that the detailed analysis of a historic building suggests even relevant possibilities to enhance its performance and at the same time to respect and maintain its aesthetic, material and construction features. Similarly, energy upgrade solutions compatible with cultural value can be identified focusing on the peculiarities of each building and taking into consideration the hygrothermal behaviour of traditional constructions. This work deals with the energy efficiency of historic buildings by focusing on performances and compatible improvements of the envelope. The study involves local contexts, where the characteristics of the architectural heritage are comparable and strategies specific to the building stock can be developed through an analysis of features related to its energy performance. In order to demonstrate this assumption, the architectural heritage of Palermo has been chosen as the main case study. The first part of this work contextualises energy efficiency in the field of historic architecture. In the first chapter this topic is considered as part of the wider concept of sustainability, in connection with the principles of conservation, restoration and protection of historic buildings. The second chapter reviews the most relevant paths of scientific research, while the third discusses several energy upgrade measures, proposed by literature and sometimes applied to monumental buildings as well. The methodology followed in the case study of Palermo can be extended to different local contexts. It is described in the fourth chapter and ranges from the envelope component to the urban scale. As to the area of Palermo, the methodology is related to the detailed data available about materials and construction techniques of its architectural heritage and to the local regulation for the preservation of historic constructions. Following this multi-scale approach, the fifth chapter discusses the results of laboratory and in situ measurements aimed at describing the thermal and hygrometric properties of local historic masonry. The sixth chapter categorises part of the historic centre of Palermo on the basis of building geometry, aggregation in the urban fabric and conservation restraints. The main purpose is relating the typologies set by the local urban regulation to the energy performance of buildings. The seventh chapter analyses three constructions, selected as representative of the corresponding building category. Their current performances and the effectiveness of envelope upgrade measures are assessed through dynamic thermal simulations. The interconnection of these scales of analysis provides a contribution to a general framework of knowledge, which would support the compatible energy improvement of the architectural heritage of Palermo.

La monografia tratta l’efficienza energetica degli edifici storici sotto due profili. A livello generale ne esamina l’intreccio con i principi della conservazione, con la disciplina del restauro, con le prescrizioni di tutela; ripercorrendo il fervente dibattito sul tema, propone una panoramica sui principali campi d’indagine della ricerca scientifica e sugli interventi di miglioramento energetico proposti per il patrimonio culturale. Delineato un quadro d’insieme, il volume si sofferma sulla ricca e variegata architettura storica di Palermo, muovendosi tra la letteratura tecnica disponibile, il Piano Particolareggiato Esecutivo e il Manuale del recupero del centro storico. L’approfondimento, che spazia dai componenti dell’involucro all’aggregato urbano, intende contribuire allo sviluppo di un quadro di conoscenze che integri il miglioramento energetico nelle buone pratiche del recupero e della conservazione degli edifici storici palermitani.