Nuove strategie d'intervento sul patrimonio costruito. La prefabbricazione leggera nella valorizzazione del tessuto edilizio esistente/ New intervention strategies on built heritage. The light prefabrication for the enhancement of the existing building fabric

Today it's possible to highlight some international studies, plans and cultural projects that have worked on the issue of density, the consumption of soil, the exploitation of existing assets as an opportunity for sustainable development of the city, promoting initiatives that would promote the recovery or the conversion of existing buildings through the use of infill spaces, like as roofing and building envelope, with elevations operations, additions and supplements. This phenomenon has led to a rethinking of development strategies of the urban fabric, on the one hand as a possible growth model to consumption of ground zero, and second to regulate informal practices in urban and architectural terms. The paper proposes, through a critical analysis of some representative case studies, new intervention strategies for the enhancement of existing buildings, with the intention to understand the values of their sustainability. In Europe this define an interpretative framework of possible solutions for intervention on existing built environment. Focusing on the architectural scale, it shows the range of solutions pursued by the technological point of view, related to the physical condition of the building and the context of action. If from the composition approach prevail different attitudes, from technological it is prevalent the use of industrialized light systems , meeting the need of weight reduction and times shipyard. In particular, the prefabricated systems are characterized as the solution most frequently used in different contexts, also between their very distant. These systems applied according to several degrees of prefabrication, adapt to the different starting conditions of the building, the site and the objectives of development inherent in the project. They allow a strict control of the process, from the planning stage to construction, which results in a careful control of costs and a reduction of the yard times to simple assembly phase. These conditions, combined with the environmental performance of wood, can reach high levels of environmental and economic sustainability, showing the effectiveness of these technologies in renewal strategies on the existing urban fabric.