Energy resilience to climate change of historic urban district in Mediterranean area

The scientific sources of utmost importance in impact evaluation and vulnerability caused by climate changes agree to future exposure of Mediterranean area towards an arid climate and of extreme events as heatwaves. Concerning energy issues, residential building stock represent the main object of strategies because of their responsibility in GHGs emissions as well as in ensuring safety and health for their inhab-itant. For that reason, European and national strategies moved towards the improve-ment of building envelope and changing primary sources in order to reduce climate-altering emissions and mitigate effects in a long-term perspective. In addition, climatologist activities in monitoring and testing external changes define a positive contribute in studying future exposure and necessities, supporting the inter-relations between cli-mate, socio-economic and technologies developments. However, the necessity to reduce impacts of uncontrollable events encouraged studies of local urban features and reactions at the same scale in order to reduce the amplification consequences defined by the Urban Heat Island (UHI) effect. Despite they derive from external un-controllable factors, at local scale amplification potentialities of UHI are strictly dependent on built environment and human activities, too. In that sense, several strategies moved towards the identification of best practices in new urban asset and improvement of optical properties in horizontal surfaces (pavements, roofs), supporting and enhancing the adaptability of built urban context and enhancing built market towards cool, reflective and green solutions. In the whole residential built stock in Mediterranean area, buildings in historic urban districts represent an exception in traditional transformation management because of constructional and functional characteristics for specific building typologies and ages can be analysed. Adaptation, transformation and persistence necessities involved in Resilience as the key feature to ensure all them. Borrowing the widest meaning in an energy point of view, Energy resilience is introduced as key feature in management and planning adaptability and energy improvement of traditional building stock in historic district as the “capacity to undergo to the external changes, adapting and transforming itself in order to ensure his persistence”. In detail of them, adaptability as the capacity to react to external conditions – above all for summer temperatures - and transformability, which concerns inherent opportunity for the envelope to be enhanced, should be highlighted in order to promote an energy resilient system of their retrofit. To support all goals, a robust methodology is proposed, embodying the well-established structure of the refurbishment process for the built heritage –analysis, diagnosis and intervention – and the required features of resilience thinking to highlight the refer-ence points of complexity of the strategies. Moreover, undergoing the specificity of all building cases and the management of the whole as a unicum system, the proposed methodology follows a scalar approach: from the district to the buildings in order to provide the types and his behaviours, while opposite process is useful to promote in-tegrated and structured actions. In detail, the methodology concerns six phases: 1. Analytic phase as the systematic investigation of environmental, architectural and constructional features and regulation frame in energy improve-ment and preservation thresholds; 2. Taxonomy phase represents the codification of all collected data in previous scale aiming at the identification of “types” to support the concept of geocluster and to analyse and to perform their representativeness; in depth, types derive from the characterization at district, canyon and finally building scales; 3. Monitoring and testing phase of local behaviour constitutes the main instrument useful to monitor external dynamic processes and test them at different scale; key tool is the direct measure of micro-climate following the direct procedure of evaluation of UHI effect with not-standard instru-ments; consequentially, horizontal analysis at district scale can be evalu-ated with the support of Envimet©. 4. Diagnosis phase concerns the assessment of energy behaviours (bioclimatic attitudes and deficiencies) of the type referring to the environmental conditions. In detail, diagnosis is the result of the iterative process of evaluation of energy consumption variations following widespread strategies useful for mitigation and adaptation purposes. 5. Taxonomy of suitable interventions concerns the phase of the methodology in which deficiencies are evaluated with the transformability capacity of the system and the formal significance of the envelope, in order to provide a system of solutions. 6. Finally, assessment of priorities of intervention at district scale which de-lineate a system of recurrent Minimum Units of Energy “Resilient” Interventions (MUERI), as the result of adaptabilities and transformabilities inherent features; supporting common priorities and controlled actions. To support the methodology, an application on a pilot case, representative of the rigorous frame of landscape maintenance in Apulia Region, in the South of Italy, is presented and discussed. In detail, historic district of Molfetta is representative of several historic coastal towns in the same area, characterized by compact and dense urban arrangement and use of local calcarenitic limestone as construction material. Bioclimatic and critical features are evaluated, supporting results with experimental measures of local micro-climate and the characterization of the whole in a deep canyon compounded by tower houses assessed in series in long block. The high shading effect and good optical properties of materials ensure that exposure during middays of summer period could be reduced. However, previous process of decay transformed locally the district, introducing some exceptions. In addition, roofs represent the weak element in energy requirements but they offer good opportunity of enhancement because of his inherent capacity to be transformed. Considering that frame, thesis is divided in three parts. Starting from the critical review of literature at different level of analysis, chapters 1 focuses on climate changes analysing processes, measures and impacts at global – in actual and future projection – and local micro-scale; strategies and solutions already verified, with a specific focus on the energy effect on buildings and resilient experiences, in chapter 2. As second part, third chapter introduces and frames historic urban districts and their values, correlating them with resilience meaning and previous experiences in energy retrofit; then, fourth chapter delineates the methodology of application.