2.3 Findings and Discussion
After the Guidelines evaluation, some key finding are here exposed:
- In both Guidelines, the first part is dedicated to knowing the case, meant as lecture and evaluation of possibilities and constraints for a retrofit action (identifying where and how intervene) and not as identification of the main building needs for the assessment of interventions. Hence, it would be necessary to introduce a criteria list composed by previously defining objectives which we intend to achieve. The difference among them is that criteria are guiding principles, while the objectives are specific to the individual case. The whole of criteria and objectives is useful to check the congruence of all retrofit measures according to the preservation needs [8, 16, 35].
- Speaking of the energy performance assessment, the building should be examined considering its thermo-physical behaviour, taking advantage of the knowledge acquired during the elaboration of the restoration project [35]. This means that it is necessary to be able to think and to evaluate non-standard solutions, allowing to respond to the specific case’s needs. Hence, the aim of an improvement action is not "doing everything", but "doing only what you need, where you need it", moving from the idea of ‘Best Available Technology’ to ‘Allowed Best Technology’.
- It is important to avoid considering the improvement actions as a simple saving of money or energy (sustainability does not mean spending less). Improving the performance also means avoiding degradation, not losing important and delicate parts (such as paintings, frescoes, wooden works, etc.), postponing restoration works. A cost-benefit analysis should be considered in a broad sense, including the entire useful life cycle of components or interventions.
- Interventions should be carefully evaluate on building thermal comfort - this point is missing in both documents-, assessing users' comfort parameters (hygro-thermal, visual, acoustic) and - if present- collection needs, to avoid in the next future the need to fulfil this gap (e.g. if the building is overly sealed, probably it would be necessary to add air conditioning and forced ventilation, leading also to a cost increase, as well as an environmental damage, that will reduce the retrofit advantages).
- The assessment of measures is the most important section to be examined: absent in the Italian document, the risk assessment plays a central role in the European one, but deserves some calibration: it doesn’t allow to define a subset of final alternatives, but it is a matrix that collects all retrofit choices data for the multidisciplinary team to discuss - with the effect, however, of losing the different choices’ fallout and a global vision of actions.
- The improvement assessment should consider no single measures, but the whole of actions, considering their effects on the microclimatic change and compliance with building and users' requirements. A systemic approach is necessary to be adopted to avoid rebound effects and unintended consequences, thinking about improvements as long-term opportunities for preserving the building [36].
3. Case Studies Analysis and Selection
In order to validate the procedure, it is necessary to investigate various historic buildings on which test it. Case studies should serve to provide basic data input for the assessment procedure by the examination of the most common categories of heritage buildings in Mediterranean area. Therefore, they also increase the knowledge about the complex cause-effects between use, indoor and outdoor climate, implants and conservation state [37].
Representative buildings of outstanding significance have been selected from a stock of 103 buildings in Sicily, given by Sicily Region and included in the European project PO FESR 2014/2020. A building classification has been necessary for strategically collecting information on case studies. In Figure 6 the building stock is divided in the main 8 building categories.