to the heritage buildings efficiency improvement has recently led to the publication of two Guidelines: the European Guidelines EN 16883 (2017) [1] and the Italian ‘Guidelines for the improvement of energy efficiency in cultural heritage’ (2015) [2]. This two documents are not mandatory, but they are worth knowing and analyzing: they represent an instrument to help public authorities and designers to follow an iterative retrofit process; however, in both cases it is possible to notice some difficulties in their technical application and the need to be implemented: one challenge is to analyse them, to improve the two procedures through an in-depth study. Other instruments and researchers have been produced on this topic, but not specifically on Mediterranean context.
The intent of this research is to define an integrated assessment strategy to evaluate historic buildings retrofit options, focusing on Mediterranean climate. Final product of this study is expected to be a toolkit for public administrations, cultural heritage authorities and energy performance operators, useful to guide the planning process adopting a whole building approach, including the project data and resources.
1.1 Retrofit options assessment on historic buildings in Mediterranean area: problem statement
The assessment of energy performance in a building provides one essential baseline for identifying the need for improvement measures. For what concerns historic buildings, there are objective difficulties to verifying performances due to their construction singularity, also because their conservation state (thermal bridges, degradations, modifications of the ancient microclimatic system, etc.). Furthermore, buildings are dynamic systems that depend on the variability of external parameters, aspects such as ventilation, occupants rate, surface radiant temperatures and operating temperature should be considered in an energy evaluation.
The Mediterranean climate has heavily influenced the architects’ design choices. During the past, when air
conditioning systems did not exist yet, they used materials, and consequently processed solutions that could mitigate winter and summer climatic extremes: the Roman domus inner courtyard, that illuminated the rooms from the top and collected rainwater;
the building mass consisting of stones trulli, with an opening on the top of the dome, to ensure a good natural ventilation due to the chimney effect and to protect themselves from the heat; white and compact silhouettes of Mediterranean villages to reflect the heat from solar radiation. In the past, the relationship between design and constructive moment was mediated by the so-called rules of the art matured with the passing of time. Today, the dynamics of development of building technology and the continuous
introduction of new materials and components have made more critical the bond between the project and its
application.
1.2 European and Italian Guidelines
The two aforementioned Guidelines are certainly different, although they have the same purpose. The European document is synthetic and aims to guide the lecturer in the proposed procedure; the Italian one is very long with the same features of a volume.
In the first, despite its brevity, important concepts are highlighted. Among them, a few main concepts are: it is important to pay attention not only to exceptional buildings, but also to ancient city centers, focusing on authenticity – integrity – significance of the whole. It is also specified that “Maintenance is the best conservation measure” and in this field “non-standard measures could be considered”. In contrast, the second is a collection of restoration theory concepts (as the important distinction between improvement and adaptation, borrowed from the Italian Guidelines for seismic vulnerability assessment of historical buildings) and technical parts as a support for people performing energy analysis. The text is divided as follows: knowledge of contexts (including environmental quality assessment for historic buildings); energy efficiency assessment (in this part the retrofit procedure flowchart is exposed); energy efficiency improvement (which includes: interventions on buildings and plants, economic analysis and maintenance. Attached there are also a collection of sheets on available materials and a group of case studies.). This section is followed by illustrative papers (all dedicated to photovoltaic insertion), bibliography, glossary and an example of data sheet for the building survey. The italian guide also refers to non-standard solutions (e.g. fixing a second window or a window in contact with the first), underlining, that choices should be made taking precaution of the conservative values. Other solutions linked to the environment are quoted, as the use of trees for shading and water for the evapo-transpiration in dry climate for comfort purposes. The goal is to ‘wisely’ consider a range of possible interventions, focusing on innovative materials; then, explaining pros and cons of a set of retrofit techniques (e.g. interior insulation has a behavior totally different from an external one etc.). However, we will see that one of the main shortcomings is an imperfect integration between theoretical and technical parts.