Historical buildings: energy performance and enhancement

‘Energy efficiency of historic buildings’ is one of the top priorities in European Cultural Heritage Research agenda since about 30% of European buildings is considered as historic. Despite the recent European Directive declares the need to work on the existing buildings, the issue related to the energy performance enhancement in this context has not yet been addressed properly. This implies the analysis of limits and potentials of the current legislative framework, with particular attention to the different ways of protecting landscapes, historic centers and monumental buildings. The research deals with an issue quite overlooked in restoration studies: matching of traditional goals of conservation with the need of improving energy efficiency of historical buildings. Traditionally, protected buildings are preserved for their cultural values, which are defended mainly through limitations of the modifications required by new uses. The problem of the relationship through use, fruition and adaptation in historical buildings has been thus transformed into a “clash” of values. As a matter of fact, the knowledge on energetic behaviour of old buildings have not yet been studied in an adequate way with respect to their complexity, nor there is an agreement about the ways of upgrading general performances taking care of cultural values. Moreover, the specific study of the historical built heritage is very useful to inspire new solutions based on empirical knowledge of the typical pre-industrial world. At present, common practices are set without following any guidelines and shared priority. Taking into account the whole building under the perspective of its energy efficiency suggests to investigate historical building techniques, because only in-depth knowledge of historical materials and building techniques allows to estimate the energy performance according to most useful indicators to evaluate their efficiency. The efficiency evaluation also implies the measurement of some relevant parameters on different typologies of ancient buildings through experimental tests instead of the average data provided by available literature. For this reason, at first the present research aims to implement the database of the experimental measurements on thermal transmittance of historical materials. In this regard, the analysis has been carried out on several ancient walls made of stone, bricks and mixed materials, but there are still few information on floors, windows, etc. The proposed activity also covers the diagnostic measurements necessary for making a energy audit and for proposing the retrofit actions in a logic of balancing very different values. The second step regards the experimentation on energy simulation software and their implementations, in order to consider the characteristics of ancient buildings. At last, the most common calculation tools used for the evaluation of the building energy consumption are those used for contemporary buildings, therefore, do not contain the sufficient information regarding the technical terms and properties of historical elements and their interaction. As a result, these calculation tools have a poor flexibility to the application on historical buildings, and their modelling is not reliable apart from adjusting the inputs appropriately to obtain results close to the experimental data, and this requires the tight collaboration between the experts of restoration and building physics. The experience presented in this paper derived from the need to meet the expertises of both the disciplines of restoration and building physics, and to identify the implementation and conflict solutions which is very hard to resolve by the application of commercial software. The final goal aims to know the actual behaviour of the historical heritage in order to optimize energy efficiency requirements and effectiveness along with preservation of their inherent cultural values.