Energy efficiency: a multi-criteria evaluation method for the intervention on built heritage

The awareness that a historic building is a complex system made up of interdependent parts and endowed with a specific energetic behavior is now widespread. Therefore, the energy improvement of a historic building does not only consist of designing individual construction elements or high-performance materials. On the contrary, it is based on the ability to analyze the buildings and recognize and enhance the specific thermal characteristics of each individual situation. Over the past two decades, the publication of European directives aimed at improving the energy efficiency of existing buildings has led each country to promulgate national guidelines in order to help operators planning and implementing energy improvement actions for historic buildings. The guidelines of the Italian Ministry of Cultural Heritage prescribe a method to evaluate the effectiveness of different energy improvement interventions in historic buildings through a qualitative-quantitative analysis based on static energy simulation. However, the ministerial guidelines do not prescribe any method for the analytical evaluation of other key issues aimed at the success of any energy improvement action for the historic building. Based on the literary and standard review on EEHB 2000–2020, this paper presents a multi-criteria comparative analysis method of energy improvement techniques for historic buildings in order to support operators in choosing the most suitable action for each case study. The method analyses each energy improvement technique according to four parameters: energy efficiency (increase in expected efficiency), compatibility (ability to ensure the protection of the morphological, material, and architectural features of the historic building), durability, and cost effectiveness. The method is based on descriptive and analytic forms for the different parts of the historic building and for the different improvement actions. These have been experimentally verified on a masonry case study, representative of widespread built heritage. The result opens the possibility of implementing the national guidelines and increasing their effectiveness.