A Multi-Criteria Model for the Comparison of Building Envelope Energy Retrofits

Giuseppe Donnarumma, and Pierfrancesco Fiore

Department of Civil Engineering, University of Salerno, Fisciano 84084, Italy

Abstract: In light of the current EU guidelines in the energy field, improving building envelope performance cannot be separated from the context of satisfying the environmental sustainability requirements, reducing the costs associated withthe life cycle of the building as well as economic and financial feasibility. Therefore, identifying the “optimal” energyretrofit solutions requires the simultaneous assessment of several factors and thus becomes a problem of choice betweenseveral possible alternatives. To facilitate the work of the decision-makers, public or private, adequate decision supporttools are of great importance. Starting from this need, a model based on the multi-criteria analysis “AHP” technique isproposed, along with the definition of three synthetic indices associated with the three requirements of “EnergyPerformance”, “Sustainability Performance” and “Cost”. From the weighted aggregation of the three indices, a globalindex of preference is obtained that allows to “quantify” the satisfaction level of the i-th alternative from the point ofview of a particular group of decision-makers.

The model is then applied, by way of example, to the case-study of the energetic redevelopment of a former factory, assuming its functional conversion. Twenty possible alternative interventions on the opaque vertical closures, resultingfrom the combination of three thermal insulators families (synthetic, natural and mineral) with four energy retrofittingtechniques are compared and the results obtained critically discussed by considering the point of view of the threedifferent groups of decision-makers.

Key words: multi-criteria analysis, AHP, building envelope, energy retrofitting, sustainability