Multi-criteria optimization analysis of external walls according to ITACA protocol for zero energy buildings in the mediterranean climate

Abstract Given the recent worldwide environmental issues, there is a need to reduce the energy consumption and the greenhouse gas emissions of the building sector, keeping in mind the whole life cycle assessment of construction materials. Determining the sustainability of the products is complex, and the presence of one or more “eco” features does not necessarily make it “eco” in its entirety. The ITACA Protocol for environmental sustainability promotes the use of recycled, renewable and locally sourced materials. A multi-criteria analysis has been carried out in order to identify high energy efficiency external walls for ZEBs in the Mediterranean climate, privileging eco-friendly building materials. The modeFRONTIER optimization tool, by the use of calculation procedures developed in Matlab, was used to evaluate the dynamic performance of building components. The optimization was performed in terms of steady thermal transmittance, periodic thermal transmittance, decrement factor, time shift, areal heat capacity, thermal admittance, surface mass, thickness and ITACA score. A method for the design of new low-cost residential buildings will be defined; in particular, the final aim is to determine not a single optimal solution, but a set of possible external wall configurations among which the designer can choose the proper solution for his application, according to the Pareto front of the multi-criteria problem. The results underline that, in a warm climate, the best sequences of layers are with high surface mass for the first layer (internal side), followed by common insulating materials for the middle layer and eco-friendly insulating materials for the outer layer.