Techno-Economic Optimization of Thermal Insulation Thickness Across Italian Climatic Zones

Given the significant energy footprint of the building sector, implementing effective optimization strategies is essential. While insulating the opaque envelope is a standard intervention, insulation thickness is frequently determined by energy performance alone, complying with mandatory legislative requirements. This paper proposes a simplified technical and economic framework for identifying optimal insulation thickness. The methodology evaluates annual energy savings alongside economic indicators, such as net operational savings. Furthermore, the model incorporates critical variables, including seasonal heating system efficiency, interest rates, and depreciation rates. The proposed algorithm was validated across four Italian climatic zones, representing a diverse range of Heating Degree Days (HDDs). Furthermore, a sensitivity analysis using a One-at-a-Time (OAT) approach was conducted to evaluate how variability in specific inputs affects net seasonal operating savings. The results highlight that the profitability of the intervention is significantly more influenced by energy market volatility (fuel costs and system efficiency) than by pure financial factors like banking rates. Moreover, it indicates that energy-related inputs exert a more significant influence than economic factors. The study demonstrates that “optimal” thickness is not a static value but varies significantly (by up to 44%) depending on the Italian climatic zone - ranging, for example, from 9 cm in Naples to 13 cm in Trento.