The economic and environmental assessment on the insulation application for buildings in cities with Mediterranean climates

In this study, the heating degree-day method is used to determine the heating energy requirement of four Mediterranean cities (Antalya, Rome, Athens and Valencia). The optimum insulation thickness values are computed for stone wool (SW) and extruded polystyrene (XPS), considering natural gas and electricity as heating energy sources. The optimum insulation thickness varies between 0.010–0.046 m for XPS and 0.020–0.085 m for SW, depending on city and energy source. Applying optimum insulation thickness yields 50–80% reductions in annual heating energy cost, with corresponding economic payback periods ranging from 2.6 to 4.3 years for natural gas and 1.6–7.0 years for electricity. Life-cycle assessment (LCA) reveals that the environmental payback period varies between 0.36–0.68 years for natural gas and 0.54–7.87 years for electricity. Additionally, a novel correlation is proposed for the dependence of ratio of annual saved energy (via insulation) to the annual energy requirement (without insulation) on the ratio of insulating material’s thermal resistance to the wall’s total thermal resistance. The results confirm that application of optimum insulation provides significant economic and environmental advantages.