Environmental and economic benefits of optimal insulation thickness: A life-cycle cost analysis

The enhancement of energy performance of historic buildings is not a completely resolved theme because both the tools and European directives available to the designer are mainly designed to meet the needs of the new buildings. To improve the energy efficiency of this buildings built without technical installations and designed to exploit the climatic characteristics and local resources, it is necessary to investigate the key parameters that constitute the building envelope. This study presents a multidisciplinary approach allowing to compare the optimum insulation thickness determined from the transmittance values of historical walls measured in situ with the one calculated through literature data. In detail, the methodology includes a preliminary analysis of the historical envelope needed to carry out the in situ measurements of the thermal transmittance and an analysis of insulation material and its thickness to determine the optimal combination between the energy performance of the building and the investment cost for thermal insulation and environmental impact through the life-cycle cost analysis. After applying the methodology to a case study located in Italy, the results revealed that the exclusive use of literature data for the preparation of an energy recovery project for an existing historic building can lead to significant errors.