A probabilistic tool for evaluating the effectiveness of financial measures to support the energy improvements of existing buildings

LCC procedures are commonly used in building retrofit interventions for the evaluation of the costs and benefits of different solutions. LCC methods are also commonly applied to energy retrofit interventions according to UNI-EN 15459. However, these procedures can give significantly different results in relation to the methods used to define the economic and technical parameters used in the calculation. Several authors have highlighted how the uncertainties related to the quantification of the costs of initial investment and maintenance, the economic scenarios (inflation and interest rates), the costs of energy and labor and the »service life» of the components strongly influence the results and the assumption of different data sets can result in significantly different results. Several authors pointed out that it is necessary, prior to these procedures, to perform sensitivity analyzes, useful for understanding if and how each of these parameters can influence the results, which leads to the need to use probabilistic methods. The study reported here analyses the influence that different assumptions about the service life of building components have on the economic benefits brought by interventions of energy requalification. Specifically, through a specially developed probabilistic procedure, the influence on the global costs of different assumptions about the probability distributions and the specific parameters characterizing each of them related to the service life of components useful to realize the thermal insulation was evaluated. the envelope of existing buildings. In particular, four different probability distributions (normal, uniform, left triangular, right triangular), different values of the median have been taken into consideration for the same distribution amplitude and the global costs and the return time values have been evaluated. investment considering different alternative economic scenarios for inflation and interest rate.