Robustness of multi-objective optimization of building refurbishment to solar radiation model

The energy saving potential of existing buildings in highly urbanized world areas stimulates interest in the introduction of renovation measures. Due to the high economic impact of those interventions, special attention has to be paid to balance energy and economic performance, leading to the definition of the best combination through multi-objective approach. The recourse to building simulation, to improve the resolution and discrimination capability between different renovation configurations, forces us to consider the quality of the input data and leads to robustness issues for the optimal solution. In this regard, a reliable estimation of the global irradiation incident on various tilted surfaces is essential in order to account for the solar heat gains. Nonetheless, many meteorological stations monitor only global solar radiation on a horizontal plane. As a consequence, a variety of mathematical and empirical models have been proposed in the literature for both the subdivision of horizontal solar irradiation into direct and diffuse components and for the calculation of irradiation on tilted surfaces. Besides introducing intermodal uncertainty, no pair of diffuse and tilt irradiation models can provide results with the same reliability for worldwide localities different from those considered for the definition of each model. This research work investigates the extent to which the choice of solar irradiation models affects the confidence levels of the optimal solutions provided by multiobjective optimizations. With this purpose, several multiobjective optimizations are carried out with different solar irradiation models. Semi-detached houses, penthouses and intermediate flat in multi-storey buildings are analyzed with the purpose of broadening the representativeness of the conclusions.