Combined effects of diffuse fraction and tilted surface radiation models

The building energy balance is strictly connected with incident solar irradiation, whose reliable estimation on envelope surfaces is essential for the evaluation of building solar gains. While diffuse and beam solar components on tilted surfaces are required, meteorological stations usually measure only global radiation on horizontal plane. In the literature, several diffuse irradiance and tilted surface irradiance models are reported, nevertheless, none is suitable for any locality. In this work, we assess the variability of solar estimation for 264 couples of diffuse and tilted surface models in five European locations. The distribution of the hourly percentage deviation from the median value of the whole population is analyzed. This describes the risk of introducing in building simulation variable uncertainty levels with respect to the standard. Moreover, the quantification of uncertainty caused by the choice of solar radiation models increases the awareness of the reliability of building model predictions.