Abstract
We can mainly identify two groups of models in the literature to calculate solar irradiance incident on building envelope surfaces: horizontal diffuse irradiance models, to distinguish beam and diffuse horizontal components and irradiance models for tilted surfaces, to determine the irradiance incident on inclined surfaces. Due to the fact that solar irradiance data are different depending on location, climatic condition and topographic factors, there is no uniform solar irradiance model that can provide the same level of accuracy worldwide. Furthermore, this is even more critical in mountain areas, characterized by terrain complexity and the presence of specific local climatic conditions affecting solar radiation distribution. In this research, the performance of 22 horizontal diffuse irradiance models and 12 irradiance models for tilted surfaces was assessed to check their suitability for application in mountain regions. The analysis was carried out in the Italian Alps, specifically, in the city of Bolzano, using as a reference the global solar irradiance data collected for both horizontal and vertical surfaces. Moreover, the energy needs for space heating and cooling of 48 simplified building configurations were simulated to quantify the impact of solar irradiance models on the simulated building energy performance.