To design solar equipment and calculate energy performance of buildings solar radiation and irradiation to inclined and diferent oriented surfaces are needed. Measured data exist for horizontal surfaces only. For inclined and diferent oriented surfaces values have to be calculated. Researchers developed many models, which can be divided into two groups: isotropic and anisotropic. Most popular isotropic and anisotropic model are Liu-Jordan and Perez respectively. In several times isotropic models are replaced by anisotropic. In this work calculations and measurements for vertical and inclined surfaces with different orientations were compared. Sense and improvement of calculations due to change to Perez anisotropic model are evaluated with comparison of with some models calculated and measured data. It is confirmed, that change to Perez anisotropic model is reasonable. Transmission of radiation through the glass window was recalculated too to evaluate model change impact. It is found out that, Perez anisotropic model gives more reliable and technical usefull results. As real example, impact of solar radiation on energy performance of greenhouse built at south side of dwelling house, is evaluated.
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