In my graduation thesis I analysed the influence of building's floor plan shape on its insolation, or more precisely, on insolation of its vertical external envelope. Buildings were located on the area of the city of Ljubljana. The models of buildings were modelled using Google SketchUp 2016. Nine different models were defined, which were divided into two groups – buildings with simple (square, rectangular and circular) floor plan shapes and buildings with complex floor plans (shapes of O, H, U, T, Y and L). Analysis was carried out with the use of a Sunhours application. Insolation of the models was researched with changing theirs geometrical characteristics (height and floor plan dimensions). Insolation of analysed buildings was evaluated using two methods: comparison of the building's allyear cumulative insolation of its external envelope and comparison of the building's envelope area
normed potential of the insolation of its external envelope. I concluded that for evaluation of the buildings in terms of insolation, method with envelope area normed potential of the insolation is more suitable. External envelope's total surface area has a fundamental influence on the results in this method. Through the acquired results, the Y shape building was shown as the best in terms of insolation.