Natural lighting systems are important for the energy efficiency of the buildings. Thus the size of light openings should be optimized to provide visual comfort and decrease the energy needed to provide comfort in the environment. There exist tools to calculate solar energy gain in the buildings of mass construction with enclosing structures in the shape of horizontal and vertical planes. For structures with curvilinear surfaces systems of equations are compiled, to be solved by numerical methods with significant use of computer time. The article proposes a method of simulation solar energy gain for non-standard enclosing structures for buildings surrounded by existing housing using an apparatus of Balyuba–Naidysh point calculation (BN-calculus). Apparatus of BN-calculus allows forming of a point set optimized to match the shape of a geometrical object. Received point set is used to form elementary solid angles within which energy inflows from direct, scattered and reflected solar radiation into computational points are calculated. The sum of elementary values of energy inflows defines the total value of energy gain of the room.

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