The shading system plays a significant role in building envelope design. Also, the shading system geometry controls both the appearance and performance of the building. On the other hand, Christopher alexander -theorist and architect-developed a theory about the impact of certain geometrical rules on human beings' psychological needs. Alexander found that these rules have a great impact in removing anxiety and creating a comfortable feeling to the building occupants. Therefore, this paper

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... igates the following points: first, the external shading, second, the alexandrine rules and theory and third the relationship between alexandrine geometric rules and building sustainability. The investigation is done by analyzing 30 case studies that certified sustainable. The analysis resulted that there is a certain relation between using each of the fifteen alexandrine rule and achieving sustainability of the building.