Recent years have witnessed tremendous developments in building techniques at the world level, which have led to major changes in the design treatments of facades' openings in office buildings so the building performs its function without an increase in heat gain, especially in countries with a hot climate. On the local level, the importance is directed toward the shape of openings from the aesthetics view without paying attention to their active role in decreasing the heat gain. This research article is aimed at studying impact of design treatments for openings of office buildings' facades on reduction of the heat gain inside inner spaces. This calls for shedding light on the factors, which affect the thermal penetration through these openings and their demand from design treatments along with a study analysis for the important treatments which can be applied for these buildings. To achieve the goal of the present article, a study is conducted for facades' openings  of three office buildings at the international and regional levels, which has the same climate (hot and dry) to investigate the factors, which affect the thermal performance of  these buildings and associated reduction of energy consumption while maintaining natural lighting in their spaces. It is concluded from the study that the use of Alkolestra in front of openings achieved opacity ratio up to 60% for the eastern and western facades with a subsequent reduction of cooling loads by 20%. Also, the use of smart dynamic curtains helped in reducing penetration of solar radiation inside the building by more than 50% against 60% on using green vertical areas. The use of sun-breakers achieved shading ratios between 95% and 100% in the buildings under study. These results confirm the positive role of the design treatments for facades' openings of buildings in decreasing their heat gain.