The increasing energy consumption of residential buildings in Egypt which reached about 42% of total energy consumption in latest energy statistics, affirms the need for energy conscious design of buildings. Many researches aim at guiding new buildings design to be energy-efficient, however, retrofitting existing buildings can result in significant reductions in energy consumption. This paper outlined different window glass types led to a reduction in cooling loads via the building envelope for the existing building. This paper aims to evaluate the effect of changing windows glass types to reduce energy consumption in the hot arid climate of greater Cairo. The energy analysis carried out by employing advanced simulation via DesignBuilder software for a residential building located in Cairo; this case study analyzed the performance of seven different window glass types in a residential building façade in the different cardinal orientations. The model was validated by taking a field measurement to measure and quantify the temperature of a selected room taken within three consecutive days in May and June 2019 and compared to the simulation tool results, the average error percentage was 2.15%. The results of the simulation showed that changing glass type can reduce energy consumption by up to 18.8%, indicating the significance of energy efficient retrofitting of existing residential buildings.

Office buildings in Egypt require expensive cooling systems, which leads to significant increase in energy consumption in summer. Rising energy prices led to the need for turning to performance assessment tools to evaluate and improve buildings energy performance. There are various world-known rating systems such as Passive House (PH), LEED and BREEAM. While, this research focuses on PH standards considered nowadays to be the most rigorous voluntary energy-based standards in building. This research aims at investigating applicability and effectiveness of using PH standards to achieve energy-efficient performance and improve thermal comfort of office buildings in Egypt. Likewise, energy performance in three office buildings in Egypt was analyzed by e-QUEST simulation. One of the buildings is a new office building in CFC, the second is AEC office building, and the last building is Egypt Tours Tower. New planned office buildings in this research have been designed using PH standards and principles, as well, cost would be looked at to determine whether PH criteria is viable in Egypt. Evaluation of new proposed buildings was done by PH standards. However, final conclusions were that PH standards can be used to achieve energy-efficient performance of medium-rise office buildings in Egypt.