Energy Crisis is a global phenomenon affecting all countries. Buildings are responsible for at least 40 % of the total energy consumption in the most countries, Windows are the essential item that effect in energy efficiency of the building envelope. They are responsible for 60% of building energy consumption . The research paper reviewed the design characteristics of windows that achieve energy efficiency, Evaluation of the student service building using the simulation program (design builder). The design alternative was applied to the window on the building and extracting the reduction rates in cooling and lighting loads. Design alternative was applied in a room in the south and another room in the north. That will make the study of the alternatives is easier. This will help us to choose the best alternatives for each orientation then apply it on the whole building and calculate the saving percentage of energy consumption. The results of the rooms show the rates of reduction in energy consumption. The first alternative was changed the glassing with different types. It was found the best glass is double-low-emission (low-e) the reduction rate reached 24% in the south and 13.5% in the north. The second alternative was changed the frame of the window. It achieved a low percentage in saving energy. The third alternative was using shading. It was found the reduction rate reached 11.6% in the south. The fourth alternative was changed the window to wall ratio (once 15% / 30%) and used the light control. It was found the best window to wall ratio was 15% in the south and 30% in the north. The reduction rate reached 20% in the south and 6% in the north. The final conclusion by apply the best alternatives on the whole building (low-e glassing & horizontal shading in the south) achieved 25.7% as saving energy. The manual calculation of photovoltaic cells is applied on shading in the south orientation. It achieved annual production of energy (24637.5 kwh). That production is considered 13.5% of the whole consumption of the building.