The paper introduces the feasibility of achieving zero energy on University buildings in Egypt through retrofitting three buildings affiliated to Faculty of Engineering, Mansoura University) two of them are existing buildings and the third one is under construction (. The paper used the design Builder software, that was used to calculate energy consumption for each building and then to upgrade them. Also, a simulation tool was used to optimize the electricity consumption of the building that is under construction through getting the optimal cooling system. It is evident from the results that retrofitting decreases energy consumption by 50 -90% with the possibility of achieving zero energy by using renewable energy sources such as solar cells.