The approach of greening existing buildings, is an urgent necessity, because the greening operation provides the speed and optimal efficiency in the environmental performance, as well as keeping up with the global green architecture revolution. Therefore, greening existing buildings in Iraq is important for trends towards renewable energies, because of what the country went through economic conditions and crises and wars which kept the country away from what took place globally in this issue. The research problem is: insufficient knowledge about the importance and the mechanism of the greening of existing buildings, including its environmental and economic dimensions, by rationalization of energy consumption and preserving the environment. The research objective is: clarifying the importance of greening existing buildings environmentally and economically, providing a virtual experience for greening the presidency building of Baghdad University, through advanced computer program. The main conclusions is: there is difference representing by reducing the disbursed thermal loads amount for cooling in summer and heating in winter through the use of computerized program (DesignBuilder) and that after the implementation of greening operations on the building envelope, which confirms its effectiveness in raising the energy performance efficiency inside the building. Hence, the importance of the application of greening existing buildings approach in Iraq, to bring back Iraqi architecture to environmental and local track proper.
