Europe’s objective under the 20-20-20 target is to reduce energy consumption by 20% and increase the renewable energy sources by 20% in the overall energy mix. The EU currently imports 82% of its oil and 57% of its gas. The EU can have little influence on external energy markets and energy supply but can influence domestic energy demand. One possible solution to both the above problems is to reduce energy consumption by increasing energy efficiency. Due to increasing energy prices and relatively high percentage of building related energy consumption much effort is invested for energy efficient buildings. Current studies show that improved building energy monitoring and optimization systems can contribute to the reduction of building energy consumption by 15 to 40%. This research addresses the need for integration concepts, holistic monitoring and analysis methodologies, life-cycle oriented decision support and scenario based control strategies through the seamless integration of ubiquitous sensing infrastructures, simulation tools, BIM tools, service oriented architectures and data warehouse technologies. This paper discusses a model driven approach integrating IT systems at design, construction and operation stages of buildings so that monitoring, analysis and optimization of building energy performance can be achieved. The first prototype of the developed system is applied in the EOS Istanbul A.Ş. office building located at Istanbul Technical University Campus within the scope of Tubitak (The Scientific and Technological Research Council of Turkey) funded research project.