In the last two years, the presenters have worked on a commercial new construction project as well as retrofits of existing government buildings with the goal of eliminating GHG emissions in a financially viable way. They have developed a process based on parametric simulations, detailed financial analysis, and big data tools to arrive at the most cost-efficient design for the different scenarios. They evaluate Net Present Value, use Life Cycle Cost Analysis, and evaluate cash flow of design options in detail and in combination with the architectural, mechanical and electric design. Energy efficiency and GHG emissions are calculated using whole building energy models in EnergyPlus. They will describe the process and show examples.