This paper reports on developments of what is likely to be the greenest urban office buildings in the world. Seattle's Bullitt Center. Currently under construction, it is designed to operate 011 just the sunlight and rainwater landing on it each year along with the heat source and sink of the ground beneath it. contain 110 materials harmful to people or the environment, provide its users a healthy and delightful place to work, and be built to last 250 years. It will set a new standard for performance-based design and increase awareness of integrated approaches to energy efficient design and construction. This report focuses on the role of integrated design (ID) in achieving the performance goals for this building. Pait one is an assessment of how effectively integrated design informed the design process of the Bullitt Center. Interviews with project team members were used to identify the ID principles and implementation tools employed during the design and construction process, along with their predicted outcomes for the building's performance and realized outcomes in the design and construction process. Part two identifies the integrated design strategies aimed at energy efficiency and the energy savings achieved by each inter-connected system. Measured in terms of PV panels displaced, this analysis illustrates the imperative to match energy demand with supply. A critical element of this equation is the role of occupant engagement in managing the plug loads, predicted to account for nearly half of the building's energy use.