Energy spent for powering buildings accounts for 40% ($320 billion) of the total U.S. energy expenditure. It is estimated that substantial savings of energy can be earned by using existing hardware, energy-efficiency modeling tools and algorithms (such as "Energy Plus") for retrofit of old and the design of new buildings. But much more can be achieved with modern analysis and control tools based on dynamic systems and control theory methodology, when these are used to optimize the performance of the building system. UCSB highlights the research, commercial, and government laboratory perspectives on the problem of energy-efficient retrofit and design of building systems. (#14827)