This report from the World Business Council for Sustainable Development (WBCSD) is the result of the Energy Efficiency in Buildings (EEB) research project which aim was to develop recommendations and an actionable roadmap to transform the building sector. The project began with an inventory of current and future building stock and modeled the impacts of consumer preferences and behaviors, designs and technologies, and policies on energy consumption, focused on six markets - Brazil, China, Europe, India, Japan and the US - that represent nearly two-thirds of the world's energy use. Detailed analysis shows there is a path to achieving the necessary reductions and that, by 2050, energy savings in buildings can equal the total energy consumed in today’s transportation and industrial sectors combined. The study modeled three scenarios: complacency and inaction, inadequate action resulting in only incremental improvements in energy efficiency, intensive action that transforms the building sector and contributes proportionately to solving climate change. The third scenario is the only one that can result in the energy and carbon footprint reductions. A mix of measures tailored to specific geographies and buildings is required for a complete solution. Additional approaches include building energy codes, labeling and reporting mechanisms, appropriate energy prices and carbon costs, investment subsidies, increased and trained workforce capacity, and evolving energy-efficient designs and technologies that use passive and active approaches. Many energy efficiency projects are feasible with today’s energy costs.