Establishes building greenhouse gas (GHG) emissions and energy consumption performance levels for existing buildings. This standard provides compliance requirements that will result in improved energy efficiency and reduced GHG emissions of existing buildings. Directed toward a. Setting performance targets based on operational GHG emissions and energy consumption, b. Accommodating progressively more stringent performance targets, c. Providing a technical basis for setting building performance standards and d. Providing procedures and programs essential to energy-efficient operation, maintenance, management, and monitoring. Applies to existing buildings, portions of buildings, and building complexes, including the envelope and all systems in the building. This standard excludes industrial and agricultural processes in buildings for which the energy consumption and emissions targets do not include those processes. Dual units of measurement.