This standard applies to existing buildings@ portions of buildings@ and complexes@ including the envelope and all energy systems in the building@ except process systems. PURPOSE This standard provides criteria that will result in the conservation of energy resources in existing buildings. This standard is directed toward a. providing procedures and programs essential to energyconserving operation@ maintenance@ and monitoring@ b. increasing the energy efficiency of the energy-using systems and components@ and c. upgrading the thermal performance of the building envelope.