Energy use for heating, ventilation and air conditioning (HVAC) is one of the largest end-use categories in the buildings sector. Thus far, energy
codes and standards in the United States have focused on equipment- and component-level prescriptive efficiency requirements but do not recommend any
particular system type over another. Energy codes and standards also have performance compliance paths, but these are implemented at the whole-building
level and allow trade-offs with other end-use categories.

Building energy codes and standards are now implementing or considering HVAC system-level energy performance metrics in order to move beyond
or supplement component-level efficiency requirements. These new end-use category performance metrics have the potential to provide a new performance
path for achieving HVAC energy savings while providing maximum design flexibility.