C406.9 High performance service water heating in multifamily buildings. For a whole building, building addition or tenant space with not less than 90 percent of the conditioned floor area being Group R-2 occupancy, not less than 90 percent of the annual building service hot water energy use shall be provided by a heat pump system with a minimum COP of 3.0. This efficiency package is allowed to be taken in addition to Section C406.8.2.