For the Energy and Atmosphere Credit, Enhanced Commissioning, the Commissioning Authority (CxA) plays a crucial role in overseeing the commissioning process. The CxA must be independent of the project's design and construction team to maintain objectivity. An employee of the architecture or engineering firm involved in the project could potentially have a conflict of interest. Similarly, a member of the construction team could also have biases that might affect the commissioning process's integrity. Therefore, a sub-consultant to the architecture or engineering firm, who is not part of the project's design team, is an appropriate choice for the CxA role, ensuring independence and impartiality in the commissioning process. Reference:

LEED v4 for Interior Design and Construction Reference Guide, particularly the section on Energy and Atmosphere Credit, Enhanced Commissioning