To limit the probability that, where multiple HVAC systems serve a single space, different orders of priority for the operation of heating and, where installed, cooling appliances in the proposed and reference houses will be used as input in the energy model calculations, which could lead to inaccuracy of the model, which could lead to overestimation of the energy used by the reference building or underestimation of the energy used by the proposed building, which could lead to excessive use of energy, which could lead to an unacceptable effect on the environment.