HVAC and Major Occupancies in Ontario

I'm currently reviewing the engineering heat loss calculations for a combined garage/office structure with a residential suite above the office. The HVAC designer has assumed that the building is non-residential even though there is a residential major occupancy that would necessitate a higher degree of thermal performance from the building envelope. The area in plan of that occupancy is small (around 15% of the total area) of the building. Is he correct in doing so? Or should I treat this as a scenario where the most stringent thermal performance applies - similar to a fire safety thing. Or can I apportion the thermal performance requirements for the exterior envelope based on the exterior walls of each assembly?

Thanks.