Possibly, but it needs an assessment rather than an assumption. An addition changes the home’s heating and cooling demand, and extending ducts does not automatically provide enough capacity or airflow. Have an HVAC professional calculate the new loads and review the existing equipment and duct system. The assessment should consider the addition’s windows, insulation, ceiling height and layout, as well as the rest of the house.
Compare a suitable extension of the existing system with options such as equipment changes or a separate ductless system. Discuss temperature control, equipment location, service access and electrical needs before the addition’s design is finalised. Include this review in home addition planning so comfort is considered alongside room size and finishes. Ask for the reasoning behind the proposed system; there is no single heating and cooling solution that fits every addition.