Define the rooms that need comfort
Show the designer which bedrooms have closed doors, their locations, and the temperatures you want. Include upstairs rooms, distant corners, and other rooms that need cooling at night.
Ask for room-by-room heating and cooling needs and an explanation of how each room will receive conditioned air.
ENERGY STAR's installation guidance highlights the difficulty of air movement between rooms, especially with closed doors. That is a reason to design bedroom coverage explicitly. ENERGY STAR ductless installation guidance.
Compare coverage plans
Have the provider explain options such as separately served rooms, an appropriate compact ducted arrangement, or retaining existing cooling where needed. Ask a qualified designer to assess any proposed air-transfer arrangement and related work.
Do not choose a larger common-room unit simply because the bedrooms are too warm. Request evidence that the chosen system fits both the common area and the individual rooms.
For each option, ask about the number and placement of indoor units, controls, sound near beds, maintenance access, electrical work, and the installed equipment combination.
Be specific about a fan proposal
If the provider recommends fans, ask where they operate, whether doors must remain open, and what comfort limits are expected. Will the plan still work when someone wants privacy or dislikes fan noise?
Request a clear explanation of the conditions assumed in the design. If you already have the system, record room temperatures with doors in their normal positions and ask the provider to evaluate the difference.
Do not cut door openings or alter walls as an experiment. Any building modification belongs in a qualified assessment and written scope.
Your next step is to give the installer a floor plan marked with closed-door rooms. Choose a design that explains how those rooms are served, rather than relying on a promise that cooling will reach every bedroom.