Two ways to serve the rooms
Ducted systems distribute conditioned air through ductwork. Ductless mini-split systems use indoor units connected to outdoor equipment, and can be considered for spaces without existing ducts. The equipment layout and the rooms included in the design matter more than a label such as whole-home or zoned. Ask the provider to show which spaces the proposal addresses.
Draw the scope room by room
List the rooms to be served, where discomfort occurs and whether an addition or converted space is part of the project. Ask where indoor units, outdoor equipment and controls would go. Include access for future maintenance in the discussion. You should be able to understand the proposed layout before comparing its price with another arrangement.
Ask what happens to existing equipment
A new system may replace the current equipment or supplement it. Ask which rooms continue using the existing system, which controls remain and how the two arrangements are expected to be used. For a ducted proposal, discuss whether any duct assessment or changes are included. For a ductless proposal, ask how the provider determined the number and placement of indoor units.
Look beyond the equipment list
Installation can involve electrical work, pipe routes, drainage, supports and finishing around penetrations. Ask the provider to identify the included tasks and any work another trade must complete. In a condominium or shared property, discuss approval for exterior equipment and access before the work is scheduled. Responsibility for those approvals should be clear in the project plan.
Compare written layouts and handover
Ask each bidder for a room-by-room description, model information, controls, included installation work and exclusions. Clarify what instructions and completion records you will receive. If two proposals have different numbers of indoor units or different room coverage, ask why. This helps you compare a design for your home instead of choosing solely by the headline equipment price.