It's all about the ductwork.
Putting a new system in a home that has not had central air and heat before will require the installation of ductwork, insulation, refrigerant piping, electrical service, wiring, thermostat, condensate piping, flue piping, flue terminations, chimney liner, slabs, filter, driers, registers, grills, drain pans and evaporator coil. Beyond equipment, the most important component installed with a new system, however, is the ductwork.
Ductwork is composed of two parts, supply and return. Supply duct is attached to the outflow of the new system, delivering air to each zone in a home. The amount of air reaching each zone is determined by the size of supply ductwork connecting it to your system. Your dealer will help you determine the size of all the supply ductwork in your home.
The second part of the ductwork, the return duct, attaches to the inlet of the new system and draws air out of the spaces to be heated or cooled. Attached to the return duct is the filter. The filter should be placed as near to the furnace or air handler as possible. Ductwork can be either fiberglass or metal and must be properly sized in order to evenly distribute the proper amount of air to each room.