Our 110 year old house has no return air ducts on the 2nd or 3rd floor. The air return ducts are located on the outside of the house on the first floor and the heating ducts are on the inside walls in both the 1st and 2nd floors. I have a small wall heater in the wall of the 3rd floor.
An A/C rep said that without the air return ducts on the 2nd and 3rd floors, installing central air would not be efficient and would barely push the cool air to the top 2 floors. Is this right? He is the first one to mention this and we want to be sure the cool air will circulate throughout the house. I am even ok if we still need to have a small window A/C in the 3rd floor bedroom but want the second floor to be cool.