My daughter and son-in-law have a two story house with a finished basement. The furnace is located in the basement on the east end of the house. The main furnace duct comes from the basement to the second story on the west end of the house. The two bedrooms farthest from the plenum do not heat or cool sufficiently. Any suggestions what we can we do to get more heat in the winter and air conditioning in the summer - short of installing a second floor heating/ac unit?