I have a two story home with a three and one half ton ac unit and a eighty-five thousand btu furnance. The problem I am having is that I get great air flow downstairs both heat and air however, upstairs the air flow seems to be minimal. The furnance is located upstairs. The air is forced upto the attic where it is disperched. There are three ducts feeding the downstairs, one a fourteen inch and two eight inch. Upstairs the four bedrooms and two baths are supplied by a six inch duct to each room. The motor is set on medium speed for heat and high for airconditioning. In both summer and winter the air flow is insufficiate for the upstairs. Besides adding a separate unit for the upstairs what can I do as far as duct work is concerned?