We have a 3200 square foot home and have been having issues since we moved in. First, the house was originally wired up to a 4 ton unit that heated and cooled the whole house. Later, someone added a 3 ton unit for the downstairs. The 3 ton unit uses flex duct in the crawl to heat and cool. This unit blows great and heats and cools quick. The 4 ton unit that use to do the whole house has what I think is flex duct running throughout the house. It is hard/impossible to see this ductwork because of the way it was set up and it doesn't run through the attic upstairs. So we have vents at the ceiling of our downstairs, and vents at the floor of our upstairs that all come from the 4 ton unit setup. I blocked off the ceiling vents downstairs (because the 3 ton unit takes care of downstairs and has registers in the floor.) using magnets and simply closing them. The air coming out of both downstairs unit and upstairs unit is around 60 degrees in the summer. The difference is in the air pressure. Downstairs (3 ton) blows very hard and is awesome. Upstairs the air doesn't blow hard at all in some spots and average in others. I decided to add a return air to the upstairs unit because it was pulling from a small wall cavity and it was like a kink in a hose, the unit wasn't getting enough return air. So I designed a steel box in the attic and connected all of my returns to it, and then did the same where they go into the furnace. This helped very slightly... We also decided to have a company insulate the attic just recently to bring us up to a R45 which is what the region calls for. They used a new fiberwool insulation. Our 4 ton unit used to run all day and still couldn't get the temps down upstairs until 3 in the morning! Now, the temps are lower than they were, but our unit still runs all day trying to keep it at 76 in the summer. I am lost as to what the hell is going on. If it is my ductwork, wouldn't I have to start tearing up the ceiling to access it? And why can't my house cool itself down upstairs? Should I install an attic fan or two up in the attic? I'm just very frustrated with this situation because that 4 ton unit should be able to do the job up there. My 3 ton unit blows so much harder! HELP!