I recently posted about adding a second HVAC system to my house. You guys have pointed me towards first getting an energy audit to see where I can tighten up the house and make it more efficient. I'm pursuing that right now. Just waiting to get call backs. However, I currently evaluating the quotes that I already have. One of the guys wants to put a 2 Ton Heatpump in with a 3 ton coil in the attic. I've had one manual J calculation in the past for the upstairs and they said I was between 1.5 tons and 2 tons needed. They would go for 2 tons. I have a horrible insulation job in the attic and I'll be taking care of that after I get a system installed (I should say if). Anyway, the ductwork that currently goes from the basement to the attic on the second floor is 14 by 8 (unlined sheet metal). When it gets to the attic, it's reduced to 12 by 8 (unlined sheet metal with insulation on the outside. 9 flex duct lines run off the 12 by 8. My question is, can that size duct work handle a variable speed 2 ton unit? Will I get 800 cfm through there without it sounding like a jet engine? Thanks for any advice.