Ok so I have a brand new Goodman gmvc95 furnace with Honeywell HZ311 using two zones. I am getting ready to have my third zone installed (basement 550 sqft). So had the HVAC guy out and with the current dips my 1st stage heat/cool is around 900cfm so I need the duct work to move about that much. Anyways he said I can do a 10" ROUND duct along one wall with registers off it and then a 8" ROUND in the opposite direction with registers and that will satisfy the cfm needs OR can do several RECTANGLE ducts that will get the same cfm and will be tucked in between the joints. Both options are sheet metal. The rectangle costs a little more too.
Just FYI because it is a basement the thermostat with have a swing temp setting, there will be a de-humidifier, and there will be a automated bypass just for the basement.
Which option is better Round or rectangle sheet metal?