About 10 years ago, I had three 10" diameter runs of insulated flexible duct installed by an HVAC contractor to go from my basement forced air furnace plenum to a 2nd floor attic room, hoping to provide adequate cooling and heating to the 2nd floor attic area. Each of the 3 runs is about 25 feet long.
I have never been able to get really adequate cooling or air flow on the 2nd floor, and can only assume that the static pressure drop on these flexible ducts must be much higher than rigid ducts of the same approximate diameter and length. The installer was very careful to avoid any sharp bends or turns in the ducts when installing them, but they really seem to have a lot of pressure drop.
Is there any easy way to predict how much of an improvement I might expect by tearing out these flexible ducts and replacing them with the same size rigid 10 inch circular ducting?
The HVAC contractor who designed and installed this arrangement apparently over-stated / over-estimated the flow / volume capacity, and the CFM delivery rates were highly optimistic. I get very little cooling, and better but not great heating.
Thanks for any opinions in advance.
Smarty