Downdraft From Ceiling Registers
We have R8 insulated flex-ducts in a vented attic feeding ceiling registers on the 2nd floor. They were properly installed and pressure tested. I have noticed when outside and attic temps are significantly lower than indoor temps there is a slight down draft from the register. The registers are air sealed to the ceiling and the ducts run vertically through about 16″ of loose cellulose above the registers.
I am theorizing that when the heat is not running the volume of air in the ducts cools off in the cold attic and the vertical duct run above the register creates some stack effect. Maybe there’s another cause?
Is this a common problem and is there an easy solution? Maybe a backdraft damper above the register (or would this harm the AHU?)
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