I am going to install Panasonic exhaust fans in our bathrooms in new construction through an unvented attic.. The Panasonic fan comes with a built-in damper and their installation guides mention using a wall cap with a damper too. This means there are two dampers.
The Panasonic damper is very light plastic does not seal well and opens easily. The wall cap damper is typically metal, making it a little harder to open. Our HVAC contractor suggests not using a damper at the wall cap but this worries me.
Is the best approach to use two dampers in line?
Thanks for your advice.