When we moved into this house in 2018, the master bathroom exhaust fan was always loud and rattley. Last year I finally splurged on one of the nice panasonic units that is supposed to be silent. Test it in open air before installing it and sure enough it was as close to silent as a fan can get. One project later and the new fan is installed. Turn it on and it starts off silent but then starts ramping up is finally almost louder than the fan it replaced. It seems these fans can sense static pressure and crank up the blower to make sure they're moving the desired airflow. Now I'm remembering that I've seen birds going in and out of the exhaust vent caps on the roof. I think to myself "The birds must have built a nest on top of the screens in the caps." I finally have a roofer scheduled to come out and replace the vents with a different style so up I went to disconnect the ducts from the vents. Now the fun begins. I very quickly realize that the birds are IN the flex duct. I had to extricate two 5 - 6 foot sections of duct work complete with baby birds before I got to clean ductwork again. The caps have no screen whatsoever, and the ducts were attached to ductboard take off collars that had been screwed into the roof deck and shingled over. What should have been 10 minutes of disconnecting took two hours of removal and probably another hour of re-install after the new caps are in place and the builders again get to skate on shoddy workmanship.