On Oct 11, 12:43 am, wrote:
Is it normal to have some air coming in from the fan into the
bathroom. I have a screen at the end of the exhaust pipe and there is
a flapper damper at the fan itself, factory installed. I cant really
use a sophet vent because it restricts the air flow and causes a
whistling sound when running. There was still air coming in that way
too, but not as much. Had to be windier. Thanks!

It's not unusual, unfortunately. A couple of reasons. The spring
loaded damper at the outlet is a cheap piece and loses its seal. The
vent pipe is also a thermal short circuit to the outside air. They're
usually run through unheated spaces and consequently the air inside
loses its heat and the cold air looks for a lower spot to go lie
down. Namely, your bathroom.

R