What size OUTSIDE vent pipe do you have?
You can have your local plumber contact me VIA E mail to explain how cold air is heavier then watrm air and if the vent pipe has any restriction either diameter or excessive fittings Or a long developed lenth (run) then the vent is useless.
A lot of folks dabbling in “venting” applications forget about a FAI (fresh air inlet) which allows NATURAL circulation of the venting system.
Runing a vent without providing a means of make up air like a FAI is going to cause a vacuum where the OUTSIDE air is pulled into the structure as every time a fixture is used.
Venting if properly sized and designed is a science not pot luck.
If you have any questions please feel free to E mail me and ILL be glad to give you a crash course.