draught drafts fan backdraught

We get a terrible draught through our kitchen extractor which vents outdoors. We have tried various back-draught flaps in the duct and hoods on the outside, but to no real avail. In all cases, the wind blowing past the outlet on the wall seems to pull the flaps open and let in a draught at the...

Hi, I have a Manrose in-line shower fan that exits through a roof space and through a pipe that goes up through a flashing plate in a pitched roof. What do people find is the best option to stop back draughts happening? I’ve looked into a back draught shutter that fits on the fan spigot, but...