Venting through a roof vent or exhausting them in the attic could cause moisture problems and rot.
Bath exhaust fan through roof.
In all cases the ducting needs to conduct the exchaust to the building exterior and needs to terminate in an animal proof vent cover.
Going through the roof guarantees it will go up in the air and away from your home i would love to see a copy of the building code that suggests venting a bathroom fan through the soffit is recommended.
Vent your bath and kitchen exhaust fans through the roof through a special roof hood.
Bend over the tabs then nail the tabs to the roof.
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Pass the opposite end of the duct through the hole in roof.
Next use aviation snips to cut slits into the sheet metal sleeve.
This article describes routing bath exhaust fan duct upwards through an attic or roof space or downwards through a floor or crawl space.
Run a thick bead of tri polymer sealant along the underside of vent hood.
The best exhaust fan venting is through smooth rigid ducts with taped joints and screwed to a special vent hood.
This old house general contractor tom silva shows how to properly install a roof mounted bath fan vent.
The master bathroom and the 2nd bathroom vent through the roof and through the same opening.
The 2 pipes one a 4 master and the other a 3 2nd do not go through the ceiling but into a common box that goes through the roof.
The alternative to a roof exhaust if you re concerned about not being able to seal the hole in the roof is to exhaust through a gable end.