How much clearance (vent height) your roof vent needs depends on the pitch of your roof and the climate zone you live in.
These applications are for when Exhaust Vents are installed less than 2 feet below the peak of the roof.
3/12 roof pitch or greater:
2/12 roof pitch or less:
Bear in mind, you can always use taller collars for additional clearance in warmer zones, but you can’t use shorter collars in colder zones when dealing with low slope roofs. Custom collar heights are available.