How much clearance (height) does your roof jack vent cap need?
The answer depends on
1) The placement of the roof jack on the roof.
2) The type of roof you have (how pitched or how flat)
3) The climate zone you live in
For those who have asphalt shingle roofs or metal roofs (not flat membrane roofs) in climates zones 4 and higher, a snow guard / rain diverter should be installed above your roof jack vent cap (unless it is installed near the peak of the roof) so that the vent will be protected from sliding ice and rushing water.
For 3/12 pitch roofs or higher Roof Jacks can have a 2" tall collar when they are installed no more than 3 feet from the peak of the roof.
For 3/12 pitch roofs or higher roof jack vent caps when installed on the mid to lower portion of the roof (4 feet or lower down from the peak) and the roof pitch is 3/12 or higher you will need:
You can always use taller collars for additional clearance in warmer zones, but you can’t use shorter collars in colder zones.