You may be able to add a fan to your Ventline roof vent without removing it but it all depends on what part number you have. I spoke with my contact at Ventline who said that the VD0433 number you gave me is only for the screen on the vent.
If you have the part # V2110SP-24 that has the metal roof then my contact said that there is no way to modify it for a fan.
If you have the part # V2092SP-28 then there is a way that you could add a fan. The Replacement 12V DC Motor # BVD0218-00 and... view full answer...